Well bore measurement tool

A caliper is mounted on two springs in a free-floating manner between interlockable upper and lower packers to be set in a well bore. The caliper has radially extendible arms which are extendible in response to independent forces exerted thereon as derived from the movement of a carriage driven by a single motor contained in the caliper tool. A clutch mechanism is used to lock the arms to precision measurement transducers only after the arms have been moved radially outwardly a sufficient distance. Other transducers for generating signals indicating the total movement of the arms and for indicating the forces exerted by the springs on the arms are included in the preferred embodiment.

BACKGROUND OF THE INVENTION 
This invention relates generally to well bore measurement tools and more 
particularly, but not by way of limitation, to a fracture orientation 
caliper tool mounted between two interlockable packers. 
In fracturing a formation intersected by a well bore, it is known that two 
seals, referred to as packers, are set in the well at the upper and lower 
boundaries of the formation to be fractured. A pressurized fracturing 
fluid is then injected between the set packers through a tubing or pipe 
string on which the packers are carried into the hole. Such procedure can 
be used either when the well bore is lined with a casing or when the well 
bore is unlined (referred to herein as an open well bore, or the like). It 
is important that once the packers are set, they remain set (until 
specifically released) so that the fracturing fluid will be properly 
contained to achieve the desired fracturing and so that hazardous 
conditions are not thereby created. It is also important for the packers 
to remain set when a measuring tool, such as a precision caliper tool 
subassembly, is carried between them. Any movement of the packers that is 
communicated to a tool such as a caliper could produce false readings and 
seriously damage such a tool when it has its measurement arms extended. 
When the well bore is lined with a casing or the like, known types of 
mechanical and hydraulic slips can be used to engage the casing so that 
upward movement of the top packer, such as in response to the pressure of 
the fracturing fluid exceeding the hydrostatic pressure existing above the 
top packer, is prevented. Preventing such upward movement can also 
sometimes be accomplished to some degree by "slacking off" the tubing or 
pipe string so that the weight of the string exerts a downward acting 
force on the packers. 
When packers are to be set in open well bores, however, the aforementioned 
mechanical and hydraulic slips have not been helpful in anchoring the top 
packer against upward movement. Likewise, the use of "slacked-off" tubing 
has been inadequate in general because in deep wells where the slacked-off 
pipe weight would be sufficient to prevent upward movement, the weight has 
been known to create a force exceeding the loading characteristic of the 
packer, thereby damaging it. In shallower wells, the upward applied force 
exerted by the fracturing fluid can easily overcome the lesser pipe 
weight, thereby causing the top packer to become unseated. 
The foregoing problem particularly pertains to upward movement of the top 
packer because the lower packer has the greater fracturing fluid pressure 
acting downwardly on it, and its downward movement is limited by an anchor 
pipe testing on the bottom of the hole or engaging the side wall of the 
bore. The interconnecting construction of conventional dual packers known 
to the art is such that this downward limitation is also applicable to the 
top packer so that it is only the upward movement of the upper packer 
which is of primary concern. 
Although one can circumvent this problem by always casing or lining the 
well bore and by then using the known types of casing engaging locks, it 
is desirable to solve the problem in a manner whereby open hole packers 
can be securely set and locked in open well bores because this saves the 
time and expense of always having to case or line the well bore while 
still accomplishing reliable fracturing. 
The foregoing exemplifies the particular need for a lock by which a top or 
upper packer can be locked relative to a bottom or lower packer to prevent 
upward movement of the upper packer in response to the fracturing fluid 
pressure exerted between the two packers when the packers are used in an 
open well bore. The satisfaction of this need, however, would also provide 
an improved lock useful in other types of downhole apparatus which require 
locking against relative movement between different parts of the 
apparatus. 
There is also the need for a device which can be used with the 
interlockable packers to determine the direction of a fracture that is 
created by a hydraulic fracturing process or treatment which is applied 
between the interlocked packers. This determination can be made with an 
instrument which measures the deformation of the well bore during the 
hydraulic pressurization of a fluid contained between the two packers set 
in the well bore. Such an instrument is referred to as a caliper, of which 
there are various types known to the art, but for which there is the need 
for an improved type having several features. 
One of the desired features is a construction by which, after being run 
into the well bore beween the two packers, the caliper can be locked into 
the formation by its own force applied through a single set of implements 
which securely fasten the caliper to the formation and which also provide 
movements sensitive to the deformation of the formation. The mounting of 
this device between the packers should be in such a manner that if either 
or both of the packers moves relative to the formation, such movement does 
not affect the operation of the caliper. 
The forces which are to be applied through the single set of implements are 
preferably generated by a single drive unit to simplify the construction 
and maintenance of the caliper. Such single drive unit preferably, 
however, is capable of applying independent forces to the individual 
holding implements to accommodate the various dispositions of the caliper 
in the well bore, which has a side wall that will never be perfectly round 
and thus never evenly spaced from the caliper. Such single drive unit must 
be capable of creating forces great enough to securely fix the caliper to 
the formation. 
To further maintain simplicity of design, the implements used to secure the 
caliper to the formation should be the same ones to detect deflections of 
the formation caused by the fracturing process. Such detections should be 
highly sensitive so that accurate in situ stress measurements, which are 
fundamental to understanding rock fracture mechanics, can be obtained. In 
addition to the taking of such highly sensitive measurements, however, the 
tool should also be capable of making relatively large measurements from 
which the total radial movement of the arms can be measured to determine 
diameters or transverse dimensions of the hole in which the tool is used. 
Such an improved caliper tool should also be capable of measuring the 
forces applied to the formation engaging implements so that other 
properties of the formation can be determined. For example, rock hardness 
can be determined knowing the forces applied to the formation through the 
implements and the distances the implements have moved. 
Despite having such a novel combination of features as just described, the 
tool should also be able to maintain features found in existing tools, 
such as means for measuring pressure, temperature and orientation. 
SUMMARY OF THE INVENTION 
The present invention overcomes the above-noted and other shortcomings of 
the prior art and satisfies the aforementioned needs by providing a novel 
and improved well bore measurement tool. The present invention has 
particular utility in a double packer used in an open well bore. That is, 
with the present invention the upper packer of the double or dual packer 
assembly can be controllably locked and unlocked against upward movement 
which would otherwise occur in response to a pressure, applied through the 
tubing between the two packers, exceeding the hydrostatic pressure and the 
weight of the pipe or tubing acting downwardly on the upper packer. It is 
contemplated that the present invention could, however, have broader 
applications with respect to, in general, a downhole apparatus having an 
inner tubular member and an outer tubular member in which the inner 
tubular member is slidably disposed. 
The present invention also provides a caliper which is combined with the 
interlockable dual packers to form the overall well bore measurement tool 
of a particular embodiment of the present invention. The caliper design 
for the present invention is such that the caliper is run into the well 
bore mounted in a free-floating manner between the interlockable packers. 
The caliper utilizes a single drive unit capable of extending and 
retracting formation engagement arms which hold the caliper to the 
formation with independently exerted forces and which detect deflections 
of the formation in response to the pressurized fracturing fluid applied 
between the interlocked packers. The caliper is highly sensitive in 
detecting such deflections; however, it is also capable of taking larger 
measurements which reflect total diameters or transverse dimensions of the 
well bore. In a particular embodiment, the caliper can detect forces 
applied to the arms so that other properties, such as rock hardness, can 
be derived. This particular embodiment also incorporates other detecting 
devices for detecting such phenomena as pressure, temperature and 
orientation. 
The overall well bore measurement tool of the present invention 
incorporating both the interlockable packers and the caliper broadly 
comprises lower packer means for providing a lower seal in the well bore, 
upper packer means for providing an upper seal in the well bore, caliper 
means for measuring a deflection of the side wall of the well bore, and 
retainer means for retaining the caliper means between the lower and upper 
packer means so that the caliper means is transportable into the well bore 
with the lower and upper packer means but so that the lower and upper 
packer means are longitudinally movable relative to the caliper means when 
the caliper means engages the side wall of the well bore. This tool 
further comprises lock means for locking the upper packer means to the 
lower packer means. 
The caliper means comprises a support member; a pivot arm pivotally 
connected to the support member; sensor means for sensing a movement of 
the pivot arm when the sensor means is coupled to the pivot arm, which 
sensor means includes displacement measurement means, connected to the 
support member, for generating a signal in response to a sensed movement 
of the pivot arm, and connecting means for releasably connecting the pivot 
arm to the displacement measurement means; and actuating means, connected 
to the support member, for actuating the connecting means to connect the 
pivot arm to the displacement measurement means. In a particular 
embodiment the caliper includes a plurality of pivot arms, each of which 
includes two sections having a common pivoted connection and having their 
opposite ends pivotally connected to the support member and to a drive 
means, respectively. The drive means commonly moves the pivot arms so that 
each common pivoted connection is simultaneously moved outwardly from the 
housing, and the drive means exerts independent forces on the pivot arms. 
