CN116930244A - Nuclear magnetism graphic plate drawing method for thick oil cracks - Google Patents
Nuclear magnetism graphic plate drawing method for thick oil cracks Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 55
- 230000005311 nuclear magnetism Effects 0.000 title abstract description 20
- 239000011435 rock Substances 0.000 claims abstract description 85
- 239000010426 asphalt Substances 0.000 claims abstract description 47
- 238000011049 filling Methods 0.000 claims abstract description 47
- 238000002474 experimental method Methods 0.000 claims abstract description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 36
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 35
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 claims abstract description 28
- 238000009826 distribution Methods 0.000 claims abstract description 27
- 238000006073 displacement reaction Methods 0.000 claims abstract description 22
- 238000002591 computed tomography Methods 0.000 claims abstract description 21
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims abstract description 12
- 238000005516 engineering process Methods 0.000 claims abstract description 10
- 238000012545 processing Methods 0.000 claims abstract description 8
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical class [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 claims description 32
- 239000011159 matrix material Substances 0.000 claims description 25
- 239000012530 fluid Substances 0.000 claims description 18
- 239000007864 aqueous solution Substances 0.000 claims description 13
- 238000001228 spectrum Methods 0.000 claims description 13
- 238000005481 NMR spectroscopy Methods 0.000 claims description 12
- 239000000243 solution Substances 0.000 claims description 9
- 238000005303 weighing Methods 0.000 claims description 6
- 230000001186 cumulative effect Effects 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 238000009825 accumulation Methods 0.000 claims description 2
- 238000012163 sequencing technique Methods 0.000 claims description 2
- 239000000295 fuel oil Substances 0.000 abstract description 36
- 239000003921 oil Substances 0.000 abstract description 22
- 238000011156 evaluation Methods 0.000 abstract description 6
- 239000011148 porous material Substances 0.000 description 26
- 238000012360 testing method Methods 0.000 description 8
- 239000007788 liquid Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000000903 blocking effect Effects 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 239000010779 crude oil Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000004069 differentiation Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 238000010603 microCT Methods 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000011158 quantitative evaluation Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
- G01N24/081—Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
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Abstract
The application discloses a nuclear magnetic pattern drawing method for thick oil cracks, which comprises the following steps: obtaining a rock sample, and processing the rock sample based on a saturation method to obtain a saturated water rock sample; carrying out a micron CT scanning experiment on a saturated water rock sample to obtain a rock sample crack; performing a hot asphalt-heavy water displacement experiment on the saturated water rock sample, and performing two-dimensional nuclear magnetic scanning on the rock sample after the displacement experiment to obtain two-dimensional nuclear magnetic distribution of asphalt filling cracks; correcting the size of the asphalt filling crack based on the aperture of the rock sample crack; marking the corrected size of the asphalt filling crack in the two-dimensional nuclear magnetic distribution of the asphalt filling crack, and finishing the nuclear magnetic pattern drawing of the thick oil crack. The application combines the micrometer CT, the two-dimensional nuclear magnetism and the hot asphalt-heavy water displacement experiment, solves the problem of size distortion caused by heavy oil nuclear magnetism deviation, acquires the two-dimensional nuclear magnetism distribution of heavy oil filling cracks, and fills the application blank of the two-dimensional nuclear magnetism technology in the evaluation of the cracks of the carbonate heavy oil reservoir.
Description
Technical Field
The application belongs to the technical field of oil reservoir exploration and development, and particularly relates to a nuclear magnetic pattern drawing method for heavy oil cracks.
