Patent Publication Number: US-8528219-B2

Title: Inclination measurement devices and methods of use

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to provisional patent application 61/234,426 entitled “Inclination Measurement Devices and Methods of Use” filed on Aug. 17, 2009, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure generally relates to a downhole tool employed during hydrocarbon exploration activities. Specifically, the present disclosure relates to devices and methods for measuring inclination or deviation from a vertical axis of a downhole tool. 
     In the drilling wells for production of hydrocarbons, it is often necessary to determine the inclination of a downhole tool or a portion of a drill string. Knowledge of the inclination, otherwise known as deviation from the vertical, is often desirable to determine the direction a sub-surface end of a drill string is oriented so that adjustments may be made to properly orient the drill string while drilling a borehole. Further, measurement of the inclination of the drill string may provide an indication of the borehole inclination at the point the measurement is made. In many instances, laws or other regulations require measurement of a borehole inclination at specified interval distances, typically every 1,000 ft. Further, it is often undesirable for boreholes to intersect other boreholes, such as multiple boreholes from a single platform. Determination of inclination may assist in avoiding such intersection. 
     Conventional mechanical methods in the art for measuring drill string inclination usually involve a complicated swinging pendulum mechanism. Essentially, in the conventional mechanical prior art systems, a pendulum device swings outwardly in response to an inclination or a deviation from a vertical axis. The pendulum device moves axially through a number of increasingly restrictive rings until the pendulum “hooks” or catches one of the restrictive rings preventing further axial movement of the pendulum. These conventional mechanical methods typically involve coding systems that translate small movements of a pendulum and rod into relatively long movements of a pressure pulse knob for communicating inclination measurement information to the surface via a series of pressure wave pulses through the drilling mud. 
     Unfortunately, these conventional mechanical devices for measuring inclination suffer from a number of significant disadvantages. In particular, the pendulum mechanisms are complicated and comprise many moving parts. Consequently, these conventional mechanical systems are expensive and prone to failure, particularly in the hostile conditions normally encountered in downhole environments. Additionally, because relatively small movements of the pendulum mechanisms are typically used to signal inclination measurements, the pendulum mechanisms sometimes suffer from unacceptably poor accuracy. In some instances, the pendulum mechanisms have been known to fail to properly engage at the desired inclination due to vibration or due to excessive axial speed of the pendulum device during inclination measurement. Consequently, these devices are known to be sometimes unreliable. 
     Accordingly, mechanical devices for measuring inclination and methods are needed to address one or more of the disadvantages of the prior art. 
     SUMMARY 
     In one embodiment, a downhole tool for measuring and communicating inclination of a portion of a drill string includes a housing having a flow conduit therein for flow of drilling fluid therethrough, the flow conduit having a plurality of passage restrictions therein. A knob is axially movable within the flow conduit, wherein the knob is adapted to interact with the passage restrictions to cause a flow restriction when the knob is directly adjacent one of the passage restrictions. A spring is adapted to bias the knob in a first direction, wherein the knob is movable upon the influence of the flow of drilling fluid in a second direction wherein the second direction is opposite the first direction. The knob is operably connected to an upper shaft and a plurality of discs operably connected to the upper shaft, wherein each disc is angled with respect to the upper shaft. One or more balls are disposed on each of the discs. A catch pocket is adjacent the discs, wherein the catch pocket is adapted to engage at least one ball and arrest the upper shaft from any further axial movement in the first direction upon sufficient inclination of the upper shaft. A dampening mechanism adapted to dampen movement of the upper shaft in at least one axial direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description in conjunction with the accompanying figures, wherein: 
         FIG. 1  illustrates a downhole tool for measuring and communicating inclination in accordance with one embodiment of the present disclosure; 
         FIG. 2  illustrates a sectional view taken along the section lines  2 - 2  of the downhole tool of  FIG. 1 ; 
         FIG. 3  is an exploded view depicting internal components of the downhole tool of  FIG. 2  and omitting some components for clarity; 
         FIG. 4  depicts another exploded view depicting internal components of the downhole tool of  FIG. 2  and omitting some components for clarity; 
         FIG. 4A  shows the downhole tool of  FIG. 4  in an inclined position while the tool is moving upwardly; 
         FIG. 4B  shows the downhole tool of  FIG. 4A  in a position where downhole tool communicates an inclination angle; 
         FIG. 5  depicts yet another exploded view depicting internal components of the downhole tool of  FIG. 2  and omitting some components for clarity 
         FIG. 6  is an isometric view of a T-shaped element of the downhole tool of  FIG. 2 ; 
         FIG. 7  is a sectional view of the T-shaped element taken along the section lines  6 - 6  of  FIG. 6 ; and 
         FIG. 8  is a graphical representation of pressure measured over time by the downhole tool of  FIG. 1 . 
