A shale oil reservoir wettability judgment method and device

Abstract

The embodiment of the present application provides a shale oil reservoir wettability judgment method and device, and belongs to the technical field of oil and gas development. The shale oil reservoir wettability judgment method comprises the following steps: obtaining the intake rate and / or intake fluid saturation of a rock sample when the rock sample spontaneously absorbs fluid; judging the average wettability of the shale oil reservoir according to the intake rate and / or intake fluid saturation; judging the hydrophilic and oleophilic ability of the shale oil reservoir under the same pore radius according to the signal intensity increment S1 of the rock sample when the water-saturated state is compared with the dry state and the signal intensity increment S2 of the rock sample when the oil-saturated state is compared with the dry state; and judging the wettability of the shale oil reservoir according to the average wettability of the shale oil reservoir and the hydrophilic and oleophilic ability of the shale oil reservoir under different pore radii. The embodiment of the present application comprehensively judges the wettability of the shale oil reservoir by combining the average wettability and the hydrophilic and oleophilic ability of the shale oil reservoir under different pore radii, can reflect the wetting characteristics of oil and water in the shale oil reservoir from multiple dimensions, and makes the evaluation more comprehensive.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, specifically to a method and apparatus for determining the wettability of shale oil reservoirs, as well as a method, processor, and storage medium for optimizing the amount of fluid injected into the ground and the well shut-in time in shale oil development. Background Technology

[0002] In recent years, unconventional oil and gas resources, mainly shale oil and shale gas, have gradually become the main force driving oil and gas production growth both domestically and internationally. However, compared with conventional oil reservoirs, shale oil reservoirs have poorer physical properties, and conventional water injection for energy replenishment is no longer suitable for the exploitation of such reservoirs.

[0003] Currently, the main development method for shale oil is through volumetric fracturing of horizontal wells. The fluid injected into the well not only creates fractures but also serves to replenish energy through infiltration. Excessive fluid injection leads to longer oil breakthrough periods, larger flowback volumes, and higher water cuts after normal production, wasting water resources and increasing operating costs. Insufficient fluid injection may result in insignificant energy replenishment. Furthermore, prolonged well shut-in time can cause excessive pressure diffusion, affecting the contribution of new wells to oil production that year. Conversely, insufficient well shut-in time results in inadequate infiltration and replacement of the shale oil reservoir, impacting energy replenishment and displacement. Therefore, a reasonable fluid injection volume and shut-in time are crucial factors influencing the effectiveness of shale oil development.

[0004] The current challenges in optimizing the amount of fluid injected and the well shut-in time in shale oil horizontal well development mainly stem from the inability to accurately characterize the wettability of shale oil reservoirs.

[0005] Existing indoor evaluation methods for shale oil reservoir wettability have three main problems:

[0006] Firstly, domestic and international wettability evaluation standards mainly target medium- to high-permeability shale oil reservoirs, lacking a unified standard for wettability evaluation of tight shale oil reservoirs. Currently, there are two industry-standard quantitative wettability evaluation methods: the self-absorption method (Amott method) (Amott, 1959) and the centrifugal method (USBM method) (Donaldson et al, 1969). The self-absorption method results in low self-absorption of shale oil, making measurement difficult; furthermore, displacement is challenging, with oil-water and water-oil displacement processes being time-consuming and unlikely to achieve the required bound water state, leading to large errors in test results and a lack of consistency. The centrifugal method, due to centrifugal force limitations, is even less suitable for tight, low-permeability shale oil reservoirs.

[0007] Secondly, due to the complexity of shale oil rock minerals, the rock surface has mixed wettability characteristics, making it difficult to use the conventional wettability classification method of strong oleophilic, oleophilic, weak oleophilic, neutral, weak hydrophilic, hydrophilic, and strong hydrophilic.

[0008] Third, the shale oil production mechanism is generally considered to be the displacement of oil from small pores to large pores through adsorption, and then the oil flows into the artificial fracture system under the action of displacement pressure differential and is extracted. Different pore sizes play different roles in the shale oil production process; therefore, quantitatively evaluating the differences in wettability at different pore sizes is of great significance. Summary of the Invention

[0009] The purpose of this invention is to provide a method and apparatus for judging the wettability of shale oil reservoirs. This invention can optimize the amount of fluid injected into the ground and the well shut-in time in shale oil development.

[0010] To achieve the above objectives, embodiments of the present invention provide a method for determining the wettability of shale oil reservoirs, the method comprising:

[0011] Obtain the aspiration rate and / or aspiration fluid saturation when a rock sample spontaneously aspirates fluid, wherein the aspiration rate includes water absorption rate and oil absorption rate, and the aspiration fluid saturation includes water absorption saturation and oil absorption saturation;

[0012] The average wettability of the shale oil reservoir is determined based on the intake rate and / or the saturation of the intake fluid.

[0013] The first correspondence between pore radius and signal intensity of the rock sample in a dry state, the second correspondence between pore radius and signal intensity in a saturated water state, and the third correspondence between pore radius and signal intensity in a saturated oil state are obtained.

[0014] Based on the first, second, and third correspondences, the signal intensity increment S1 of the rock sample in the saturated water state compared with the dry state and the signal intensity increment S2 of the rock sample in the saturated oil state compared with the dry state under the same pore radius are compared to determine the hydrophilicity and oleophilicity of the shale oil reservoir under that pore radius.

[0015] The wettability of shale oil reservoirs is determined based on the average wettability of the reservoirs and the hydrophilicity and oleophilicity of the reservoirs under different pore radii.

[0016] Optionally, obtaining the intake rate and / or intake fluid saturation when the rock sample spontaneously absorbs fluid, and determining the average wettability of the shale oil reservoir based on the intake rate and / or intake fluid saturation, includes:

[0017] The weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, the pore volume of the rock sample after it absorbs water, the weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, and the pore volume of the rock sample after it absorbs oil are obtained.

[0018] Calculate the water saturation of the rock sample in its saturated state based on the weight of the rock sample before self-absorption of water, the weight of the rock sample in its saturated state with water, and the pore volume of the rock sample after self-absorption of water.

[0019] The oil saturation of the rock sample in its saturated state is calculated based on the weight of the rock sample before self-absorption of oil, the weight of the rock sample in its saturated state with oil, and the pore volume of the rock sample after self-absorption of oil.

[0020] The average wettability of the shale oil reservoir is determined based on the water saturation and oil saturation of the rock samples.

[0021] Optionally, determining the average wettability of the shale oil reservoir based on the water saturation and oil saturation of the rock sample includes:

[0022] The difference between the water saturation and oil saturation of the rock sample is used as the oil and water saturation index I1 of the shale oil reservoir.

[0023] When -a < I1 ≤ a, the average wettability of the shale oil reservoir is mixed wettability, where 0 < a < 0.5;

[0024] When -1 < I1 ≤ -a, the average wettability of the shale oil reservoir is oleophilic;

[0025] When a < I1 ≤ 1, the average wettability of the shale oil reservoir is hydrophilic.

[0026] Optionally, when -1 < I1 ≤ -a, if -1.0 < I1 ≤ -0.5, the average wettability of the shale oil reservoir is oleophilic; if -0.5 < I1 ≤ -a, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency.

[0027] When a < I1 ≤ 1, if a < I1 ≤ 0.5, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilicity; if 0.5 < I1 ≤ 1.0, the average wettability of the shale oil reservoir is hydrophilic.

[0028] Optionally, obtaining the intake rate and / or intake fluid saturation when the rock sample spontaneously absorbs fluid, and determining the average wettability of the shale oil reservoir based on the intake rate and / or intake fluid saturation, includes:

[0029] The weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, and the time required for the rock sample to reach the state of saturated water are obtained. The weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, and the time required for the rock sample to reach the state of saturated oil are also obtained.

