DEVICE AND METHOD FOR DETERMINING ORIGINAL STRATUM DIRECTION OF CORE

Abstract

The present disclosure provides a device and methods for determining the original stratum direction of a core. The device includes a confining pressure pump, a resistance meter, and a core holder composed of upper and lower portions. The present disclosure further provides three methods for determining the original stratum direction of the core. The three methods respectively use the device to measure resistance values at different positions of the core, and compare a test result with an imaging result of resistivity imaging logging data to determine the rock direction of the core in a stratum.

Claims

1. An apparatus for determining an original stratum direction of a core, comprising a core holder, a first confining pressure pump and a resistance meter, wherein, the core holder consists of an upper half part and a lower half part, wherein the upper half part is configured for accommodating a core, the lower half part is configured for accommodating and fixing the core, and sides of the upper half part and the lower half part are respectively provided with scales for determining a rotation angle of the core, the first confining pressure pump is configured for pressurizing the upper half part of the core holder, and the resistance meter is configured for measuring an electrical resistance value of the core.

2. The apparatus as claimed in claim 1, wherein the lower half part of the core holder is capable of rotating, and the upper half part of the core holder is fixed and does not rotate relative to the lower half part of the core holder.

3. The apparatus as claimed in claim 1, wherein an inner wall of the upper half part of the core holder is provided with a metal sheet which is configured for being connected to the resistance meter.

4. The apparatus as claimed in claim 3, wherein interiors of the upper half part of the core holder and the lower half part of the core holder are respectively provided with a rubber sleeve, and the rubber sleeve of the upper half part of the core holder is provided with a groove for placing the metal sheet.

5. The apparatus as claimed in claim 1, wherein the bottom of the upper half part of the core holder and the top of the lower half part of the core holder are open ends, and the top of the upper half part of the core holder is provided with an opening for marking the top of the core.

6. The apparatus as claimed in claim 1, wherein the apparatus further comprises a tray for fixing the lower half part of the core holder and driving the lower half part of the core holder and the core to rotate.

7. The apparatus as claimed in claim 1, wherein the apparatus further comprises a second confining pressure pump for pressurizing the lower half part of the core holder.

8. The apparatus as claimed in claim 7, wherein a connecting pipeline between the first confining pressure pump and the upper half part of the core holder is provided with a valve, and a connecting pipeline between the second confining pressure pump and the lower half part of the core holder is provided with a valve.

9. The apparatus as claimed in claim 4, wherein space between the upper half part and the lower half part of the core holder and the rubber sleeve is a closed space, and the closed space is filled with liquid.

10. A method for determining an original stratum direction of a core, which is performed by using the apparatus for determining an original stratum direction of a core as claimed in claim 1, wherein the method comprises: step one: displacing water in the core with saturated water by gas until the saturated water in the core reaches the original stratum water saturation; step two: putting the core which is in a stratum water saturation state into the lower half part of the core holder and fixing the core, then covering the top of the core with the upper half part of the core holder, recording an angle difference between a scale of the upper half part of the core holder and a scale of the lower half part of the core holder at this time, and marking a position of the core at this time; step three: rotating the lower half part of the core holder and the core at an appropriate angle with the upper half part of the core holder being fixed, recording a rotation angle of the core, and measuring an electrical resistance value of the core; step four: repeating step three until the core rotates 360° in total; finding the rotation angles θ.sub.max and θ.sub.min respectively corresponding to maximum electrical resistance value R.sub.max and minimum electrical resistance value R.sub.min of the core, rotating the core at the rotation angles θ.sub.max and θ.sub.min, and marking corresponding positions on the core as max and min respectively; and step five: finding the darkest and brightest positions in terms of imaging color near a coring depth in resistivity imaging logging data, corresponding geographic information of the darkest and brightest positions to the positions represented by max and min on the core respectively, and determining the original stratum direction of the core.

11. The method as claimed in claim 10, wherein when the apparatus for determining an original stratum direction of a core comprises a second confining pressure pump, step two further comprises pressurizing the lower half part of the core holder using the second confining pressure pump.

12. The method as claimed in claim 11, wherein the second confining pressure pump pressurizes the lower half part of the core holder at a pressure of 0.5-2 MPa.

13. The method as claimed in claim 10, wherein in step three, the rotation angle of the core is 1-5 degree/time.

14. The method as claimed in claim 10, wherein in step three, the measuring an electrical resistance value of the core is performed by the following steps: pressurizing the upper half part of the core holder by using the first confining pressure pump to make the metal sheet close contact with the core, connecting a circuit between the resistance meter and the core, recording an electrical resistance value displayed by the resistance meter, and then removing the pressure of the first confining pressure pump.

15. The method as claimed in claim 14, wherein the first confining pressure pump pressurizes the upper half part of the core holder at a pressure of 0.5-2 MPa.