     
    
    
     While the present disclosure is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Downhole tools are provided for measuring the inclination of a portion of a drill string. In certain embodiments, downhole tools for measuring inclination comprise a catch system for measuring inclination and a pressure pulse signaling system for communicating inclination measurement information to the surface, both of which are further described in detail below with reference to  FIGS. 1-7 . Briefly, the catch systems for measuring inclination of the present disclosure include a series of discs mounted on an upper shaft, each disc having one or more balls disposed thereon. In certain embodiments, the top surface of each consecutive disc is angled at an increasing angle such that one or more balls are displaced toward or away from an upper shaft upon achieving an inclination that corresponds to the angle of the top surface of each respective disc. The subsequent engagement of one of the balls in the catch pocket acts to arrest further movement of the upper shaft. The extent of axial movement of the upper shaft, which corresponds to a particular inclination, may then be communicated to the surface, such as via a pressure pulse signaling system. 
     Advantages of certain embodiments of the present disclosure include, but are not limited to, more accurate measurements, a more robust measuring mechanism less susceptible to false readings than conventional mechanical inclinometers, less complex than conventional mechanical devices, and increased reliability particularly with respect to a more positive retention of the catch system. Other features and benefits will be evident from the following disclosure. 
     To facilitate a better understanding of the present disclosure, the following examples of certain embodiments are given. In no way should the following examples be read to limit, or define, the scope of the invention. 
     For convenience of reference, when referring to components in axial or longitudinal relation to one another on the drill string, the term “lower” refers to components closer or proximate to the drill bit whereas “upper” refers to components away from or distal from the drill bit. 
       FIG. 1  illustrates a downhole tool  10  that is adapted to be coupled to a drill string  14 , wherein the drill string  14  includes various components such as a motor, subs, pipe and a bit. Downhole tool  10  extends from an upper end  12  to a lower end  14  and includes substantially hollow pulse ring housing  20  having bore  22  therethrough ( FIG. 2 ). A generally cylindrical tool housing  24  having outer surface  26  is coupled to pulse ring housing  20 . Lower outboard gland  28  is coupled to bottom  27  of tool housing  24 . In a preferred embodiment, pulse ring housing  20  and tool housing  24  are made of stainless steel to increase their corrosion resistance. Other metal alloys, such as, but not limited to carbon steel, may be used, depending on downhole conditions. 
     Turning now to  FIGS. 2 and 3 , pressure pulse signaling system  30  is disposed within pulse ring housing  20 . Pressure pulse signaling system  30  includes flow conduit  32  through which drilling fluid is directed as will be understood by those of ordinary skill in the art. Passage restrictions  34  are provided in series along flow conduit  32 . The operation of the flow conduit  32  and passage restrictions  34  will be explained in greater detail below. Knob  36  is disposed atop upper shaft  38  and is capable of traversing at least partially through flow conduit  32 . Upper shaft  38  extends downwardly through upper cap  40 . In one embodiment, upper shaft  38  is a hollow shaft having hole  38   a  disposed thereon. Hole  38   a  is in fluid communication with cross hole  38   b  that extends axially through upper shaft  38 . Hole  38   a  is also in fluid communication with space  41  defined between inner surface  76  and upper shaft  38 . Upper end  42  of upper cap  40  is coupled to lower end  44  of pulse ring housing  20 . Upper end  42  and lower end  44  of pulse ring housing  20  may be coupled by any means known to those of skill in the art. For example, threaded sections may be provided on upper end  42  and lower end  44 . Other methods of coupling metal parts are known to those of skill in the art. Gland  46  is disposed around the upper shaft  38 . Upwardly turned wiper seal  48  is disposed above gland  46  and downwardly turned wiper seal  50  is disposed below gland  46 . Those of ordinary skill in the art with the benefit of this disclosure will recognize that other known seals may be used in the place of the wiper seals shown in  FIGS. 2 and 3 . Top cover  52  is disposed around upper cap  40 . Bottom portion  54  of upper cap  40  is threadably coupled to top end  56  of tool housing  24 . 
