JPS6015883B2 - Borehole surveying device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for surveying a borehole or the like with measurements of the gravitational component in order to obtain the trajectory of the borehole relative to a known ground reference point, such as the ground circle where the borehole begins.

Surveys of boreholes and the like are often performed using instruments or probes that move through the borehole and measure the slope and azimuth at successive points.

The oblique angle, ie the angle at which the tangent to the porehole deviates from the vertical, can be measured with a pendulum or an accelerometer. direction,
That is, the angle of the borehole with respect to a reference direction, such as north, is typically measured using a magnetic compass or a gyro compass. These angles, along with the borehole, are used to determine the coordinates of each point along the borehole relative to a reference, eg ground zero. The pendulum that measures tilt may take the form of a servo accelerometer that responds to gravitational acceleration.

Servo accelerometers are readily available, small, rugged, and accurate. Measuring azimuth is not so easy. Magnetic compasses and other devices for measuring the earth's magnetic field are susceptible to errors due to magnetic anomalies in the earth. Gyrocompasses have several drawbacks, such as large size, bearing wear, sensitivity to shock, drift and precession errors, and the need for long setup times for stability during measurements. According to the invention, an apparatus is provided in which the borehole trajectory can be determined by measuring the gravitational component and distance along the borehole, such as the linear servo accelerometer described above. Surveying is performed by providing data while the probe is moved through the borehole, and from this data the borehole trajectory is determined. The speed and accuracy of surveys based on servo accelerometer measurements are far superior to those made by other instruments. Moreover, a probe that uses an accelerometer and does not require a compass to measure orientation can be housed in a small diameter case and is durable. One feature of the invention is a borehole surveying device or probe having first and second pairs of accelerometers with each pair of input axes forming a measurement plane.

The accelerometer is mounted through the borehole with two measurement planes spaced from each other and perpendicular to the respective local borehole tangent and the borehole axis. The two pairs of accelerometers are connected with flexible, non-friction connectors to follow the borehole trajectory while maintaining the angular relationship between the accelerometer pairs about the borehole axis. The apparatus further includes means for obtaining an indication of the borehole trajectory from the accelerometer signal. Another feature of the invention is that the probe has first and second sections each having a set of accelerometers attached thereto.

These sections are connected by connectors such as cables or pipes that are not flexible about their longitudinal axes, but are flexible about an axis perpendicular to this axis. This connection ensures that the distance along the borehole between the probe sections remains constant, that there is no runout at the connection between the two sections, and that each pair of accelerometers It is ensured that it follows the borehole axis and can freely rotate around the borehole axis. More specifically, the two probe sections are connected by a cable or pipe that is resilient to bending along the borehole axis but rigid to deflection stresses about that axis. Instead, the two sets of accelerometers have one common case that is flexible so as to follow the borehole trajectory, yet unyielding so as to resist runout. You can also do this. Yet another feature of the invention includes measuring the acceleration of gravity (along an orthogonal axis) in a plane intersecting the borehole axis at successive points along the borehole. There is a method of measuring.

The slope of the porehole in each measurement plane can be found from the vector sum of the two gravity components measured by the corresponding accelerometer pair.

This is known in the prior art. The main feature of the invention is that the incremental change in borehole orientation between two measurement planes can be determined from the four output signals of the two accelerometer pairs and the distance along the borehole between the measurement planes. That's what it means. The borehole trajectory can be determined by slope, orientation and borehole length. More specifically, as the probe is moved along the borehole, gravity measurements from two acceleration pairs and relative distance measurements along the borehole trajectory are made, and from these measurements a three-dimensional porehole profile is obtained. The course is decided.

Further features and advantages of the invention will become readily apparent from the following description of the drawings.

Although the invention will be described below with reference to boreholes, such as for oil or gas wells, it can also be applied to other mining or drilling applications, such as surveying underground structures such as mine shafts.