Each pivot arm moves independently of the others, thus providing a precise 
measurement, via the displacement measurement means, of the well bore 
shape.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiment of the present invention will be described with 
reference to a dual packer assembly 2 disposed in an open well bore 4. 
This particular construction is schematically illustrated in FIG. 1 
(although not so illustrated because of the schematic nature of FIG. 1, 
the bore 4 has an irregular side wall, not a smooth side wall, as known to 
the art). 
The dual packer assembly 2 schematically illustrated in FIG. 1 includes a 
bottom or lower packer section 6 of conventional design (such as the lower 
end of a Halliburton Services No. 2 NR packer assembly). Spaced above the 
lower packer section 6 is a top or upper packer section 8 which includes 
at least part of a conventional upper packer assembly (such as the top 
portion of a Halliburton Services No. 2 NR packer assembly), but which 
also incorporates the novel and improved lock by which the packers can be 
interlocked in the present invention. 
Shown mounted within a slotted sleeve 9 extending between the packer 
sections 6, 8 is a caliper tool 10 which is also part of the present 
invention. Although a caliper tool generally exemplifies a device whose 
proper operation can require that the top packer section 8 not be 
displaced when the fracturing pressure, applied to the volume of the well 
bore 4 which is between the packer sections and in which the caliper tool 
10 is disposed, exerts a force that exceeds any downwardly acting weight 
of the pipe on which the packer assembly 2 and the tool 10 are lowered 
into the well and the force of any hydrostatic head acting downwardly on 
the upper packer section 8, the caliper tool 10 of the preferred 
embodiment is constructed and mounted so that at least some movement of 
the packers is tolerated. However, the use of a caliper with the packers 
does generally illustrate the need for the lock of the present invention 
by which the upper packer section 8 can be effectively locked to the lower 
packer section 6, which is anchored by an anchor pipe 12 into the bottom 
or the side of the hole 4, to prevent upward movement of the packer of the 
section 8. Even used alone the packers can need to be interlocked to 
prevent unseating the top packer, which unseating could possibly allow the 
fracturing fluid to escape to the surface where a hazardous situation 
could result. The preferred embodiment of this lock is illustrated within 
the downhole apparatus shown in FIGS. 2A-2F. 
The downhole apparatus illustrated in FIGS. 2A-2F in conjunction with the 
lock of the present invention is an example of the upper packer section 8. 
This apparatus broadly includes an inner tubular member 14 and an outer 
tubular member 16, both of which include a plurality of components. The 
inner member 14 is slidable relative to the outer member 16, but these two 
members can be locked together by a lock 18 of the present invention. 
The inner tubular member 14 of the upper packer section 8 is characterized 
in the preferred embodiment as a mandrel assembly including a packer 
mandrel 20 (FIGS. 2C-2F) and a locking mandrel 22 (FIGS. 2A-2C). The 
packer mandrel 20 is a cylindrical tube of conventional design having a 
lower externally threaded end for engaging a lower adapter 24 of a 
conventional type used for connecting (through the caliper tool 10 in the 
FIG. 1 configuration) to the lower packer section 6 anchored on the bottom 
or in the side wall of the well bore 4 by the anchor pipe 12. The packer 
mandrel 20 has an internally threaded throat at its other end for 
threadedly coupling with an externally threaded end of the locking mandrel 
22, which locking mandrel 22 forms part of the lock 18 and will be more 
particularly described hereinbelow. 
The outer tubular member 16 is characterized in the preferred embodiment as 
an upper packer carrying assembly having a packer 26 (FIGS. 2D-2E) 
connected (such as by a bolting fastening means including the nut and bolt 
combination 28 shown in FIG. 2D) to a packer carrier sleeve. The packer 
carrier sleeve includes a packer retaining collar 30, to which the packer 
26 is fastened, and a connecting sleeve 32, to which the retaining collar 
30 is connected by a quick change coupling 34 (FIGS. 2B-2D). The packer 
carrier sleeve of the outer tubular member 16 also includes a locking 
sleeve 36 (FIGS. 2A-2C) which is threadedly connected to the connecting 
sleeve 32 and which forms another part of the lock 18 to be more 
particularly described hereinbelow. 
The packer 26 of the preferred embodiment is made of a composition (e.g., 
an elastomer) of a type as known to the art. It has an annular shape 
defining a hollow interior in which the packer mandrel 20 is slidably 
received. Providing lower support to the packer 26 are a packer support 38 
(shown in FIG. 2E as being splined with the packer mandrel 20), a rubber 
packer shoe 40, a packer shoe support 42 and a coupling collar 44 
threadedly interconnecting the shoe support 42 with the lower adapter 24 
(FIGS. 2E-2F). These elements are of conventional designs known to the art 
and thus will not be further described. 
The packer retaining collar 30, the connecting sleeve 32, and the quick 
change coupling 34 are also of conventional designs and will not be 
particularly described because these designs are known to the art. It will 
be noted, however, that the coupling between the packer retaining collar 
30 and the connecting sleeve 32 includes a known type of seal 46 retained 
in between the packer retaining collar 30 and the connecting sleeve 32 and 
adjacent the packer mandrel 20 as shown in FIG. 2D. Additionally, the 
connecting sleeve 32 is shown as having a splined interconnecting 
relationship with the packer mandrel 20 as identified by the reference 
numeral 48 in FIG. 2C. 
The outer tubular member 16 connects at its upper end to an upper adapter 
50 (FIG. 2A) having a conventional design for connecting to the tubing or 
pipe string (not shown) on which the dual packer assembly 2, and the 
caliper tool 10 in the FIG. 1 example, are run into the open well bore 4. 
The upper adapter 50 carries a seal 52 for providing a sliding fluid seal 
between the upper adapter 50 and the locking mandrel 22. 
The lock 18 includes not only the aforementioned locking mandrel 22 and the 
locking sleeve 36, but also a latching mechanism 54. Each of these 
elements will be more particularly described with primary reference to 
FIGS. 2A-2C, 3C, and 4. 
The locking mandrel 22 is a means for connecting part of the lock 18 with 
the packer mandrel 20 inside the portion of the upper packer section 8 
defining the outer tubular member 16. The locking mandrel 22 is an 
elongated member having a cylindrical inner surface 56 defining a 
longitudinal channel 58 extending throughout the length of the locking 
mandrel 22. The channel 58 of the preferred embodiment is disposed axially 
through the mandrel 22. 
The mandrel 22 also has a cylindrical protuberant portion 60 extending 
radially outwardly from the main body of the mandrel 22. Milled or 
otherwise defined in the protuberant portion 60 are four cavities 62, 64, 
66, 68 (FIGS. 2B and 3) which extend through the outer surface of the 
protuberant portion 60 and into the protuberant portion 60 transversely to 
the length of the mandrel 22. In the preferred embodiment these cavities 
extend radially with respective parallel side walls or surfaces extending 
perpendicularly from a respective bottom wall or surface. Associated with 
each of the four cavities are two slots extending longitudinally from 
opposite ends of the respective cavity. The two slots associated with the 
cavity 62 are identified in FIG. 2B by the reference numerals 70, 72. For 
the cavities 64, 66, 68, slots 74, 76, 78, respectively, corresponding to 
the slot 72 for the cavity 62, are shown in FIG. 3. The cavities 62, 64, 
66, 68 are disposed in two pairs of diametrically opposed cavities whereby 
one pair includes the cavities 62, 66 and the other pair includes the 
cavities 64, 68. These cavities and slots open towards or face the locking 
sleeve 36. 
The mandrel 22 also includes a cylindrical outer surface 80 defining a 
lower sealing surface engaged by a seal 82 (FIG. 2C) retained in a recess 
84 of the locking sleeve 36. The diameter of the surface 80 is less than 
the outermost diameter of the protuberant portion 60 so that a radially 
extending annular shoulder 86 is defined therebetween. 
The mandrel 22 has another cylindrical outer surface 88. The outer surface 
88 extends longitudinally from the end of the protuberant portion 60 
opposite the end thereof from which the surface 80 extends. The surface 88 
has the same diameter as the surface 80; therefore, there is also a 
radially extending annular shoulder defined between the surface 88 and the 
outermost portion of the protuberant portion 60, which annular shoulder is 
identified in FIG. 2B by the reference numeral 90. The outer surface 88 
defines an upper sealing surface engaged by the seal 52 carried by the 
upper adapter 50. The seal 52 and the seal 82 have the same size so that a 
hydraulically balanced seal is created between the locking mandrel 22 and 
the locking sleeve 36 on opposite sides of the protuberant portion 60. 
