Method for evaluating oil and gas enrichment capacity of shale oil reservoir

Abstract

The present application relates to a kind of shale oil reservoir oil and gas enrichment ability evaluation method, with the arithmetic mean of adsorption contribution index and pore reservoir index as oil and gas enrichment index, to evaluate oil and gas enrichment ability;0<Oil and gas enrichment index≤0.25, oil and gas enrichment ability is IV class;0.25<Oil and gas enrichment index≤0.50, oil and gas enrichment ability is III class;0.5<Oil and gas enrichment index≤0.75, oil and gas enrichment ability is II class;0.75<Oil and gas enrichment index≤1, oil and gas enrichment ability is I class.The present application first uses adsorption contribution index and pore reservoir index to evaluate the adsorption capacity and reservoir capacity of rock pore to oil and gas, further calculates to obtain oil and gas enrichment index, and establishes the division standard of oil and gas enrichment ability, carries out oil and gas enrichment ability evaluation.

Description

Technical Field

[0001] The present invention relates to the field of petroleum and natural gas engineering, and in particular to a method for evaluating the oil and gas enrichment capacity of a shale oil reservoir during the exploration and development process. Background Art

[0002] China's oil and gas exploration and development is gradually entering the era of unconventional oil and gas. PetroChina recently estimated conventional oil resources at 46.9 billion tons and unconventional oil resources at 55.9 billion tons. The proportion of unconventional resources in production is increasing annually. PetroChina's cumulative proven shale oil reserves are 1.818 billion tons, primarily distributed in the Ordos Basin, Junggar Basin, Songliao Basin, and Bohai Bay Basin. Resource potential determines, and achieving efficient shale oil exploration and development is of vital strategic importance to safeguarding national energy security. Reservoir oil and gas accumulation capacity is a key factor in directly evaluating reserves and geological sweet spots, and it influences the formulation of subsequent oilfield development technology policies and the overall development of the oilfield. Therefore, quantitatively evaluating oil and gas accumulation capacity is crucial for the high-quality development of oilfields.

[0003] By investigating the literature and patents related to unconventional enrichment capacity, the following patents are related to the invention patent of this application: (1) In the patent application proposal with patent application number CN202410141768.4 and titled "A method, system, equipment and medium for predicting oil and gas enrichment", the method includes obtaining regional Bouguer gravity anomaly, residual Bouguer gravity anomaly and sedimentary layer thickness to identify the position of the fault plane, apparent depth of the fault and other information, and then predicting the oil and gas enrichment information of the target basin based on the fault influencing factor. (2) In the patent application proposal with patent application number CN201911373290.3 and titled “Method and Apparatus for Predicting Tight Sandstone Oil and Gas Enrichment Zones”, the method divides the completed wells in the work area into different types according to the thickness value and / or daily production value of the oil and gas sand bodies of the completed wells; for a plurality of seismic attributes, the matching rate of each seismic attribute to different types of completed wells in the work area is determined, and a multi-attribute weighted calculation is performed on the plurality of seismic attributes to obtain the probability distribution parameters of the oil and gas attributes of the work area; and based on the probability distribution parameters of the oil and gas attributes of the work area, the tight sandstone oil and gas enrichment zone of the work area is predicted. (3) In the patent application proposal with patent application number CN202210502367.8 and titled “A method, device, storage medium and electronic equipment for oil and gas enrichment evaluation”, the method generates an oil and gas filling adjustment model, an oil and gas preservation evaluation model and an oil and gas enrichment prediction model based on the fault activity period, the matching degree of the accumulation period and the fracture permeability of the target fault zone to realize the evaluation of the oil and gas enrichment pattern of the target fault zone.