The term porehole in this invention should be interpreted in a broad sense unless the context of the sentence requires it to have a different meaning. The representation of the borehole trajectory may also be in the form of three-dimensional coordinates or plots of the existing borehole, for example in order to determine its physical position. An indication of the trajectory may also be obtained while drilling a borehole to monitor the drilling operation and allow the operator or drill controller to direct the drill in the desired course. The invention is not limited to any particular trajectory representation. In FIG. 1, the borehole 2 extends downward from a point 20a on the ground surface and is filled with an iron pipe 21.

The probe has a first section 22 and a spaced second section 23, the two sections being connected by a cable or pipe 24. The probe is lowered into the borehole by a hoisting cable 25. This cable provides power to the probe and also has conductors that send signals from the probe to circuitry on the ground. A pair of accelerometers (not shown in Figure 1) are located in the first section of the probe.
2, whose detection axes x, y are preferably at right angles to each other and form a measuring plane at right angles to the longitudinal axis of the section of the probe.

The axis of the deep seed coincides with the axis of the porehole. Similarly, a pair of accelerometers (not shown in Figure 1) in the second section 23 of the probe have their detection axes X', Y' at right angles to each other and to the longitudinal axis of this section 23 and the borehole axis. to form a perpendicular measurement plane. As will be described later, the coordinates of the borehole position are determined by the inclination angle with respect to the gravity vector and the zenith angle of each measurement plane.

These angles are easily and accurately measured by accelerometers placed perpendicularly in a measurement plane perpendicular to the borehole axis. However, its axes detect mutually unrelated vectors in a plane with known poses within the borehole (
The measurement results of the gravity vector at any pair of accelerometers (that is, the detection axes are not colinear or parallel) may be geometrically converted into an inclination angle and a zenith angle. A typical probe has a section case diameter of 5 to 7.6 arcs (2 to 3 inches).
However, it is not possible to install two servo accelerometers side by side. Thus, the accelerometer pairs are axially separated in sections 22, 23, but sufficiently close together compared to the spacing between pairs of accelerometers that are considered common. A third accelerometer is added to each paper, and its detection axis is
It may also be perpendicular to the axis of the other accelerometer in the pair, as indicated by Z.

This third accelerometer improves accuracy and can also be activated if the X or Y accelerometer is malfunctioning. Both ends of the cable or pipe 24 are connected to sections 22,2 of the probe.
3 and serves to space these sections within the borehole 20. The cable 24 is malleable so that it bends to follow the borehole, but resists chafing so that one section does not rotate relative to the other. By doing this,
A predetermined relationship between the accelerometer axes X,X' and Y,Y is maintained. Preferably, the sections 22, 23 of the probe are aligned in the crosswise direction, with the axes x and x' parallel to each other, forming a plane passing through the longitudinal axis of the probe. Similarly, the axes Y, Y' are made parallel to form a second plane passing through the probe axis, perpendicular to the previous plane. It is not essential that the corresponding axes be parallel; it is only necessary that they have a constant relationship. However, parallel detection axes simplify processing of the signals generated by the accelerometer. Each accelerometer is
Preferably, the accelerometer is a servo accelerometer or has an electronic circuit (not shown) that generates an analog signal representing the magnitude of the gravitational acceleration component along the detection axis of the accelerometer. Such an accelerometer is described in US Pat. No. 3,702,073. The probe electronics, described in more detail below, multiplexes the analog signals, converts them to digital signals, and applies this signal via the conductors of the hoisting cable 25 to the circuitry at the borehole head. The acceleration signal is applied to an input of data storage unit 26. The output of the data storage unit 26 is applied to a processor 27 which derives a representation of the borehole trajectory as described below. The transducer 28 associated with the hoisting cable 25 is
A signal ΔL indicating the position of the probe within the porehole is provided to the processor 27. A keyboard and display 30 are connected to processor 27.

The borehole trajectory can be expressed by the coordinate size of a triaxial system. A keyboard is provided for operator input and control. The display of the borehole trajectory is
You can also print it out or record it for later use. Devices for performing this action are known and are not shown in the drawings. The probe sections 22, 23 have cylindrical pressure cases.