     With reference to  FIG. 5 , lower end  60  of upper shaft  38  has threaded portion  62 . Threaded portion  62  of lower end  60  partially extends through and is coupled to coupler  64  that has internal threads  66  disposed thereon. O-ring  70  is disposed around lower end  60  of upper shaft  38  above threaded portion  62 . An outer portion of O-ring  70  is received within notch  72  provided on the internal surface of the coupler  64 . Flanges  74  extend outwardly from the coupler  64  and abut inner surface  76  of tool housing  30 . Downwardly turned wiper seal  78  is disposed within recess  80  on underside  82  of flange  74 . Wiper seal  78  is retained in position by ring  84  that protrudes outwardly from coupler  64 . Shoulder  86  also extends outwardly from coupler  64 . Sleeve  88  extends downwardly from shoulder  86  through the inner diameter of biasing mechanism  89  such as spring  90  that retains shoulder  86  on a top portion thereof. In one embodiment of the downhole tool  10 , biasing mechanism  89  may include any apparatus capable of biasing upper shaft  38  in an upper or first direction, including but not limited to electrical or mechanical biasing mechanisms known in the art, coiled springs, or any other springs known to those of ordinary skill in the art. 
     Inner surface  100  of sleeve  88  is threaded and adapted to couple upper shaft  38  to upper threaded portion  102  of lower shaft  104 . A hole  104   a  is provided on lower shaft  104  and is in fluid communication with cross hole  104   b  that extends upwardly through a portion of lower shaft  104   b . Hole  104   a  is in fluid communication with hole  38   b  of upper shaft  38 . Lower shaft  104  extends downwardly through spring  90  and housing  30  into lower cap  106 . Lower cap  106  has threaded section  108  that is coupled to threaded lower end  110  of housing  30 . Upper end  112  of lower cap  106  has relatively flat surface  114  where bottom end  116  of spring  90  rests. Fill ports  120  are provided on external surface  122  of lower cap  106 . Fill ports  120  are in fluid communication with space  124  defined by housing  30 , lower cap  106 , and coupler  64  via fluid passages  126  provided within lower cap  106 . Space  124  is also in fluid communication with cross hole  104   b.    
     Partially threaded recess  140  is disposed at bottom end  142  of lower cap  106 . Threaded portion of recess  140  is adapted to be coupled with external threaded section  141  of lower outboard gland  28 . First upwardly turned wiper seal  144  is disposed around top portion  146  of partially threaded recess  140 . Wiper seal  144  is retained in position by second gland  146  that is provided beneath wiper seal  144 . Second downwardly turned wiper seal  145  is disposed between recess  140  and lower shaft  104  such that wiper seal  145  and abuts second gland  146 . In a preferred embodiment, wiper seal  145  is capable of maintaining a seal when exposed to 5000 psi pressure. In other embodiments, wiper seal  145  is adapted to withstand pressures greater than 5000 psi. Those of ordinary skill in the art with the benefit of this disclosure will recognize that other known seals that are capable of withstanding the downhole pressures to which the seals are exposed may be used in place of the wiper seals shown in  FIG. 5 . 
       FIGS. 6 and 7  illustrate T-shaped element  160  comprising disc  162  and disc spacer  164  depending downwardly therefrom. Disc  162  and disc spacer  164  have void  166  disposed therethrough to accommodate upper shaft  38 . In one preferred embodiment, disc spacer  164  is made of aluminum. In another preferred embodiment, disc  162  is made of ferrous steel. In yet another preferred embodiment, disc  162  is made of titanium. In yet another embodiment, disc  162  is made of a ceramic material. 