The protuberant portion 60 can travel longitudinally or axially within a 
volume 91 defined between facing surfaces of the locking mandrel 22 and an 
inner surface 92 of the locking sleeve 36. This volume is also between the 
longitudinally spaced, circumferential seals 52, 82. This volume is 
defined in part by the inner surface 92 of the locking sleeve 36 being 
offset radially outwardly from an inner surface 94 of the locking sleeve 
36. This offset is established across a radial annular shoulder 95 which 
faces the shoulder 86 of the locking mandrel 22. The locking sleeve 36 has 
a cylindrical outer surface 96 and a threaded outer cylindrical surface 98 
radially inwardly offset from the surface 96 for engaging an internal 
thread of the connecting sleeve 32. 
Defined along the inner surface 92 is a locking sleeve engagement surface 
100 comprising in the preferred embodiment grooves or serrations or teeth 
defining engagement means for interlocking with cooperating elements of a 
latch member forming part of the latching mechanism 54. The locking sleeve 
engagement surface 100 is not coextensive with the length of the surface 
92 so that the latching mechanism 54 is longitudinally movable between a 
longitudinally located unlatched or disengagement position, located in the 
preferred embodiment relatively closer to the shoulder 95 than to the 
opposite end of the volume adjacent a radial annular surface 101 of the 
upper adapter 50, and a longitudinally located latchable or engagement 
position, wherein at least part of the latching mechanism overlies at 
least a portion of the locking sleeve engagement surface 100. 
The latching mechanism 54 of the preferred embodiment includes latch member 
means, slidably disposed in at least one of the cavities 62, 64, 66, 68, 
for engaging the packer carrying sleeve assembly (specifically, the 
locking sleeve engagement surface 100 in the preferred embodiment) when 
the latch member means is moved to the aforementioned longitudinal 
engagement position and then to a radially located latched or engagement 
position. The latching mechanism 54 also includes actuating pressure 
communicating means, disposed in the tubular member on which the latch 
member means is mounted, for communicating an actuating pressure to the 
latch member means so that the latch member means moves towards the other 
tubular member, and into the radial engagement position, in response to 
the actuating pressure. The latching mechanism 54 also includes biasing 
means, connected to the tubular member on which the latch member means is 
mounted, for exerting a biasing force against the latch member means in 
opposition to a force exerted on the latch member means by the actuating 
pressure so that the latch member means is biased away from the other 
tubular member and thus towards a radial disengagement position which is 
out of engagement with the locking sleeve engagement surface 100 even 
though the locking member means even partially overlies the engagement 
surface 100 and is thus at a longitudinal latchable or engageable 
position. Thus, this biasing force tends to move the latch member means 
deeper into its respective cavity. The latching mechanism 54 still further 
includes hydrostatic pressure communicating means, disposed in the tubular 
member on which the latch member means is not mounted, for communicating a 
hydrostatic pressure to the latch member means so that a force exerted by 
the hydrostatic pressure is applied to the latch member means in 
opposition to a force exerted on the latch member means by the actuating 
pressure. 
The latch member means of the preferred embodiment includes four latch 
members, each disposed in a respective one of the cavities 62, 64, 66, 68. 
Because each of these latch members is identical, only a latch member 102 
principally shown in FIG. 2B will be described. The latch member 102 
includes a gripping member or means 104 for defining a latch member 
engagement surface 106 (see also FIG. 4) facing the inner surface 92 of 
the locking sleeve 36. The gripping means 104 of the preferred embodiment 
is constructed of an oblong carrier block 108 and a plurality of gripping 
teeth 110 defined in the preferred embodiment by carbide inserts retained 
in the carrier block 108 at oblique angles thereto to give a tilted 
configuration to the carbide inserts which facilitates their ability to 
bite or grip into the locking sleeve engagement surface 100 of the locking 
sleeve 36. The teeth 110 are received along a rectangular planar surface 
111 of the carrier block 108, and they define a plurality of protuberances 
extending from the surface of the carrier block 108. Milled or otherwise 
defined in opposite ones of the curved ends of the oblong block 108 are 
respective recesses 112, 114. The recess 112 has a curved lower surface 
116. Parallel planar surfaces 118, 120 extend from opposite edges of the 
surface 116. The recess 114 has a curved lower surface 122 and parallel 
planar surfaces 124, 126 extending from opposite edges of the surface 122. 
The latch member 102 also includes seal means 128, detachably connected to 
the carrier block 108, for providing a sliding seal between the latch 
member 108 and the inner side walls of the cavity 62 in which the latch 
member 102 is disposed. The seal means 128 includes a seal support member 
130 having an oblong configuration similar to that of the carrier block 
108 and similar to the shape of the cavity 62. A peripheral groove 132 is 
defined around the perimeter of the seal support member 130. The groove 
132 receives a seal assembly 134 comprising an O-ring or other suitable 
fluid member and also comprising a seal back-up ring which reduces the 
friction of the movable seal and which reinforces the primary seal ring 
against high pressure differentials that may exist across the sealing 
structure. 
The seal support member 130 is connected to the carrier block 108 by a 
suitable connector means whereby the two are releasably connected to 
enable the carrier block 108 to be released from the seal support member 
130, such as when the latch member engagement surface defined by the 
gripping teeth 110 is worn out and is to be replaced with another such 
gripping means. In the preferred embodiment this connector means includes 
a dovetail tenon 136, protruding from a central portion of the seal 
support member 130, and a mortise 138, defined centrally along and 
transversely across a surface of the carrier block 108 for slidably 
receiving the dovetail tenon 136. 
These components of the latch member 102 define a slidable body which is 
movable within the cavity 62. Corresponding components define a plurality 
of other latch members respectively disposed in the cavities 64, 66, 68 
for simultaneous slidable movement with the latch member 102. These 
movements occur in response to an actuating pressure provided through the 
tubing or pipe string from the surface and into the channel 58 of the 
locking mandrel 22 for communication into the cavities 62, 64, 66, 68 
through respective ones of the plurality of actuating pressure 
communicating means contained in the preferred embodiment of the present 
invention. Because each of these communicating means is identical in the 
preferred embodiment, only the one associated with the cavity 62 will be 
particularly described hereinbelow. 
In the preferred embodiment the actuating pressure communication means 
communicates a hydraulic pressure from the axial channel 58 into the 
cavities 62, 64, 66, 68 of the locking mandrel 22. This pressure exerts a 
force against the latch member 102 and the other similar latch members. 
This force, when sufficiently strong, moves the latch members radially 
outwardly so that at least portions of the engagement surfaces thereof 
interlock with at least a portion of the locking sleeve engagement surface 
100 of the locking sleeve 36 when these portions are radially aligned. 
This radial alignment is achieved after the packers have been set as will 
be more particularly described hereinbelow. 
To provide this communication to the cavity 62, the preferred embodiment 
actuating pressure communicating means associated with the cavity 62 
includes two holes 140, 142 defined by respective transverse walls of the 
locking mandrel 22. These walls extend between the channel 58 and the 
transverse cavity 62. In the preferred embodiment these walls are 
specifically radially extending walls. The actuating pressure communicated 
through these holes can be derived from the fracturing fluid pumped down 
through the central channel extending through the entire upper packer 
section 8 for introduction into the open well bore volume encompassed 
between the spaced packers of the lower and upper packer sections 6, 8. 
The biasing means of the preferred embodiment latch mechanism 54 includes 
two spring members for each of the latch members. Because the spring 
members are identical, only the two associated with the latch member 102 
shown in FIG. 2B will be described. These spring members are identified by 
the reference numerals 144, 146. The spring member 144 has a support 
portion 148 and an engagement portion 150 extending at an obtuse angle 
from the support portion 148. The spring member 144 is made of a resilient 
material so that the engagement portion 150 can bend relative to the 
support portion 148, but with a resulting biasing force being created 
tending to return the engagement portion 150 to its rest position shown in 
FIG. 2B. This action provides a biasing force which acts in opposition to 
the direction of the hydraulic actuating pressure applied through the 
holes 140, 142 and thereby tends to move the latch member 102 deeper into 
the cavity 62. This acts as a return force when the actuating pressure is 
removed. 