16. A method for determining an original stratum direction of a core, which is performed by using the apparatus for determining an original stratum direction of a core as claimed in claim 1, wherein the method comprises: step one: displacing water in the core with saturated water by gas until the saturated water in the core reaches the original stratum water saturation; step two: putting the core which is in a stratum water saturation state into the lower half part of the core holder and fixing the core, then covering the top of the core with the upper half part of the core holder, recording an angle difference between a scale of the upper half part of the core holder and a scale of the lower half part of the core holder at this time, and marking a position O of the core at this time; step three: dividing a circumferential position of the core into N equal parts along 360° with the position O as an end point, rotating the lower half part of the core holder and the core at an appropriate angle with the upper half part of the core holder being fixed, recording a rotation angle of the core, and measuring an electrical resistance value of the core; step four: repeating step three, measuring and recording an electrical resistance value of each position in the N equal parts, and marking the electrical resistance values as A.sub.1, A.sub.2, A.sub.3, . . . , A.sub.N in sequence according to the order of position; and step five: (1) defining a maximum electrical resistance value in A.sub.1 to A.sub.N as A.sub.max, and defining δn.sub.1,2, δn.sub.2,3, . . . , δn.sub.N-1,N, . . . , δn.sub.2N-1,2N, and a calculation method of δn.sub.1,2, δn.sub.2,3, . . . , δn.sub.N-1,N, . . . δn.sub.2N-1,2N being as follows: $δ n_{1, 2} = \frac{A_{2} - A_{1}}{A_{\max}}, δ n_{2, 3} = \frac{A_{3} - A_{2}}{A_{\max}}, .Math., δ n_{N - 1, N} = \frac{A_{N} - A_{N - 1}}{A_{\max}},$ $δ n_{N, N + 1} = δ n_{N, 1} = (A_{1} - A_{N}) / A_{\max}, δ n_{N + 1, N + 2} = δ n_{1, 2}, .Math., δ n_{2 N - 1, 2 N} = δ n_{N - 1, N};$ (2) dividing a circumferential position of the coring depth in a wellbore into N equal parts along 360°, and recording electrical resistance values measured at each position in a resistivity imaging logging data as B.sub.1, B.sub.2, B.sub.3, . . . , B.sub.N; (3) defining a maximum electrical resistance value in B.sub.1 to B.sub.N as B.sub.max, and defining δm.sub.1,2, δm.sub.2,3, . . . , δm.sub.N-1,N, δm.sub.N,N+1, and a calculation method of δm.sub.1,2, δm.sub.2,3, . . . , δm.sub.N-1,N, δm.sub.N,N+1 being as follows: $δ m_{1, 2} = \frac{B_{2} - B_{1}}{B_{\max}}, δ m_{2, 3} = \frac{B_{3} - B_{2}}{B_{\max}}, .Math., δ m_{N - 1, N} = \frac{? - B_{N - 1}}{B_{\max}}, δ m_{N, N + 1} = δ m_{N, 1} = (B_{1} - B_{N}) / B_{\max};$ $? indicates text missing or illegible when filed$ (4) defining $H (ω) = \overset{N}{\underset{i = 1}{.Math.}} (.Math. δ n_{i + ω - 1, i + ω} - δ m_{1, i + 1} .Math.), ω = 1, 2 .Math. N;$ finding a minimum value in H(1), H(2), . . . H(ω), defining the minimum value as H(α), in this case ω=α, corresponding position information of A.sub.α to position information of B.sub.1, and determining the original stratum direction of the core.

17. The method as claimed in claim 16, wherein when the apparatus for determining an original stratum direction of a core comprises a second confining pressure pump, step two further comprises pressurizing the lower half part of the core holder using the second confining pressure pump.

18. The method as claimed in claim 17, wherein the second confining pressure pump pressurizes the lower half part of the core holder at a pressure of 0.5-2 MPa.

19. The method as claimed in claim 16, wherein in step three, the rotation angle of the core is 1-5 degree/time.

20. The method as claimed in claim 16, wherein in step three, the rotation angle of the core is (360/N) degree/time.

21. The method as claimed in claim 16, wherein in step three, the measuring an electrical resistance value of the core is performed by the following steps: pressurizing the upper half part of the core holder by using the first confining pressure pump to make the metal sheet close contact with the core, connecting a circuit between the resistance meter and the core, recording an electrical resistance value displayed by the resistance meter, and then removing the pressure of the first confining pressure pump.

22. The method as claimed in claim 21, wherein the first confining pressure pump pressurizes the upper half part of the core holder at a pressure of 0.5-2 MPa.