     Several T-shaped elements  160  are stacked in series on upper shaft  38  (See  FIGS. 2 and 4 ) to define ball spaces  165 A- 165 G between respective discs  162 A- 162 G. T-shaped elements  160  typically are machined to form a precision fit of 1/1000 inch between void  166  and the upper shaft  138 . Top surface or upper surface  167  of each disc  162 A- 162 G of T-shaped element  160  is machined to have a known inclination angle relative to the vertical axis of the downhole tool  10 . In certain embodiments, the inclination angle of top surface or upper surface  167 A- 167 G of each disc  162 A- 162 G is incrementally different. For example, top surface  167 A of disc  162 A is machined to have an angle of about −1 degree is relative to the perpendicular of the vertical axis  163  of downhole tool  10 ( FIG. 2 ). Top surface  167 B of disc  162 B may be machined to have an angle of about 1 degree relative to vertical axis  163 . Top surface  167 C of disc  163 C may be machined to have an angle of about 2 degrees and so forth. In one embodiment, the inclination of top surfaces  167 A- 167 G of successive discs  162 A- 162 G differs by about 0.5°. Other embodiments may include more or fewer discs that have varying inclinations such as but not limited to 0.125° or 0.75°. The present disclosure is not limited to embodiments having seven ( 162 A- 162 G) discs. More or fewer discs may be installed on upper shaft  38  depending on the expected operating conditions. Balls  168 A- 168 G are disposed on each top surface  167 A- 167 G within ball spaces  165 A- 165 G defined between respective discs  162 A- 162 G. As will be explained in greater detail below, balls  168 A- 168 G are used to measure an inclination of the downhole tool  10  from the earth&#39;s vertical axis when at least one of balls  168 A- 168 G rolls on respective top surfaces  167 A- 167 G and is caught in catch pocket  170  that is machined on inner surface  76  of housing  30 . The combination of housing  30 , upper shaft  38 , T-shaped elements  160 A- 160 G, and catch pocket  170  form catch system  173  ( FIG. 4 ). Wiper seal  145  protects the components of catch system  173  from downhole pressures. In one preferred embodiment, catch system  173  components are made of a titanium, carbide, and stainless steel. In another preferred embodiment, upper shaft  38  and/or other components of catch system  173  are coated with a nickel/tungsten coating to make such parts resistant to chloride exposure in drilling environments. 
     With continuing reference to  FIG. 4 , retainer ring  174  is disposed around upper shaft  38 . Recess  176  is formed on retainer ring  174  and is adapted to receive upwardly turned wiper seal  178 . Wiper seal  178  is in contact with inner surface  76  of housing  30 . O-ring  180  is disposed between the retainer ring  174  and upper shaft  38 . 
     In certain embodiments of the present invention, T-shaped elements  160  may be replaced in the field by operators of the inclination measurement tool. In those embodiments, T-shaped elements  160  with certain inclination angles relative to the vertical axis of downhole tool  10  are designed to be unstacked and replaced with alternative T-shaped elements with different inclination angles relative to the vertical axis of downhole tool  10 . Typically, the replacement of T-shaped elements  160  may be accomplished through the use of common hand tools. 
     Catch System 
     In one preferred embodiment, discs  162 A- 162 G and other components of downhole tool  10  are comprised of a mix of titanium, carbide, and stainless steel. Other alloys including, but not limited to carbon steel may also be used for the components of downhole tool  10 . As discussed above, each top surface  167  of discs  162 A- 162 G is inclined at an inclination to the vertical axis  163  of the downhole tool  10 . For example, in one embodiment, top surface  167 A of disc  162 A is angled at an angle of −1° (i.e. negatively angled). Top surface  167 B of disc  162 B is angled at a positive angle of 1° with respect to the downhole tool  10 . Top surface  167 C of disc  162 C is angled at a positive angle of 2° with respect to the vertical axis  163  the downhole tool  10 . Top surface  167 D of disc  162 D is angled at a positive angle of 3° with respect to the vertical axis  163  of downhole tool  10 . Likewise, top surface  167 E of disc  161 E is angled at a positive angle of 4° with respect to the vertical axis  163  of the downhole tool  10 , top surface  167 F of disc  161 F at 5°. In this way, the angle of each top surface  167 A- 167 G of discs  162 A- 162 G increases proportionally along the length of the vertical axis  163  the downhole tool  10 . As used herein, the term “positive angle” refers to an angle or slope between any top surface  167  of the discs  162 A- 162 G and the vertical axis  163  of the downhole tool  10  that allows displacement of a respective ball  168  toward upper shaft  38  when the upper shaft  38  is in the vertical position with respect to the Earth&#39;s gravity vector. Balls  168 A- 168 G are preferably high mass and non-magnetic. In one embodiment, the balls  168  are preferably comprised of carbide. Similarly, the term “negatively angled,” as used herein, refers to any angle between any top surface  167  of discs  162 A- 162 G and upper shaft  38  that allows displacement of a respective ball  168  away from upper shaft  38  when upper shaft  38  is in the vertical position with respect to the Earth&#39;s gravity vector. 
