CN110895255A - Method for evaluating oil extraction content in shale organic matter and inorganic matter - Google Patents

Method for evaluating oil extraction content in shale organic matter and inorganic matter Download PDF

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CN110895255A
CN110895255A CN201910484040.0A CN201910484040A CN110895255A CN 110895255 A CN110895255 A CN 110895255A CN 201910484040 A CN201910484040 A CN 201910484040A CN 110895255 A CN110895255 A CN 110895255A
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shale
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CN110895255B (en
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秦学杰
蒲军
付育璞
李子靳
朱超凡
宫厚健
桑茜
李亚军
董明哲
苏玉亮
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Sinopec Exploration and Production Research Institute
China University of Petroleum East China
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China University of Petroleum East China
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Abstract

The invention discloses a method for evaluating the oil extraction content in shale organic matters and inorganic matters, which comprises the following steps: cleaning and drying an experimental shale sample, and then carrying out nuclear magnetic resonance analysis to obtain a substrate relaxation time spectrogram; performing nuclear magnetic resonance analysis after the experiment shale sample is completely saturated with oil, and subtracting the peak area in the obtained relaxation time spectrogram after the saturated oil from the peak area in the substrate relaxation time spectrogram to obtain a first T2A relaxation time spectrum; centrifuging the experimental shale sample after completely saturating the oil, then performing nuclear magnetic resonance analysis, and subtracting the peak area in the obtained relaxation time spectrogram after centrifugation from the peak area in the substrate relaxation time spectrogram to obtain a second T2A relaxation time spectrum; for the first T2Relaxation time spectrum and second T2And dividing the area of the relaxation time spectrogram and calculating a ratio to obtain the oil extraction content in the organic matter and the inorganic matter respectively. The method can obtain the oil-extractable content of organic matters and inorganic matters under different displacement forces, and provides important basis for the exploitation scheme of shale oil.

Description

Method for evaluating oil extraction content in shale organic matter and inorganic matter
Technical Field
The invention relates to the field of petroleum engineering, in particular to a method for evaluating the oil extraction content of shale organic matters and inorganic matters.
Background
With the rapid development and the continuous improvement of science of society, the demand of crude oil is greatly increased, the increase of the recoverable reserves of conventional oil gas is limited, and the potential of unconventional oil gas gradually enters the eye line of people and becomes a new star in oil exploration and development. The exploitation of shale oil and gas has been successful greatly in the united states, which has led to the shale oil and gas revolution, the production of shale oil and gas in the united states has been rapidly increased, the energy market in the united states has also changed greatly, and the global energy pattern has been affected accordingly. The successful recovery of shale oil and gas in the united states provides significant inspiration and experience, and some of the dense and shale oils that were once thought to be of little value to recover are also beginning to be valued.
Shale oil refers to oil stored in organic-rich, predominantly nanoscale pore sizes, shale formations. The shale is not only a hydrocarbon source rock of petroleum, but also a reservoir rock of petroleum, the internal structure of the shale is complex, pore roars are distributed in a multi-scale mode, and the radius of the main roar is in the nanometer level. Shale is rich in organic kerogen, which adsorbs and dissolves a portion of the crude oil, which is more difficult to access than crude oil present in the free state in inorganic matter. Meanwhile, the shale has high organic matter content, and the absorption of soluble crude oil can account for more than half. Therefore, the method has very important significance for developing the shale oil and improving the yield of the shale oil by pertinently researching the absorption of the miscible crude oil in the organic matter. At present, researches on improving the recovery ratio of shale oil are carried out, but only the total recovery ratio is researched, the shale oil exists in inorganic matter and organic matter in shale, the organic matter and the inorganic matter have different interaction with the shale oil, the contribution of crude oil in the organic matter and the inorganic matter to the total oil recovery content cannot be distinguished, and an effective solution cannot be provided for the utilization of the crude oil in the organic matter.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for evaluating the oil extraction content of shale organic matters and inorganic matters. Aiming at the problem that shale oil utilization conditions in organic matters and inorganic matters are not described clearly, the method can divide the dynamic consumption of shale oil in organic matters and inorganic matters, respectively calculate the oil recovery content of organic matters and inorganic matters in shale under stratum conditions, analyze the calculated data, further select the exploitation mode of shale oil in the block and provide important reference basis for shale oil exploitation.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for evaluating the oil extraction content of organic matters and inorganic matters in shale comprises the following steps:
cleaning and drying an experimental shale sample, and then carrying out nuclear magnetic resonance analysis to obtain a substrate relaxation time spectrogram;
performing nuclear magnetic resonance analysis on an experimental shale sample after completely saturating oil to obtain a relaxation time spectrogram after saturating oil, and subtracting the areas of corresponding peaks in the relaxation time spectrogram after saturating oil and a base to obtain a first T2A relaxation time spectrum;
the experimental shale sample after being completely saturated with oilCentrifuging at a set rotation speed, performing nuclear magnetic resonance analysis to obtain a centrifuged relaxation time spectrogram, and subtracting the areas of corresponding peaks in the centrifuged relaxation time spectrogram and the substrate relaxation time spectrogram to obtain a second T2A relaxation time spectrum;
for the first T2Relaxation time spectrum and second T2The peak area of the relaxation time spectrogram is divided by 10ms, and the oil recovery content in the organic matter and the inorganic matter is obtained respectively through calculation.