The support portion 148 is received in the slot 70, and the engagement 
portion 150 extends as a spring finger into the recess 112 of the latch 
member 102. The spring member 144 is secured in the slot 70 by suitable 
connecting means which achieves the aforementioned construction wherein 
the end of the spring member 144 defined by the engagement portion 150 
overhangs the cavity 62 and engages the carrier block 108 within its 
recess 112 to exert a radially inwardly directed force on the block 108 
and thus on the overall latch member 102. This connecting means comprises 
in the preferred embodiment a spring backup or support member 152 placed 
adjacent the support portion 148 of the spring member 144, and the 
connecting means also includes a screw or bolt 154 extending through holes 
defined in the support portion 148 and the spring support member 152 and 
into a radially extending threaded bore extending from the slot 70 into 
the protuberant portion 60 of the locking mandrel 22. 
The spring member 146 is constructed and situated similarly to the spring 
member 144, except that it has a support portion 156 which is secured in 
the slot 72 by a spring support member 158 and a screw or bolt 160. This 
allows an engagement portion 162 of the spring member 146 to extend into 
the recess 114 of the latch member 102. Therefore, the spring member 146 
extends in an opposite direction towards the spring member 144 and in a 
manner so that the engagement portion 162 overhangs the cavity 62 and 
engages the carrier block 108 to exert a radially inwardly directed force 
on the block 108. 
The biasing means also includes a retaining ring 164 freely disposed 
between the screws or bolts 154, 160 and partially overlying the spring 
members 144, 146 and the carrier block 108. The ring 164 acts as a safety 
backup to prevent the spring members 144, 146 from becoming too outwardly 
extended. 
The hydrostatic pressure communicating means of the latching mechanism 54 
includes four radial passages defined through the locking sleeve 36 so 
that a pressure existing externally of the locking sleeve 36 is 
communicated internally thereof to exert a radially inwardly directed 
force on the latch member 102 and, in particular, on the carrier block 108 
thereof. These four passages are equally spaced around the circumference 
of the locking sleeve 36 so that only one, identified as a hole 166, is 
shown in FIG. 2B. In the preferred embodiment each of these holes has a 
one-half inch diameter; however, any suitable size hole can be used. The 
hole 166, and its three counterparts, extend radially through the locking 
sleeve 36 along the shoulder 95 defined between the offset inner surfaces 
92, 94. This provides communication passages for allowing the hydrostatic 
pressure existing outside the upper packer section 8 and above the packer 
26 to be communicated into the volume 91 within the locking sleeve 36 
between the seals 52, 82. These holes also allow the hydraulic chamber or 
volume 91 to fill with fluid as the dual packer assembly 2 is run in the 
hole, thereby balancing the internal and external pressures across the 
latch members during this time. 
To use the lock, the packer assembly 2 is attached to a tubing or pipe 
string (not shown) and run into the well bore 4 in a manner as known to 
the art. When the dual packer assembly 2 is at the appropriate location, 
the packer 26 and the packer of the lower packer section 6 are set, also 
in a manner as known to the art. In running this structure into the well 
bore 4, the inner and outer tubular members of the upper packer section 8 
are situated as shown in FIGS. 2A-2F; however, when the packers are set, 
relative movement between the inner and outer tubular members occurs so 
that the latch member 102, and the other three latch members disposed in 
the cavities 64, 66, 68, have at least portions of their latch member 
engagement surfaces radially aligned with at least a portion of the 
locking sleeve engagement surface 100. At this time, but prior to a 
sufficient actuating pressure being applied down through the tubing or 
pipe string and into the channel 58 of the locking mandrel 22, the spring 
members of the biasing means are holding the respective latch members in 
their radial unlatched positions, which are relatively radially inward 
positions, such as is illustrated by the position of the latch member 102 
in FIG. 2B. These latch members are also held in these unlatched radial 
positions by the hydrostatic pressure existing in the annulus between the 
locking sleeve 36 and the surface of the well bore 4. This hydrostatic 
pressure is exerted on the latch members by being communicated thereto 
through the radial passages of the hydrostatic pressure communicating 
means (e.g., the hole 166). Locating the lock 18 above the top packer 26 
isolates and limits the outside or external force acting radially inwardly 
on the latch members to the hydrostatic pressure. 
When the hydraulic lock of the preferred embodiment of the present 
invention is to be actuated, whereby the latch members are moved into 
their engagement positions with the gripping teeth of the latch members 
interlocking with the locking sleeve engagement surface 100, a fluid is 
flowed down the tubing or pipe string into the channel 58 and pressurized 
until a sufficiently strong radially outwardly directed force is exerted 
through the actuating pressure communicating means (e.g., the holes 140, 
142) on each of the latch members. A sufficient force is one which exceeds 
the forces exerted by the spring members and the hydrostatic pressure. The 
application of this radially outwardly directed force simultaneously moves 
each of the latch members radially outwardly to lock the inner tubular 
member 14 to the outer tubular member 16. This in effect locks the packer 
26 to the lower packer section 6 because the inner tubular member 14 is 
connected to the lower packer section 6 through the lower adapter 24. As 
long as the tubing pressure exceeds the hydrostatic pressure and the 
biasing force of the spring members, the latch members lock into the outer 
housing of the upper packer section 8, thereby preventing upward movement 
of the top packer 26. Once the fracturing or other actuating pressure is 
removed, the latch members are returned to their original radially 
disengaged positions by the hydrostatic pressure and the retracting spring 
members of the biasing means. 
As indicated generally in FIG. 1, mounted between the lower packer section 
6 and the upper packer section 8 is the caliper tool 10. The preferred 
embodiment of a means for mounting the caliper tool 10 between the two 
packer sections is illustrated in FIGS. 5A-5B. Broadly, this mounting is 
achieved by retainer means for retaining the caliper 10 between the lower 
and upper packers so that the caliper is transportable into the well bore 
with the two packers but so that the two packers are longitudinally 
movable relative to the caliper when the caliper engages the side wall of 
the well bore. 
This retainer means in the preferred embodiment includes the slotted sleeve 
9 shown in FIGS. 5A-5B as having a cylindrical wall 200 having an upper 
end adapted for connecting with the upper packer section 8 and having a 
lower end adapted for connecting with the lower packer section 6 through a 
bypass valve section 202 (directional references, such as "upper" and 
"lower," are made with regards to orientations shown in the drawings and 
to normal orientation of the tool 10 in a vertical well bore). Near the 
upper end of the wall 200 there is defined one or more ports 204 through 
which fluid flow to or from the interior hollow region of the upper packer 
section 8 and to or from an upper cavity 206 defined within the slotted 
sleeve 9 by the portion of the wall 200 through which the ports 204 are 
defined and by an annular wall 208. Defined through an intermediate 
portion of the wall 200 are a plurality of slots 210 through which 
engagement implements of the caliper tool 10 extend as will be more 
particularly described hereinbelow. The slots 210 are spaced 
circumferentially around the wall 200 as is apparent in FIG. 5A. 
Mounted within a cavity 212 defined in the slotted sleeve 9 below the wall 
208 is an inner spring housing 214, which has a lower end (not shown) 
connected to the anchor pipe to which the lower packer section 6 is 
connected. The housing 214 has a cylindrical wall 216 through which a 
plurality of slots 218 are defined. The housing 214 is held within the 
slotted sleeve 9 so that the longitudinally extending slots 218, 210 are 
radially aligned so that the extendible implements of the caliper tool 10 
can be extended radially therethrough. 
The wall 216 terminates at its upper end in an end wall 220 through which 
an aperture 222 is defined for providing fluid communication between the 
cavity 212 of the slotted sleeve 9 and a cavity 224 of the spring housing 
214. It is within the cavity 224 that the caliper tool 10 is received. 
Extending axially from the end wall 220 is a wet connector adapter 226 
having a cylindrical shape defining a neck within which is defined a 
throat. The throat receives the wet connector, or an electrical coupling 
thereof, in a manner as known to the art for making an electrical 
connection between a wireline and the caliper tool 10. 
The lower end of the cavity 224 of the housing 214 is defined by a radial 
wall 228. The wall 228 defines not only the bottom of the cavity 224, but 
also the top of a cavity 230 in which a magnetometer 232 is disposed. The 
magnetometer 232 is one type of device by which the position of the 
caliper tool 10 relative to magnetic north can be determined. Other 
position locating instruments such as an inclinometer or a gyroscope can 
also be used. Alternatively, a pipe tally can be made. 