[0030] The water absorption rate of the rock sample is calculated based on its weight before self-absorption of water, its weight when saturated with water, and the time required for the rock sample to reach saturation.

[0031] The oil absorption rate of the rock sample is calculated based on the weight of the rock sample before self-absorption, the weight of the rock sample in the oil-saturated state, and the time required for the rock sample to reach the oil-saturated state.

[0032] The average wettability of the shale oil reservoir is determined based on the water absorption rate and oil absorption rate of the rock sample.

[0033] Optionally, determining the average wettability of the shale oil reservoir based on the water absorption rate and oil absorption rate of the rock sample includes:

[0034] The ratio of the water absorption rate to the oil absorption rate of the rock sample is used as the oil and water absorption rate index I2 of the shale oil reservoir.

[0035] When 0.75 < I2 ≤ 1.0, the average wettability of the shale oil reservoir is mixed wettability;

[0036] When I2 < 0.5, the average wettability of the shale oil reservoir is oleophilic;

[0037] When 0.5 < I2 ≤ 0.75, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency;

[0038] When 1.25 < I2, the average wettability of the shale oil reservoir is hydrophilic;

[0039] When 1.0 < I2 ≤ 1.25, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilic tint.

[0040] Optionally, obtaining the intake rate and / or intake fluid saturation when the rock sample spontaneously absorbs fluid, and determining the average wettability of the shale oil reservoir based on the intake rate and / or intake fluid saturation, includes:

[0041] The weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, the pore volume of the rock sample after it absorbs water, and the time required for the rock sample to reach the state of saturated water are obtained. The weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, the pore volume of the rock sample after it absorbs oil, and the time required for the rock sample to reach the state of saturated oil are also obtained.

[0042] Based on the weight of the rock sample before self-absorption of water, the weight of the rock sample in the saturated water state, the pore volume of the rock sample after self-absorption of water, and the time required for the rock sample to reach the saturated water state, calculate the water saturation and water absorption rate of the rock sample in the saturated water state.

[0043] Based on the weight of the rock sample before self-absorption of oil, the weight of the rock sample in the oil-saturated state, the pore volume of the rock sample after self-absorption of oil, and the time required for the rock sample to reach the oil-saturated state, calculate the oil saturation and oil absorption rate of the rock sample in the oil-saturated state.

[0044] The average wettability of the shale oil reservoir is determined based on the water saturation, oil saturation, water absorption rate, and oil absorption rate of the rock sample.

[0045] Optionally, determining the average wettability of the shale oil reservoir based on the water saturation, oil saturation, water absorption rate, and oil absorption rate of the rock sample includes:

[0046] The difference between the water saturation and oil saturation of the rock sample is taken as the oil and water saturation index I1 of the shale oil reservoir, and the ratio of the water absorption rate to the oil absorption rate of the rock sample is taken as the oil and water absorption rate index I2 of the shale oil reservoir.

[0047] The ratio of the oil and water saturation index I1 to the oil and water absorption rate index I2 of the shale oil reservoir is used as the wetting strength index I of the shale oil reservoir. The average wettability of the shale oil reservoir is determined based on the wetting strength index I.

[0048] Optionally, determining the average wettability of the shale oil reservoir based on the wetting strength index I includes:

[0049] When -0.15 < I ≤ 0.10, the average wettability of the shale oil reservoir is mixed wettability;

[0050] When I < -1.0, the average wettability of the shale oil reservoir is oleophilic;

[0051] When -1.0 < I ≤ -0.15, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency;

[0052] When 0.50 < I, the average wettability of the shale oil reservoir is hydrophilic;

[0053] When 0.10 < I ≤ 0.50, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilic symmetry.

[0054] Optionally, the water saturation of the rock sample in a saturated water state can be calculated using the following formula:

[0055] S wn =(W wn -W1) / ρw) / V p1

[0056] In the formula, S wnW represents the water saturation of the rock sample in a saturated water state. wn ρw is the weight of the rock sample in a saturated water state; W1 is the weight of the rock sample before self-absorption of water; ρw is the density of simulated water during the self-absorption process; Vp1 is the pore volume of the rock sample after self-absorption of water.

[0057] The oil saturation of the rock sample in its saturated oil state is calculated using the following formula:

[0058] S on =(W on -W2) / ρo) / V p2

[0059] In the formula, S on W represents the oil saturation of the rock sample in a saturated oil state. on W1 is the weight of the rock sample in its saturated oil state; W2 is the weight of the rock sample before self-absorption of oil; ρo is the density of the simulated oil during the self-absorption process of the rock sample; Vp2 is the pore volume of the rock sample after self-absorption of oil.

[0060] Optionally, the water absorption rate of the rock sample can be calculated using the following formula:

[0061] V wn =(W wn -W1) / ρw) / V) / t wi

[0062] In the formula, V wn W represents the water absorption rate of the rock sample. wn ρw is the weight of the rock sample in its saturated water state; W1 is the weight of the rock sample before self-absorption; ρw is the density of the simulated water during the self-absorption process; V is the total volume of the rock sample; t wi The time required for a rock sample to reach a water-saturated state;

[0063] The oil absorption rate of the rock sample was calculated using the following formula:

[0064] V on =(W on -W2) / ρo) / V) / t oi

[0065] In the formula, V on W represents the oil absorption rate of the rock sample. on W1 is the weight of the rock sample in its saturated oil state; W2 is the weight of the rock sample before self-absorption; ρo is the density of the simulated oil during the self-absorption process of the rock sample; V is the total volume of the rock sample; t oi This refers to the time required for a rock sample to reach a saturated oil state.

[0066] Optionally, obtaining the first correspondence between pore radius and signal intensity when the rock sample is in a dry state, the second correspondence between pore radius and signal intensity when the sample is in a saturated water state, and the third correspondence between pore radius and signal intensity when the sample is in a saturated oil state includes:

[0067] Nuclear magnetic resonance T2 spectra were obtained for rock samples in dry, water-saturated, and oil-saturated states, respectively; wherein the nuclear magnetic resonance T2 spectrum represents the relationship between T2 value and signal intensity.

[0068] Based on the relationship between T2 value and signal intensity, and the conversion relationship between T2 value and pore radius, the first correspondence between pore radius and signal intensity in the dry state of the rock sample, the second correspondence between pore radius and signal intensity in the saturated water state, and the third correspondence between pore radius and signal intensity in the saturated oil state are obtained.

[0069] Optionally, comparing the signal intensity increment S1 of rock samples in a saturated water state versus a dry state and the signal intensity increment S2 of rock samples in a saturated oil state versus a dry state under the same pore radius to determine the hydrophilicity and oleophilicity of the shale oil reservoir at that pore radius includes:

[0070] When the signal intensity increment S1 of the rock sample in the saturated water state is greater than the signal intensity increment S2 of the rock sample in the saturated oil state compared to the dry state, the hydrophilicity of the shale oil reservoir under this pore radius is greater than its oleophilicity.

[0071] When the signal intensity increment S1 of the rock sample in the saturated water state is not greater than the signal intensity increment S2 of the rock sample in the saturated oil state compared to the dry state, the oleophilicity of the shale oil reservoir under this pore radius is greater than its hydrophilicity.

[0072] Optionally, the determination method further includes:

[0073] The pore radii with hydrophilicity greater than oleophilicity and pore radii with oleophilicity greater than hydrophilicity are respectively divided into the first interval range and the second interval range;

[0074] The left boundary of the first interval and / or the second interval is taken as the critical pore radius for this oil-water reversal, and the right boundary is taken as the critical pore radius for the next oil-water reversal.