     Normally, when upper shaft  38  is in the vertical position with respect to the Earth&#39;s gravity vector, each of balls  168 B-G disposed on each disc  162  rolls toward upper shaft  38  due to the slope of each top surface  167  of disc  162  with the exception of the ball  162 A disposed on the disc  161 A. Because top surface  167  of disc  162 A is negatively angled (i.e. slopes downward away from upper shaft  38  toward the surface  76  of the housing  24 ), any ball disposed on disc  162 A will roll away from upper shaft  38  when downhole tool  10  is in the vertical position with respect to the Earth&#39;s gravity vector due to the influence of gravity. 
     As upper shaft  38  is inclined or deviated from the Earth&#39;s gravity vector or vertical axis, the Earth&#39;s gravity vector successively influences each respective ball  168  so as to successively displace each successive respective ball  168  away from upper shaft  38  towards housing  24  upon successively sufficient deviation of upper shaft  38 . For example, any deviation greater than about 1° from the vertical will cause ball  168 B to roll away from upper shaft  38  and to engage housing  24  because top surface  167  of disc  162 B is angled at a positive angle of 1° with respect to upper shaft  38  Likewise, any deviation of upper shaft  38  greater than about 2° from the vertical will cause ball  168 C to roll away from upper shaft  38  and to engage housing  24 , and so on for each ball  168 D- 168 E. In this way, the more deviation that upper shaft  38  experiences, the more balls  168  will move away from upper shaft  38  so as to engage housing  24 . 
     Upper shaft  38  is capable of axial movement in both directions within housing  24 . During drilling operations, pressurized drilling mud flowing through the bore  22  of the downhole tool  10  exerts a downward force against the components of the downhole tool  10 , thereby compressing spring  90  and displacing balls  168  away from the catch pocket  170 . However, once drilling mud is no longer pumped through bore  22 , spring  90  exerts upward pressure on upper shaft  38  and causes discs  162  and balls  168  disposed thereon in the upward direction. Catch pocket  170  engages any ball  168  that has rolled away from upper shaft  120  so as to arrest any further upward axial movement of upper shaft  38 . Consequently, only one of the balls  168 A- 168 G will be caught in the catch pocket  170 . The displaced ball in the highest position closest to the upper shaft  38  will be caught in the catch pocket  38  thereby stopping further upward movement of the upper shaft  38  and communicating a number of pulses that is indicative of the inclination of one of top surfaces  167 A- 167 G of one of discs  162 A- 162 G bearing one of balls  168 A- 168 G that was caught in catch pocket  170 . In this way, catch system  173  determines the inclination of upper shaft  38 . The inclination of upper shaft  38  is communicated to pressure sensing instrumentation as will be explained in greater detail below. 
     For example, consider a upper shaft  38  that is deviated from vertical by an angle of about 3.5°. As illustrated in  FIG. 4A , balls  168 E- 168 G will not engage the catch pocket  170  as disc  162 B moves past catch pocket  170  because balls  168 E- 168 G are not displaced away from upper shaft  38  when upper shaft  38  is deviated by about 3.5° due to the respective inclination angles of top surfaces  167  of discs  162 E- 162 G (4°, 5°, and 6° respectively). 
