Correction method for movable hydrocarbon content of shale oil with high gas-oil ratio based on phase state and rock pyrolysis

Abstract

The present invention discloses a method for correcting the movable hydrocarbon content of shale oil with a high gas-oil ratio based on phase state and rock pyrolysis, comprising the following steps: 1. According to the formation fluid properties of the target block, simulate and prepare the fluid under the original formation conditions; 2. Perform PVT experiments and fluid physical property tests on the configured fluid to obtain the well flow composition and deviation coefficient; 3. Establish a theoretical shale movable hydrocarbon content prediction model to calculate the theoretical movable hydrocarbon content of shale and the light hydrocarbon correction coefficient; 4. According to the light hydrocarbon correction coefficient, determine the light hydrocarbon content of the shale oil after recovery and the original total oil content. The present invention fully considers the actual reservoir geological conditions on site and the fluid characteristics of different types of shale oil reservoirs. Based on the fluid property characteristics of high gas-oil ratio shale oil reservoirs with a high proportion of light components and strong volatility, combined with PVT and existing rock pyrolysis methods, the movable hydrocarbon content of shale oil with a high gas-oil ratio is corrected. This allows the pyrolysis parameter S1 of shale to more objectively and accurately characterize the movable hydrocarbon content of shale.

Description

Technical Field

[0001] The present invention relates to the technical field of shale gas development, and in particular to a method for correcting movable hydrocarbon content of high gas-oil ratio shale oil based on phase state and rock pyrolysis. Background Art

[0002] At present, the supply of conventional oil and gas resources cannot meet the growing energy demand, and the contradiction between oil and gas supply and demand is rising rapidly. Unconventional oil and gas energy accounts for an increasingly large proportion of energy supply, and the exploration and development of shale oil and gas is also receiving more and more attention. As an important part of oil and gas exploration, resource calculation is one of the indispensable links in shale oil exploration. The parameters selected in the resource evaluation process are significantly different from those of conventional oil and gas resource evaluation. Previous researchers proposed to use the parameter pyrolysis S1 that reflects the hydrocarbon content of mudstone to evaluate shale oil resources. In the actual experimental analysis process, due to the influence of coring methods, core storage conditions, experimental test analysis technology, and kerogen adsorption and swelling, S1 has light hydrocarbon loss, resulting in the measured S1 being lower than the underground oil content of the in-situ shale oil, which is difficult to directly reflect the in-situ oil content information of underground shale oil.

[0003] At present, the existing technology generally uses the light hydrocarbon recovery amount S1 and the difference between the pyrolysis of samples before and after oil washing to recover the total oil content S of shale. c =S0+ΔS1+△S2. This method only considers gaseous hydrocarbons C in the recovery of light hydrocarbons. 1-5 The loss of light hydrocarbon components C 5-14 There is a problem of loss during the process of drilling cores and long-term storage of cores in the core library, which makes the oil content evaluation after the recovery of light hydrocarbons inaccurate and different from the actual value. Therefore, it is necessary to study a method for correcting the movable hydrocarbon content of high gas-oil ratio shale oil based on phase state and rock pyrolysis. Summary of the invention

[0004] The purpose of the present invention is to provide a method for correcting the amount of movable hydrocarbons in shale oil with a high gas-oil ratio based on phase state and rock pyrolysis, which solves the technical problem that the existing methods all correct the resource amount of shale oil reservoirs with high maturity, low gas-oil ratio and small proportion of light hydrocarbon components, but ignore the high proportion of light hydrocarbon components and high light hydrocarbon losses in volatile oil reservoirs and condensate oil reservoirs with high gas-oil ratio.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for correcting the amount of movable hydrocarbons in high gas-oil ratio shale oil based on phase state and rock pyrolysis, comprising the following steps:

[0006] S1. According to the formation fluid properties of the target block, simulate and prepare the fluid under the original formation conditions;

[0007] S2. Perform PVT experiment and fluid physical property test on the fluid configured in S1 to obtain the well flow composition and deviation coefficient;

[0008] S3. Establish a theoretical shale movable hydrocarbon amount prediction model to calculate the theoretical shale movable hydrocarbon amount and light hydrocarbon correction coefficient;

[0009] S4. Determine the light hydrocarbon content and the original total oil content of the recovered shale oil based on the light hydrocarbon correction coefficient obtained in S3.

[0010] In some embodiments, the formation fluid properties of the target block in S1 include formation temperature, formation pressure, gas-oil ratio, and deviation coefficient, and the fluid under in situ conditions is simulated and prepared based on the above parameters.