[0075] Accordingly, embodiments of the present invention also provide a method for optimizing the amount of fluid injected into the ground and the well shut-in time in shale oil development, the optimization method comprising:

[0076] Based on the aforementioned method for determining the wettability of shale oil reservoirs, the wettability of shale oil reservoirs is determined;

[0077] Based on the wettability of the shale oil reservoir, the amount of fluid injected into the ground and the well shut-in time in shale oil development are adjusted.

[0078] Accordingly, this embodiment of the invention also provides a shale oil reservoir wettability determination device, which is used to execute the shale oil reservoir wettability determination method.

[0079] Accordingly, this invention also provides an adjustment device for the amount of fluid injected into the ground and the well shut-in time in shale oil development. The adjustment device for the amount of fluid injected into the ground and the well shut-in time in shale oil development is used to execute the optimization method for the amount of fluid injected into the ground and the well shut-in time in shale oil development.

[0080] Accordingly, embodiments of the present invention also provide a machine-readable storage medium storing instructions for causing a machine to execute the shale oil reservoir wettability determination method or the optimization method for the amount of fluid injected into the ground and the well shut-in time in shale oil development.

[0081] Accordingly, embodiments of the present invention also provide a processor for running a program, wherein the program, when run, is used to execute the shale oil reservoir wettability judgment method or the optimization method for the amount of fluid injected into the ground and the well shut-in time in shale oil development.

[0082] This invention assesses the average wettability of shale oil reservoirs by measuring the intake rate and the saturation of the intake fluid. It then determines the hydrophilic and oleophilic properties of shale oil reservoirs at different pore radii by analyzing the signal intensity increments under saturated water and oil conditions. Average wettability reflects the macroscopic wettability of the shale oil reservoir, while the hydrophilic and oleophilic properties of the shale oil reservoir at different pore radii reflect its microscopic hydrophilic and oleophilic properties at different pore radii. This invention combines average wettability and the hydrophilic and oleophilic properties of shale oil reservoirs at different pore radii to assess the wettability of shale oil reservoirs. This multi-dimensional assessment of the oil and water wetting characteristics of shale oil reservoirs provides a more comprehensive evaluation and offers a theoretical basis for optimizing the amount of fluid injected into shale oil horizontal wells and the well-clogging time.

[0083] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0084] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0085] Figure 1 This is a flowchart of a method for determining the wettability of shale oil reservoirs provided in an embodiment of the present invention;

[0086] Figure 2 This is a schematic diagram of the experimental apparatus for determining the average wettability of shale oil reservoirs provided in an embodiment of the present invention;

[0087] Figure 3 These are the T2 spectra of nuclear magnetic resonance tests on rock samples in dry and saturated water states, as provided in this embodiment of the invention.

[0088] Figure 4 These are the T2 spectra of rock samples under dry and saturated oil conditions as provided in this embodiment of the invention.

[0089] Figure 5 These are the NMR T2 spectrum comparison curves for self-water absorption and self-oil absorption experiments provided in this embodiment of the invention;

[0090] Figure 6 This is a graph showing the weight and time data of rock samples during the self-absorption process provided in an embodiment of the present invention;

[0091] Figure 7 This is a graph showing the weight and time data of rock samples during the self-aspirating oil process provided in an embodiment of the present invention;

[0092] Figures 8A-8F This is a nuclear magnetic resonance T2 spectrum data diagram of self-absorbing water and self-absorbing oil experiments provided in the embodiments of the present invention. Detailed Implementation

[0093] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0094] Figure 1 This is a flowchart of a method for determining the wettability of shale oil reservoirs provided in an embodiment of the present invention.

[0095] like Figure 1 As shown, the method for determining the wettability of shale oil reservoirs includes:

[0096] S110: Obtain the aspiration rate and / or aspiration fluid saturation when a rock sample spontaneously aspirates fluid, wherein the aspiration rate includes water absorption rate and oil absorption rate, and the aspiration fluid saturation includes water absorption saturation and oil absorption saturation;

[0097] S120: Determine the average wettability of the shale oil reservoir based on the said intake rate and / or intake fluid saturation;

[0098] S130: Obtain the first correspondence between pore radius and signal intensity when the rock sample is in a dry state, the second correspondence between pore radius and signal intensity when the rock sample is in a saturated water state, and the third correspondence between pore radius and signal intensity when the rock sample is in a saturated oil state;

[0099] S140: Based on the first correspondence, the second correspondence and the third correspondence, compare the signal intensity increment S1 of the rock sample in the saturated water state with the dry state and the signal intensity increment S2 of the rock sample in the saturated oil state with the dry state under the same pore radius, and determine the hydrophilicity and oleophilicity of the shale oil reservoir under the pore radius.

[0100] S150: Determine the wettability of the shale oil reservoir based on the average wettability of the shale oil reservoir and the hydrophilicity and oleophilicity of the shale oil reservoir under different pore radii.

[0101] In this embodiment of the invention, the average wettability of the shale oil reservoir can be determined through steps S110 and S120, and the hydrophilic and oleophilic properties of the shale oil reservoir under different pore radii can be determined through steps S130 and S140. The average wettability reflects the macroscopic wettability of the shale oil reservoir, while the hydrophilic and oleophilic properties of the shale oil reservoir under different pore radii reflect the microscopic hydrophilic and oleophilic properties of the shale oil reservoir under different pore radii. This embodiment of the invention combines the average wettability and the hydrophilic and oleophilic properties of the shale oil reservoir under different pore radii to determine the wettability of the shale oil reservoir, which can reflect the wetting characteristics of oil and water in the shale oil reservoir from multiple dimensions, making the assessment more comprehensive.

[0102] In steps S110 and S120, any of the following methods can be used to determine the average wettability of the shale oil reservoir:

[0103] 1) Obtain the water saturation and oil saturation of the rock sample, and determine the average wettability of the shale oil reservoir based on the water saturation and oil saturation.

[0104] 2) For example, the method first obtains the weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, the pore volume of the rock sample after it absorbs water, the weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, and the pore volume of the rock sample after it absorbs oil.

[0105] 3) Further, based on the weight of the rock sample before self-absorption of water, the weight of the rock sample in a water-saturated state, and the pore volume of the rock sample after self-absorption of water, the water saturation of the rock sample in a water-saturated state is calculated; based on the weight of the rock sample before self-absorption of oil, the weight of the rock sample in a oil-saturated state, and the pore volume of the rock sample after self-absorption of oil, the oil saturation of the rock sample in a oil-saturated state is calculated.

[0106] Finally, the average wettability of the shale oil reservoir is determined based on the water saturation and oil saturation of the rock samples.

[0107] Specifically, the difference between the water saturation and oil saturation of the rock sample is used as the oil and water saturation index I1 of the shale oil reservoir;

[0108] When -a < I1 ≤ a, the average wettability of the shale oil reservoir is mixed wettability, where 0 < a < 0.5 (e.g., a is 0.1).

[0109] When -1 < I1 ≤ -a, the average wettability of the shale oil reservoir is oleophilic;

[0110] When a < I1 ≤ 1, the average wettability of the shale oil reservoir is hydrophilic.

[0111] More preferably, when -1 < I1 ≤ -a, if -1.0 < I1 ≤ -0.5, the average wettability of the shale oil reservoir is classified as oleophilic, and if -0.5 < I1 ≤ -a, the average wettability of the shale oil reservoir is classified as mixed wettability with a slight oleophilic tendency.