Preferably, shale cores are rich in organic kerogen, oil molecules will be present in the inorganic and organic pores in a free state when the core is saturated with oil, and in addition, the organic matter will adsorb and dissolve a portion of the crude oil, which is more difficult to access than crude oil in the free state. The first T obtained by NMR analysis is due to the fact that relaxation times of adsorbed and dissolved oil molecules are much shorter than those of free state and the pore diameter of organic pores is much smaller than that of inorganic pores in NMR analysis2Relaxation time spectrum and second T2In the relaxation time spectrogram, 10ms is taken as a boundary line of organic matter and inorganic matter storage spaces, the change of the area of the peak of the relaxation time spectrogram smaller than 10ms represents the variation of simulated oil in the organic matter, the oil recovery content in the organic matter is obtained through calculation according to the change of the area of the peak of the relaxation time spectrogram before and after centrifugation, the change of the area of the peak of the relaxation time spectrogram larger than 10ms represents the variation of the simulated oil in the inorganic matter, and the oil recovery content in the inorganic matter is obtained through calculation according to the change of the area of the peak of the relaxation time spectrogram before and after.
Preferably, at said first T2In the relaxation time spectrogram, the peak area of the relaxation time spectrogram smaller than 10ms is recorded as S1And the peak area of the relaxation time spectrogram with the length of more than 10ms is recorded as S2At said second T2In the relaxation time spectrogram, the peak area of the relaxation time spectrogram smaller than 10ms is recorded as S11And the peak area of the relaxation time spectrogram with the length of more than 10ms is recorded as S21η oil recovery content in organic matter11And the extractable oil content in inorganic matter η21Can be expressed by the following formula:
Figure BDA0002084774390000021
Figure BDA0002084774390000022
in the formula, η11Is the oil-extracting content in the organic matter,
S1is a first T2The peak area of the relaxation time spectrogram of less than 10ms in the relaxation time spectrogram,
S11is a second T2The peak area of the relaxation time spectrogram of less than 10ms in the relaxation time spectrogram,
η21is the content of oil extraction in inorganic substances,
S2is a first T2The peak area of the relaxation time spectrogram of more than 10ms in the relaxation time spectrogram,
S21is a second T2Peak area of relaxation time spectrum of more than 10ms in relaxation time spectrum.
Preferably, the oil is the simulated oil dodecane.
Preferably, the set rotating speed range is 3000-12000 r/min.
Preferably, the time of the centrifugation treatment is 60 min.
Preferably, the process of completely saturating the oil with the experimental shale sample is as follows: cleaning and drying the experimental shale sample, enabling the vacuum degree of the experimental shale sample to reach 0.1Pa by a vacuumizing mode, setting a set saturation pressure for the experimental shale sample, and saturating oil in the experimental shale sample.
Preferably, the saturation pressure is in the range of 10 to 20 MPa.
The invention also discloses application of the method in evaluating the oil extraction content of shale organic matters and inorganic matters.
The invention has the following beneficial effects:
(1) the prior art means can characterize the total amount of mobile fluid in shale, but can not specifically describe the utilization conditions in organic matter and inorganic matter respectivelyT2In the relaxation time spectrogram, the extractable content of organic matters and inorganic matters in the shale can be respectively obtained by simply dividing the area with the boundary of 10ms and calculating the ratio.