Contained within the cavity 224 of the housing 214 is the caliper tool 10, 
which is specifically retained within the cavity 224 by an upper spring 
234 and a lower spring 236. The spring 234 extends between the inner 
surface of the wall 220 and a top surface of the caliper tool 10, and the 
spring 236 extends between a lower surface of the caliper tool 10 and an 
upper surface of the wall 228 as shown in FIGS. 5A-5B. Thus, the springs 
234, 236 and the caliper 10 are held within the housing 214 which is in 
turn retained within the slotted sleeve 9 connected to the packer sections 
6, 8. The springs 234, 236 effect a free-floating mounting construction so 
that the caliper 10 is free to move longitudinally within the housing 214 
which thereby allows movement relative to the packer sections 6, 8. In the 
preferred embodiment the springs 234, 236 allow approximately one or two 
inches of longitudinal movement. This is important in the preferred 
embodiment of the present invention wherein the caliper 10 is directly 
locked to the well bore 4 once it is placed in use, which locked 
engagement is not to be disturbed even if the interlocked packer sections 
6, 8 should move. The springs 234, 236 also provide cushioning for the 
caliper tool 10 on its trips into and out of the well bore. 
The bypass valve section 202 partially shown in FIG. 5B is of a suitable 
type as known to the art. It includes at least one port 238 through which 
fluid can flow when the valve of the section 202 is open. When the valve 
is open, this allows fluid flow between the upper port or ports 204 of the 
slotted sleeve 9 and the port 238 of the bypass valve section 202 whereby 
the fluid flows around the caliper tool 10 and its spring carrier section. 
The caliper tool 10 illustrated in FIGS. 5A-5B is only partially shown for 
purposes of simplicity. The tool 10 is shown as generally including an 
upper section 240 in which the electronics and the drive motor are 
supported. Also supported by the section 240 are transducers which respond 
to the movement of the radially extendible implements of the tool 10. Two 
of these implements, which are connected at their upper ends to the upper 
section 240, are identified in FIG. 5A by the reference numeral 242. Other 
transducers which can be included within the upper section 240 are 
pressure transducers and temperature transducers and any other suitable 
ones which can be accommodated within the size constraints of such a 
downhole apparatus. The extendible members 242 are connected at their 
lower ends to a lower section 244 which forms part of the drive means for 
moving the extendible members 242 with independent forces. Force 
indicating transducers can also be included within the section 244 for 
indicating the magnitudes of the independent forces applied to each of the 
extendible members 242. Not shown in FIG. 5A, but part of the preferred 
embodiment of the caliper tool 10, is a coupling mechanism by which each 
of the extendible members 242 is connectible to a respective movement 
detecting sensor contained within the upper section 240. The components of 
each of these sections will be more particularly described with reference 
to the preferred embodiments illustrated in FIGS. 6-11. 
The preferred embodiment shown in FIG. 6 has the outer coverings of the 
upper section 240 and lower section 244 removed to show their general 
internal constructions. Also removed is the coupling mechanism for 
coupling the members 242 to the sensors; rather, this coupling mechanism 
is shown in the embodiment of FIG. 7. The upper section 240 has a 
plurality of longitudinal support rods 246. Connected to these support 
rods 246 are two lateral support plates 248, 250 which are longitudinally 
spaced from each other. An upper end lateral plate 252 is connected to the 
ends of the rods 246 opposite the plate 248. The rods 246 are spaced near 
the outer perimeter of the plates 248, 250, 252 so that the working 
components of the upper section 240 can be mounted interiorly of the rods 
246 and between the spaced plates 248, 250, 252. These working components 
include an electric motor 254 of a suitable type known to the art, such as 
a standard well logging tool motor. Also mounted in this region are 
printed circuit boards containing suitable circuitry for conditioning the 
various electrical signals applied to or generated in the present 
invention. A motor control circuit for controlling the motor 254 is also 
included. These circuits are not shown or further described because they 
are of any suitable type readily known to those skilled in the art for 
performing the functions of the present invention which will be more 
particularly described hereinbelow. 
The lower section 244 of the embodiment shown in FIG. 6 includes a carriage 
255 having an outer covering 256 (shown in FIG. 5A) and end support plates 
258, 260 between which connecting rods 262 extend to longitudinally space 
and support the end plates 258, 260. The end plates 258, 260 have a 
plurality of longitudinally aligned apertures defined therethrough near 
their outer perimeters. Spring guide rods 264 are slidably disposed 
through the apertures. There are six such pairs of apertures and six such 
spring guide rods in the preferred embodiment to correspond to the six 
extendible members 242 used in the preferred embodiment. The top end of 
each of the rods 264 is pivotally connected to the end of a respective one 
of the extendible members 242 as is shown in FIG. 6. 
Each of the spring guide rods 264 has a retaining collar 266 for retaining 
a respective spring 268 between the support plate 260 and the collar 266. 
The springs 268 are compressed in response to suitable movement of the 
carriage which occurs through a ball screw coupling mechanism 270 which 
couples the carriage 255 to the motor 254. 
In response to longitudinal movement of the carriage 255 of the lower 
section 244, each of the extendible members 242 is radially moved inwardly 
or outwardly depending upon the longitudinal direction of movement of the 
carriage. Each of the members 242 defines a pivot arm comprising a longer 
strut or arm section 272 and a shorter strut or arm section 274 which are 
pivotally connected at a pivot joint 276. The end of the strut 272 
opposite the pivot joint 276 is pivotally connected to a retaining plate 
278 of the upper support section 240 at a pivot joint 280. The end of the 
strut 274 opposite the joint 276 is connected at a pivot joint 282 to a 
respective portion of the support plate 258. These pivot connections are 
of any suitable type, such as a pin and clevis type of coupling where a 
bifurcated portion is pinned to a retaining tab received between the 
bifurcations. 
A more detailed description of at least some of the foregoing elements and 
the functions of these elements will be more particularly described with 
reference to the embodiment shown in FIGS. 7-11, which embodiment shows a 
more detailed construction than is shown in the FIG. 6 embodiment. It is 
to be understood that the embodiments shown in FIGS. 6 and 7-11 have many 
similar components and are functionally identical. Common or similar items 
between the FIG. 6 and FIG. 7 embodiments are indicated by like reference 
numerals. 
The upper section of the embodiment shown in FIG. 7 includes a support 
framework similar to that shown in FIG. 6. It is also shown in FIG. 7 to 
be enclosed in a covering or housing 284. The housing 284 is positioned 
adjacent the housing 214. The housing 284 is connected to the support 
wall, or bulkhead, 278 by screws or other suitable means. 
Attached into a beveled aperture 285 defined axially in the top wall of the 
housing 284 is a wet connector adapter 287. The adapter 287 includes a 
beveled plug 289 having a seal member 291 retained thereon. The plug is 
secured in the beveled aperture 285 by a cylindrical threaded receiving 
sleeve 293 threadedly connected into the aperture 285. The sleeve 293 
receives a wet connector member 295 when it is lowered into the well bore 
at the end of a wireline. In the preferred embodiment the wet connector 
tool from which the member 295 extends is of any suitable type, such as of 
a type used by Welex, but adapted for the particular use with the present 
invention. One feature of such an adaptation could be to use a slip joint 
construction intermediate the wet connector tool and the member 295. Such 
a slip joint would accommodate the approximately seven inches of vertical 
displacement that can be encountered in setting the upper packer section 
of the preferred embodiment. 
The upper section of the embodiment shown in FIG. 7 includes the motor 254 
mounted on a support bracket 286 which is connected to the support plate 
248 by screws, one of which is identified by the reference numeral 288. 
The shaft of the motor is coupled to a coupling or connecting rod 290 
which connects the motor shaft to a ball screw shaft 292 of the ball screw 
coupling mechanism 270. Associated with the drive shaft of the motor 254 
and the connecting shaft 290 is a gear 294 shown in FIG. 9. The gear 294 
is associated with four other gears 296, 298, 300, 302 to provide a gear 
drive sized to count twenty-two rotations of the ball screw shaft 292 in 
the preferred embodiment. When these twenty-two revolutions have occurred, 
a pin 304 on the gear 302 engages an upward direction limit switch of 
limit switches 306. This deactivates the motor 254 from further driving 
the ball screw shaft 292. These gears and the limit switch are located in 
a compartment or region 308 shown in FIG. 7 to be disposed between the 
longitudinally spaced plates 248, 250. A roller bearing 310 and a thrust 
bearing 312 are used to provide suitable support to the shaft 290. These 
bearings are supported in oppositely facing cavities axially defined in 
the bulkhead 278. This is an alternative construction of the bulkhead from 
the thinner one shown in the FIG. 6 embodiment. In the FIG. 6 embodiment, 
thrust bearings are mounted on both sides of the bulkhead block. 