23. A method for determining an original stratum direction of a core, which is performed by using the apparatus for determining an original stratum direction of a core as claimed in claim 1, wherein the method comprises: step one: displacing water in the core with saturated water by gas until the saturated water in the core reaches the original stratum water saturation; step two: putting the core which is in a stratum water saturation state into the lower half part of the core holder and fixing the core, then covering the top of the core with the upper half part of the core holder, recording an angle difference between a scale of the upper half part of the core holder and a scale of the lower half part of the core holder at this time, and marking a position O of the core at this time; step three: dividing a circumferential position of the core into N equal parts along 360° with the position O as an end point, rotating the lower half part of the core holder and the core at an appropriate angle with the upper half part of the core holder being fixed, recording a rotation angle of the core, and measuring an electrical resistance value of the core; step four: repeating step three, measuring and recording an electrical resistance value of each position in the N equal parts, and marking position codes as P.sub.1, P.sub.2, P.sub.3, . . . , P.sub.N in sequence according to the order of position; and step five: (1) defining subscript of the position code corresponding to the maximum electrical resistance value of P.sub.1 to P.sub.N as N.sup.1, N.sup.2, . . . , N.sup.γ, wherein γ is number of maximum electrical resistance values of P.sub.1 to P.sub.N, and γ≤N, defining dn groups values comprising dn.sub.1,2, dn.sub.2,3, . . . , dn.sub.γ,γ+1, . . . , dn.sub.2γ-1,2γ; and a calculation method of dn.sub.1,2, dn.sub.2,3, . . . , dn.sub.γ,γ+1, dn.sub.2γ-1,2γ being as follows: when 1≤i≤γ−1, dn.sub.i,i+1=N.sup.i+1−N.sup.i; when i=γ, dn.sub.i,i+1=dn.sub.i,1=N.sup.1+N−N.sup.i; and when i>γ, dn.sub.i,i+1=dn.sub.i-γ,i+1-γ=N.sup.i+1-γ−N.sup.i-γ; (2) dividing a circumferential position near the coring depth in a wellbore into N equal parts along 360°, and recording the electrical resistance values measured at each position in a resistivity imaging logging data, and marking position codes of each position as Q.sub.1, Q.sub.2, Q.sub.3, . . . , Q.sub.N; (3) defining subscript of the position code corresponding to the maximum electrical resistance value of Q.sub.1 to Q.sub.N as M.sup.1, M.sup.2, . . . , M.sup.β, wherein β is number of maximum electrical resistance values of Q.sub.1 to Q.sub.N, and β=γ, defining dm groups values comprising dm.sub.1,2, dm.sub.2,3, . . . , dm.sub.β,β+1; and a calculation method of dm.sub.1,2, dm.sub.2,3, dm.sub.β,β+1 being as follows: when 1≤i≤β−1, dm.sub.i,i+1=M.sup.i+1−M.sup.i; and when i=β, dm.sub.i,i+1=dm.sub.i,1=M.sup.1+N−M.sup.i; and (4) comparing dn.sub.1+η,2+η, dn.sub.2+η,3+η, . . . , dn.sub.γ+η,γ+1+η with dm.sub.1,2, dm.sub.2,3, . . . dm.sub.β,β+1 in turn according to the order of dn.sub.1+η,2+η, dn.sub.2+η3+η, . . . dn.sub.γ+η,γ+1+η, wherein η=0, 1, 2, . . . , γ−1, when the dn groups values and the dm group values are the same respectively in turn, defining value of (1+η) being α, corresponding position information of P.sub.N.sup.α to position information of Q.sub.M.sup.1, and determining the original stratum direction of the core.

24. The method as claimed in claim 23, wherein N.sup.1, N.sup.2, . . . , N.sup.γ in step five (1) are subscripts of the position codes corresponding to the minimum electrical resistance values in P.sub.1, P.sub.2, P.sub.3, . . . P.sub.N; and M.sup.1, M.sup.2, . . . , M.sup.β in step five (3) are subscripts of the position codes corresponding to the minimum electrical resistance values in Q.sub.1, Q.sub.2, Q.sub.3, . . . Q.sub.N.

25. The method as claimed in claim 23, wherein when the apparatus for determining an original stratum direction of a core comprises a second confining pressure pump, step two further comprises pressurizing the lower half part of the core holder using the second confining pressure pump.

26. The method as claimed in claim 25, wherein the second confining pressure pump pressurizes the lower half part of the core holder at a pressure of 0.5-2 MPa.

27. The method as claimed in claim 23, wherein in step three, the rotation angle of the core is 1-5 degree/time.

28. The method as claimed in claim 23, wherein in step three, the rotation angle of the core is (360/N) degree/time.

29. The method as claimed in claim 23, wherein in step three, the measuring an electrical resistance value of the core is performed by the following steps: pressurizing the upper half part of the core holder by using the first confining pressure pump to make the metal sheet close contact with the core, connecting a circuit between the resistance meter and the core, recording an electrical resistance value displayed by the resistance meter, and then removing the pressure of the first confining pressure pump.