(2) The device adopted by the method has a simple structure, does not need complicated chromatographic test and other analytical equipment, and only needs a saturation device, a centrifugal device and nuclear magnetic test equipment.
(3) The method of the invention adopts the nuclear magnetic signal of the alkane in the rock core as the method for measuring the residual alkane amount in the rock core, and the measurement is rapid and accurate.
(4) The method provided by the invention adopts a centrifugal method to simulate a high-pressure displacement process, is quick and convenient, and can obtain the oil-extractable content in organic matters and the oil-extractable content in inorganic matters under different displacement forces through different centrifugal rotating speed settings. Meanwhile, in the centrifugal process, all parts in the rock core are acted by centrifugal force, so that the problem that the rock core cannot reach in the displacement process is avoided, and the obtained data has theoretical guiding significance.
(5) The method can obtain the minimum movable radius of the micropores in the shale besides the oil extraction content in organic matters and inorganic matters, and can provide important parameters and basis for numerical simulation and actual development of oil reservoirs.
Drawings
FIG. 1 is the first T of saturated dodecane in core a2A relaxation time spectrum;
FIG. 2 is a second T of a core a of fully saturated dodecane after centrifugation at different rotational speeds2A relaxation time spectrogram, wherein the centrifugal forces calculated according to the centrifugal rotation speed are respectively as follows: a was 0.179MPa, B was 0.716MPa, C was 1.618MPa, and D was 2.862 MPa.
FIG. 3 is the first T of saturated dodecane in core b2A relaxation time spectrum;
FIG. 4 is a second T of a core b of fully saturated dodecane after centrifugation at different rotational speeds2A relaxation time spectrum of the sample to be measured,wherein the centrifugal forces calculated according to the centrifugal rotation speed are respectively as follows: a is 0.179MPa, B is 0.716MPa, C is 1.618MPa, D is 2.862 MPa;
FIG. 5 is a second T after centrifugation of core a of fully saturated KCl solution at different rotational speeds2A relaxation time spectrogram, wherein the centrifugal forces calculated according to the centrifugal rotation speed are respectively as follows: a is 0.238MPa, B is 0.950MPa, C is 2.175MPa, and D is 3.801 MPa;
FIG. 6 is the second T after centrifugation of core b of fully saturated KCl solution at different rotational speeds2A relaxation time spectrogram, wherein the centrifugal forces calculated according to the centrifugal rotation speed are respectively as follows: a is 0.238MPa, B is 0.950MPa, C is 2.175MPa, and D is 3.801 MPa;
FIG. 7 is a graph comparing the recoverable and recoverable water content of inorganic material in the core, wherein (A) is a graph comparing core a and (B) is a graph comparing core B;
FIG. 8 is a schematic view of a core saturation apparatus in example 1 of the present invention;
the device comprises a vacuum pump 1, a saturated fluid storage tank 2, a rock core saturation container 3, a constant pressure pump 4, a thermostat 5, a fourth stop valve 6, a fifth stop valve 7, an intermediate container 8, a first three-way joint 301, a first stop valve 101, a second stop valve 102, a third stop valve 103.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
A method for evaluating the oil extraction content of shale organic matters and inorganic matters comprises the following steps:
(1) fully cleaning an experimental shale sample, and drying in an oven;
(2) putting the dried experimental shale sample into a MacroMR nuclear magnetic resonance analysis and imaging system to perform relaxation time spectrum test on the experimental shale sample to obtain a substrate relaxation time spectrum;
(3) putting an experimental shale sample into a core saturation device, vacuumizing the experimental shale sample and the core saturation device by a vacuum pump 1 to ensure that the vacuum degree reaches 0.1Pa, setting the saturation pressure of 10-20MPa, and injecting simulated oil dodecane into the core saturation device;
(4) taking out an experimental shale sample of saturated simulated oil, placing the experimental shale sample into a MacroMR nuclear magnetic resonance analysis and imaging system to perform relaxation time spectrogram test on the experimental shale sample in a completely saturated state, subtracting corresponding peak areas in the obtained relaxation time spectrogram after saturated oil and a substrate relaxation time spectrogram to obtain a first T2A relaxation time spectrum;
(5) putting the test shale sample in a fully saturated oil state into a GL-21M high-speed centrifuge, setting a centrifugal rotating speed of 3000-12000 r/min, centrifuging for 60min, and performing high-speed centrifugation treatment;