An elastic center retainer 31 on the outside of the case contacts the inner wall of the iron pipe 21 of the borehole and orients the pressure case so that the longitudinal axis of the pressure case substantially coincides with the longitudinal axis of the borehole. The pressure case of the second section 23 of the probe is divided into two parts 32, 33. Cable 24 is connected to section 32. Accelerometers X', Y are provided within section 32. The second section of the probe 2
The second portion 33 of 3 also has a center retainer 31 on its outside and is as long as necessary to maintain proper pith alignment with the borehole. The parts 32, 33 of said pressure case are connected by a swivel joint (not shown) such that part 32 is free to rotate relative to part 33 and maintain the desired relationship with the first section 22. Borehole surveys are performed by moving a probe through the borehole in either direction from one end to the pond end, while collecting and processing data.

Surveying can be done when the probe is lowered into the borehole or raised from the bottom. To increase accuracy, data may be collected and the measurements averaged as the probe is moved in any direction. The azimuth of the borehole can be referenced to the outside world by establishing the initial azimuthal conditions of the probe at the earth's surface.

For example, the probe may be aligned to a certain standard and alignment may be verified using a measuring instrument. Figure 2 shows a diagram of the accelerometer and signal processing circuitry within the probe. The first section 22 of the probe includes X, Y and Z accelerometers with analog signal outputs ax, aY, az. The second section 23 has analog signal outputs ax', aY, az
'X',Y',Z' accelerometers are provided.
A power source 37 on the earth's surface is connected to a power source 38 inside the probe via a hoisting cable 25.

The analog signal of the accelerometer is applied to sample and hold circuits 39 and 39', multiplexed via A/D converters 40 and 40' to signal control hawk 41, and sent to the ground via this signal control device. This signal control device 41 includes sample and hold circuits 39 and 39' and A-D converters 40 and 40.
′ gives timing. The signals from cable length transducer 28 (FIG. 1) are correlated with the accelerometer signal to identify the borehole point from which each signal set was extracted. Sources of measurement error are minimized by providing a temperature sensor 42, 42' in each probe section together with a temperature control device 43, 43' to keep the temperature of the heat sensitive element within desired limits. I can do it.

The analog temperature signals t, t' are sampled and sent to the earth's surface along with the accelerometer signal. This temperature signal is utilized within the temperature compensation circuit 26 in order to minimize any further temperature errors. Section 22 of the probe,
23 must be long enough to keep the axis of the section aligned with the axis of the borehole.

The maximum length is limited by the minimum radius of curvature of the borehole lining. Within this limit, typical probe section lengths are approximately between 60 skins and 90 skins (2 feet and 3 feet). The spacing between the accelerometer pairs should be at least approximately 3 to 4.5 feet (10 to 15 feet). The maximum distance is determined by operational considerations. Typical probe lengths are approximately between 15 and 45 feet (50 and 150 feet). Figures 3 to 12 illustrate the geometric relationships underlying obtaining the borehole trajectory from the gravity component signals provided by the two pairs of accelerometers.

Figure 13 shows a chart of some relationships. The symbols and terms used in the drawings and their description will be explained below. ○ Ground reference NEG Gohi, east, downward (gravity) unit direction vector NEG Center of circle Cn in NEG coordinate system ○ Coordinates C of n
Curve C of the borehole Projection Cn of the upper part of the borehole Unit circle Cn′ at the nth cross section of the borehole
Or Cn+, unit circle ○n in the n+1-th cross section of the porehole Center of Cn ○n ○n upward projection 1 Distance from Cn to Cn' along the borehole curve C Xn'Yn Two orthogonal angles at ○n The accelerometers Xn', Yn' curve C is a straight line, and the detection angle
Two orthogonal accelerometers at ○n' when n' points in the same direction.

Similarly, detection axes Yn and Yn' point in the same direction. aXn'
aYn, axn, aYn' ×n, Yn, ×n', Yn
' acceleration signal Zn from the zenith of Cn, that is, the point ln closest to the ground of Cn ○Unit vector 1n from n to Zn
When looking at the borehole from above, unit horizontal vector Kn, Kn' clockwise 900 degrees from in. Local unit vector 00n Zn tangent to the borehole axis in the plane formed by Q, 0n, 0n'. or point 900n on Cn indicated by in. Point Q on Cn indicated by in. Center An, ln of the borehole curve with radius rn between 0n and 0n'. Orientation and inclination of the borehole axis ln, ln'
Incline of circles Cn, Cn' ○n, 0n' Vector from ○n to ○i ○, 0n'
vectors 0n, 0n' in the ENG coordinate system.