Also defined through the bulkhead 278 is a channel 314 which communicates 
pressure to a pressure transducer 316 coupled to the channel 314 and 
mounted within the upper section of the embodiment shown in FIG. 7. In the 
preferred embodiment this pressure transducer is of a type known to the 
art for detecting a pressure within the range between 0 and 5,000 pounds 
per square inch. This is thus capable of measuring the pressure existing 
in the well bore as communicated to the channel 314 through the slots in 
the sleeve 9 and the housing 214. 
Also mounted in the upper section of the embodiment shown in FIG. 7 are a 
plurality of means for measuring the total radial distance each of the 
extendible implements 242 moves in response to the motor 254 and other 
drive components contained in the lower section of the preferred 
embodiment of the caliper tool 10. In the preferred embodiment each of 
these measurement means is a resistance potentiometer 318 having an 
actuating arm 320 coupled to a connecting rod 322 which engages a 
protuberant shoulder portion 324 of the respective pivot arm 242 under 
biasing of a spring 326 shown mounted between the body of the device 318 
and a coupling/retaining collar 328. Because of this direct and continuous 
engagement between the coupling rod 322 and the shoulder 324, the 
potentiometer 318 generates an electrical signal which is proportional to 
the total movement of the respective pivot arm. Because there are six 
pivot arms in the preferred embodiment, there are also six potentiometers 
318. The potentiometers 318 associated with oppositely disposed ones of 
the arms are paired so that the signals generated by each pair gives an 
indication of the total diameter or transverse dimension of the well bore 
defined across the respective pair of pivot arms. Each potentiometer 318 
and its connecting rod 322 are mounted longitudinally in the upper section 
of the caliper tool 10. The protuberant shoulder 324 is shaped so that it 
maintains contact with the end of the rod 322 throughout the full range of 
radial movement of the respective pivot arm. 
Although not shown in the drawings, also included in the upper section of 
the preferred embodiment of the caliper tool 10 is a temperature 
transducer of a type as known to the art. For example, one having a range 
of up to 500.degree. F. could be used. 
The lower section of the embodiment shown in FIG. 7 has elements similar to 
the corresonding lower section of the embodiment shown in FIG. 6 as 
indicated by the use of the same reference numerals. The view shown in 
FIG. 7, however, is of a section of the spring guide rods 264 without 
showing the connecting rods 262. Also, only two of the pivot arms 242 are 
shown in FIG. 7 to simplify the drawing; however, each of the six arms 242 
is similarly constructed to the one fully described hereinbelow. This view 
also shows the ball screw coupling mechanism 270 and other features of the 
preferred embodiment lower section 244 not shown in FIG. 6. As to the rods 
264, FIG. 7 shows that each passes through respective upper and lower 
seals 334, 336 which have equal areas to provide pressure balancing 
between the seals. The seals 334 are retained in the support plate 258, 
and the seals 336 are retained in the support plate 260. 
Extending axially from the support plate 258 is a neck portion 338 into 
which the lower portion of the coupling rod 290 and the upper portion of 
the ball screw shaft 292 extend and couple. A seal 340 mounted at the top 
of the neck portion 338 sealingly engages the rod 290. The neck portion 
338 has a stepped or offset outer appearance whereby a radial annular 
shoulder 342 is defined between cylindrical, longitudinal surfaces 330, 
332. 
Mounted below the support plate 258 opposite the neck portion 338, but 
axially aligned therewith, is a ball screw sleeve 343 which cooperatively 
receives the ball screw shaft 292. The sleeve 343 cooperates with the 
carriage 255 so that rotation of the shaft 292 drives the carriage up or 
down depending upon the direction of rotation 
Depicted by dashed lines in FIG. 7 are alternative embodiments of a sensor 
means for generating respective electrical signals corresponding to the 
force exerted by a respective one of the plurality of springs 268. There 
can be one such sensor means for each combination of spring guide rod 264 
and spring 268. One of these alternative embodiments is a linear 
potentiometer 344. There is one such potentiometer connected to a 
respective one of the spring guide rods 264 (such as specifically to the 
respective retaining collar 266) so that the respective potentiometer 
generates an electrical signal corresponding to the displacement of the 
respective retaining collar 266 and thus of the respective spring 268. 
Knowing the nature of the spring, one can use this displacement to 
determine the force exerted by the spring. An alternative device is a load 
cell 346, mounted colinearly beneath the respective spring, for generating 
an electrical signal proportional to the load. Use of either of these 
devices, or of any other suitable device by which the force exerted by 
each respective spring can be determined, is useful for providing 
information from which in situ stress measurements can be made, 
particularly in association with the deflection measurements taken in 
response to movements of the extendible arms 242. One specific measurement 
that can be derived is the hardness factor of the formation. 
From the foregoing descriptions of the upper and lower sections of the 
caliper tool 10, it is readily apparent that the motor 254, the coupling 
rod 290, the ball screw coupling mechanism 270, the carriage 255, and the 
rod 264/spring 268 assemblies are combined to define the preferred 
embodiment of a drive means for commonly moving all six of the pivot arms 
242 so that the pivoted joints 276 of the arms are simultaneously moved 
outwardly from the caliper tool 10 and for exerting independent forces on 
the pivoted arms for application to the well bore 4. This occurs when the 
motor 254 moves the carriage longitudinally upwardly as viewed in either 
FIG. 6 or FIG. 7. This movement occurs until the pin 304 of the gear 302 
engages the upward direction limit switch of the limit switches 306. 
Oppositely, these components retract the pivoted arms 242 radially 
inwardly when the motor 254 drives the carriage in the longitudinally 
opposite direction until the pin 304 engages the downward direction 
limiting switch of the switches 306. 
When the arms 242 are extended radially outwardly into engagement with the 
well bore 4, engagement with the well bore occurs through points or tips 
347 connected to the ends of the sections 272 of the arms 242. In the 
preferred embodiment, two of the arms 242 are provided with carbide points 
for penetrating the formation to rigidly lock the caliper tool thereto, 
and the other four arms are provided with more rounded points. In the 
preferred embodiment it is anticipated that the holding force applied to 
any one of the arms can be up to 250 pounds; however, any suitable force 
can be designed for by using an appropriate type of compression spring for 
the springs 268. The particular magnitude of force applied by any one 
spring depends on how far the respective pivot arm is extended, which 
depends on the size and shape of the well bore. 
The final principal structural part of the preferred embodiment of the 
caliper tool 10 to be described is the means by which deformations of the 
well bore are detected. This means is contained substantially centrally 
within the caliper tool 10. This means is generally identified in FIG. 7 
by the reference numeral 348. This includes sensor means for sensing 
movements of the pivot arms when the sensor means are coupled to the pivot 
arms. There is one such sensor means for each of the six pivot arms in the 
preferred embodiment. The means 348 also includes actuating means for 
actuating each of the sensor means after the drive means has pivoted the 
pivot arms 242 into engagement with the side wall of the well bore 4 so 
that each of the sensor means senses only movements of the pivot arms 
occurring after the pivot arms are pivoted into such engagement with the 
side wall of the well bore. 
Each sensor means includes a displacement measurement means, connected to 
the support member defined by the upper section 240 of the caliper tool 
10, for generating an electrical signal in response to movement of the 
respective one of the pivot arms associated with that displacement 
measurement means. In the preferred embodiment the displacement 
measurement means is a linearly variable differential transformer 
transducer of a suitable type known to the art, such as a Schaevitz XS-C 
series transducer (e.g., model 149 XS-C). This type of transducer has only 
a limited range of total measurable linear displacement (e.g., +0.15 
inch), but within that range a precision of 0.0001 inch or smaller is 
provided. This permits the well bore deformations (which are anticipated 
to be no more than approximately 0.1 inch) to be measured by the present 
invention with a resolution of at least 0.001 inch. 
One of these transducers is identified by the reference numeral 350 in FIG. 
7. Each transducer 350 has a body mounted longitudinally in the preferred 
embodiment within the housing of the upper section 240. Slidably disposed 
within the body is a movable member, sometimes referred to as an armature, 
which moves longitudinally relative to the caliper tool 10. This mounting 
is longitudinal in the preferred embodiment because of space limitations; 
however, it is contemplated that other dispositions of the transducers can 
be achieved if suitable transducers and tool sizes can be accommodated. 
When the movable member slides within the transducer body, an electrical 
signal is generated. When the movable member is connected to the 
respective arm 242, this signal is generated in response to movement of 
the arm 242 brought about by deformation of the well bore 4. 