[0112] When a < I1 ≤ 1, if a < I1 ≤ 0.5, the average wettability of the shale oil reservoir is classified as mixed wettability with a slight hydrophilicity; if 0.5 < I1 ≤ 1.0, the average wettability of the shale oil reservoir is classified as hydrophilic.

[0113] 4) Obtain the water absorption rate and oil absorption rate of the rock sample, and determine the average wettability of the shale oil reservoir based on the water absorption rate and oil absorption rate;

[0114] 5) For example, the method first obtains the weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, the time required for the rock sample to reach the saturated water state, the weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, and the time required for the rock sample to reach the saturated oil state.

[0115] Furthermore, the water absorption rate of the rock sample is calculated based on its weight before self-absorption of water, its weight when saturated with water, and the time required for the rock sample to reach saturation with water; the oil absorption rate of the rock sample is calculated based on its weight before self-absorption of oil, its weight when saturated with oil, and the time required for the rock sample to reach saturation with oil.

[0116] Finally, the average wettability of the shale oil reservoir is determined based on the water absorption rate and oil absorption rate of the rock samples.

[0117] Specifically, the ratio of the water absorption rate to the oil absorption rate of the rock sample is used as the oil and water absorption rate index I2 of the shale oil reservoir;

[0118] When 0.75 < I2 ≤ 1.0, the average wettability of the shale oil reservoir is mixed wettability;

[0119] When I2 < 0.5, the average wettability of the shale oil reservoir is oleophilic;

[0120] When 0.5 < I2 ≤ 0.75, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency;

[0121] When 1.25 < I2, the average wettability of the shale oil reservoir is hydrophilic;

[0122] When 1.0 < I2 ≤ 1.25, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilic tint.

[0123] 6) Obtain the water saturation, oil saturation, water absorption rate, and oil absorption rate of the rock sample. Based on the water saturation, oil saturation, water absorption rate, and oil absorption rate of the rock sample, determine the average wettability of the shale oil reservoir.

[0124] For example, the method first obtains the weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, the pore volume of the rock sample after it absorbs water, and the time required for the rock sample to reach the saturated water state, as well as the weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, the pore volume of the rock sample after it absorbs oil, and the time required for the rock sample to reach the saturated oil state.

[0125] Furthermore, based on the weight of the rock sample before self-absorption of water, the weight of the rock sample in a water-saturated state, the pore volume of the rock sample after self-absorption of water, and the time required for the rock sample to reach a water-saturated state, the water saturation and water absorption rate of the rock sample in a water-saturated state are calculated; based on the weight of the rock sample before self-absorption of oil, the weight of the rock sample in an oil-saturated state, the pore volume of the rock sample after self-absorption of oil, and the time required for the rock sample to reach an oil-saturated state, the oil saturation and oil absorption rate of the rock sample in an oil-saturated state are calculated.

[0126] Finally, the average wettability of the shale oil reservoir is determined based on the water saturation, oil saturation, water absorption rate, and oil absorption rate of the rock samples.

[0127] Specifically, the difference between the water saturation and oil saturation of the rock sample can be used as the oil and water saturation index I1 of the shale oil reservoir; the ratio of the water absorption rate to the oil absorption rate of the rock sample can be used as the oil and water absorption rate index I2 of the shale oil reservoir; and the ratio of the oil and water saturation index I1 to the oil and water absorption rate index I2 of the shale oil reservoir can be used as the wetting strength index I of the shale oil reservoir. Based on the wetting strength index I, the average wettability of the shale oil reservoir can be determined.

[0128] When -0.15 < I ≤ 0.10, the average wettability of the shale oil reservoir is mixed wettability;

[0129] When I < -1.0, the average wettability of the shale oil reservoir is oleophilic;

[0130] When -1.0 < I ≤ -0.15, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency;

[0131] When 0.50 < I, the average wettability of the shale oil reservoir is hydrophilic;

[0132] When 0.10 < I ≤ 0.50, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilic symmetry.

[0133] The following describes the calculation methods for water saturation, oil saturation, water absorption rate, and oil absorption rate in the three embodiments described above.

[0134] The water saturation of the rock sample in a saturated water state can be calculated using the following formula:

[0135] S wn =(W wn -W1) / ρw) / V p1

[0136] In the formula, S wn W represents the water saturation of the rock sample in a saturated water state. wn ρw is the weight of the rock sample in a saturated water state; W1 is the weight of the rock sample before self-absorption of water; ρw is the density of simulated water during the self-absorption process; Vp1 is the pore volume of the rock sample after self-absorption of water.

[0137] The oil saturation of the rock sample in its saturated oil state can be calculated using the following formula:

[0138] S on =(W on -W2) / ρo) / V p2

[0139] In the formula, S on W represents the oil saturation of the rock sample in a saturated oil state.on W1 is the weight of the rock sample in its saturated oil state; W2 is the weight of the rock sample before self-absorption of oil; ρo is the density of the simulated oil during the self-absorption process of the rock sample; Vp2 is the pore volume of the rock sample after self-absorption of oil.

[0140] The water absorption rate of the rock sample can be calculated using the following formula:

[0141] V wn =(W wn -W1) / ρw) / V) / t wi

[0142] In the formula, V wn W represents the water absorption rate of the rock sample. wn ρw is the weight of the rock sample in its saturated water state; W1 is the weight of the rock sample before self-absorption; ρw is the density of the simulated water during the self-absorption process; V is the total volume of the rock sample; t wi The time required for a rock sample to reach a water-saturated state;

[0143] The oil absorption rate of the rock sample can be calculated using the following formula:

[0144] V on =(W on -W2) / ρo) / V) / t oi

[0145] In the formula, V on W represents the oil absorption rate of the rock sample. on W1 is the weight of the rock sample in its saturated oil state; W2 is the weight of the rock sample before self-absorption; ρo is the density of the simulated oil during the self-absorption process of the rock sample; V is the total volume of the rock sample; t oi This refers to the time required for a rock sample to reach a saturated oil state.

[0146] In step S130, when obtaining the first correspondence between pore radius and signal intensity in the dry state of the rock sample, the second correspondence between pore radius and signal intensity in the saturated water state, and the third correspondence between pore radius and signal intensity in the saturated oil state, the nuclear magnetic resonance T2 spectra of the rock sample in the dry state, the saturated water state, and the saturated oil state can be obtained respectively; wherein, the nuclear magnetic resonance T2 spectrum represents the relationship between T2 value and signal intensity; then, based on the relationship between T2 value and signal intensity, and the conversion relationship between T2 value and pore radius, the first correspondence between pore radius and signal intensity in the dry state of the rock sample, the second correspondence between pore radius and signal intensity in the saturated water state, and the third correspondence between pore radius and signal intensity in the saturated oil state are obtained.

[0147] In step S140, based on the first correspondence, the second correspondence, and the third correspondence, the signal intensity increment S1 of the rock sample in the saturated water state compared to the dry state and the signal intensity increment S2 of the rock sample in the saturated oil state compared to the dry state under the same pore radius are compared. When determining the hydrophilicity and oleophilicity of the shale oil reservoir under the pore radius, the signal intensity increment S1 of the rock sample in the saturated water state compared to the dry state can be greater than the signal intensity increment S2 of the rock sample in the saturated oil state compared to the dry state, and it can be determined that the hydrophilicity of the shale oil reservoir under the pore radius is greater than its oleophilicity.

[0148] If the signal intensity increment S1 of the rock sample in the saturated water state is not greater than the signal intensity increment S2 of the rock sample in the saturated oil state compared to the dry state, it is determined that the oleophilicity of the shale oil reservoir under this pore radius is greater than its hydrophilicity.