The angle from the zenith Zn to the Xn accelerometer axis is from Zn to ○n
Azimuth of the bending direction from 0n to ○n' 3 Azimuth of the curve of the borehole from 0n to ○n' 6 Quantity g used in geometric analysis Gravitational system number Mn Transformation matrix Mn+ between (i, j, k) n' and (i, j, k) n, (i, i, k) n' and (N, E,
G) transformation matrix between

Note that (i, j, k) n' = (i, i, k) elbow, Figure 3 shows the rectangular coordinate system NE whose origin is the ground reference ○.
A three-dimensional diagram with G is shown.

Borehole curve C extends downward under the northeast quadrant. Curve C is the projection of the porehole curve onto the ground. The coordinate NE forms a horizontal plane on the ground. G extends downward at right angles to this plane and represents the direction of gravity. Circles Cn and C
n'' has the center of ○n and On'' on the borehole carp. The planes of these circles are perpendicular to the borehole curve and are separated by a distance 1 along the borehole equal to the spacing of the accelerometer pairs in the probe. ○n and ○n'
The borehole curve in between is assumed to be a circular arc with radius rn centered at Qn in FIG. The probe is moved through the borehole and readings are taken from two pairs of accelerometers at successive sensor locations spaced apart by a distance 1 equal to the sensor pair spacing. As will be explained later, the change in the angle of orientation between the borehole's nostalgic slope and the accelerometer at each accelerometer position is
It can be determined from accelerometer readings. If the measurement is ground reference 0
Starting at , if the orientation of this point is known, the orientation of any point along the borehole can be determined by adding the orientation increments. The survey may begin at the ground reference ○ and proceed to the bottom of the borehole, or it may begin at the bottom of the borehole and continue to the ground reference. In the latter case, the actual borehole orientation at various locations is not known until the survey is complete and the accumulated incremental orientation measurements and the ground reference orientation are added. The slope and azimuth of each point on the borehole curve C and the distance along the curve can be used to derive the position of each point of the borehole in the Cartesian coordinate system NEC.

The acceleration signals ax and aY from a pair of orthogonal accelerometers are determined by the inclination 1 of the plane of this accelerometer and the orientation angle between the zenith, that is, the point closest to the ground on the unit circle, and the detection axis of the X accelerometer. Determine.

In FIG. 6, the unit circle CH is horizontal, and the unit circle Cn is inclined with respect to the unit CH about a diameter jn, 1 inch. FIG. 7 shows a detailed view taken perpendicular to the vector Xn. From the figure, we can see the following: ox - accelerometer signal axn n g COS n Sinln Y - accelerometer reading aYn = g COS ~ Jukan) Sin1n n - g Sin n Sinln and Goho = - Since the accelerometer signals axn and aYn are known, n and l
Both n can be determined.

These decisions are made for unit circles Cn and Cn'.
From this information and the assumption that the borehole follows an arc between position n barbs, the change in orientation up to barb n can also be determined. To be more specific, axn2 10aYzu = g2 (co〆n 10sin2n) sin21n thus (aXh20aYf) chin = g
Sinln or 1n=A to SinG machine 20 and 2 rare This gives the mirror slope of the porehole at ○n.