Background
The ocean oil gas resources are rich, and the carbonate stratum is the main material. The cracks are the main storage space and migration channels of the oil and gas reservoirs, and the clear crack distribution characteristics are the key problems of deep sea carbonate reservoir evaluation. Currently, crack evaluation methods are mainly classified into two categories: 1) Direct observation methods, such as an optical microscope, a scanning electron microscope and the like, wherein the observation result is a two-dimensional image and semi-quantitative; 2) The indirect observation method mainly comprises mercury intrusion, one-dimensional nuclear magnetic resonance (NMR T2), CT scanning and the like, and the test result is a quantitative pore size distribution curve. In the method, only NMR and CT can realize nondestructive testing of samples, but CT test can only be carried out in-house test, and underground test can not be carried out; the one-dimensional nuclear magnetic resonance NMR only has one function of T2, and has no T1 function, so that even if the underground test can be carried out, the two-dimensional nuclear magnetic pattern plate cannot be obtained. .
Currently, two-dimensional nuclear magnetism technology T1-T2 is mature gradually, two-dimensional nuclear magnetism consists of two parts of T2 and T1, T1 is related to fluid properties, and T2 is related to pore diameters. However, the related technology for evaluating the nuclear magnetism of the crack by utilizing the two-dimensional nuclear magnetism is lacking at present, and when the crack is filled with heavy component crude oil, the two-dimensional nuclear magnetism characteristics of the crack are obviously different from those of the light oil reservoir. Therefore, it is highly desirable to provide a nuclear magnetic pattern drawing method for thick oil cracks.
Disclosure of Invention
The application aims to provide a nuclear magnetic pattern drawing method for thick oil cracks, which combines micro CT, two-dimensional nuclear magnetism and hot asphalt-heavy water displacement experiments, avoids using conventional aqueous solution to influence heavy oil nuclear magnetic signal identification, solves the problem of size distortion caused by heavy oil nuclear magnetic offset, obtains the two-dimensional nuclear magnetic T1-T2 distribution of heavy oil filling cracks, fills the application blank of the two-dimensional nuclear magnetic technology in carbonate rock evaluation, and solves the problems in the prior art.
In order to achieve the above purpose, the application provides a nuclear magnetic pattern drawing method for thick oil cracks, which comprises the following steps:
obtaining a rock sample, and processing the rock sample based on a saturation method to obtain a saturated water rock sample;
performing a micron CT scanning experiment on the saturated water rock sample to obtain a rock sample crack;
performing a hot asphalt-heavy water displacement experiment on the saturated water rock sample, and performing two-dimensional nuclear magnetic scanning on the rock sample after the displacement experiment to obtain two-dimensional nuclear magnetic distribution of asphalt filling cracks;
correcting the size of the asphalt filling crack based on the aperture of the rock sample crack;
marking the corrected size of the asphalt filling crack in the two-dimensional nuclear magnetic distribution of the asphalt filling crack, and finishing the nuclear magnetic pattern drawing of the thick oil crack.
Optionally, the process of obtaining a rock sample comprises: and selecting a large-size full-diameter sample based on the fractured carbonate rock to obtain a rock sample.
Optionally, the process of obtaining a saturated water rock sample comprises: drying, weighing and measuring the rock sample to obtain first mass and total volume of the rock sample; and vacuumizing the dried rock sample, and pressurizing a saturated potassium iodide heavy water solution for 24 hours to obtain a saturated water rock sample.
Optionally, the process of obtaining a rock sample fracture comprises: performing a micrometer CT scanning experiment on the saturated water rock sample to obtain a plurality of hole seams; and distinguishing the hole and the slit based on a digital image processing technology to obtain a matrix hole and a slit.
Optionally, the process of performing a hot bitumen-heavy water displacement experiment on the saturated water rock sample comprises: placing the saturated water rock sample into a clamp holder, adding confining pressure for fixation, and injecting hot asphalt flooding saturated potassium iodide heavy aqueous solution into the saturated water rock sample; and stopping the displacement experiment when the displaced saturated potassium iodide heavy aqueous solution reaches the volume of the crack, otherwise, continuing.