30. The method as claimed in claim 29, wherein the first confining pressure pump pressurizes the upper half part of the core holder at a pressure of 0.5-2 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] FIG. 1 is a schematic diagram before and after a core removal from the stratum. Wherein, Figure a shows a core in the stratum, and Figure b shows that the core produces α Angle offset after the core being taken out of a cylinder, and Figure c shows that the core produces β Angle offset when a small sample is drilled on the full diameter core;

[0069] FIG. 2 is a structural diagram of the apparatus for determining an original stratum direction of a core provided by this disclosure;

[0070] FIG. 3 is a structural decomposition diagram of the core holder of embodiment 1;

[0071] FIG. 4 is a schematic diagram of the scale of the upper half part of the core holder marking the core rotation angle according to embodiment 1;

[0072] FIG. 5 is a schematic diagram of the scale of the lower half part of the core holder marking the core rotation angle according to embodiment 2;

[0073] FIG. 6 is a resistivity imaging diagram of a well in embodiment 2;

[0074] FIG. 7 is a schematic diagram of the distribution of A.sub.1, A.sub.2, . . . , A.sub.10 in embodiment 3; and

[0075] FIG. 8 is a schematic diagram of the distribution of B.sub.1, B.sub.2, . . . , B.sub.10 in embodiment 3.

SYMBOL DESCRIPTION OF MAIN COMPONENTS

[0076] Tray 1 handle 11 core holder 2 upper half part of the core holder 21 lower half part of the core holder 22 opening 23 metal sheet 24 first confining pressure pump 31 second confining pressure pump 32 valve 311 valve 321 resistance meter 4 core 5 the darkest position 6 the brightest position 7

DETAILED DESCRIPTION

[0077] In order to have a clearer understanding of the technical features, purposes and beneficial effects of this disclosure, the technical solution of this disclosure will be described in detail below, but it cannot be understood as limiting the implementable scope of this disclosure.

Embodiment 1

[0078] The embodiments of this disclosure provide an apparatus for determining an original stratum direction of a core, and the structure thereof is shown in FIG. 2; wherein, Figure a is a three-dimensional view of the apparatus, and Figure b is a cross-sectional view of the core holder and the resistance meter. As shown in Figure a of FIG. 2, the apparatus includes a tray 1, a core holder 2, a first confining pressure pump 31, a second confining pressure pump 32 and a resistance meter 4.

[0079] In this embodiment, side of the tray 1 is provided with a handle 11, which can drive the tray 1 to rotate.

[0080] FIG. 3 is a structural decomposition diagram of the core holder 2. As shown in FIG. 3, the core holder 2 is a hollow cylinder (barrel) as a whole, which consists of the upper half part 21 of the core holder and the lower half part 22 of the core holder. The upper half part 21 of the core holder and the lower half part 22 of the core holder are cylindrical with openings at both ends, and their diameters are the same. The bottom of the upper half part 21 of the core holder and the top of the lower half part 22 of the core holder are connected to each other through their open ends to form a cavity for accommodating a core 5.

[0081] As shown in FIG. 3, a closed end of the upper half part 21 of the core holder is provided with an opening 23, and the bottom thereof is provided with a scale. As shown in Figure b of FIG. 2, the upper half part 21 of the core holder is internally provided with a rubber sleeve (not shown in the figure), the rubber sleeve is provided with a groove (not shown in the figure), and there is a group of opposite metal sheets 24 near the core 5 in the groove. The metal sheet 24 is connected to the resistance meter 4 through a wire. The scale of the upper half part 21 of the core holder is used to record the change of a rotation angle of the core 5 (as shown in FIG. 4); the opening 23 is used to mark the core position at the top of core 5; and the metal sheet 24 may closely contact the core 5 and connect the circuit between the core 5 and the resistance meter 4.

[0082] A closed end of the lower half part 22 of the core holder is fixed on the tray 1 by welding. The top of the lower half part 22 of the core holder is provided with a scale, and the interior of the lower half part 22 of the core is provided with a rubber sleeve for fixing the core 5. By pressurizing the lower half part 22 of the core holder, the rubber sleeve may be in close contact with the core 5, so that the lower half part 22 of the core holder and the core 5 may rotate together with the tray 1. The scale on the lower half part 22 of the core holder is used to record the change of angle during core rotation (as shown in FIG. 5). During core rotation, the specific rotation angle may be determined by calculating the angle difference between the scale of the lower half part 22 of the core holder and the scale of the upper half part 21 of the core holder.

[0083] The apparatus provided in this embodiment is provided with two confining pressure pumps, namely, the first confining pressure pump 31 and the second confining pressure pump 32. The first confining pressure pump 31 is connected to the upper half part 21 of the core holder, and a connecting pipeline therebetween is provided with a valve 311. The first confining pressure pump 31 is used to pressurize the upper half part 21 of the core holder. The second confining pressure pump 32 is connected to the lower half part 22 of the core holder, and a connecting pipeline therebetween is provided with a valve 321. The second confining pressure pump 32 is used to pressurize the lower half part 22 of the core holder.

[0084] The resistance meter 4 is connected to the metal sheet 24 through a wire to measure the electrical resistance value of the core 5.

Embodiment 2

[0085] The embodiments of this disclosure provide a method for determining an original stratum direction of a core, which is performed by the apparatus provided in Embodiment 1.