○n' is calculated in the same way. This is represented by step 43 in FIG. Figure 8 shows three identical zero circles, circle CH is horizontal or parallel to the ground, circle CH has a zenith Zn and is perpendicular to the porehole at ○n, formed by jn and -jn. Circle C centered on the pith
It is tilted to H. The circle Cn' has a zenith Zn' and is perpendicular to the borehole at Cn';
and -Vn as an axis by an angle of 28. The above circle Cn' becomes circle C at jn' and -in'.
Intersect with H. Turning point on circle Cn
t) Tn is 90o apart from Vn and -Vn. angle 2
Corresponding to the rotation of 8, the turning point Tn on the circle Cn is the circle Cn'
Move to Un above. Therefore, both Tn and Un are 90 from Vn.
It is at 0. In FIG. 8, Qn is the angle between Zn and Tn, and 6n is the angle between Zn' and Un. Figure 10 shows circles C superimposed along the axial direction of the borehole.
n and Cn' are shown. The following can be seen from FIGS. 8 and 10. Q=kuZn ○ Tn=kujn ○
Vn and 6 = Mu Zn O Un = 2 jn' ○ Vn Therefore, the transition of the zenith is y = ■ n-'s n' = Ku Zn ○ × Mu Zn'OX' = Ku Zn ○ Zn' = 2 jn ○ j
n' (when the right angle Zn ○ jn is turned clockwise by an angle y) = Q-6 The spherical triangle in FIG. 9 is on the right side of the circle in FIG.

In this triangle, if A=m-ln' akoq B=ln b=6 C:23, then according to the spherical sine law, Sina sin b sin A-sin B or SinQ sin6 Sin(m-L')-s ``Ty=Q-6, so SinQ・sin(Q-y).
COSQS1nysin ln'Therefore, nQSin2Sin ln' C○StsuSin 1n'-Sin 1n Since y=n1 of n', all the magnitudes of the right term in the equation are known from the four acceleration signals. Q can be determined.

The angle of curvature can be determined as follows using the law of triangles.

Cot No. Sin1'Next a ten Ganne nl/XA-B)-sinl/Xa-b) C=28, so UtB=meter Mitsubishi Ashi three main n(Old days-Gei(1n+1n
')〉Sin (Q-wo)'s enjoyment (1n11n') Sin u■nQCOS21 COSQSin2).

t back (・n0・n′) Sin = ■SQ (nenQ‐■t
Consideration-1) ■tki (・n+・n') Since the magnitude of the right term of this equation is known, angle 3 can be obtained by calculation.

The two quantities 6, Q and 8 are known in step 44 of FIG.

Figure 5 shows the geometric meaning of Q, that is, the upper probe center ○
The azimuth angle of the center ○n' of the lower probe as seen straight down along the tangent of the borehole at n is shown. The angle 23 in FIGS. 3 and 4 indicates the extent to which the borehole cross section Cn' is oriented relative to the borehole cross section Cn. The positions of vectors i, i and k in FIGS. 3 and 8 can be related to successive circles by a coordinate transformation matrix as follows.

Therefore, Mn+,=Mn·Mn The matrix Mn has already been obtained from previous measurements and calculations.

It is only necessary to derive the matrix Mn'.
Based on FIG. 8, the table of the vectors Un, Vn, Kn by the three circles lm1n, kn is as follows. Un=
in(cosQncos28n) 10jn(sinQncos23n) 10Kn(1sin28n) Vn=in(1sinQn) 10jn(cosQn)+kn(0) Kn=in(cosQnsin28n) −jn(sin Qn sin28n)+k n(cos
28n) The two vectors (in, 1n,
The coordinate transformation M that relates kn) and (in', jn', kn') can be obtained via the (Un, Vn, Kn) symbol.

in'=Cos6nun-sin6nVn=in(co
s6ncosQncos23nten sin6nSinQn
) ten jn (Cos6finQncos26n-sin6
ncosQn) tenkn (one cos6buin28n)in
′=sin6nun ＋Cos6nVn=in(sin
6ncosQnCoS23n-Cos6nS1nQn)
10jn(sin6nsinQncos28n10cos6
n cos Qn) ten kn (one sin6 n sin28 n) k
n'=in(cos.

n sin23n) ten in (sinQnsin28n) ten kn (cos28n) This means that the coordinates, depth matrix Mn (slap 45 in Figure 3) are assembled as follows.

In this case a・,=COS 8 Cos Q cos 280si
n 6Sin Qa, 2Cos 6 Cos Q C
os 28-sin 6COS Q In practice, the processor stores a coordinate transformation matrix from the previous local coordinates i, i, k of the spherical coordinate system NEC of the ground ○.

This means that the computer already knows the matrix Mn, which is the case.