Optionally, the acquiring process of the fracture volume includes: the mass of the saturated water rock sample is second mass, and the fluid mass of the saturated potassium iodide heavy water solution in the rock sample is obtained based on the first mass, the second mass and the crack content of the rock sample; based on the ratio of the fluid mass to the fluid density, a fracture volume is obtained.
Optionally, the acquiring process of the crack content includes: obtaining a total porosity of the rock sample based on the first mass, the second mass, the total volume of the rock sample, and the fluid density of the saturated potassium iodide heavy aqueous solution; acquiring the porosity and CT porosity of a matrix hole, and acquiring crack porosity based on the porosity and CT porosity of the matrix hole; based on the ratio of the fracture porosity to the total porosity, the fracture content is obtained.
Optionally, the process of performing a two-dimensional nuclear magnetic scanning experiment on the rock sample after the displacement experiment comprises: cooling the saturated water rock sample after the displacement experiment, and then performing two-dimensional nuclear magnetic resonance scanning to obtain two-dimensional nuclear magnetic distribution of asphalt filling cracks; the two-dimensional nuclear magnetic distribution of the asphalt filled fracture comprises a fracture longitudinal relaxation spectrum and a fracture transverse relaxation spectrum.
Optionally, before correcting the size of the asphalt filling crack, the method further comprises: obtaining the mass of the actually driven fluid based on the volume of the saturated potassium iodide heavy aqueous solution actually driven and the corresponding fluid density; and acquiring a mass difference value of the first mass and the second mass of the rock sample, and acquiring the asphalt filling crack content based on the ratio of the mass of the fluid actually driven to the mass difference value.
Optionally, the process of correcting the size of the asphalt filled fracture includes: sequencing the crack apertures obtained by the micron CT scanning experiment in order from small to large, and drawing a crack aperture accumulation curve; normalizing the cumulative curve until the maximum value of the crack content is reached; and (3) obtaining a difference value between the crack content and the asphalt filling crack content, marking a point with an ordinate of an accumulated curve equal to the difference value as a first target point, drawing a horizontal line along the first target point and comparing the accumulated curve with a second target point, drawing a vertical line along the second target point and comparing the ordinate of the accumulated curve with a third target point, wherein the aperture size corresponding to the third target point is the asphalt filling crack size.
The application has the technical effects that:
the application combines the micrometer CT, the two-dimensional nuclear magnetism and the hot asphalt-heavy water displacement experiment, avoids using the conventional aqueous solution to influence the heavy oil nuclear magnetism signal identification, solves the problem of size distortion caused by heavy oil nuclear magnetism deviation, obtains the two-dimensional nuclear magnetism T1-T2 distribution of heavy oil filling cracks, fills the application blank of the two-dimensional nuclear magnetism technology in the evaluation of the carbonate heavy oil reservoir cracks, and has scientificity and universality.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is a schematic diagram of a CT porosity versus total porosity model in an embodiment of the present application;
FIG. 2 is a flow chart of a method for drawing a nuclear magnetic pattern of a thick oil fracture in an embodiment of the application.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
It should be noted that the steps illustrated in the flowcharts of the figures may be performed in a computer system such as a set of computer executable instructions, and that although a logical order is illustrated in the flowcharts, in some cases the steps illustrated or described may be performed in an order other than that illustrated herein.
Example 1
As shown in fig. 1, in this embodiment, a method for drawing a nuclear magnetic pattern of a thick oil fracture is provided, which includes the following steps:
s1: saturation method for calculating total porosity t 。
S11: and (5) preparing a rock sample. Preparation of large-size sample (5-7 cm in length, 6cm in diameter or 10cm in diameter) from fractured carbonate rock
S12: and (5) drying the rock sample. Drying and standing the rock sample at 200 ℃ to room temperature for standby, and weighing the weight m of the dried rock sample d Measuring total volume V b 。
S13: rock sample saturated potassium iodide heavy water solution (KI-D2O). Vacuum pumping the dried sample, pressurizing (32 MPa) saturated KI-D2O (2000-5000 ppm) for 24 hours, and measuring the mass m of the saturated rock sample s . The heavy water did not show a nuclear magnetic signal in the nuclear magnetic experiments according to this example.