     Nevertheless, at a deviation of 3.5°, balls  168 A- 168 D will be displaced away from upper shaft  38  and the ball  168 D will engage catch pocket  170  as disc  162 D moves upward, because the vertical deviation of upper shaft  38  by 3.5° is sufficient to cause displacement of the ball  168 D away from the upper shaft  38  so ball  168 D engages catch pocket  170 . Similarly, balls  168 A- 168 C are also displaced because the inclination of top surfaces  167 A- 167 C are −1°, 1°, and 2°. However, balls  168 A- 168 C do not engage catch pocket  170  because ball  168 D would have already engaged catch pocket  170  thereby preventing further upper axial movement of upper shaft  38 . As will be explained below, this proportional axial movement of upper shaft  38  indicates that upper shaft  38  is deviated at an angle between 3° and 4°. 
     In a like manner, other deviations of upper shaft  38  will result in engagements of at least one of balls  168 A- 168 G with catch pocket  170  to arrest upper shaft  38  at other axial displacements of upper shaft  38 . As will be explained further below, these proportional axial movements of upper shaft  38  and its consequent arrests may be communicated to the surface via a pressure pulse signaling system. 
     Pressure Pulse Signaling System 
     As discussed above, upper shaft  38  is forced upward by spring  90  when the flow of pressurized drilling mud is discontinued. Upward motion of upper shaft  38  causes knob  36  to extend through one or more passage restrictions  34 . As knob  36  is moves past each passage restriction  34 , a pressure pulse is generated in the flowing drilling mud that may be detected at a surface  190  ( FIG. 2 ) via a pressure transducer (not shown). Measurements of and between such pulses are known to persons of ordinary skill in the art including, without limitation, being graphically represented on a display which may be a strip recorder or any other display known in the art. Another example of displays of such pulses and measurement that may be used is an industrial touch screen or other computer. 
     As shown in  FIG. 4B , for an example drill string having an inclination of 3.5°, ball  168 D on upper surface  162 D with an angle of 3° is the uppermost ball to move into catch pocket  170 . This is because, among upper surfaces  167 A- 167 G, upper surface  167 D has the angle which is most immediately less than upper shaft  38 &#39;s 3.5° deviation from the Earth&#39;s gravity vector Likewise, ball  168 E on upper surface  162 E with angle 4° has not moved into catch pocket  170 . Among upper surfaces  167 A- 167 G, upper surface  167 E has the angle most immediately greater than upper shaft  38 &#39;s 3.5° deviation from the Earth&#39;s gravity vector. Communicating that ball  168 D has moved from adjacent shaft  38  upon upper surface  167 D to engage catch pocket  170  and that ball  168 E has not moved from adjacent shaft  38  upon upper surface  167 E to engage catch pocket  170 , communicates that upper shaft  38 &#39;s deviation from the Earth&#39;s gravity vector at tool  10 &#39;s point of measurement is between the 3° deviation of upper surface  167 D and the 4° deviation of upper surface  167 E, namely, that the drill string&#39;s inclination at tool  10  is between 3° and 4°. 
     This method is applicable to any inclination angles of the drill string and to any set of chosen upper surface inclination angles. Discs can be chosen with different angles and used within the tool as desired for different circumstances as long as the discs have greater positive angles from the lower end of tool  10  to the upper end of tool  10 . 
     Upper shaft  38 &#39;s axial movement, or lack thereof, responsive to biasing mechanism  90  urging upper shaft  38  upward and the described movement of some or all of the balls  168 A- 168 D in the catch system comprised of balls  168 A- 168 G, upper surfaces  167 A- 167 G and catch pocket  170  causes knob  36  to change knob  36 &#39;s position relative to passage restrictions  34 . The relative location of the discs  162  relative to catch pocket  170  and of knob  36  relative to passage restrictions  34  is fixed and known. The correspondence between the distances between upper surfaces  167 A- 167 D and the distances between passage restrictions  34  need not be a one-to-one correspondence or a constant correspondence. All that is required is that pulses resulting from any particular upper surface&#39;s ball arresting further upward movement of knob  36  on upper shaft  38  through passage restrictions  34  be discernable and communicate knob  36 &#39;s position relative to passage restrictions  34 . 
     The described structure and method of operation causes tool  10  to be capable of communicating an upper and a lower range of drill string inclinations at tool  10 &#39;s point of measurement when the flow of drilling fluid is temporarily halted and the upwardly biased shaft  38  and knob  36  cause a measurable pulse in the drilling fluid in cooperation with passage restrictions  34  to communicate which balls  168 A- 168 G have been caught in catch pocket  170  responsive to tool  10 &#39;s inclination. 