[0004] By comparison, researchers have primarily evaluated oil and gas enrichment capacity from the perspectives of influencing factors, enrichment patterns, enrichment patterns, and enrichment conditions. This application, from a completely new perspective, utilizes the adsorption contribution index and pore size reservoir index, two key factors influencing oil and gas enrichment capacity, to evaluate the adsorption and reservoir capacity of rock pores for oil and gas. This approach further calculates the oil and gas enrichment index and establishes classification criteria, ultimately achieving quantitative evaluation. Summary of the Invention

[0005] The present invention aims to address the above-mentioned problems and proposes a method for evaluating the oil and gas enrichment capacity of shale oil reservoirs.

[0006] The technical solution of the present invention is:

[0007] A method for evaluating the oil and gas enrichment capacity of a shale oil reservoir uses the arithmetic mean of the adsorption contribution index and the pore size storage index as the oil and gas enrichment index to evaluate the oil and gas enrichment capacity. When the oil and gas enrichment index is 0 < 0.25 or less, the oil and gas enrichment capacity is Class IV; when the oil and gas enrichment index is 0.25 < 0.50 or less, the oil and gas enrichment capacity is Class III; when the oil and gas enrichment index is 0.5 < 0.75 or less, the oil and gas enrichment capacity is Class II; and when the oil and gas enrichment index is 0.75 < 1 or less, the oil and gas enrichment capacity is Class I.

[0008] The specific solution process of the adsorption contribution index is as follows:

[0009] (3)

[0010] Where: is the adsorption contribution index, dimensionless; It is the minimum pressure when the adsorption amount is 0.5 times the maximum adsorption amount, in MPa; is the maximum adsorption capacity, unit is m 3 / kg; It is the pressure when the adsorption amount is 0.5 times the maximum adsorption amount, in MPa; The maximum adsorption capacity of the target block rock sample, unit: m 3 / kg;

[0011] The pressure at which the adsorption capacity is 0.5 times the maximum adsorption capacity and maximum adsorption capacity The specific solution process is as follows: take a rock sample from the target block to make the first rock sample, and obtain the pressure through high pressure adsorption experiment. With pressure The first rock sample quality at The relationship between the pressure and the pressure is expressed as The first rock sample quality at Converted into adsorption amount :

[0012] (1)

[0013] Where: is the adsorption capacity, unit is m 3 / kg; For pressure The mass of the first rock sample at the time, in kg; is the initial mass of the first rock sample, in kg; is the density of methane under standard conditions, in kg / m 3 ;

[0014] According to adsorption theory, build pressure and adsorption capacity Relationship:

[0015] (2)

[0016] Fitting the experimental results of the high-pressure adsorption experiment, the pressure at which the adsorption amount is 0.5 times the maximum adsorption amount is obtained P 0.5 and maximum adsorption capacity .

[0017] The specific solution process of the pore size reservoir index is as follows:

[0018] (6)

[0019] Where: is the pore size reservoir index, dimensionless; is the low-pressure aperture fractal dimension, dimensionless; is the high-pressure aperture fractal dimension, dimensionless;

[0020] The low-pressure aperture fractal dimension and high-pressure aperture fractal dimension The specific solution process is to establish a low-pressure aperture fractal dimension model and a high-pressure aperture fractal dimension model, which are:

[0021] (4)

[0022] (5)

[0023] Where: is the volume, unit is m 3 ;

[0024] is the low-pressure fitting coefficient, dimensionless; is the high pressure fitting coefficient, dimensionless;

[0025] Take a rock sample from the target block and make a second rock sample. Through mercury injection experiment, obtain the pressure / differential pressure and volume. The relationship between the low-pressure and high-pressure mercury injection experiments was fitted to obtain the low-pressure pore fractal dimension. and high-pressure aperture fractal dimension .

[0026] The specific solution process of the oil and gas enrichment index is as follows:

[0027] (7)

[0028] Where: is the oil and gas enrichment index, dimensionless.

[0029] Preferably, the specific process of obtaining the first rock sample is as follows: taking a rock sample from the target reservoir, crushing it to 80 mesh, drying and removing water, and taking 10g as the first rock sample; the pressure is The first rock sample quality at Obtained by high-pressure magnetic suspension balance adsorption instrument.