S14: calculating the total porosity t 。
Ø t =((m s -m d )/ρ)/V b (equation 1)
Where ρ is the fluid density.
S2：KI-D 2 O-CT um Scanning to calculate crack content S f And dimension r f 。
S21: saturated KI full diameter sample micrometer CT scanning experiment (KI-D 2 O-CT um ) Digital image processing techniques distinguish apertures. Calculating the pore diameter r of the matrix pore m (matrix pore 2) and crack pore diameter r f (crack 3).
In fig. 1 "matrix pore 1" represents a matrix pore lost below the resolution of the CT scanner, with a porosity of one 1 The method comprises the steps of carrying out a first treatment on the surface of the "matrix pore 2" represents the matrix porosity identified by CT scan, which porosity is equal to 2 The method comprises the steps of carrying out a first treatment on the surface of the "crack 3" represents all cracks identified by CT scan, and is otherwise evident 3 =Ø f 。
The matrix pores below the resolution of the CT instrument are regarded as skeletons, affected by the resolution, so the S21 result is not a true complete pore distribution of the rock sample, belonging to pseudo-pore distribution. According to the method, the porosity is calculated by a saturated fluid method, so that the problem of inaccurate calculation of the crack content caused by the loss of the porosity in CT scanning is solved, and meanwhile, the problem of rapid increase of experimental cost caused by excessive invalid CT scanning is avoided.
S22: calculation of crack porosity f 。
Ø CT =Ø 2 +Ø 3 （Ø CT <Ø t Formula 2
Ø f =Ø 3 (equation 3)
Wherein, is a cylinder CT Is CT porosity.
S23: calculating the crack content S f 。
S f =Ø 3 /Ø t =Ø f /Ø t (equation 4)
S24: calculating the aperture r of the crack f And drawing a bar graph.
S25: calculating the fracture volume V f 。
m f =(m s -m d )*(1-S f ) (equation 5)
V f =m f Rho (equation 6)
Wherein m is f Is V (V) f Corresponding to the fluid mass.
S3: hot pitch flooding KI-D2O two-dimensional nuclear magnetic resonance experiments.
S31: and placing the saturated water rock sample into a clamp holder and applying confining pressure for fixation.
S32: experiments were performed with bitumen representing heavy oil, with heat-injected bitumen (80 ℃) driving KI-D2O.
S33: the water yield measuring method.
A measuring cylinder is placed at the outlet end of the holder to collect the drained water. A gas pipe is additionally arranged at the position, close to the core, of the outlet end of the core holder, hot air is blown in at regular time, firstly, asphalt condensation is prevented from blocking the gas outlet, and secondly, water drops are prevented from being stuck to the pipe wall of the outlet end to influence liquid outlet metering.
S34: two-dimensional nuclear magnetic resonance test for obtaining heavy oil filling crack distribution T fH 。
When the volume of the driven water (the liquid outlet amount) is equal to the volume of the cracks, the hot asphalt fills all the cracks, and only the cracks have asphalt nuclear magnetic signals. Cooling the rock sample to room temperature to test a two-dimensional nuclear magnetic T1-T2 spectrum to obtain a two-dimensional nuclear magnetic spectrum T of a crack under the state of filling heavy oil fH ，T fH Reflecting the two-dimensional nuclear magnetic distribution of heavy oil filling cracks. T (T) fH Comprising a longitudinal relaxation spectrum T1 of a crack under the state of filling heavy oil fH And the crack is transverse under the state of filling heavy oilRelaxation spectrum T2 fH Two parts.
S4: hot asphalt-heavy water displacement experiment end conditions.
S41: under ideal conditions, the liquid output V reaches V f And stopping the displacement experiment, otherwise, continuing to inject the hot asphalt.