(6) taking out the centrifuged experimental shale sample, placing the centrifuged experimental shale sample into a MacroMR nuclear magnetic resonance analysis and imaging system for relaxation time spectrum test, and subtracting corresponding peak areas in the obtained centrifuged relaxation time spectrum and the substrate relaxation time spectrum to obtain a second T2A relaxation time spectrum;
(7) at the first T2In the relaxation time spectrogram, the peak area of the relaxation time spectrogram smaller than 10ms is recorded as S1And the peak area of the relaxation time spectrogram with the length of more than 10ms is recorded as S2At said second T2In the relaxation time spectrogram, the peak area of the relaxation time spectrogram smaller than 10ms is recorded as S11And the peak area of the relaxation time spectrogram with the length of more than 10ms is recorded as S21η oil recovery content in organic matter11And the extractable oil content in inorganic matter η21Can be expressed by the following formula:
Figure BDA0002084774390000051
Figure BDA0002084774390000052
in the formula, η11Is the oil-extracting content in the organic matter,
S1is a first T2The peak area of the relaxation time spectrogram of less than 10ms in the relaxation time spectrogram,
S11is a second T2Less than 10ms in relaxation time spectrumThe peak area of the relaxation time spectrogram,
η21is the content of oil extraction in inorganic substances,
S2is a first T2The peak area of the relaxation time spectrogram of more than 10ms in the relaxation time spectrogram,
S21is a second T2Peak area of relaxation time spectrum of more than 10ms in relaxation time spectrum.
(8) Sequentially increasing the centrifugal rotation speed, and repeating the steps (5) to (6) to obtain the T of the experimental shale sample under different centrifugal forces2And (3) obtaining the oil-extractable content in the organic matter and the oil-extractable content in the inorganic matter under different centrifugal forces through the formula (1) and the formula (2) by the relaxation time spectrogram.
The core of the shale can be regarded as a combination body consisting of inorganic substances and organic substances, in the process of vacuumizing and saturation, when oil and water are in inorganic micropores, the direction of capillary force is consistent with the flowing direction, the capillary force is self-absorption power, and the oil and the water can enter the inorganic micropores in a self-absorption mode. In the organic micropores, the flowing direction of oil is consistent with the direction of capillary force, and the oil can enter the organic micropores by self-absorption, while the flowing direction of water is opposite to the capillary force, so that the water cannot enter the organic micropores. Therefore, when the oil is saturated, the oil can enter organic matters in an adsorption mutual soluble state and can enter micropores of inorganic matters and organic matters in a free state. The oil in the organic matters which adsorbs the mutual soluble state is difficult to flow, and the oil in the inorganic and organic micropores can flow out only by overcoming the capillary force. When water is saturated, water can only enter the inorganic micropores, and the water in the inorganic micropores can flow out only by overcoming the capillary force.
According to equation (3) for capillary force, capillary force is not only related to the radius of the capillary, but also to the properties of the fluid. When the radius r of the capillary tube is fixed, the capillary tube force P of water or oil can be respectively calculated for two different fluids of water or oilc waterCapillary force P of the oilc oil. When water in inorganic pores is given a little more than Pc waterThe driving force of (3) is that all water in the inorganic pore capillary with the radius r flows out. Also, when inorganicOil in the mesopores to be slightly larger than Pc oilWhen the driving force is (3), all the oil in the inorganic pore capillary having a radius of r flows out.
Figure BDA0002084774390000053
In the formula, PcIs the capillary force; r is the capillary radius, σ is the interfacial tension of the fluid and air, and θ is the contact angle of the fluid and the capillary wall;
the actual core has strong heterogeneity, the radius of the capillary is changed, and in combination with the process of taking centrifugal force as driving force, we deform the formula (3), as shown in the formula (4):
Figure BDA0002084774390000061
during centrifugation, when P iscRadius is greater than r when equal to centrifugal forcepcCan flow out of the capillary tube, so we define rpcAs a centrifugal force PcThe smallest radius of mobility of the fluid in the porous medium.