[0030] Preferably, the specific process for obtaining the second rock sample is: taking a rock sample from the target reservoir, processing it into a standard cylindrical core with a height of 5 cm and a diameter of 2.5 cm, and using it as the second rock sample. The mercury injection experiment is carried out using a mercury injection instrument.

[0031] The technical effects of the present invention are:

[0032] (1) This invention is the first to use the two main factors affecting oil and gas enrichment capacity (adsorption contribution index and pore size storage index) to evaluate the adsorption and storage capacity of rock pores for oil and gas, further calculate the oil and gas enrichment index, and establish the classification standard of oil and gas enrichment capacity to evaluate oil and gas enrichment capacity;

[0033] (2) The present invention calculates the low-pressure / high-pressure pore fractal dimension by establishing a low-pressure pore fractal dimension model and a high-pressure pore fractal dimension model, thereby achieving quantitative characterization of the pore complexity of low-pressure large pores and high-pressure small pores, and thus achieving the evaluation of rock storage capacity;

[0034] (3) Based on the curve of actual pressure and adsorption amount, the adsorption contribution index is calculated to achieve quantitative evaluation of the rock's adsorption capacity for oil and gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram showing the relationship between pressure, differential pressure and volume under low pressure conditions.

[0036] Figure 2 This is a diagram showing the relationship between pressure, differential pressure and volume under high pressure conditions.

[0037] Figure 3 This is a curve of pressure and adsorption capacity. DETAILED DESCRIPTION

[0038] Example 1

[0039] A method for evaluating the oil and gas enrichment capacity of a shale oil reservoir uses the arithmetic mean of the adsorption contribution index and the pore size storage index as the oil and gas enrichment index to evaluate the oil and gas enrichment capacity. When the oil and gas enrichment index is 0 < 0.25 or less, the oil and gas enrichment capacity is Class IV; when the oil and gas enrichment index is 0.25 < 0.50 or less, the oil and gas enrichment capacity is Class III; when the oil and gas enrichment index is 0.5 < 0.75 or less, the oil and gas enrichment capacity is Class II; and when the oil and gas enrichment index is 0.75 < 1 or less, the oil and gas enrichment capacity is Class I.

[0040] Example 2

[0041] A method for evaluating the oil and gas enrichment capacity of a shale oil reservoir is as follows:

[0042] (1) Two rock samples from the same target reservoir are taken and used for high-pressure adsorption experiment and mercury injection experiment respectively, and the experimental results of high-pressure adsorption experiment and mercury injection experiment are obtained (the experimental results of mercury injection experiment in low pressure area and the experimental results of mercury injection experiment in high pressure area);

[0043] (2) According to adsorption theory, construct the pressure as shown in formula (2) and adsorption capacity The relationship between the adsorption capacity and the maximum adsorption capacity is obtained by fitting the experimental results of the high-pressure adsorption experiment to obtain the pressure when the adsorption capacity is 0.5 times the maximum adsorption capacity. P 0.5 and maximum adsorption capacity , and then the adsorption contribution index is calculated by formula (3) ;

[0044] (3) Establish the low-pressure aperture fractal dimension model shown in formula (4) and the high-pressure aperture fractal dimension model shown in formula (5). Formula (4) fits the experimental results of the mercury injection experiment in the low-pressure area, and formula (5) fits the experimental results of the mercury injection experiment in the high-pressure area, and obtains the low-pressure aperture fractal dimension and high-pressure aperture fractal dimension , and then the pore size storage index is calculated by formula (6): ;

[0045] (4) The oil and gas enrichment index is calculated by formula (7) to evaluate the oil and gas enrichment capacity.