This deformation sensor means also includes connecting means for releasably 
connecting the respective one of the pivot arms 242 to its respective 
transducer 350. This connecting means includes a coupling line extending 
from the pivot arm 242. In the preferred embodiment this coupling line is 
a connector strap 352 which is a long thin strip of stainless steel having 
one end connected in alignment with the pin or tip 347 contacting the 
formation at the pivot joint 276. The strap 352 extends through an 
engagement means, subsequently described, and around a guide shoe 354 
having a curved edge 356 along which the strap extends and bends 
90.degree. so that the other end of the strap extends transversely to the 
first-mentioned end of the strap, which firstmentioned end extends 
transversely to the longitudinal direction of the caliper 10. The guide 
shoe 354 is mounted on an L-shaped bracket 355 which is connected by two 
Allen screws to a circular support plate 370 as shown in FIGS. 7 and 10. 
This other end of the strap 352 is connected by suitable means to the 
carriage 255 of the drive means. In the preferred embodiment this is 
accomplished by a spring 358 located within the carriage 255 as shown in 
FIG. 7. The spring 358 has one end connected (such as by a hook and eye 
connection) to the strap 352 and has its other end connected to a 
connecting plate 360 attached to the bottom support plate 260. The spring 
358 is used to eliminate slack and keep tension on the strip or strap 352 
at all times in view of the difference in ratio of the two lever sections 
or struts that make up the extendible arm 242 and further in view of the 
non-linear travel ratio between the contact point of each arm and the 
spring drive assembly in the lower section of the caliper 10. This tension 
does not adversely affect the measuring system once the strap 352 is 
locked in its measuring position. 
To lock the strap 352 in its measuring position, the connecting means of 
the deformation sensor means includes the aforementioned engagement means 
which is used for engaging the coupling line with the respective 
transducer 350 when the engagement means is in an engagement position and 
for disengaging the coupling line from the transducer when the engagement 
means is in a disengagement position. This engagement means in the 
preferred embodiment clamps the strap 352 to the movable member of the 
respective transducer 350 in response to the actuating means which in turn 
is responsive to the drive means. This clamp means includes an L-shaped 
lever or elbow member 362 having arm sections 364, 366 connected in 
transverse (specifically, perpendicular) relationship to each other. The 
arm section 364 includes a fork element 365 (see FIG. 8) having an open 
bifurcated end which receives and is screwed or otherwise suitably 
connected to a transverse extension integrally formed with the arm section 
366 but forming part of the arm section 364. 
This member 362 is used to accommodate the 90.degree. change in direction 
between the direction of wall deflection and the direction of the travel 
of the movable member, or armature, of the transducer 350 when the 
transducer 350 is mounted longitudinally as illustrated in FIG. 7. In the 
preferred embodiment the elbow member 362 has a one-to-one ratio supported 
on a Bendix flexure spring pivot 368 secured to an L-shaped bracket 369 
connected by Allen screws to the support plate 370 as shown in FIGS. 7 and 
10. The plate 370 is connected by elongated members 371 as part of the 
framework of the upper section 240 of the caliper tool 10. This type of 
connection provides a spring pivot that allows precise centering of the 
rotation of the L-shaped lever 362 with almost no friction and hysteresis. 
These devices have substantially zero backlash which is of utmost 
importance when measuring for resolution on the order of 0.001 inch, as is 
to be done in the preferred embodiment of the present invention. 
Therefore, this design and mounting of the elbow member 362 allows for 
automatic centering of the armature or movable member in the transformer 
350 when the member 362 is disengaged from the respective arm 242. This 
armature is connected to the arm 366 of the lever 362 by a small thin 
strip 372, which is connected thereto by screws as illustrated in FIG. 7. 
This thin strip, which in the preferred embodiment is on the order of 
0.004 inch thick and between 0.187 inch to 0.025 inch wide and made of 
stainless steel, is used so that displacement movement passes at a precise 
distance from this flexure pivot and so that any side load due to rotation 
of the L-shaped member 362 is relieved. 
To lock one strap 352 to one elbow member 362 (there is one of each for 
each pivot arm 242) so that movement of the respective pivot arm 242 is 
coupled through the respective elbow member 362 to the armature of the 
respective transducer 350, the arm portion 364 of the elbow member 362 has 
a self-locking spring loaded clutch mechanism having a preferred 
embodiment shown in FIG. 8. The fork element 365 of the arm portion 364 is 
connected to the transverse extension from the arm portion 366 so that a 
curved surface 376 on this transverse extension lies within the central 
opening of the bifurcated extensions of the fork element 365. The strap 
352 can be clamped to the surface 376 by a clutch roller member 378, which 
comprises a cylindrical sleeve 379 and a cylindrical pin 381 extending 
axially through and beyond both ends of the sleeve 379 as shown in FIG. 
11. The member 378 is urged into frictional engagement with the strap 352 
by a holding piston or anvil 380 biased towards the strap 352 by a spring 
382. This construction allows a connection which communicates well bore 
deformation between the pin 347 engaging the formation and the armature of 
the transformer 350 with little or no backlash of the one-to-one ratio 
coupling system. 
The roller 378, by means of its pin 381, has two smaller diameter ends 
which are received in aligned slots 383 of the fork element 365. One of 
these slots 383 is shown in FIG. 8. A larger diameter central cylindrical 
portion, defined by the sleeve 379, of the member 378 extends between the 
slots so that the roller 378 does not inadvertently come out of these 
slots. 
The anvil 380 and the spring 382 are received in the central opening of the 
fork element 365 so that they can move longitudinally as guided by a guide 
rod 384 of the anvil 380. The guide rod 384 passes through a hole 385 
defined through the closed end of the fork element 365. The face of the 
anvil 380 biased by the spring 382 towards the roller 378 is shown in FIG. 
8 as having a shallow slope converging to a central area which contacts 
the roller 378. The slope of this convergence is kept shallow (e.g., less 
than approximately 13.degree.) to make the clutch mechanism self-locking 
when it is released to engage the roller 378. 
Movement of the roller 378 in opposition to the biasing force exerted by 
the spring 382 is effected by means of the actuating means which in the 
preferred embodiment includes a spider 386 mounted for relative movement 
between the support plate 370 and the respective rollers 378. Coil springs 
388, one of which is shown in FIG. 10, are held between the support plate 
370 and the spider 386 to bias the spider 386 towards the rollers 378. 
Although FIG. 10 shows a bolt 393 and a self-locking nut 395 associated 
with the spring 388, such nut and bolt are used for assembly but are not 
required to hold the plate 370 and the spider 386 together after assembly 
as is apparent when viewing the overall assembly in FIGS. 7 and 10. The 
spider 386 has a central cylindrical hub 389 from which extend radial 
fingers, one of which fingers is identified in FIGS. 10 and 11 by the 
reference numeral 390. There are six such fingers, each of which is 
associated with a respective one of the pivot arms 242 and the 
accompanying connecting assembly. Each finger 390 is bifurcated, and each 
bifurcation has connected to its outer end a pawl 391 having a groove for 
receiving the respective end of the pin 381 of the roller 378 when the 
springs 388 urge the pawls 391 towards their respective aligned clutches 
having the rollers 378. Different aspects of this construction are 
illustrated in FIGS. 7-11. The hub 389 has an axial channel through which 
the rod 290 is slidingly received. 
The springs 388 bias the spider 386 towards a spider engaged position 
wherein each pawl 391 engages the respective pin 378 aligned therewith and 
moves it to its clutch disengaged position away from the respective strap 
352. Thus, the cumulative force exerted by the springs 388 is greater than 
the cumulative force exerted by the springs 382 within the elbow members 
362 in the preferred embodiment. 
The spider 386 is moved in response to movement of the drive means to a 
spider disengaged position, wherein the pawls 391 of the spider 386 
disengage from the pins 378 so that each pivot arm 242 is thereby 
connected to its respective transducer 350 under the engagement force 
exerted by the springs 382. In the preferred embodiment shown in FIG. 7, 
this occurs when the carriage 255 is moved sufficiently longitudinally 
upwardly that the shoulder 342 of the neck portion 338 engages the lower 
surface of the hub 389 of the spider 386 and moves the spider 
longitudinally upwardly. This occurs in the preferred embodiment just 
prior to the gearing assembly illustrated in FIG. 9 counting the 
twenty-two revolutions and engaging the upward direction limiting switch. 