[0149] More preferably, the pore radii with hydrophilicity greater than oleophilicity and pore radii with oleophilicity greater than hydrophilicity can be divided into a first interval range and a second interval range respectively; the left boundary of the first interval range and / or the second interval range is taken as the critical pore radius during this oil-water reversal, and the right boundary is taken as the critical pore radius during the next oil-water reversal.

[0150] The inventors of this application have discovered that dry rocks can spontaneously absorb fluids (water and oil) under capillary pressure. Due to differences in the mineral composition of the rock, the organic matter content in the pores, the structure of the pore throats, and external conditions, the amount of oil and water spontaneously absorbed, as well as the rates of spontaneous oil and water absorption, vary. This invention provides a method for determining the wettability of shale oil reservoirs by comprehensively considering the self-absorbed water and oil volume, as well as the water and oil absorption rates, under the capillary force of the rock itself. Based on the self-absorbed water and oil volume, water absorption rate, and oil absorption rate, the method evaluates the differences in wettability among different shale oil reservoirs. Through nuclear magnetic resonance (NMR) technology, the method analyzes the distribution of oil and water in rock samples with different pore sizes, further quantifying the influence of different pore sizes on the self-absorbed water and oil volume, providing a theoretical basis for optimizing the reasonable amount of fluid injected into shale oil horizontal wells and the well-closing time.

[0151] The following examples illustrate the method for determining the wettability of shale oil reservoirs.

[0152] In the example, Figure 2 This is a schematic diagram of the experimental apparatus provided in an embodiment of the present invention.

[0153] First, experimental samples were prepared. Core samples from the target shale oil reservoir were drilled in their original state without washing the oil, resulting in columnar sections with a diameter of 2.5 cm and a length of 3.0 cm. It was recommended that the core samples from the target well's shale oil reservoir be freshly retrieved from the well bottom, as this minimizes the loss of organic matter and preserves the original state of the shale oil reservoir. If fresh core samples were unavailable, existing core samples could be subjected to pressurized saturated aging treatment, followed by immersion in simulated oil (simulated oil: oil used in the experiment, prepared according to the People's Republic of China Petroleum and Natural Gas Industry Standard SY-T 5345-2007, Method for Determination of Two-Phase Relative Permeability in Rocks) for at least one week.

[0154] Then, cut experimental samples (hereinafter referred to as samples) with a length of 0.5-0.7 cm and place them in an oven to dry at a low temperature of 50°C for at least 2 hours. After the drying time is longer than 2 hours, weigh the samples with a balance, weighing them once every 30 minutes. When the sample weight change is less than 1‰, the drying process is over. Remove the samples and place them in a desiccator for experimental use.

[0155] Further, the sample was removed from the desiccator and weighed using a balance. The weight W1 was recorded. Then, the sample was subjected to the first nuclear magnetic resonance test to obtain the T2 spectrum data of the sample background (the nuclear magnetic resonance test was conducted in accordance with the People's Republic of China Petroleum and Natural Gas Industry Standard SY / T 6490-2007).

[0156] Further, the sample after the first test was placed in a wide-mouth bottle, and simulated water was added (simulated water: water used in the experiment, prepared according to the People's Republic of China Petroleum and Natural Gas Industry Standard SY-T 5345-2007 Method for Determination of Relative Permeability of Two Phases in Rocks), and the density ρ of the simulated water was tested. w Then, the self-absorption process of the sample was initiated (self-absorption process: the process of filling the sample with simulated water through capillary force). During the self-absorption process, the sample weight W was measured and recorded every 10 minutes using a balance. wi and time T wi Before each weighing, the surface water of the sample must be wiped away with a damp gauze, and there should be no obvious water droplets on the sample. The self-absorption process ends when the self-absorption time is greater than 72 hours and the sample weight change is less than 1‰. Then, a second NMR test is performed to obtain the T2 spectrum data of the self-absorption of the test sample (NMR testing is conducted according to the People's Republic of China Petroleum and Natural Gas Industry Standard SY / T 6490-2007). The T2 spectrum data obtained from the first and second NMR tests are plotted as an NMR spectrum of the aqueous phase, as shown below. Figure 3 As shown. After water absorption is complete, the pore volume of the sample is measured and recorded.

[0157] Further, the sample that has completed the second NMR test was soaked in water for 2 hours. After soaking, the sample was wiped dry and placed in an oven at a low temperature of 50°C for at least 2 hours. After the drying time exceeded 2 hours, the sample was weighed using a balance every 30 minutes. The drying process was considered complete when the sample weight change was less than 1‰. The sample was then removed and placed in a desiccator for experimental use.

[0158] Further, the sample was removed from the desiccator, weighed, and the weight W2 was recorded. The sample was then placed in a wide-mouth bottle, simulated oil was added, and the density ρ of the simulated water was tested. o The self-aspiration oil process of the sample begins (self-aspiration oil process: the process of filling the sample with simulated oil through capillary force). During the self-aspiration oil process, the sample weight W is measured and recorded every 10 minutes using a balance. oi and time T oi Before each weighing, the surface oil of the sample must be wiped away with a damp gauze, and there should be no obvious oil droplets on the sample. The self-absorption process ends when the self-absorption time is greater than 72 hours and the sample weight change is less than 1‰. Then, a third NMR test is performed to obtain the T2 spectrum data of the self-absorption oil in the test sample (NMR testing is conducted according to the People's Republic of China Petroleum and Natural Gas Industry Standard SY / T 6490-2007). The T2 spectrum data obtained from the first and third NMR tests are plotted as the T2 spectrum of the oil phase, as shown below. Figure 4 As shown.

[0159] A comparison curve of the T2 spectrum of the self-absorbing water and self-absorbing oil experiments was plotted by combining the T2 spectrum data obtained from the first, second and third NMR tests (see...). Figure 5 Using the T2 spectrum data obtained from the first, second, and third nuclear magnetic resonance tests, we plotted the T2 spectrum comparison curves of the self-absorbing water and self-absorbing oil experiments, and calculated the signal intensity increment S1 of the rock sample in the saturated water state compared to the dry state, and the signal intensity increment S2 of the rock sample in the saturated oil state compared to the dry state.

[0160] Further, the sample after the third NMR test is placed in an oil washing apparatus for oil washing (the process must be performed according to the People's Republic of China Petroleum and Natural Gas Industry Standard SY-T 5336-2006 Core Analysis Methods). Care must be taken to prevent the sample from shedding any residue during the oil washing process. After oil absorption is complete, the pore volume V of the sample is measured. P2 And record it.

[0161] Further, the water saturation, oil saturation, water absorption rate, and oil absorption rate of the sample were calculated. (1) Water saturation: the proportion of water in the pore volume.

[0162] S wi =(Wwi -W1) / ρw) / V p

[0163] Using the weight W at the end of the self-priming process wn The water saturation S at the end of the self-absorption process is calculated using the above formula. wn ;

[0164] S wi —Sample in T wi Water saturation at time, decimal; W wi —Sample in T wi Weight at time, g; W1—weight of sample before self-absorption process, g; ρw—density of simulated water, g / cm³ 3 Vp—Pore volume of the sample, cm³ 3 S wn —Water saturation of the sample at the end of the self-absorption process; W wn —Sample weight at the end of the self-absorption process;

[0165] Among them, the sample weight W during the self-absorption process wi and time T wi Data formation Figure 6 Simulated water density ρ w =1.036g / cm 3 Simulated oil density ρ o =0.792g / cm 3 , W1=6.614g, W2=6.592g, Vp=0.2774cm 3 The sample length is 0.67 cm, the sample diameter is 2.497 cm, and the total sample volume is V = 4.163 cm³. 3 ;

[0166] extract Figure 6 The last set of data determined W wn W wn =6.701g;

[0167] S wn =(W wn -W1) / ρw) / V p = (6.701 - 6.614) / 1.036 / 0.2774 = 0.30;

[0168] (2) Oil saturation: The proportion of simulated oil in the pore volume.

