Method and device for making measurements characterizing geological formations, in a horizontal borehole formed from an underground way

A method is provided for making measurements in geological formations from a horizontal borehole or a borehole with limited slant with respect to the horizontal, formed in the wall of an underground way. It includes essentially a probe containing measuring instruments, adapted to be introduced and pushed into the borehole at the end of an elongate element such as a semirigid tube which is wound off a storage reel, straightened and moved linearly by feed means. The tube passes through a sealing element disposed at the orifice of the borehole. It contains a transmission cable for connecting the probe to a control and recording assembly and it communicates through a rotary hydraulic and electric collector with a pumping system provided for filling the bored hole with fluid before making the measurements.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method and device for making 
measurements characterizing geological formations in a horizontal borehole 
or a borehole slightly slanting with respect to the horizontal, formed 
from an underground way, such as a gallery, a tunnel etc. 
The device of the invention finds its application particularly in the study 
of formations where galleries or tunnels are being pierced, so as to 
facilitate the advance of the cutting systems used. 
2. Description of the Prior Art 
A device is known which is used in coal mines for exploring the formations 
in front of a gallery in the course of construction for defining the 
contours of a seam and to locate prior to mining the gas pockets which are 
likely to explode. This device includes a machine for horizontal boring 
formed essentially by a drilling tool fixed to the end of a hollow rod, a 
system for driving the rod, and a measuring device formed of a probe with 
a cross section less than that of the drilling rod, fixed to the end of a 
cable transmitting the data measured by the probe. 
With a hole drilled beforehand, the probe is introduced into the drilling 
rod and pushed to the end of the rod by pumping means. This prior device 
is described in the U.S. Pat. No. 4,498,532. 
This type of device lends itself well to investigations carried out using 
probes which may operate inside a tube or a rod, generally made from 
metal, and so to the use of radiation probes: gamma, neutron rays whose 
penetration power is very limited. The distance over which a probe can be 
driven into the formations is limited to the relatively small length of 
the tube unless it is formed of a string of rods which are progressively 
connected to each other. But in this case, the previous step for conveying 
the probe to the bottom of a borehole of several hundreds of meters in 
length is very long and that considerably delays the effective taking of 
measurements. Furthermore, the necessity during the withdrawal phase to 
remove the successive sections of the rod string, involves stoppages and 
it is impossible to carry out continuous measurements. 
Another known method consists in fixing a probe to the end of a rod having 
a lateral outlet and in connecting the electric connectors of the probe to 
a cable which extends to the outside through this side outlet. The rod 
provided with its probe is engaged in the borehole and as it is gradually 
lowered tube sections are added and the cable is unwound. To the drawbacks 
already mentioned relating to the slowness of the operations for 
connecting the tube sections tegether, is added the presence of the cable 
on the outside, which greatly complicates the construction of a sleeve for 
sealingly closing the borehole in that this latter may not be filled with 
the liquid required for coupling an acoustic measuring probe with the 
formations, for example. 
SUMMARY OF THE INVENTION 
The method of the invention which is adapted to taking measurements in 
geological formations from a horizontal borehole or a borehole with a 
limited slant with respect to the horizontal, avoids the above mentioned 
drawbacks. It includes fixing a probe containing measuring instruments to 
an elongate element adapted to be wound on a storage reel, introducing the 
probe into the borehole and linearly moving the elongate element from the 
underground way as it unwinds from the storage reel, said elongate element 
being sufficiently rigid for driving the probe along the borehole, 
providing continuous measurement cycles during movement thereof and 
rewinding the elongate element on the storage reel as the probe is 
withdrawn. 
The use of a windable elongate element and feed means ensuring unwinding 
and driving of this element along a borehole over a distance which may 
reach several hundreds of meters, until the probe reaches the depth chosen 
for the measurements, and then rewinding thereof on a storage reel, allow 
previous exploration of the formations in front of a cutting face to be 
carried out rapidly. This advantage is particularly appreciable 
considering the speed of advance of modern machines, used for driving 
tunnels or galleries. Another important advantage is due to the fact that 
the unwinding and rewinding of the elongate element being effected without 
any interruption, measurements may be made continuously along the whole of 
the borehole.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, it can be seen that the device includes a storage reel 
1 on which is wound an elongate element formed for example by a semirigid 
tube 2 of known type. The reel is driven by a hydraulic motor 3. The tube 
2 winding off reel 1 passes into a feed device 4. This latter includes for 
example two rows of aligned rollers 15 for straightening it, driving 
tracks 6 actuated by a hydraulic motor (not shown) as well as counting 
means for determining the length of the tube introduced into the borehole. 
The machines used for driving galleries or tunnels 7 generally include a 
shield 8 in which numerous orifices are formed for different tools and 
particularly drilling tools. Through one of these orifices 9 is introduced 
the tool of a drilling system adapted for drilling a hole 10 which may 
reach several hundreds of meters and of a sufficient diameter for 
introducing therein a measuring probe 11 containing appropriate measuring 
instruments. Once the hole is drilled, a sealing element 12 is fitted on 
orifice 9 of shield 8, of the packing type including (FIG. 2) a plate 13 
with a central cylindrical part 14 having a central bore 15 whose section 
is adapted to that of tube 2. On this central part 14 is screwed a lid 16 
having a passage section also adapted to that of the tube. A disk 17 made 
from a deformable material is disposed between the central part 14 and lid 
16 and, compressed by screwing the lid, is intimately applied about the 
tube. Fixing means (not shown) are provided for fixing the plate 13 to 
shield 8. Plate 13 includes an orifice to which is fitted a pipe 18 
connected (FIG. 1) to a fluid pumping system 10 through a valve 20. 