In the formula (4), r is r for oilpc oilThe meaning of is represented in PcRadius of greater than r under centrifugal forcepc oilThe oil in the hole can flow out completely; for water, rpc waterThe meaning of is represented in PcRadius of greater than r under centrifugal forcepc waterAll water in the holes can flow out, then, when r ispc＝rpc oil＝rpc waterWhen the representative radius is larger than rpcThe water or oil in the hole can flow out, and the volume of the water or oil flowing out is equal, namely the water and oil are extracted in equal amount. Meanwhile, under the vacuum condition, the gas-liquid interface of oil or water does not exist in the saturation process of the oil and the water, the oil or the water is slowly spread and enters pores, and the oil and the water can be considered to be fully saturated into all communicated capillary tubes in the rock core, namely the volume of the oil and the water saturated into the inorganic substance is the same. Therefore, when rpc＝rpc oil＝rpc waterThe content of water flowing out of the inorganic pores is equal to that of oil flowing out of the inorganic pores, that is, the content of recoverable water in the inorganic pores is equal to that of recoverable oil in the inorganic pores. Then the content of recoverable water in the inorganic matter is used as rpc waterPlotting and the amount of recoverable oil in inorganic matter versus rpc oilPlotted, the curves of the two figures should coincide. Due to the presence of shale oil in organic and inorganic matter in shale, according to the prior art, by nuclear magnetic T2The total amount of oil recovery in inorganic substances and organic substances in the shale can be measured through the peak area change of the spectrogram, so that the oil recovery content in the organic substances can be accurately calculated through the difference between the total amount of oil recovery in the inorganic substances and the organic substances and the oil recovery content in the inorganic substances.
The method of the invention is a limit for dividing organic matters and inorganic matters by 10ms in a nuclear magnetic spectrum, which is established on the basis of analyzing a large amount of experimental data, and the feasibility of the dividing method is proved by the following examples 1, 2 and verification examples.
Example 1
Selecting a washed oil and dried shale core a from a 7-section long section in the south of the jaw, wherein the length is 5.236cm, the diameter is 2.47cm, cleaning and drying the rock, putting the dried core into a MacroMR nuclear magnetic resonance analysis and imaging system to perform nuclear magnetic test on the shale core to obtain a substrate T2A relaxation time spectrogram curve; putting the core into a core saturation device shown in fig. 8, opening a first stop valve 101 and a second stop valve 102, vacuumizing a core and core saturation container 3 through a vacuum pump 1 to enable the vacuum degree to reach 0.1Pa, and closing the first stop valve 101 and the second stop valve 102; opening a first stop valve 101 and a third stop valve 103, injecting simulated oil dodecane into the rock core saturation container 3, closing the first stop valve 101 and the third stop valve 103, injecting simulated oil into the rock core saturation container 3 through a constant pressure pump 4, setting the pressure of the constant pressure pump 4 to be 16MPa, and opening a fourth stop valve 6 and a fifth stop valve 7 to saturate the rock core until the pumping amount V of the constant pressure pump 4 is reached0The fourth stop valve 6 and the fifth stop valve 7 are closed when the change is not caused; taking out the rock core and putting the rock core into a MacroMR nuclear magnetic resonance analysis and imaging systemTesting the shale rock core a in a fully saturated oil state, subtracting corresponding peak areas in the obtained relaxation time spectrogram after saturated oil and the base relaxation time spectrogram to obtain a first T2Relaxation time spectra, as shown in FIG. 1, at a first T2The relaxation time spectrogram is defined by 10ms, and when the relaxation time is less than 10ms, the peak area of the spectrogram represents the internal oil storage amount of the organic matter and is recorded as S15235.357, when the relaxation time is more than 10ms, the peak area of the spectrogram is the internal oil storage amount of the inorganic substance and is recorded as S2＝8876.335。
And putting the core a into a GL-21M high-speed centrifuge, setting the rotating speed of the centrifuge to be 3000 r/min, and performing a centrifugation experiment, wherein the centrifugation time is set to be 60min in order to ensure that the core a is sufficiently centrifuged. Taking out the rock core A, placing the rock core A into a MacroMR nuclear magnetic resonance analysis and imaging system to perform relaxation time spectrogram test on the centrifuged shale a, subtracting corresponding peak areas in the obtained centrifuged relaxation time spectrogram and a substrate relaxation time spectrogram to obtain a second T2The relaxation time spectrogram, as shown in fig. 2(a), when the relaxation time is less than 10ms, the peak area of the spectrogram is the residual amount of the oil in the organic matter after centrifugation and is recorded as S115219.301, the simulated oil yield is the difference between peak areas of the two spectrograms, the calculation is carried out by the formula (1), and the content of the organic matter capable of producing oil is
Figure BDA0002084774390000071
When the relaxation time is more than 10ms, the peak area of the spectrogram is the residual amount of inorganic internal oil after centrifugation and is recorded as S218053.590, the yield is the difference between the peak areas of the two spectrograms, and the content of oil extracted in inorganic substances is
Figure BDA0002084774390000072
The centrifugal force is increased in sequence, the centrifugal force is set to be 6000 r/min, 9000 r/min and 12000 r/min respectively, and the T under different centrifugal forces can be obtained by adopting the same test method2The relaxation time spectrograms are shown in fig. 2(B) - (D), and the same data processing method can be used to obtain the oil recovery content of the core a under different centrifugal forces, as shown in table 1.