[0169] S oi =(W oi -W2) / ρo) / V p

[0170] Using the weight W at the end of the self-priming oil process on The oil saturation S at the end of the self-suction process is calculated using the above formula. on ;

[0171] S oi —Sample in T oi Oil saturation at time, decimal; W oi —Sample in T oi Weight of the sample before the self-aspirating process, g; W2—weight of the sample before the self-aspirating process, g; ρo—density of the simulated oil, g / cm³ 3 Vp—Pore volume of the sample, cm³ 3 Vp—Pore volume of the sample, cm³ 3 S on —The oil saturation of the sample at the end of the self-absorption process; W on —The weight of the sample at the end of the self-priming process.

[0172] Among them, the sample weight W during the self-aspirating oil process oi and time T oi Data formation Figure 7 ,extract Figure 7 The last set of data determined W on W on =6.781g;

[0173] S on =(W oi -W2) / ρo) / V p = (6.781 - 6.592) / 0.792 / 0.2774 = 0.86;

[0174] (3) Water absorption rate: the amount of water absorbed per unit volume per unit time of the sample.

[0175] V wi =(W wi -W1) / ρw) / V) / t wi

[0176] V wi —Sample in T wi The water absorption rate at that time, a decimal; W wi —Sample in T wi Weight at time, g; W1—weight of sample before self-absorption process, g; ρw—density of simulated water, g / cm³ 3 V—total volume of the sample, cm³ 3 ;t wi —A certain time period during the self-absorption of water by the sample, min.

[0177] Among them, extraction Figure 6Time and weight data for serial number 14, time t wi =4800min, W wi =6.696g;

[0178] V wi =(W wi -W1) / ρw) / V) / t wi

[0179] =(6.696-6.614) / 1.036 / 4.163 / 4800=0.00000396cm3 / m

[0180] (4) Oil absorption rate: the amount of oil absorbed per unit volume of sample per unit time.

[0181] V oi =(W oi -W2) / ρo) / V) / t oi

[0182] V oi —Sample in T oi Oil saturation at time, decimal; W oi —Sample in T oi Weight of the sample before the self-aspirating process, g; W2—weight of the sample before the self-aspirating process, g; ρo—density of the simulated oil, g / cm³ 3 V—total volume of the sample, cm³ 3 ;t oi —A certain time period during the self-absorption of water by the sample, min.

[0183] Among them, extraction Figure 7 Time and weight data for serial number 12, time t oi =4855min, W oi =6.776g;

[0184] V oi =(W oi -W2) / ρo) / V) / t oi

[0185] =(6.776-6.592) / 0.792 / 4.163 / 4855=0.0000115 cm 3 / min.

[0186] (5) Oil and water absorption saturation index I1:

[0187] I1=S wn -S on

[0188] S wn —Water saturation of the sample at the end of the self-absorption process; Son —The oil saturation of the sample at the end of the self-absorption process; I1—the oil and water saturation index.

[0189] The wettability of the sample was determined using the oil and water saturation index I1.

[0190] When -1.0 < I1 ≤ -0.5, the wettability of the sample is oleophilic; when -0.5 < I1 ≤ -0.1, the wettability of the sample is mixed wetting with a slight oleophilic tendency; when -0.1 < I1 ≤ 0.1, the wettability of the sample is mixed wetting; when 0.1 < I1 ≤ 0.5, the wettability of the sample is mixed wetting with a slight hydrophilic tendency; when 0.5 < I1 ≤ 1.0, the wettability of the sample is hydrophilic.

[0191] Where, I1=S wn -S on =0.30-0.86=-0.56, therefore the average wettability of sample Y60 is determined to be oleophilic.

[0192] (6) Oil and water absorption rate index I2:

[0193] I2= V wi / V oi

[0194] V wi —The amount of water absorbed per unit volume of sample per unit time; V oi — The amount of oil absorbed per unit volume per unit time of the sample; I2 — the oil and water absorption rate index.

[0195] The wettability of the sample was determined using the oil and water absorption rate index I2.

[0196] When 1.25 < I2, the wettability of the sample is hydrophilic; when 1.0 < I2 ≤ 1.25, the wettability of the sample is mixed wettability - slightly hydrophilic; when 0.75 < I2 ≤ 1.0, the wettability of the sample is mixed wettability; when 0.5 < I2 ≤ 0.75, the wettability of the sample is mixed wettability - slightly oleophilic; when I2 < 0.5, the wettability of the sample is oleophilic.

[0197] Where, I2= V wi / V oi =0.00000396 / 0.0000115=0.34, therefore the average wettability of sample Y60 is determined to be oleophilic.

[0198] (7) Wetting strength index I:

[0199] （8）I = I1 / I2

[0200] (9) Use the wettability index I to identify the wettability of rock samples.

[0201] (10) When I ≤ -1.0, the wettability of the sample is oleophilic; when -1.0 < I ≤ -0.15, the wettability of the sample is mixed wetting - slightly oleophilic; when -0.15 < I ≤ 0.10, the wettability of the sample is mixed wetting; when 0.10 < I ≤ 0.50, the wettability of the sample is mixed wetting - slightly hydrophilic; when 0.50 < I, the wettability of the sample is hydrophilic.

[0202] (11) (8) Determine the hydrophilicity and oleophilicity of shale oil reservoirs with different pore radii:

[0203] like Figure 5 As shown, when S1≥S2, it is considered that the hydrophilicity is greater than the oleophilicity under this pore radius. The left boundary of the pore radius interval is the pore radius value when the current oil-water reversal occurs, and the right boundary is the pore radius value when the next oil-water reversal occurs (oil-water reversal: the relative size of S1 and S2 changes). All intervals of pore radii where the hydrophilicity is greater than the oleophilicity are statistically grouped together.

[0204] When S1≤S2, it is determined that the oleophilic ability is greater than the hydrophilic ability under this interval of pore radius. The left boundary of the interval of pore radius is the pore radius value when the current oil-water reversal occurs, and the right boundary is the pore radius value when the next oil-water reversal occurs (oil-water reversal: the relative size of S1 and S2 changes). All intervals of pore radius where the oleophilic ability is greater than the hydrophilic ability are statistically grouped together.

[0205] Figure 8 is formed using the T2 spectrum data from the first to the third nuclear magnetic resonance (NMR) tests. Based on the data in Figure 8, we can obtain:

[0206] The range of pore radii where hydrophilicity is greater than oleophilicity includes:

[0207] [0.0002, 0.0007], [1.0966, 1.6667];

[0208] The range of pore radii where the oleophilicity is greater than the hydrophilicity includes:

[0209] [0.0008, 0.9537], [1.9163, 10.2265];

[0210] In summary, the average wettability of Y60 samples is oleophilic. The pore radii in which the hydrophilicity is greater than the oleophilicity are: [0.0002, 0.0007] and [1.0966, 1.6667]; the pore radii in which the oleophilicity is greater than the hydrophilicity are: [0.0008, 0.9537] and [1.9163, 10.2265].

[0211] The purpose of this invention is to objectively evaluate the wettability characteristics of tight shale oil reservoirs in core samples, provide technical support for optimizing the amount of fluid injected into the ground and the well shut-in time, achieve the dual goals of artificial fracturing and energy replenishment in horizontal wells, reduce investment costs from the source, and increase single-well production.