S42: : under practical conditions, hot asphalt can enter large-size cracks, but can not enter all cracks due to the influence of viscosity, so that the displacement experiment is stopped when water is not discharged.
S43: according to the actual water yield V fH Calculating the asphalt filling crack content S fH 。
S fH =1-m fH /(m s -m d )=1-ρ*V fH /(m s -m d ) (equation 7)
S5: correcting asphalt filling crack size r fH 。
S51: calculating asphalt filling crack size r based on combined S24 saturated sample CT scanning result fH 。
S52: drawing r in order of small to large size f Cumulative curve, normalization processing of cumulative curve to maximum value S f 。
S53: obtaining crack content S f With asphalt filling crack content S fH Is equal to the difference value, the ordinate of the cumulative curve is equal to the point mark a of the difference value.
S54: and drawing a horizontal line along the A and intersecting the accumulated curve at the point B, and drawing a vertical line along the point B and intersecting the horizontal coordinate at the point C.
S55: the pore size corresponding to the C point is the cut-off pore diameter r of heavy oil filling cracks fH 。
The size of the crack is the inherent property of the rock and is not influenced by oil products, but the viscosity of the oil products can influence the filling range of the crack, so that r cannot be directly used f Representing the size of the heavy oil filling crack, the actual filling crack size r needs to be calculated fH . The pore nuclear magnetic signals are also affected by the properties of oil products, and compared with light oil, the nuclear magnetic spectrum of heavy oil can be left biased, so that the nuclear magnetic distribution of heavy oil filling cracks needs to be calibrated independently.
S6: and drawing a two-dimensional nuclear magnetic spectrum of the heavy oil filling fracture.
S61: step S34 is actual asphalt filled fracture nuclear magnetic spectrum.
S62: two-dimensional nuclear magnetic spectrum abscissa T2 of heavy oil filled fracture fH Dimension r of the position mark fH 。
S7: and (5) ending.
In the embodiment, the full-diameter sample micrometer CT scanning and heavy oil displacement experiment is utilized to calibrate the distribution of two-dimensional nuclear magnetism (T1-T2) of cracks, and the result is suitable for evaluating the crack development characteristics of the heavy oil reservoir of the fractured carbonate rock. The method comprises the following steps: 1) Rock sample saturated potassium iodide heavy aqueous solution (KI-D2O); 2) Measuring the total porosity by a weighing method; 3) Micron CT scan (KI-D) 2 O-CT um ) Quantifying the crack content and the pore diameter; 4) Performing a hot asphalt flooding KI-D2O two-dimensional nuclear magnetic experiment; 5) Correcting the heavy oil filling crack content; 6) And drawing a crack two-dimensional nuclear magnetism T1-T2 distribution chart, and correcting the aperture range of heavy oil filling.
CT scanning is the basis of quantitative evaluation of cracks, and in the embodiment, nuclear magnetic crack calibration is carried out on the basis of CT hole-crack distribution. Potassium iodide has the effect of enhancing CT signals, and does not affect NMR signal accuracy. The use of potassium iodide solution is critical to achieving accurate identification of matrix pores and cracks using micro-CT. Potassium iodide has the effect of enhancing CT signal intensity without affecting NMR testing. The CT image becomes bright after the potassium iodide solution is saturated in the pores, so that CT differentiation of the pores, cracks and skeleton particles of the rock sample matrix is increased. The application performs CT scanning on a saturated potassium iodide sample, and mainly plays 2 roles. 1) The large amount of cracks develop to cause the poor degree of discrimination of the rock sample hole seams, and the application uses potassium iodide to facilitate discrimination of 'matrix holes 2' and 'cracks'. 2) The increase in CT signal intensity facilitates accurate extraction of the "matrix pore 2" under resolution permitting conditions, thereby defining the "matrix pore 1" and "matrix pore 2" boundaries. The existing method for distinguishing the matrix holes from the non-matrix holes by using the CT image is many, and the embodiment adopts the existing artificial intelligent image processing technology to extract the matrix holes and cracks, so that the details of CT identification classification technology are not discussed deeply.