[0086] Taking a well as an example, firstly, resistivity imaging logging is performed on the well, and the test results are shown in FIG. 6. Coring operation is carried out, and full diameter core samples were taken at the depth of 5666.5 m. The determining the original stratum direction of the core by using the above apparatus includes the following steps:

[0087] Step one: water in the core 5 with saturated water is displaced by gas until the saturated water in the core 5 reaches the original stratum water saturation.

[0088] Step two: the core 5 in the stratum water saturation state is put into the lower half part 22 of the core holder and the core 5 is fixed, then the core 5 is covered with the upper half part 21 of the core holder, then an angle difference between the scale of the upper half part 21 of the core holder and the scale of the lower half part 22 of the core holder is adjusted to 0°, and the position of the core 5 at this time is marked on the top of the core 5 through the opening 23.

[0089] Step three: a pressure of 0.5-2 MPa is applied to the lower half part 22 of the core holder by using the second confining pressure pump 32 to make the rubber sleeve inside the lower half part 22 of the core holder in close contact with the core 5;

[0090] the tray 1 rotates counterclockwise to rotate the core 5 and the lower half part 22 of the core holder at the same time. When the rotation reaches a certain angle, stop the rotation, and a pressure of 0.5-2 MPa is applied to the upper half part 21 of the core holder by using the first confining pressure pump 31 to make the metal sheet 24 in the upper half part 21 of the core holder in close contact with the core 5. At this time, the difference between the scale of the upper half part 21 of the core holder and the scale of the lower half part 22 of the core holder is the rotation angle of the core 5. The rotation angle of the core and the electrical resistance value displayed by the resistance meter 4 at this time are recorded;

[0091] and then, the pressure of the first confining pressure pump 31 is removed to separate the metal sheet 24 inside the upper half part 21 of the core holder from the core 5.

[0092] Step four: step three is repeated. The rotation angle of core 5 is controlled to 5 degree/time until the cumulative rotation angle of core 5 reaches 360°.

[0093] Table 1 shows the test results of electrical resistance values of the core. It can be seen from table 1 that the maximum and minimum electrical resistance values measured during the rotation of core 5 are 93 Ω.Math.m and 50 Ω.Math.m respectively, and the corresponding rotation angles are 140° and 5° respectively. Then the tray 1 rotates according to 140° and 5°, and the corresponding positions max and min after two rotations of core 5 are marked through opening 23.

[0094] Step five: the positions of max and min marked on core 5 are compared with the resistivity imaging data in FIG. 6. The specific method is to find the darkest position 6 and the brightest position 7 of the imaging color at the depth of 5666.5 m shown in FIG. 6. As can be seen from FIG. 6, the angle of the brightest position 6 is 0°, and the corresponding geographical direction is due West. The angle of the darkest position 7 is 140°, and the corresponding geographical direction is 45° South by East. Then, the specific direction of the core in the geological body may be determined by taking the geographical direction of the darkest position 6 (due West direction of the stratum) corresponding to the position marked max on the core and taking the geographical direction of the brightest position 7 (the direction of 45° South by East of the stratum) corresponding to the position marked min on the core. The above position is the direction of the core in the geological body.

TABLE-US-00001 TABLE 1 Cumulative rotation angle resistance (°) (Ω .Math. m) 5.00 50.00 10.00 53.19 15.00 54.78 20.00 56.37 25.00 57.96 30.00 59.56 35.00 61.15 40.00 62.74 45.00 64.33 50.00 65.93 55.00 67.52 60.00 69.11 65.00 70.70 70.00 72.30 75.00 73.89 80.00 75.48 85.00 77.07 90.00 78.67 95.00 80.26 100.00 81.85 105.00 83.44 110.00 85.04 115.00 86.63 120.00 88.22 125.00 89.81 130.00 91.41 135.00 92.00 140.00 93.00 145.00 91.41 150.00 89.81 155.00 88.22 160.00 86.63 165.00 85.04 170.00 83.44 175.00 81.85 180.00 80.26

Embodiment 3

[0095] The embodiments of this disclosure provide a method for determining an original stratum direction of a core, including the following steps:

[0096] Step one: water in the core 5 with saturated water is displaced by gas until the saturated water in the core 5 reaches the original stratum water saturation.

[0097] Step two: the core 5 in the stratum water saturation state is put into the lower half part 22 of the core holder and the core 5 is fixed then the core 5 is covered with the upper half part 21 of the core holder, then an angle difference between the scale of the upper half part 21 of the core holder and the scale of the lower half part 22 of the core holder is adjusted to 0°, and the position O of the core 5 at this time is marked on the top of the core 5 through the opening 23.