[0212] This invention employs an indoor experimental evaluation method, utilizing the characteristic that dry rocks can spontaneously absorb fluids (water and oil) under capillary pressure. Depending on the rock's mineral composition, the amount of organic matter in the pores, the structure of the pore throats, and the influence of external conditions, the amount of oil and water spontaneously absorbed, as well as the rates of spontaneous oil and water absorption, vary. The mixed wetting index is then used to determine the average wettability of the shale oil reservoir.

[0213] Meanwhile, further assessment of the hydrophilic and oleophilic capabilities of shale oil reservoirs under different pore radii provides a theoretical basis for optimizing the reasonable amount of fluid injected into the ground and the well shut-in time in the development of shale oil horizontal wells. This achieves the goals of increasing single-well production, improving recovery rate, and reducing investment, thus promoting the large-scale and efficient development of shale oil.

[0214] The method provided by this invention is simple and easy to operate, offering a specific standard for evaluating the wettability of tight shale oil reservoirs. Compared to the Amott test and USBM test, it is not limited by the small pore throat and strong capillary force of shale oil reservoirs, making it simpler and easier to implement.

[0215] Furthermore, this method offers simple and rapid sample preparation, with the testing process involving only self-absorption without displacement, taking approximately 72 hours, which is short in duration. It utilizes rate to characterize wettability, resulting in more accurate measurements. Simultaneously, this method is suitable for shale oil reservoirs with mixed wettability and small pore throats, and can quantitatively characterize the changes in wettability of different pore sizes during self-absorption under formation conditions, thereby guiding the optimization of fluid injection volume and well shut-in time.

[0216] Furthermore, this method requires simple testing equipment, has a clear testing principle, and takes less time. Shale oil reservoirs have well-developed micro- and nano-pores and strong heterogeneity.

[0217] Accordingly, this embodiment of the invention also provides a shale oil reservoir wettability determination device, which is used to execute the shale oil reservoir wettability determination method.

[0218] Accordingly, this invention also provides an adjustment device for the amount of fluid injected into the ground and the well shut-in time in shale oil development. The adjustment device for the amount of fluid injected into the ground and the well shut-in time in shale oil development is used to execute the optimization method for the amount of fluid injected into the ground and the well shut-in time in shale oil development.

[0219] Accordingly, embodiments of the present invention also provide a machine-readable storage medium storing instructions for causing a machine to execute the shale oil reservoir wettability determination method or the optimization method for the amount of fluid injected into the ground and the well shut-in time in shale oil development.

[0220] Accordingly, embodiments of the present invention also provide a processor for running a program, wherein the program, when run, is used to execute the shale oil reservoir wettability judgment method or the optimization method for the amount of fluid injected into the ground and the well shut-in time in shale oil development.

[0221] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0222] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0223] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0224] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0225] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0226] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0227] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0228] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0229] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for determining the wettability of shale oil reservoirs, characterized in that, The method for determining the wettability of shale oil reservoirs includes: Obtain the aspiration rate and / or aspiration fluid saturation when a rock sample spontaneously aspirates fluid, wherein the aspiration rate includes water absorption rate and oil absorption rate, and the aspiration fluid saturation includes water absorption saturation and oil absorption saturation; The average wettability of the shale oil reservoir is determined based on the intake rate and / or the intake fluid saturation. The first correspondence between pore radius and signal intensity of the rock sample in a dry state, the second correspondence between pore radius and signal intensity in a saturated water state, and the third correspondence between pore radius and signal intensity in a saturated oil state are obtained. Based on the first, second, and third correspondences, the signal intensity increment S1 of the rock sample in the saturated water state compared with the dry state and the signal intensity increment S2 of the rock sample in the saturated oil state compared with the dry state under the same pore radius are compared to determine the hydrophilicity and oleophilicity of the shale oil reservoir under that pore radius. The comparison of the signal intensity increment S1 of rock samples in a saturated water state versus a dry state and the signal intensity increment S2 of rock samples in a saturated oil state versus a dry state under the same pore radius, yields the hydrophilicity and oleophilicity of shale oil reservoirs at that pore radius, including: When the signal intensity increment S1 of the rock sample in the saturated water state is greater than the signal intensity increment S2 of the rock sample in the saturated oil state compared to the dry state, the hydrophilicity of the shale oil reservoir under this pore radius is greater than its oleophilicity. When the signal intensity increment S1 of the rock sample in the saturated water state is not greater than the signal intensity increment S2 of the rock sample in the saturated oil state compared with the dry state, the oleophilicity of the shale oil reservoir under this pore radius is greater than its hydrophilicity. The wettability of shale oil reservoirs is determined based on the average wettability of the reservoirs and the hydrophilicity and oleophilicity of the reservoirs under different pore radii.

2. The method for determining the wettability of shale oil reservoirs according to claim 1, characterized in that, The process of obtaining the spontaneous fluid aspiration rate and / or fluid saturation of rock samples, and determining the average wettability of shale oil reservoirs based on the aspiration rate and / or fluid saturation, includes: The weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, the pore volume of the rock sample after it absorbs water, the weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, and the pore volume of the rock sample after it absorbs oil are obtained. Calculate the water saturation of the rock sample in its saturated state based on the weight of the rock sample before self-absorption of water, the weight of the rock sample in its saturated state with water, and the pore volume of the rock sample after self-absorption of water. The oil saturation of the rock sample in its saturated state is calculated based on the weight of the rock sample before self-absorption of oil, the weight of the rock sample in its saturated state with oil, and the pore volume of the rock sample after self-absorption of oil. The average wettability of the shale oil reservoir is determined based on the water saturation and oil saturation of the rock samples.

3. The method for determining the wettability of shale oil reservoirs according to claim 2, characterized in that, The determination of the average wettability of shale oil reservoirs based on the water saturation and oil saturation of rock samples includes: The difference between the water saturation and oil saturation of the rock sample is used as the oil and water saturation index I1 of the shale oil reservoir. When -a < I1 ≤ a, the average wettability of the shale oil reservoir is mixed wettability, where 0 < a < 0.5; When -1 < I1 ≤ -a, the average wettability of the shale oil reservoir is oleophilic; When a < I1 ≤ 1, the average wettability of the shale oil reservoir is hydrophilic.

4. The method for determining the wettability of shale oil reservoirs according to claim 3, characterized in that, When -1 < I1 ≤ -a, if -1.0 < I1 ≤ -0.5, the average wettability of the shale oil reservoir is oleophilic; if -0.5 < I1 ≤ -a, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency. When a < I1 ≤ 1, if a < I1 ≤ 0.5, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilicity; if 0.5 < I1 ≤ 1.0, the average wettability of the shale oil reservoir is hydrophilic.

5. The method for determining the wettability of shale oil reservoirs according to claim 1, characterized in that, The process of obtaining the spontaneous fluid aspiration rate and / or fluid saturation of rock samples, and determining the average wettability of shale oil reservoirs based on the aspiration rate and / or fluid saturation, includes: The weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, and the time required for the rock sample to reach the state of saturated water are obtained. The weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, and the time required for the rock sample to reach the state of saturated oil are also obtained. The water absorption rate of the rock sample is calculated based on its weight before self-absorption of water, its weight when saturated with water, and the time required for the rock sample to reach saturation. The oil absorption rate of the rock sample is calculated based on the weight of the rock sample before self-absorption, the weight of the rock sample in the oil-saturated state, and the time required for the rock sample to reach the oil-saturated state. The average wettability of the shale oil reservoir is determined based on the water absorption rate and oil absorption rate of the rock sample.