Specifically, when the pivot arms 242 are fully retracted within the tool 
10, the shoulder 342 is spaced three inches below the bottom surface of 
the hub 389. As the drive motor 254 rotates the screw shaft 292 to extend 
the pivot arms 242, the upper and lower sections 240, 244 move relatively 
towards each other and the hub 389 moves relatively towards the shoulder 
342. After a sufficient length of this relative movement between the hub 
389 and the shoulder 342, the shoulder enages the hub; however, this point 
of engagement is reached before the twenty-two revolutions of the screw 
shaft have been counted. Thus, the shaft continues to rotate so that the 
shoulder 342 pushes the spider 386 against the springs 388 towards the 
support plate 370. This continues for another 1/4 inch when the twenty-two 
rotation count is reached, thereby stopping further operation of the drive 
motor 254. This movement is related so that the pivot arms 242 are moved 
into engagement with the well bore before the last 1/4-inch linear 
movement of the shoulder 342. This keeps the clutches in the elbow members 
362 disengaged until after the pivot arms 242 engage the well bore. A 
clutch disengaged position is illustrated in FIGS. 7 and 10, and a clutch 
engaged position is illustrated in FIG. 8. 
Therefore, when the spider 386 is in its full downward position relative to 
the support plate 370, the pawls 391 engage the rollers 378 and hold them 
at their clutch disengagement positions wherein the clamp members defined 
by the rollers 378 release the straps 352. When the spider 386 is in its 
upwardmost position relative to the support plate 370 so that the pawls 
391 disengage the rollers 378, this allows the rollers 378 to be 
automatically biased by the springs 382 towards the straps 352 to engage 
them and thereby hold them adjacent the engagement surfaces 376 of the 
elbow members 362. 
Both in summary and supplementation of the foregoing, the caliper tool 10 
is used to measure the deformation of the well bore 4, such as an 
expansion thereof occurring in response to a fracturing process. In the 
preferred embodiment the diameter of the tool 10 was chosen to be 
approximately eight inches in view of the general size of well bores with 
which the tool is contemplated to be used. To adequately cover changes in 
the shape of the well bore, a six-arm design is used in the preferred 
embodiment of the tool 10. The six arms 242 are uniformly spaced at 
60.degree. displacements around the central section of the tool 10. The 
corresponding transducers 350 associated with the arms 242 are likewise 
arranged within the tool 10 at 60.degree. spacings. These are located 
around the interior of the tool 10 so that the center is left open for the 
single motor 254 used in the preferred embodiment and the single main 
power shaft driven by the motor 254. 
In the preferred embodiment of the overall tool of the present invention, 
the caliper 10 is supported by springs on each end between upper and lower 
packer sections. These springs are of a type which allow for approximately 
one to two inches of longitudinal freedom of movement of the caliper 10 
between the upper and lower packer sections. The instrument carrier 
section in which the caliper 10 is housed between the packer sections has 
six slots through which the arms 242 extend into contact with the 
formation intersected by the well bore 4. The preferred embodiment of the 
caliper 10 receives and sends electrical signals over a wireline extended 
through the well bore and the upper packer section into connection, via a 
wet connector, at the top of the caliper 10. 
One principal feature of the preferred embodiment is that each of the arms 
242 is mechanically fixed to two portions of the caliper tool to provide 
an increased degree of rigidity required for making the precise 
measurements taken with the present invention. 
Another feature of the preferred embodiment is that each of the arms 242 is 
driven by an independent force, but from a common, single power source. 
This independent drive force is important because the well bores to be 
measured are not absolutely round so that each arm 242 will likely need to 
be moved a different radial distance. These differences are accommodated 
in the preferred embodiment by using individual compression springs on the 
end of each arm. This yields different force loads on each of the arms. In 
the preferred embodiment it is anticipated that the arms move no more than 
approximately 0.1 inch during measurement of a formation deflection; 
therefore, it is desirable to exert through the springs 268 contact forces 
or pressures up to approximately 250 pounds of force. This is effected by 
appropriate selection of spring characteristics. Suitable types of springs 
include helical springs or Bellville spring washers. 
Still another feature of the present invention is the means by which the 
precise measurements are obtained. Although in the preferred embodiment a 
caliper arm may have to extend on the order of approximately two inches 
from its fully retracted position within the caliper tool 10 to its 
engagement position coupling with the well bore 4, the range of precision 
transducers is more limited, such as between .+-.0.015 for full-scale 
deflections. This is a limitation of the linearly variable differential 
transformer 350 used in the preferred embodiment; however, this limitation 
is offset by the precision achieved by such a device. This transducer has 
a multi-coil cylindrical configuration with a central movable armature 
which slides longitudinally relative to the coils, thereby causing the 
output voltage to vary linearly with the armature displacement. No 
electronic amplifiers are required so that less support circuitry is 
needed. Furthermore, a single known type of integrated circuit chip 
supports these types of devices. It is contemplated that suitable 
transducers are currently available for use in the preferred embodiment of 
the present invention which requires resolving increments of 0.001 inch 
for .+-.0.1 inch of travel. Because such a device could not provide 
appropriate output over the full range of travel from the fully retracted 
position within the tool 10, the present invention utilizes the clutch 
mechanism to lock the precision measuring transducers 350 to the arms only 
after the arms are in their engaged position with the well bore 4 (more 
specifically, only after the screw shaft has rotated a predetermined 
number of times). 
The operation of the preferred embodiment of the present invention is as 
follows. Power is provided through the aforementioned wireline to the 
caliper tool 10 after the upper and lower packers have been set and the 
wet connector has been attached in manners as known to the art. In the 
preferred embodiment, the packers are locked by the locking mechanism 
found in the upper packer section 8. Power for operating the motor 254 is 
contemplated to be provided at 60 hertz, power to the instrument section 
is contemplated to be at 400 hertz, and the data signals are contemplated 
to be sequential DC levels. 
When a suitable signal is first applied to the tool 10, the motor 254 is 
actuated to rotate in a direction which draws the upper and lower sections 
240, 244 longitudinally closer together so that the arms 242 are pivoted 
radially outwardly. This is accommodated in a contemplated particular 
embodiment by releasing an electric brake on the electric motor, actuating 
an alternate action relay to select the appropriate motor coil controlling 
the direction of rotation of the drive shaft, and bypassing a closed limit 
switch. 
As the motor rotates its drive shaft to open the caliper arms, the gears 
shown in FIG. 9 rotate in correspondence to the main drive shaft. When 
twenty-two revolutions have occurred, the gears have been rotated so that 
the pin 304 engages the appropriate limit switch which deactivates the 
motor 254. During at least part of this maximum movement, the load is 
transferred to the compression springs 268 on each of the spring guide 
rods 264. As this load is transferred, the spring guide rods 264 move 
relative to the spring container carriage 255 (specifically, relative to 
the plates 258, 260). Sufficient movement of this carriage causes the neck 
portion 338 thereof to engage the spider 386. Sufficient movement of the 
spider 386 releases the rollers 378 so that the straps 352 are clamped to 
their respective transducers 350 through the interconnecting couplings. 
A second control signal actuates the downhole electronics to measure or 
record the data obtained through the various transducers. This is 
performed in a manner as known to the art. To determine the amount of bore 
wall deflection from these data, a first reading is made when the 
transducers 350 are first clamped to the pivot arms 242. This provides 
base or "zero point" information. The fracturing fluid is then applied and 
another reading of the transducers 350 taken. The differences between 
these data and the first data are the amounts of detected movement. 
When the motor controlling signal is removed from the motor 254, an 
electric brake on the motor locks the motor shaft to keep the drive shaft 
from creeping. The alternate action relay releases and resets to its next 
action of allowing the motor to reverse and retract the measuring arms the 
next time a suitable control signal is applied to the motor 254. The 
limiting function of the limit switch is bypassed so the electric motor 
will operate during its next cycle. This next application of a suitable 
signal causes the motor to reverse and retract the arms. A limit switch 
detects when the linear movement in this direction has been reached. 
Once the pivot arms are retracted, another control signal is sent to again 
activate the downhole electronics for purposes and in a manner as known to 
the art. 
Thus, the present invention is useful for detecting movements or 
deformations of a well bore and thus provides information useful for 
determining hole orientation and fracture height. The caliper of this 
invention utilizes a single drive motor and means for exerting a 
respective independent force on each of several pivot arms in response to 
the operation of such motor. The caliper is capable of providing precise 
measurements of detected deflections within a narrow range, which 
measurements can be taken only after the arms have been extended 
sufficiently and a clutch mechanism released to clamp the arms to 
respective precision transducers. Furthermore, this invention utilizes a 
free-floating construction wherein the caliper is mounted on springs 
between two interlockable packers. The caliper rigidly holds itself to the 
formation by the arms which are mechanically restrained at both ends to 
provide a rigid holding action with the formation. 
Thus, the present invention is well adapted to carry out the objects and 
attain the ends and advantages mentioned above as well as those inherent 
therein. While preferred embodiments of the invention have been described 
for the purpose of this disclosure, numerous changes in the construction 
and arrangement of parts can be made by those skilled in the art, which 
changes are encompassed within the spirit of this invention as defined by 
the appended claims.