[0046] Specific experimental cases

[0047] The following describes in detail the specific embodiments of the present invention based on the accompanying drawings and a shale oil reservoir rock sample from a certain block. A method for evaluating the oil and gas enrichment capacity of a shale oil reservoir is as follows:

[0048] This method was applied to the Q block, a typical continental shale oil major development area in a certain basin in China. The block is divided into three sub-layers, Q1 to Q3, vertically. A full-diameter downhole rock sample from the Q1 layer, the target layer of Well FH, was taken and numbered FH-1.

[0049] 1. Grind the FH-1 rock sample to 80 mesh, dry and remove water, and take 10g as the first rock sample FH-1-1. Record the initial mass of the first rock sample. ; Use high-pressure magnetic suspension balance adsorption instrument to obtain pressure With pressure The first rock sample quality at The relationship between and pressure is expressed as The first rock sample quality at Converted into adsorption amount , get pressure and adsorption capacity The curve graph between Figure 3 As shown;

[0050] Build pressure and adsorption capacity The functional relationship between is shown in formula (2), and Figure 3 The maximum adsorption capacity was obtained by fitting 2.78m 3 / kg, is 8.65MPa, The maximum adsorption capacity of the target rock sample is 7.32MPa. 5.12m 3 / kg; Combined with formula (3), the adsorption contribution index is calculated It is 0.46, which is used to evaluate the adsorption capacity of rock pores for oil and gas.

[0051] 2. Process the FH-1 rock sample into a standard cylindrical core with a height of 5 cm and a diameter of 2.5 cm as the second rock sample FH-1-2; use a mercury intrusion porosimeter to test the second rock sample FH-1-2, and obtain the relationship between pressure, differential pressure and volume under low pressure conditions ( Figure 1 ) and the relationship between pressure, differential pressure and volume under high pressure conditions ( Figure 2 );

[0052] The low-pressure aperture fractal dimension model and the high-pressure aperture fractal dimension model are established respectively; the low-pressure and high-pressure turning point is the point where the slope of the data turns from positive to negative, and the low-pressure and high-pressure turning point is 10MPa; using formula (4) to fit Figure 1Get the low-pressure aperture fractal dimension D u is 2.839, and is fitted using formula (5) Figure 2 Get the high pressure aperture fractal dimension D d is 2.599; the pore size storage index is calculated by formula (6): It is 0.66.

[0053] 3. Calculate the oil and gas enrichment index using formula (7): is 0.56, and the oil and gas enrichment capacity of the target layer Q1 in the FH well is classified as Class II.

[0054] Traditional methods generally use the geological reserves of the target reservoir to evaluate the oil and gas enrichment capacity of the reservoir. The larger the geological reserves of the target reservoir, the better the oil and gas enrichment capacity. It is known that the geological reserves of the target layer Q1 in the FH well are expressed as the sum of free gas and adsorbed gas, with a value of 4.78×10 9 m 3 The geological reserves of the same type of reservoir range from 0.42×10 9 m 3 -8.91×10 9 m 3 The following formula is used to evaluate the oil and gas migration capacity:

[0055] Where: is the traditional oil and gas migration capacity index, dimensionless; is the reservoir permeability, m 3 ; is the maximum permeability of the same type of reservoir, m 3 ; is the minimum permeability of the same type of reservoir, m 3 .

[0056] Conventional oil and gas migration capacity index The value is 0.51, which is also a Class II reservoir according to the classification rules in this application.

[0057] The present invention has been specifically described above through examples. It is necessary to point out that the present embodiments are merely preferred embodiments of the present invention and do not limit the present invention in any way. They are not limited to the forms disclosed herein and should not be construed as excluding other embodiments. Modifications and simple variations made by those skilled in the art that do not depart from the technical concept and scope of the present invention are all within the scope of protection of the technical solution of the present invention.