[0098] Step three: a circumferential position of the core is divided into 10 equal parts (defining N=10) along 360° by taking the position O as an end point, the distribution of the 10 parts being shown in FIG. 7. A pressure of 0.5-2 MPa is applied to the lower half part 22 of the core holder through the second confining pressure pump 32 to make the rubber sleeve inside the lower half part 22 of the core holder in close contact with the core 5;

[0099] the tray 1 rotates counterclockwise to rotate the core 5 and the lower half part 22 of the core holder at the same time. When the rotation reaches a certain angle, stop the rotation, and a pressure of 0.5-2 MPa is applied to the upper half part 21 of the core holder by using the first confining pressure pump 31 to make the metal sheet 24 in the upper half part 21 of the core holder in close contact with the core 5. At this time, the difference between the scale of the upper half part 21 of the core holder and the scale of the lower half part 22 of the core holder is the rotation angle of the core 5. The rotation angle of the core and the electrical resistance value displayed by the resistance meter 4 at this time are recorded;

[0100] and then, the pressure of the first confining pressure pump 31 is removed to separate the metal sheet 24 inside the upper half part 21 of the core holder from the core 5.

[0101] Step four: step three is repeated. The electrical resistance values of each position are measured and recorded, which is recorded as A.sub.1, A.sub.2, . . . , A.sub.10 in sequence according to order of the positions. See Table 2 for the test results of electrical resistance value.

TABLE-US-00002 TABLE 2 Code A.sub.1 A.sub.2 A.sub.3 A.sub.4 A.sub.5 A.sub.6 A.sub.7 A.sub.8 A.sub.9 A.sub.10 Resistivity (Ω) 1 3 5 1 2 5 2 1 5 1

[0102] Step five:

[0103] 1. According to table 2, the maximum resistance A.sub.max is 5Ω. The ratio δn.sub.i,i+1 of the difference between the electrical resistance values of two adjacent positions to the maximum electrical resistance value is calculated:

[0104] (1) when 1≤i≤9, 6n.sub.i,i+1=(A.sub.i+1−A.sub.i)/A.sub.max, for example, δn.sub.1,2=(A.sub.2−A.sub.1)/A.sub.max=(3−1)/5=0.4, δn.sub.2,3=(A.sub.3−A.sub.2)/A.sub.max=(5−3)/5=0.4;

[0105] (2) when i=10, δn.sub.10,11=δn.sub.10,1=(1−1)/5=0; and

[0106] (3) δn.sub.11,12=δn.sub.1,2=0.4, δn.sub.12,13=δn.sub.2,3=0.4, . . . , and so on.

[0107] The calculation results of δn.sub.i,i+1(i≤10) are summarized in Table 3.

TABLE-US-00003 TABLE 3 δn.sub.1, 2 δn.sub.2, 3 δn.sub.3, 4 δn.sub.4, 5 δn.sub.5, 6 δn.sub.6, 7 δn.sub.7, 8 δn.sub.8, 9 δn.sub.9, 10 δn.sub.10, 11 0.4 0.4 −0.8 0.2 0.6 −0.6 −0.2 0.8 −0.8 0

[0108] 2. The circumferential position of coring depth in a wellbore is divided into 10 equal parts along 360°, and the distribution of the 10 parts is shown in FIG. 8. The electrical resistance values of 10 positions are measured respectively and recorded as B.sub.1, B.sub.2, . . . , B.sub.10. The results are shown in Table 4.

TABLE-US-00004 TABLE 4 Code B.sub.1 B.sub.2 B.sub.3 B.sub.4 B.sub.5 B.sub.6 B.sub.7 B.sub.8 B.sub.9 B.sub.10 Resistivity (Ω) 10 2 2 6 9 2 6 10 4 6

[0109] In the Table 4, the maximum electrical resistance value B.sub.max is 10Ω.

[0110] 3. The ratio δm.sub.i,i+1 of the electrical resistance difference between two adjacent positions to the maximum resistance is calculated, the calculation method being as follows:

[0111] when 1≤i<10,δm.sub.i,i+1=(B.sub.i+1−B.sub.i)/B.sub.max;

[0112] when i=10,δm.sub.10,11=δm.sub.10,1=(B.sub.1−B.sub.10)/B.sub.max;

[0113] The calculation results of δm.sub.i,i+1 (i≤10) are summarized in Table 5.

TABLE-US-00005 TABLE 5 δm.sub.1, 2 δm.sub.2, 3 δm.sub.3, 4 δm.sub.4, 5 δm.sub.5, 6 δm.sub.6, 7 δm.sub.7, 8 δm.sub.8, 9 δm.sub.9, 10 δm.sub.10, 11 −0.8 0 0.4 0.3 −0.7 0.4 0.4 −0.6 0.2 0.4

[0114] 4. the difference between the values in Table 5 and values in Table 3 is calculated in turn, and then all the calculated differences are summed. The formula used for calculation is:

[00004] $H (ω) = \overset{N}{\underset{i = 1}{.Math.}} (.Math. ? - ? .Math.),$ $? indicates text missing or illegible when filed$

where, ω=1, 2, 3, . . . 10. The values of H(1), H(2), . . . H(10) are calculated.