TABLE 1 core a oil recovery content in organic and inorganic substances under different centrifugal forces
Figure BDA0002084774390000073
Example 2
Selecting a washed oil and dried shale core b, taking the shale core b from a 7-section long section in the south of the jaw, wherein the length of the shale core b is 5.276cm, the diameter of the shale core b is 2.51cm, putting the core into a MacroMR nuclear magnetic resonance analysis and imaging system, and performing nuclear magnetic test on an unsaturated shale dry sample to obtain a substrate T2A relaxation time spectrogram curve; putting the rock core into a rock core saturation container, opening a first stop valve 101 and a second stop valve 102, vacuumizing the rock core and the rock core saturation container 3 through a vacuum pump 1 to enable the vacuum degree to reach 0.1Pa, and closing the first stop valve 101 and the second stop valve 102; opening a first stop valve 11 and a third stop valve 103, injecting simulated oil into the rock core saturation container 3, closing the first stop valve 101 and the third stop valve 103, injecting the simulated oil into the rock core saturation container 3 through a constant pressure pump 4, setting the pressure of the constant pressure pump 4 to be 16MPa, opening a fourth stop valve 6 and a fifth stop valve 7 to saturate the rock core until the pumping amount V of the constant pressure pump 4 is equal to0The fourth stop valve 6 and the fifth stop valve 7 are closed when the change is not caused; taking out the rock core, placing the rock core into a MacroMR nuclear magnetic resonance analysis and imaging system to test the shale in a completely saturated oil state, subtracting the peak area corresponding to the obtained relaxation time spectrogram and the substrate relaxation time spectrogram to obtain a first T of saturated dodecane2Relaxation time spectrum, as shown in fig. 3.
Taking 10ms as a boundary on a relaxation time spectrogram, and recording the peak area of the spectrogram representing the internal oil storage amount of the organic matter as S when the relaxation time is less than 10ms19431.989, when the relaxation time is more than 10ms, the peak area of the spectrogram is the internal oil storage amount of the inorganic substance and is recorded as S21451.989; putting the core into a GL-21M high-speed centrifuge, setting the centrifugal rotation speed to be 3000 r/min, performing a centrifugal experiment, and setting the centrifugal time to be 60min in order to ensure that the core is sufficiently centrifuged. Taking out the rock core, putting the rock core into a MacroMR nuclear magnetic resonance analysis and imaging system to perform relaxation time spectrogram measurement on the centrifuged shaleSubtracting the peak area corresponding to the obtained relaxation time spectrogram and the substrate relaxation time spectrogram to obtain a centrifuged second T2The relaxation time spectrogram has the result shown in FIG. 4(A), and when the relaxation time is less than 10ms, the peak area of the spectrogram is the residual amount of the interior of the organic matter after centrifugation and is recorded as S119064.887, the yield is the difference between the two curve areas and the recovery is reported as
Figure BDA0002084774390000081
When the relaxation time is more than 10ms, the peak area of the spectrogram is the internal residual amount of the inorganic substance after centrifugation and is recorded as S211187.904, the yield is the difference between the two curve areas and the recovery is reported as
Figure BDA0002084774390000082
The centrifugal force is increased in sequence, the centrifugal force is set to be 6000 r/min, 9000 r/min and 12000 r/min respectively, and the T under different centrifugal forces can be obtained by adopting the same test method2The relaxation time spectra are shown in fig. 4(B) - (D), and the same data processing method can be used to obtain the extractable content of the core B under different centrifugal forces, as shown in table 2.