Claims

1. A method for evaluating the oil and gas enrichment capacity of a shale oil reservoir, characterized in that: The arithmetic mean of the adsorption contribution index and the pore size storage index is used as the oil and gas enrichment index to evaluate the oil and gas enrichment capacity. When the oil and gas enrichment index is 0 < ≤ 0.25, the oil and gas enrichment capacity is Class IV; when the oil and gas enrichment index is 0.25 < ≤ 0.50, the oil and gas enrichment capacity is Class III; when the oil and gas enrichment index is 0.5 < ≤ 0.75, the oil and gas enrichment capacity is Class II; when the oil and gas enrichment index is 0.75 < ≤ 1, the oil and gas enrichment capacity is Class I. The specific solution process of the adsorption contribution index is as follows: (3) Where: is the adsorption contribution index, dimensionless; It is the minimum pressure when the adsorption amount is 0.5 times the maximum adsorption amount, in MPa; is the maximum adsorption capacity, unit is m 3 / kg; It is the pressure when the adsorption amount is 0.5 times the maximum adsorption amount, in MPa; The maximum adsorption capacity of the target block rock sample, unit: m 3 / kg; The pressure at which the adsorption capacity is 0.5 times the maximum adsorption capacity and maximum adsorption capacity The specific solution process is as follows: take a rock sample from the target block to make the first rock sample, and obtain the pressure through high pressure adsorption experiment. With pressure The first rock sample quality at The pressure is converted to The first rock sample quality at Converted into adsorption amount : (1) Where: is the adsorption capacity, unit is m 3 / kg; For pressure The mass of the first rock sample at the time, in kg; is the initial mass of the first rock sample, in kg; is the density of methane under standard conditions, in kg / m 3 ; According to adsorption theory, build pressure and adsorption capacity Relationship: (2) Fitting the experimental results of the high-pressure adsorption experiment, the pressure at which the adsorption amount is 0.5 times the maximum adsorption amount is obtained P 0.5 and maximum adsorption capacity ; The specific solution process of the pore size reservoir index is as follows: (6) Where: is the pore size reservoir index, dimensionless; is the low-pressure aperture fractal dimension, dimensionless; is the high-pressure aperture fractal dimension, dimensionless.

2. The method for evaluating the oil and gas enrichment capacity of a shale oil reservoir according to claim 1, characterized in that: The low-pressure aperture fractal dimension and high-pressure aperture fractal dimension The specific solution process is to establish a low-pressure aperture fractal dimension model and a high-pressure aperture fractal dimension model, which are: (4) (5) Where: is the volume, unit is m 3 ; is the low-pressure fitting coefficient, dimensionless; is the high pressure fitting coefficient, dimensionless; Take a rock sample from the target block and make a second rock sample. Through mercury injection experiment, obtain the pressure / differential pressure and volume. The relationship between the low-pressure and high-pressure mercury injection experiments was fitted to obtain the low-pressure pore fractal dimension. and high-pressure aperture fractal dimension .

3. The method for evaluating the oil and gas enrichment capacity of a shale oil reservoir according to claim 2, characterized in that: The specific solution process of the oil and gas enrichment index is: （7） Where: is the oil and gas enrichment index, dimensionless.

4. The method for evaluating the oil and gas enrichment capacity of a shale oil reservoir according to claim 1, wherein: The specific process of obtaining the first rock sample is as follows: a rock sample is taken from the target reservoir, crushed to 80 mesh, dried and dehydrated, and 10 g is taken as the first rock sample.

5. The method for evaluating the oil and gas enrichment capacity of a shale oil reservoir according to claim 1, characterized in that: The pressure is The first rock sample quality at Obtained by high-pressure magnetic suspension balance adsorption instrument.

6. The method for evaluating the oil and gas enrichment capacity of a shale oil reservoir according to claim 2, characterized in that: The specific process of obtaining the second rock sample is as follows: a rock sample is taken from the target reservoir, and processed into a standard cylindrical rock core with a height of 5 cm and a diameter of 2.5 cm, which is used as the second rock sample.

7. The method for evaluating the oil and gas enrichment capacity of a shale oil reservoir according to claim 2, characterized in that: The mercury intrusion experiment is performed by a mercury intrusion instrument.

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