Update the transformation matrix Mn to obtain the local coordinates in′,
The product of the matrices is determined in order to transform in', kn' into MM, which transforms in', kn' into the gobal coordinate system NEG. Mn+,=Mn·Mn Please refer to step 46 in FIG.

In Fig. 11, when viewed along the borehole in the direction of vector kn (Figs. 3, 4 and 5), the borehole from ○n to ○n' has an azimuth of Qn clockwise from the zenith Zn, and It is assumed that the porehole curves along the circular path by an arc 28n.

Now, if 1 is the length of the borehole from ○n to ○n', then the local position vector ○nOn'' from 0n to ○n' can be expressed as follows (steps in Figure 13). 47).

(onon')=in(sa.

Cape Misaki n) 10in (ZinQnSin28n) 10kn (7smQnsin28n) When the column vector ○non' is written in the NEG coordinate system, it is 0non
'=Mn(0non') (Step 48 in Figure 13) As can be seen from Figure 12, 〇〇n+. 200n′ko〇〇n+〇n〇n′ko), 0
0n is memorized from a previous calculation.

The position of ○n' with respect to the ground reference 0 is determined in this manner. By the vector 00n' indicating the position ○n',
The zenith An' (see Figure 13) is expressed as follows, where the leg size n' = magazine), Nn', En', Gn'', and the vector 00n' in the NEC coordinate system with the ground reference ○. coordinates (step 49 in FIG. 13).

Derivation of the borehole trajectory from the gravity vector signal is preferably performed by a programmed digital processor.

FIGS. 14 and 15A are charts showing the derivation of trajectories in the NEG coordinate system. The illustration and description assume the use of accelerometer signals from a distance 1 within the borehole. The scalar inputs to FIG. 14 are the digital gravity vector signals ax, aY and ax′,
aY′.

Each block in the diagram algebraically or verbally represents the action performed by that block. The program is written in a common language and involves some of the geometry mentioned above. Ax and aY are combined with gravity g in step 50 and an arcsine function is used in step 51 to obtain the oblique angle 1 at a location within the borehole.

Similarly, ax' and aY' are used in steps 52 and 53 to obtain the neck oblique angle r at the second point of the borehole. In step 54, the ratio of ax and aY is obtained, and in step 55, the inverse positive function further gives the magnitude of the angle (see Figures 3, 6 and 8). Similarly, step 56
, 57, ax' and aY' are combined to provide a signal representing the angle'. In step 58, the -' of the difference gives the angle y, the shift angle of the zenith between successive locations along the borehole (see FIG. 10). The forehead oblique angles 1, 1' and the zenith shift angle y are combined in steps 60, 61 to determine an angle y representing the orientation of the borehole between successive positions. In steps 62, 63 said angles are combined with the inclination angles 1, 1' and the zenith shift angle y to derive the bend angle B. The scalar quantities Q, 3, and 1 are
Form the input for the matrix/vector program shown in FIG. 15A.

The symbol M in FIG. 15A is from (i, i, k)n' to (i, i
,k) represents the transformation matrix of the borehole local coordinates to n, and Mn′ is (i, i.k)n′ to
represents the transformation matrix of spherical coordinates to . The first zenith of the probe is measured with surveying instrument 35 (FIG. 1) and this information is entered into the system via keyboard 30'.

In step 70, a spherical matrix Mo(Ao, lo
) determines the starting position of the probe. The shape of matrix Mo is indicated in Figure 15B by footnote *. For the first measurement position, n=0, the matrix from step 70 is applied via gate 71 to matrix multiplier 72. The angle and y are subtracted in step 73 to give angle 6, which is further subtracted in step 74 by angle Q.
and B to give the matrix Mn.

This matrix Mn has the form shown in FIG. 15B with footnote **. Matrix Mn is multiplied by matrix Mn in step 75 to provide a transformed spherical matrix MM, for the next position along the borehole. This matrix is delayed in step 76 so that n is 1
or larger, it is added to the matrix multiplier via gate 77 and then becomes Mn for the measurement. Angle 8 and Q are combined in step 78 to form vector ○n
This vector is multiplied by the matrix NL in step 72 (see FIGS. 11 and 12).