[0115] Specific calculation process is for example as follows:

H(1)=|0.44−(−0.8)|+|0.4−0|+|−0.8−0.4|+|0.2−0.3|+|0.64−(−0.7)|+|−0.6−0.4|+|−0.2−0.4|+|0.8−(−0.6)|+|−0.8−0.2|+|0−0.4|=8.6.

[0116] The calculation results of H(ω) are summarized in Table 6.

TABLE-US-00006 TABLE 6 H(1) H(2) H(3) H(4) H(5) H(6) H(7) H(8) H(9) H(10) 8.6 4 4.2 8.6 5.8 3 3.4 8 1.4 6.6

[0117] It can be seen from Table 6 that the value of H(9) is the smallest. The position information of A.sub.9 corresponds to the position information of B.sub.1, thus the specific direction of the core in the geological body is determined.

Embodiment 4

[0118] The embodiments of this disclosure provide a method for determining an original stratum direction of a core, including the following steps:

[0119] Step one: water in the core 5 with saturated water is displaced by gas until the saturated water in the core 5 reaches the original stratum water saturation.

[0120] Step two: the core 5 in the stratum water saturation state is put into the lower half part 22 of the core holder and the core 5 is fixed, then the core 5 is covered with the upper half part 21 of the core holder, then an angle difference between the scale of the upper half part 21 of the core holder and the scale of the lower half part 22 of the core holder is adjusted to 0°, and the position O of the core 5 at this time is marked on the top of the core 5 through the opening 23.

[0121] Step three: a circumferential position of the core is divided into 10 equal parts (defining N=10) along 360° by taking the position O as an end point. A pressure of 0.5-2 MPa is applied to the lower half part 22 of the core holder through the second confining pressure pump 32 to make the rubber sleeve inside the lower half part 22 of the core holder in close contact with the core 5;

[0122] the tray 1 rotates counterclockwise to rotate the core 5 and the lower half part 22 of the core holder at the same time. When the rotation reaches a certain angle, stop the rotation, and a pressure of 0.5-2 MPa is applied to the upper half part 21 of the core holder by using the first confining pressure pump 31 to make the metal sheet 24 in the upper half part 21 of the core holder in close contact with the core 5. At this time, the difference between the scale of the upper half part 21 of the core holder and the scale of the lower half part 22 of the core holder is the rotation angle of the core 5. The rotation angle of the core and the electrical resistance value displayed by the resistance meter 4 at this time are recorded;

[0123] and then, the pressure of the first confining pressure pump 31 is removed to separate the metal sheet 24 inside the upper half part 21 of the core holder from the core 5.

[0124] Step four: step three is repeated. The electrical resistance values of each position are measured and recorded, which is recorded as P.sub.1, P.sub.2, . . . , P.sub.10 in sequence according to order of the position. See Table 7 for the test results of electrical resistance value.

TABLE-US-00007 TABLE 7 Position code P.sub.1 P.sub.2 P.sub.3 P.sub.4 P.sub.5 P.sub.6 P.sub.7 P.sub.8 P.sub.9 P.sub.10 Resistivity (Ω) 1 3 5 1 2 5 2 1 5 1

[0125] Step five:

[0126] (1) the position codes P.sub.3, P.sub.6 and P.sub.9 corresponding to the maximum resistivity (5Ω) in Table 7 are found, and then the number of maximum electrical resistance values γ=3; the subscripts of the codes are marked as N.sup.1=3, N.sup.2=6, N.sup.3=9, and do groups of values including dn.sub.1,2, dn.sub.2,3, dn.sub.3,4, . . . , dn.sub.2γ-1,2γ (i.e., dn.sub.5,6) are defined. The calculation method of the values are as follows:

[0127] when 1≤i≤γ−1, dn.sub.i,i+1=N.sup.i+1−N.sup.i, for example, dn.sub.1,2=N.sup.2−N.sup.1=6−3=3;

[0128] when i=γ, dn.sub.i,i+1=N.sup.1+N−N.sup.i, for example, dn.sub.3,4=N.sup.1+N−N.sup.3=3+10−9=4; and

[0129] when i>γ, dn.sub.i,i+1=dn.sub.i-γ,i+1-γ=N.sup.i+1-γ−N.sup.i-γ, for example, dn.sub.4,5=dn.sub.1,2=3.

[0130] After calculation, the calculation results of dn.sub.1,2 to dn.sub.5,6 are summarized in Table 8.

TABLE-US-00008 TABLE 8 dn.sub.1, 2 dn.sub.2, 3 dn.sub.3, 4 dn.sub.4, 5 dn.sub.5, 6 3 3 4 3 3

[0131] (2) the circumferential position of coring depth in a wellbore is divided into 10 equal parts along 360°, which are recorded as Q.sub.1, Q.sub.2, . . . , Q.sub.10 See Table 9 for electrical resistance values at 10 positions.