TABLE 2 core b oil recovery content in organic and inorganic substances under different centrifugal forces
Figure BDA0002084774390000083
Verification example
KCl solution with mass fraction of 8% is selected as contrast fluid, a contrast experiment is carried out in the same saturated shale core, and due to the oleophilic characteristic of organic matter, the KCl solution can only enter inorganic micropores to obtain the recoverable water content in inorganic matter, so that the recoverable water content in the inorganic matter of the shale saturated with simulated oil is along with rpcThe variation curve of (A) and the recoverable water content obtained from shale with 8% KCl solutionpcIf the two curves are basically overlapped, it shows that the contents of oil and water in inorganic substance are identical, so that it can be proved that the difference value of T2Relaxation time spectrumThe accuracy of the division of organic and inorganic matter in 10 ms.
The surface tensions sigma of the simulated oil and the KCl solution are respectively 28.0mN/m and 68.5mN/m, and the contact angles theta of the simulated oil and the KCl solution and the shale are respectively 0 degrees and 55 degrees.
According to the calculation method of the centrifugal gas-oil displacement process in oil layer physics, the centrifugal force P in the centrifugal process is calculated by the following formula:
Figure BDA0002084774390000091
wherein △ rho is the density difference between the fluid and the air, kg/m3The density difference between dodecane and 8% KCl and air is 753kg/m3And 1000kg/m3Omega is the angular velocity of the centrifuge, rad/s, R is the distance from the center of the core to the axis of the centrifuge, 0.078825m, d is the diameter of the core, 0.025m, α is the core inclination angle, 56 degrees;
and then, fully cleaning the centrifuged shale samples in the embodiment 1 and the embodiment 2, putting the shale samples into an oven for drying and weighing, wherein the weight of the dried core dry sample is the same as that of the core dry sample before the experiment. Changing the simulated oil into a KCl solution with the concentration of 8%, performing a KCl solution experiment on the dried rock core with the concentration of 8%, and obtaining the T of the residual KCl solution in the rock cores a and b after centrifugation at different rotating speeds by adopting the same test method2Relaxation time spectra, as shown in fig. 5 and 6. It can be seen that for cores a and b of saturated water, the water peak on the right side of greater than 10ms changes significantly before and after centrifugation, reflecting the change in water content in the inorganic mass. The same data processing procedure was used to obtain the extractable water content of the inorganic material as shown in table 3. It should be noted that, because the shale contains a certain amount of clay, the clay absorbs a certain amount of water, so the peak on the left side of less than 10ms does not represent the peak of water entering the organic matter, and the left side is generally considered as the peak of water absorbed in the clay.
TABLE 3 mined Water content in cores a and b inorganic substances at different centrifugal forces
Figure BDA0002084774390000092
The results of the above tests are plotted to obtain a graph comparing the contents of recoverable dodecane and KCl in the inorganic substances in cores a and b, respectively, as shown in FIG. 7, where the content of recoverable KCl in the inorganic substances is shown to be rpcPlotting the content of recoverable dodecane in inorganic matter versus rpcPlotting the variable curves of the extractable content of dodecane and KCl solutions both very well, thus demonstrating the first T2Relaxation time spectrum and second T2The division and ratio calculation of the peak area larger than 10ms in the relaxation time spectrogram can accurately reflect the oil recovery content in inorganic substances. So can prove at T2The accuracy of dividing organic matters and inorganic matters in 10ms in the relaxation time spectrogram.