The output of this multiplication, ○n ○n', is the vector adder 80
, and here it is added to the NEC coordinates for point ○n. At the first measurement location (borehole in the ground) this coordinate is 000. As a result of vector addition, NEG coordinates representing one point of the porehole are obtained. This result is added as an input to a vector adder 80 for the next measured position via a unit delay device 81. The NEG coordinates obtained from successive accelerometer measurements represent the trajectory of the borehole. Survey instruments using servo accelerometers as described herein provide reliable results unless the borehole is within approximately one degree of true vertical or horizontal.

If such a situation arises, it is necessary to supplement the accelerometer measurements with some other borehole trajectory measurements.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of an embodiment of the present invention, FIG. 2 is a block diagram of an adder and a circuit for transmitting acceleration signals to the earth's surface, and FIGS. Geometric diagrams illustrating the derivation of inclination and incremental azimuth and borehole location coordinates;
Figure 13 is an expanded system diagram showing in chart form the derivations shown geometrically in Figures 3 to 12; Figures 14 and 15;
Figure A is a block diagram of a system for deriving borehole trajectories from accelerometer signals with measurements taken at positions separated by a distance equal to the accelerometer spacing;
5A is a diagram illustrating the contents of blocks 70 and 74 in FIG. 5A. FIG. 20...Borehole, 22...First section, 23...Second section, 24...Connection device, 25...Hoisting cable, 26...Data storage Unit, 27... Processor, 30... Keyboard and display, 31... Center holder, X
, Y, Zu, Y...detection pulp. FIG. l FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG. 6 FIG. 7 FIG. 8 FIG. 9 FIG. l0FIG. 11 FIG. 12 FIG. l3 FIG. 14 Figure 15A Figure 15B

Claims (1)

Claims: 1. A first pair of accelerometers having a detection axis forming a first plane. a second pair of accelerometers having sensing axes forming a second plane; mounting means for said accelerometer pairs for passing through the borehole with said accelerometer pairs spaced apart and in constant angular relation to each other about the borehole axis; and detection of said accelerometers from each accelerometer; a device for extracting a signal representative of the component of gravity along an axis; a device for obtaining a signal representative of the inclination angle of the borehole at each location from the accelerometer signal at spaced locations along the borehole; A borehole surveying device comprising: a device for extracting a signal representing an incremental azimuth angle of a borehole; 2. A first section having an axis extending along the borehole axis and a second section spaced apart from the first section having an axis extending along the borehole axis, connecting these two sections so that there is no constant change therebetween. a probe moved within the borehole, the probe having a connecting device maintaining a spacing of a second pair of accelerometers in said second section having a perpendicular sensing axis forming a sensing surface perpendicular to the axis of the borehole; and a sensing axis of said accelerometer from each accelerometer; a device for extracting a signal indicative of the gravitational component along the borehole; flexible to bend along the axis and to prevent rotation of one section relative to the other so as to maintain the mutual angular relationship of both sections about the borehole axis; A borehole surveying device characterized by: 3 a first housing section having a longitudinal axis; a second housing section having a longitudinal axis and longitudinally spaced apart from said first housing section; A connecting device that is twist-free about its longitudinal axis and flexible about an axis perpendicular to the longitudinal axis in order to maintain the longitudinal spacing and constant angular relationship between the sections. a probe lowered into the borehole by a hoisting cable, and an apparatus for positioning the first and second housing sections within the borehole such that the axes of the sections substantially coincide with the axis of the borehole; a first pair of accelerometers in a first housing section, the sensing axes of the pair of accelerometers being at right angles to each other to form a plane perpendicular to the axis of the first housing section; a second pair of accelerometers in the second housing section, the sensing axes of the sensors being perpendicular to each other to form a plane perpendicular to the axis of the second housing section; A device for extracting a signal representing the gravitational component along the detection axis, a device for measuring the position of the probe in the borehole and generating a signal representing that position, and an accelerometer and a device for generating a display of the borehole trajectory in response to the position signal. A borehole surveying device consisting of a measuring device.