       FIG. 8  depicts a graphical plot  192  of pressure (PSI) and time (seconds) measured by a pressure transducer in one embodiment of downhole tool  10 . It takes approximately 2-5 minutes to obtain a reading from tool  10  when upper shaft  38  is inclined or deviated from the vertical. It is also believed that the tool  10  is capable of returning a neutral reading about 2-5 minutes after the flow of drilling fluid through tool  10  is discontinued. It is believed that the efficiency of tool  10  in reading deviations of a well bore may result in significant time and expense savings when compared to prior art systems. 
     In order to further improve the efficiency of tool  10 , dampening axial movement of upper shaft  38  and knob  36  may be provided. Specifically, positive retention of balls  168  in catch pocket  170  may be more likely where axial movement of upper shaft  38  is limited to a controlled rate of speed. Such dampening may be provided by introducing a dampening fluid, for instance, a silicone fluid into downhole tool  10  via fill ports  120 . As will be understood by those of skill in the art, various viscosities of silicone fluid and/or other suitable fluids may be used. For example Silicone Fluid 5 Centistoke, 10 Centisoke, 50 Centistoke and/or any other suitable fluid known to those of skill in the art may be used. During the movement of the catch assembly  173 , dampening fluid may be transported from space  124  to space  41  via cross holes  104   b ,  38   b  and holes  104   a  and  38   a . A bidirectional flow regulator such as a check valve may be disposed within hole  38   a  or  104   a  to regulate the rate of flow of the dampening fluid and improve the reliability of the downhole tool  10 . 
     In certain embodiments, catch pocket  170  may optionally comprise sloped surface  171 . As would be recognized by a person of ordinary skill in the art with the benefit of this disclosure, sloped surface  171  allows release of balls  168 A- 168 G from catch pocket  170  when upper shaft  38  and discs  162 A- 162 G move to a lower or second position. Without the corresponding disc  162  holding a ball  158  in catch pocket  170 , gravity pulls balls  168 A- 168 G from catch pocket  170 . In this way, catch pocket  170  arrests balls  168 A- 168 G travelling in a first direction (e.g. towards an upper position) but releases balls  168 A- 168 G to travel in a second direction (e.g. towards a lower position). Once released into bore  22 , balls  168 A- 168 G are movably carried within bore  22  by discs  168 A- 168 G. In yet another embodiment, catch pocket  170  may be formed as integral to housing  24  or may be formed of an additional element that is operably affixed to housing  24 . 
     Furthermore, it is explicitly recognized that any number of discs  162  may be used in combination with catch system  173  as desired. Moreover, the angling of discs  162 A- 162 G may be adjusted to offer finer or cruder increments of measurement. For example, disc  162 A- 162 G could be angled in 0.5°, 0.25°, or other increasing increments so as to provide a more accurate measurement than the aforementioned example where 1° angle increments were utilized. The angles defined by top surfaces  167 A- 167 G may be any chosen angle as long as the angle increases incrementally in the first direction. One of ordinary skill in the art would recognize that the number of discs  162 A- 162 G can be changed depending on expected operating conditions. 
     In an alternative embodiment, the vertical distance between the top surfaces  167 A- 167 G are not constant distances and the veridical distances between the corresponding passage restrictions  34  corresponds to such variable distances between top surfaces  167 A- 167 G. The correspondence between the top surfaces  167 A- 167 G and the distances between passage restrictions need not be either a one to one correspondence or a constant correspondence. All that is required is that pulses resulting from any of balls  168 A- 168 G arresting further upward movement of the upper shaft be discernable and known. 
     It is explicitly recognized that any of the elements and features of each of the devices described herein are capable of use with any of the other devices described herein with no limitation. Furthermore, it is explicitly recognized that the steps of the methods herein may be performed in any order except unless explicitly stated otherwise or inherently required otherwise by the particular method. 
     The present invention is applicable to measuring inclination relative to the direction of gravity where conventional methods are inappropriate. The present invention is also applicable to measuring inclination relative to forces other than the earth&#39;s gravity. 
     Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.