Probe 1 is fixed to the end of tube 2 by a sealed connector 21 (FIG. 3). By 
means of this connector the measuring instruments contained in the probe 
are connected to the conductors of a multiconductor cable 22 running along 
the tube 2. Apertures 23 are formed in the vicinity of connector 21 in the 
wall of tube 2, for providing communication between the inside of the tube 
and the borehole 10. The section of the probe is generally greater than 
that of tube 2. 
At its opposite end, the tube communicates with the pumping system 19 and 
with a control and recording device 24 (FIG. 1) via a rotary hydraulic and 
electric collector 25 (FIG. 4). 
The collector 25 includes a hollow rod 26 which is fixed to the hub 27 of 
reel 1. Its side wall is provided with apertures 28 and its end opposite 
the reel with a bore 29. The part of the rod provided with apertures 28 is 
engaged inside a fixed ring 30. Seals 31 provide sealing between rod 26 
and ring 30. A radial opening 32 in the ring provides communication 
between the inside of rod 26 and the pipe 33 connecting the pumping system 
19. The end of tube 2 opposite the probe is engaged in a radial orifice 34 
provided in the hub 27 of the reel. 
The different conductors of the multiconductor cable 22 housed in tube 2 
are connected, via a sealing element 35 closing the bore 29, to different 
contacts 36 at the periphery of the male part 37, rotating with the hub of 
the reel, of an electric connector. Different slip rings 38 of the fixed 
female part 40 of the electric connector provide, via a cable 39, electric 
connection of the different conductors of cable 22 with the control and 
recording system 24 (FIG. 1). The associated rod 26 and ring 30 allow a 
flow of fluid to be formed between tube 2 and the pumping system 19. 
A synchronizing element 41 controls the hydraulic motor driving tracks 6 
and motor 3 so as to maintain the linear feed speed of the straightened 
tube and the rotational speed of reel 1 equal. 
Reel 1, its support, the hydraulic motor 3 and the pumping system 19 are 
advantageously disposed on a sledge 42 which is moved along the gallery 7 
as it advances. 
The device operates in the following way: 
With a hole of appropriate section and length bored in front of shield 1, 
the measurement probe 11 is engaged therein. After passing through the 
feed device 4 and the straightening rollers 5, the end of tube 2 winding 
off reel 1 is fitted through the sealing element 12 (FIG. 2) and is 
connected to the probe. With the sealing element 12 fixed to shield 8, the 
feed device 4 is actuated so as to cause tube 2 and probe 11 which is 
secured thereto to advance through the borehole. 
This movement continues without interruption until the probe reaches the 
required depth. From the counting means of the feed device 4 the depth of 
tube 2 driven into the borehole is known. 
When good coupling between the probe and the surrounding formations is 
required, the bored hole is filled with the fluid provided by the pumping 
system 19. For driving out the air pockets which may form in the annular 
space about the tube, a flow of water may be provided through the 
hydraulic circuit 18, 20, 22, 2, 23. Advantageously a pumping device is 
used capable of establishing in the circuit a flow of fluid in one 
direction or in the opposite direction. This allows the slant of the 
borehole to be adapted with respect to the horizontal. If the borehole 
slopes upwardly, the air pockets are driven out more readily by injecting 
fluid through pipe 18, return to the pumping system 19 taking place 
through the inside of tube 2. If on the contrary, the borehole slopes 
downwardly, fluid is injected through the inside of tube 2, the return 
taking place through pipe 18. 
With the holes suitably filled with fluid and maintained under pressure if 
required, the probe is actuated and the operations for rewinding tube 2 on 
reel 1 are carried out, these two actions being able to be conducted 
simultaneously so as to make continuous measurements along the borehole. 
They may also be conducted alternately so as to obtain a discontinuous set 
of measurements. 
The data collected is transferred to the control and recording device 24 
(FIG. 1), through cable 22. The exact position of the probe inside the 
borehole is known at all times through the counting means of the feed 
system 4. 
When all the measurement data has been recorded, the sealing element 12 is 
removed and the probe is withdrawn from orifice 9 which may again be used 
for the boring operations of the tunnel or gallery. 
From the recorded date, a representation of the formations to be bored can 
be obtained and so the progress of the boring operations is optimized. 
Without departing from the scope and spirit of the invention, the tracks 
for driving the semirigid tube may be replaced by any equivalent means 
such as a motor driven roller assembly. 
Similarly, the semirigid tube may be replaced by any elongate element able 
to be wound on a storage reel and sufficiently rigid for transmitting to 
the probe the forces required for driving it. It may for example be a 
conventional well logging cable possibly made rigid by external armouring, 
the whole being possibly provided with a protective sheath.