The invention combines the nuclear magnetic resonance technology and the centrifugal experiment to obtain the nuclear magnetic resonance T2The method for calculating the oil extraction content of shale oil organic matter and inorganic matter is obtained by dividing the boundary of the organic matter and the inorganic matter on the relaxation time spectrogram, and the accuracy of the method is fully verified through experimental data.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. A method for evaluating the oil extraction content of shale in organic matters and inorganic matters is characterized by comprising the steps of cleaning and drying an experimental shale sample, and then carrying out nuclear magnetic resonance analysis to obtain a substrate relaxation time spectrogram;
performing nuclear magnetic resonance analysis on the fully saturated oil of the experimental shale sample to obtain a relaxation time spectrum after the saturated oilSubtracting the area of the peak in the relaxation time spectrogram after the saturated oil from the area of the peak in the substrate relaxation time spectrogram to obtain a first T2A relaxation time spectrum;
centrifuging the completely saturated oil experiment shale sample at a set rotating speed, performing nuclear magnetic resonance analysis to obtain a centrifuged relaxation time spectrogram, and subtracting the areas of corresponding peaks in the centrifuged relaxation time spectrogram and the substrate relaxation time spectrogram to obtain a second T2A relaxation time spectrum;
for the first T2Relaxation time spectrum and second T2The peak area of the relaxation time spectrogram is divided by 10ms, and the oil recovery content in the organic matter and the inorganic matter is obtained respectively through calculation.
2. The method for evaluating the oil recovery content of shale in organic and inorganic substances as claimed in claim 1, wherein the first T is2Relaxation time spectrum and second T2In the relaxation time spectrogram, 10ms is taken as a boundary line of organic matter and inorganic matter storage spaces, the change of the area of the peak of the relaxation time spectrogram smaller than 10ms represents the variation of simulated oil in the organic matter, the oil recovery content in the organic matter is obtained through calculation according to the change of the area of the peak of the relaxation time spectrogram before and after centrifugation, the change of the area of the peak of the relaxation time spectrogram larger than 10ms represents the variation of the simulated oil in the inorganic matter, and the oil recovery content in the inorganic matter is obtained through calculation according to the change of the area of the peak of the relaxation time spectrogram before and after.
3. The method for evaluating the oil recovery content of shale in organic and inorganic substances as claimed in claim 2, wherein the first T is2In the relaxation time spectrogram, the peak area of the relaxation time spectrogram smaller than 10ms is recorded as S1And the peak area of the relaxation time spectrogram with the length of more than 10ms is recorded as S2At said second T2In the relaxation time spectrogram, the peak area of the relaxation time spectrogram smaller than 10ms is recorded as S11And the peak area of the relaxation time spectrogram with the length of more than 10ms is recorded as S21η oil recovery content in organic matter11And the extractable oil content in inorganic matter η21Can be expressed by the following formula:
Figure FDA0002084774380000011
Figure FDA0002084774380000012
in the formula, η11Is the oil-extracting content in the organic matter,
S1is a first T2The peak area of the relaxation time spectrogram of less than 10ms in the relaxation time spectrogram,
S11is a second T2The peak area of the relaxation time spectrogram of less than 10ms in the relaxation time spectrogram,
η21is the content of oil extraction in inorganic substances,
S2is a first T2The peak area of the relaxation time spectrogram of more than 10ms in the relaxation time spectrogram,
S21is a second T2Peak area of relaxation time spectrum of more than 10ms in relaxation time spectrum.
4. The method for evaluating the oil recovery content of shale in organic and inorganic substances according to claim 1, wherein the oil is simulated oil dodecane.
5. The method for evaluating the oil recovery content of shale in organic matters and inorganic matters as claimed in claim 1, wherein the rotation speed of the centrifugal treatment is in a range of 3000-12000 r/min.
6. The method for evaluating the oil recovery content of shale in organic and inorganic substances according to claim 5, wherein the time of the centrifugal treatment is 60 min.
7. The method for evaluating the oil recovery content of shale in organic and inorganic substances according to claim 1, wherein the process of fully saturating the oil with the experimental shale sample is as follows: cleaning and drying the experimental shale sample, enabling the vacuum degree of the experimental shale sample to reach 0.1Pa by a vacuumizing mode, setting a set saturation pressure for the experimental shale sample, and saturating oil in the experimental shale sample.
8. The method for evaluating the oil recovery content of shale in organic and inorganic substances according to claim 7, wherein the saturation pressure is in a range of 10-20 MPa.
9. Use of the method according to any one of claims 1 to 8 for evaluating the oil recovery content of shale organic and inorganic materials.
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