TABLE-US-00009 TABLE 9 Position code Q.sub.1 Q.sub.2 Q.sub.3 Q.sub.4 Q.sub.5 Q.sub.6 Q.sub.7 Q.sub.8 Q.sub.9 Q.sub.10 Resistivity (Ω) 10 2 2 6 10 2 6 10 4 6

[0132] (3) the position codes Q.sub.1, Q.sub.5 and Q.sub.8 corresponding to the maximum resistivity (10Ω) in Table 9 are found, and then the number of maximum electrical resistance values 13=3; the subscripts of the codes are marked as M.sup.1=1, M.sup.2=5, M.sup.3=8 in turn, and dm groups of value including dm.sub.1,2, dm.sub.2,3, . . . dm.sub.β,β+1 (i.e., dm.sub.3,4) are defined. The calculation method of the values are as follows:

[0133] when 1≤i≤β−1, dm.sub.i,i+1=M.sup.i+1−M.sup.i, for example, dm.sub.1,2=M.sup.2−M.sup.1=5−1=4, dm.sub.2,3=M.sup.3−M.sup.2=8−5=3; and

[0134] when i=β, dm.sub.i,i+1=dm.sub.i,1=M.sup.1+N−M.sup.β, for example, dm.sub.3,4=M.sup.1+N−M.sup.3=1+10−8=3.

[0135] (4) dn.sub.1+η,2+η, dn.sub.2+η,3+72, . . . dn.sub.γ+η,γ+1+η, are compared with dm.sub.1,2, dm.sub.2,3, dm.sub.β,β+1 in turn according to the order of dn.sub.1+η,2+η, dn.sub.2+η,3+72, . . . dn.sub.γ+η,γ+1+η, where η=0, 1, 2, respectively,

[0136] set η=0, then dn.sub.1,2, dn.sub.2,3, dn.sub.3,4 (that is, 3, 3, 4) are compared with dm.sub.1,2, dm.sub.2,3, dm.sub.3,4 (that is, 4, 3, 3) according to the order of dn.sub.1,2, dn.sub.2,3, dn.sub.3,4, it can be seen that the two groups of data are not the same in turn, thus continue to compare;

[0137] set η=1, then dn.sub.2,3, dn.sub.3,4, dn.sub.4,5 (that is, 3, 4, 3) are compared with dm.sub.1,2, dm.sub.2,3, dm.sub.3,4 (that is, 4, 3, 3) according to the order of dn.sub.2,3, dn.sub.3,4, dn.sub.4,5, it can be seen that the two groups of data are not the same in turn, thus continue to compare; and

[0138] set η=2, then dn.sub.3,4, dn.sub.4,5, dn.sub.5,6 (that is, 4, 3, 3) are compared with dm.sub.1,2, dm.sub.2,3, dm.sub.3,4 (that is, 4, 3, 3) according to the order of dn.sub.3,4, dn.sub.4,5, dn.sub.5,6, it can be seen that at this time, the two groups of data are the same in turn, the value of (1+η) is 3, and the position information of P.sub.N.sup.3 (that is, P.sup.9) corresponds to the position information of Q.sub.M.sup.1 (that is, Q.sup.1) to determine the original stratum direction of the core.

Embodiment 5

[0139] In this embodiment, by taking the core electrical resistance value (Table 7 data) measured in embodiment 4 and the electrical resistance value (Table 8 data) in resistivity logging data as the original data, the original direction of the core tested in embodiment 4 in the stratum is determined by using the method in embodiment 3.

[0140] The data in Table 7 and Table 8 are processed according to the method provided in embodiment 3, and H(ω) value is calculated wherein ω≤10, and the calculation results are summarized in Table 10.

TABLE-US-00010 TABLE 10 H(1) H(2) H(3) H(4) H(5) H(6) H(7) H(8) H(9) H(10) 8.8 4 4.4 8.8 5.6 3.2 3.6 8 1.2 6.8

[0141] In Table 10, H(9) is the minimum value, and the position information of A.sub.9 corresponds to the position information of B.sub.1, and then the specific direction of the core in the geological body is determined. This result is also consistent with the comparison result of embodiment 4.

[0142] It can be seen from embodiments 3-5 that the method adopted in embodiment 3 is applicable to the comparison of core resistance test results with corresponding logging data in all the cases. The method adopted in embodiment 4 is applicable to the case where the number of maximum electrical resistance values of core resistance test results is the same as that of logging data, or the number of minimum electrical resistance values of resistance test results is the same as that of logging data.

[0143] It can be seen from the results of embodiments 2-5 that by using the apparatus and method provided by this disclosure, by measuring the anisotropic electrical resistance value of the core and comparing the results of the corresponding relationship between the measured position and the electrical resistance value with the stratum logging information, the actual direction of the core distribution in the stratum may be accurately obtained, thereby solving the problem that it is difficult to identify the direction of the core in the stratum after field coring.

DEVICE AND METHOD FOR DETERMINING ORIGINAL STRATUM DIRECTION OF CORE

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G01B5/24

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G01N33/24

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G01V3/18

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G01V3/38

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