6. The method for determining the wettability of shale oil reservoirs according to claim 5, characterized in that, The determination of the average wettability of shale oil reservoirs based on the water absorption rate and oil absorption rate of rock samples includes: The ratio of the water absorption rate to the oil absorption rate of the rock sample is used as the oil and water absorption rate index I2 of the shale oil reservoir. When 0.75 < I2 ≤ 1.0, the average wettability of the shale oil reservoir is mixed wettability; When I2 < 0.5, the average wettability of the shale oil reservoir is oleophilic; When 0.5 < I2 ≤ 0.75, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency; When 1.25 < I2, the average wettability of the shale oil reservoir is hydrophilic; When 1.0 < I2 ≤ 1.25, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilic tint.

7. The method for determining the wettability of shale oil reservoirs according to claim 1, characterized in that, The process of obtaining the spontaneous fluid aspiration rate and / or fluid saturation of rock samples, and determining the average wettability of shale oil reservoirs based on the aspiration rate and / or fluid saturation, includes: The weight of the rock sample before it absorbs water, the weight of the rock sample when it is saturated with water, the pore volume of the rock sample after it absorbs water, and the time required for the rock sample to reach the state of saturated water are obtained. The weight of the rock sample before it absorbs oil, the weight of the rock sample when it is saturated with oil, the pore volume of the rock sample after it absorbs oil, and the time required for the rock sample to reach the state of saturated oil are also obtained. Based on the weight of the rock sample before self-absorption of water, the weight of the rock sample in the saturated water state, the pore volume of the rock sample after self-absorption of water, and the time required for the rock sample to reach the saturated water state, calculate the water saturation and water absorption rate of the rock sample in the saturated water state. Based on the weight of the rock sample before self-absorption of oil, the weight of the rock sample in the oil-saturated state, the pore volume of the rock sample after self-absorption of oil, and the time required for the rock sample to reach the oil-saturated state, calculate the oil saturation and oil absorption rate of the rock sample in the oil-saturated state. The average wettability of the shale oil reservoir is determined based on the water saturation, oil saturation, water absorption rate, and oil absorption rate of the rock sample.

8. The method for determining the wettability of shale oil reservoirs according to claim 7, characterized in that, The method of determining the average wettability of shale oil reservoirs based on the water saturation, oil saturation, water absorption rate, and oil absorption rate of rock samples includes: The difference between the water saturation and oil saturation of the rock sample is taken as the oil and water saturation index I1 of the shale oil reservoir, and the ratio of the water absorption rate to the oil absorption rate of the rock sample is taken as the oil and water absorption rate index I2 of the shale oil reservoir. The ratio of the oil and water saturation index I1 to the oil and water absorption rate index I2 of the shale oil reservoir is used as the wetting strength index I of the shale oil reservoir. The average wettability of the shale oil reservoir is determined based on the wetting strength index I.

9. The method for determining the wettability of shale oil reservoirs according to claim 8, characterized in that, The determination of the average wettability of shale oil reservoirs based on the wettability index I includes: When -0.15 < I ≤ 0.10, the average wettability of the shale oil reservoir is mixed wettability; When I < -1.0, the average wettability of the shale oil reservoir is oleophilic; When -1.0 < I ≤ -0.15, the average wettability of the shale oil reservoir is mixed wettability with a slight oleophilic tendency; When 0.50 < I, the average wettability of the shale oil reservoir is hydrophilic; When 0.10 < I ≤ 0.50, the average wettability of the shale oil reservoir is mixed wettability with a slight hydrophilic symmetry.

10. The method for determining the wettability of shale oil reservoirs according to any one of claims 2-4 and 7-9, characterized in that, The water saturation of the rock sample in a saturated water state is calculated using the following formula: S wn =((W wn -W1) / ρw) / V p1 In the formula, S wn W represents the water saturation of the rock sample in a saturated water state. wn ρw is the weight of the rock sample in a saturated water state; W1 is the weight of the rock sample before self-absorption of water; ρw is the density of simulated water during the self-absorption process; Vp1 is the pore volume of the rock sample after self-absorption of water. The oil saturation of the rock sample in a saturated oil state is calculated using the following formula: S on =((W on -W2) / ρo) / V p2 In the formula, S on W represents the oil saturation of the rock sample in a saturated oil state. on W1 is the weight of the rock sample in a saturated oil state; W2 is the weight of the rock sample before self-absorption of oil; ρo is the density of the simulated oil during the self-absorption process of the rock sample; Vp2 is the pore volume of the rock sample after self-absorption of oil.

11. The method for determining the wettability of shale oil reservoirs according to any one of claims 5-9, characterized in that, The water absorption rate of the rock sample was calculated using the following formula: V wn =((W wn -W1) / ρw) / V) / t wi In the formula, V wn W represents the water absorption rate of the rock sample. wn ρw is the weight of the rock sample in its saturated water state; W1 is the weight of the rock sample before self-absorption; ρw is the density of the simulated water during the self-absorption process; V is the total volume of the rock sample; t wi The time required for a rock sample to reach a water-saturated state; The oil absorption rate of the rock sample was calculated using the following formula: V on =((W on -W2) / ρo) / V) / t oi In the formula, V on W represents the oil absorption rate of the rock sample. on ρo is the weight of the rock sample in its saturated oil state; W2 is the weight of the rock sample before self-absorption; ρo is the density of the simulated oil during the self-absorption process of the rock sample; V is the total volume of the rock sample; to oi This refers to the time required for a rock sample to reach a saturated oil state.

12. The method for determining the wettability of shale oil reservoirs according to claim 1, characterized in that, The acquisition of the first correspondence between pore radius and signal intensity in a dry state of rock samples, the second correspondence between pore radius and signal intensity in a water-saturated state, and the third correspondence between pore radius and signal intensity in a oil-saturated state includes: Nuclear magnetic resonance T2 spectra were obtained for rock samples in dry, water-saturated, and oil-saturated states, respectively; wherein the nuclear magnetic resonance T2 spectrum represents the relationship between T2 value and signal intensity. Based on the relationship between T2 value and signal intensity, and the conversion relationship between T2 value and pore radius, the first correspondence between pore radius and signal intensity in the dry state of the rock sample, the second correspondence between pore radius and signal intensity in the saturated water state, and the third correspondence between pore radius and signal intensity in the saturated oil state are obtained.

13. The method for determining the wettability of shale oil reservoirs according to claim 1, characterized in that, The determination method also includes: The pore radii with hydrophilicity greater than oleophilicity and pore radii with oleophilicity greater than hydrophilicity are respectively divided into the first interval range and the second interval range; The left boundary of the first interval and / or the second interval is taken as the critical pore radius for this oil-water reversal, and the right boundary is taken as the critical pore radius for the next oil-water reversal.

14. A method for optimizing the amount of fluid injected into the well and the well shut-in time in shale oil development, characterized in that, The optimization method includes: Based on the method for determining the wettability of shale oil reservoirs according to any one of claims 1-13, the wettability of shale oil reservoirs is determined; Based on the wettability of the shale oil reservoir, the amount of fluid injected into the ground and the well shut-in time in shale oil development are optimized.

15. A device for determining the wettability of shale oil reservoirs, characterized in that, The shale oil reservoir wettability determination device is used to perform the shale oil reservoir wettability determination method according to any one of claims 1-13.

16. A machine-readable storage medium storing instructions for causing a machine to execute the shale oil reservoir wettability assessment method according to any one of claims 1-13 of this application or the optimization method for the amount of fluid injected into the ground and the well shut-in time in shale oil development according to claim 14.

17. A processor, characterized in that, The program is used to run a procedure, wherein the program is executed to perform the method for determining the wettability of shale oil reservoirs according to any one of claims 1-13 or the method for optimizing the amount of fluid injected into the ground and the well shut-in time in shale oil development according to claim 14.

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