In the embodiment, the full-diameter sample is used for carrying out experiments instead of the traditional centimeter-level plunger, so that the problem of crack loss caused by strong heterogeneity is solved. Meanwhile, due to the influence of the core size and the instrument resolution, CT can only identify holes and slits higher than the instrument resolution (about 30-50 um), so that a large number of matrix pores can be ignored, and the defect can be corrected by calculating the porosity through a saturated weighing experiment in the embodiment.
The gas drive experiment is used for realizing physical state division of matrix holes and cracks. The fracture belongs to a dominant seepage channel, gas can preferentially pass through the fracture, and therefore water in the fracture can be discharged out of the rock before the matrix pores. It typically takes more than 2 hours to complete a CT scan of a full diameter sample, and during this period of time the gas drive experiment may have been completed, so a continuous CT cycle scan is impractical. In the embodiment, the crack content is quantified through CT scanning and weighing experiments of saturated samples, so that excessive invalid CT scanning is avoided.
Asphalt is high in viscosity and is difficult to press into rock pores in a saturated mode, and the embodiment adopts a hot asphalt flooding mode to obtain the heavy oil filling crack quantity, which is obviously different from the gas flooding mode to obtain the crack distribution in a light oil filling state. Asphalt flooding also cannot ensure that asphalt enters all cracks, so the experiment is ended when water is no longer discharged, and the heavy oil filling crack amount is corrected through water yield.
In the embodiment, KI-D2O is used for replacing a conventional aqueous solution, so that CT signals are enhanced to facilitate accurate extraction of crack information, and no visible nuclear magnetic signals exist in the experiment of the solution, and the aqueous solution can be prevented from influencing the identification of heavy oil nuclear magnetic signals.
A gas pipe is additionally arranged at the position, close to the core, of the outlet end of the core holder, hot air is blown in at regular time, firstly, asphalt condensation is prevented from blocking the gas outlet, and secondly, water drops are prevented from being stuck to the pipe wall of the outlet end to influence liquid outlet metering.
This embodiment is applicable to heavy oil layers. The size of the crack is the inherent property of the rock and is not influenced by oil products, but the oil products influence the filling range of the crack, so that the r is calculated additionally fH . The nuclear magnetic signals of the pores are affected by oil products, and compared with light oil, the nuclear magnetic spectrum of heavy oil is left biased, so that the nuclear magnetic distribution of heavy oil filling cracks needs to be calibrated independently.
Aiming at the problem that the identification of the carbonate fracture is difficult due to the magnetic migration of the heavy oil core, the embodiment provides a method for calibrating the two-dimensional nuclear magnetism T1-T2 distribution of the carbonate heavy oil reservoir fracture. By adopting a hot asphalt displacement KI solution nuclear magnetic resonance experiment, a crack two-dimensional nuclear magnetic T1-T2 distribution plate is drawn, the quantitative relation between heavy oil nuclear magnetic and the size is defined, the application blank of the two-dimensional nuclear magnetic technology in the crack evaluation of the carbonate heavy oil reservoir is filled, and the method has scientificity and universality.
The present application is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present application are intended to be included in the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims (10)
1. The nuclear magnetic pattern drawing method for the thick oil cracks is characterized by comprising the following steps of:
obtaining a rock sample, and processing the rock sample based on a saturation method to obtain a saturated water rock sample;
performing a micron CT scanning experiment on the saturated water rock sample to obtain a rock sample crack;
performing a hot asphalt-heavy water displacement experiment on the saturated water rock sample, and performing two-dimensional nuclear magnetic scanning on the rock sample after the displacement experiment to obtain two-dimensional nuclear magnetic distribution of asphalt filling cracks;
correcting the size of the asphalt filling crack based on the aperture of the rock sample crack;
marking the corrected size of the asphalt filling crack in the two-dimensional nuclear magnetic distribution of the asphalt filling crack, and finishing the nuclear magnetic pattern drawing of the thick oil crack.
2. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 1, wherein,
the process of obtaining a rock sample includes: and selecting a large-size full-diameter sample based on the fractured carbonate rock to obtain a rock sample.
3. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 1, wherein,
the process of obtaining a saturated water rock sample comprises: drying, weighing and measuring the rock sample to obtain first mass and total volume of the rock sample; and vacuumizing the dried rock sample, and pressurizing a saturated potassium iodide heavy water solution for 24 hours to obtain a saturated water rock sample.
4. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 1, wherein,
the process of obtaining a rock sample fracture includes: performing a micrometer CT scanning experiment on the saturated water rock sample to obtain a plurality of hole seams; and distinguishing the hole and the slit based on a digital image processing technology to obtain a matrix hole and a slit.
5. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 1, wherein,
the process of performing a hot bitumen-heavy water displacement experiment on the saturated water rock sample comprises: placing the saturated water rock sample into a clamp holder, adding confining pressure for fixation, and injecting hot asphalt flooding saturated potassium iodide heavy aqueous solution into the saturated water rock sample; and stopping the displacement experiment when the displaced saturated potassium iodide heavy aqueous solution reaches the volume of the crack, otherwise, continuing.
6. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 5, wherein,
the fracture volume acquisition process comprises the following steps: the mass of the saturated water rock sample is second mass, and the fluid mass of the saturated potassium iodide heavy water solution in the rock sample is obtained based on the first mass, the second mass and the crack content of the rock sample; based on the ratio of the fluid mass to the fluid density, a fracture volume is obtained.
7. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 6, wherein,
the acquisition process of the crack content comprises the following steps: obtaining a total porosity of the rock sample based on the first mass, the second mass, the total volume of the rock sample, and the fluid density of the saturated potassium iodide heavy aqueous solution; acquiring the porosity and CT porosity of a matrix hole, and acquiring crack porosity based on the porosity and CT porosity of the matrix hole; based on the ratio of the fracture porosity to the total porosity, the fracture content is obtained.
8. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 1, wherein,
the two-dimensional nuclear magnetic scanning experiment process for the rock sample after the displacement experiment comprises the following steps: cooling the saturated water rock sample after the displacement experiment, and then performing two-dimensional nuclear magnetic resonance scanning to obtain two-dimensional nuclear magnetic distribution of asphalt filling cracks; the two-dimensional nuclear magnetic distribution of the asphalt filled fracture comprises a fracture longitudinal relaxation spectrum and a fracture transverse relaxation spectrum.
9. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 1, wherein,
before correcting the size of the asphalt filling crack, the method further comprises the following steps: obtaining the mass of the actually driven fluid based on the volume of the saturated potassium iodide heavy aqueous solution actually driven and the corresponding fluid density; and acquiring a mass difference value of the first mass and the second mass of the rock sample, and acquiring the asphalt filling crack content based on the ratio of the mass of the fluid actually driven to the mass difference value.
10. The method for drawing the nuclear magnetic pattern of the thick oil fracture according to claim 9, wherein,
the process of correcting the size of the asphalt filled fracture comprises the following steps: sequencing the crack apertures obtained by the micron CT scanning experiment in order from small to large, and drawing a crack aperture accumulation curve; normalizing the cumulative curve until the maximum value of the crack content is reached; and (3) obtaining a difference value between the crack content and the asphalt filling crack content, marking a point with an ordinate of an accumulated curve equal to the difference value as a first target point, drawing a horizontal line along the first target point and comparing the accumulated curve with a second target point, drawing a vertical line along the second target point and comparing the ordinate of the accumulated curve with a third target point, wherein the aperture size corresponding to the third target point is the asphalt filling crack size.
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