[0011] In some embodiments, in S3, the theoretical shale movable hydrocarbon amount prediction model is:

[0012]

[0013] In the formula, S KD is the theoretical movable hydrocarbon content, mg / g; P p is the formation pressure, MPa; V b is the core volume, m 3 ; is the porosity, %; S O is the oil saturation, %; M is the relative molecular mass, dimensionless; Z is the deviation coefficient, dimensionless; R is the molar gas constant, 0.008314; T p is the formation temperature, K; m b is the core weight, g.

[0014] In some embodiments, due to the large loss of light hydrocarbons in the placed ordinary sample, the calculated movable hydrocarbon amount includes all components of the free hydrocarbon amount, and it is necessary to further determine the light hydrocarbon correction factor, that is, the movable hydrocarbon amount S KD Total difference of S1 and movable hydrocarbon content S1 of segmented pyrolysis of common samples KD Ratio.

[0015] The calculation expression of the light hydrocarbon correction coefficient is:

[0016]

[0017] Where K is the light hydrocarbon correction factor, dimensionless; S KD is the theoretical movable hydrocarbon content, mg / g; S 1总 =S 1-1 +S 1-2 , S 1-1 is the light oil content, S 1-2 is the light medium oil content, S 1总 Light hydrocarbon content.

[0018] In some embodiments, in S4, the calculation expression of the light hydrocarbon content of the recovered shale oil is:

[0019] S 轻烃 =KS 1总 +S 1总 (3)

[0020] The calculation expression of the original total oil content after recovery is:

[0021] S TOL =KS 1总 +S 1总 +S 2-1 (4)

[0022] In the formula, S 2-1 It is light and heavy oil content.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention fully considers the actual reservoir geological conditions on site and the fluid properties of different types of shale oil reservoirs. Based on the fluid properties of high gas-oil ratio shale oil reservoirs with high proportion of light components and strong volatility, combined with PVT and existing rock pyrolysis methods, the mobile hydrocarbon content of high gas-oil ratio shale oil is corrected. This allows the pyrolysis parameter S1 of shale to more objectively and accurately characterize the mobile hydrocarbon content of shale. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0026] Figure 2 This is a schematic diagram of the light hydrocarbon content and the calculation of the movable hydrocarbon content by staged pyrolysis of the core according to an embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the total oil content and the corrected total oil content of the core segmented pyrolysis according to the embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] See also Figure 1-Figure 3 A method for correcting movable hydrocarbons in high gas-oil ratio shale oil based on phase state and rock pyrolysis, characterized in that it comprises the following steps:

[0030] S1. According to the properties of the formation fluid of the target block, the formation fluid is prepared. The formation temperature and formation pressure are estimated based on the gas-oil ratio obtained from the hydrocarbon generation experiment and the formation depth of the formation fluid of the target block, and the fluid under the original formation conditions is simulated and prepared.

[0031] S2. Perform PVT experiment and fluid physical property test on the fluid configured in S1 to obtain the well flow composition, deviation coefficient, sample fluid viscosity and condensate density; the well flow composition includes CO2, N2, C1, C2, C3, iC4, nC4, iC5, nC5, C6, C7, C8, C9, C 10 , C 11+ Etc. At the same time, the basic data of the core are tested, including volume, dry weight, porosity, oil saturation and density.

[0032] S3. Establish a theoretical shale movable hydrocarbon prediction model to calculate the theoretical shale movable hydrocarbon content and light hydrocarbon correction coefficient. Specifically, the theoretical shale movable hydrocarbon content S is established by performing segmented pyrolysis on ordinary shale samples. KD Compared with ordinary shale staged pyrolysis S 1总 Total light hydrocarbons correction model.

[0033] The specific method is as follows:

[0034] The core was crushed to less than 100 mesh, and the temperature-increasing pyrolysis experiment was carried out with a rock pyrolysis analyzer to measure the light oil S 1－1 , light medium oil S 1－2 and light and heavy S 2－1 Since a large amount of light hydrocarbons are lost in the ordinary samples placed, the calculated movable hydrocarbon content includes all components of the free hydrocarbon content. Therefore, it is necessary to further determine the light hydrocarbon correction factor, that is, the shale movable hydrocarbon content S KD Segmented pyrolysis of common samples 1总 Total difference and shale movable hydrocarbon content S KD ratio;

[0035] The theoretical shale movable hydrocarbon prediction model is:

[0036]

[0037] In the formula, S KD is the theoretical movable hydrocarbon content, mg / g; P p is the formation pressure, MPa; V b is the core volume, m 3 ; is the porosity, %; S O is the oil saturation, %; M is the relative molecular mass, dimensionless; Z is the deviation coefficient, dimensionless; R is the molar gas constant, 0.008314; T p is the formation temperature, K; mb is the core weight, g.

[0038] The calculation expression of light hydrocarbon correction factor is:

[0039]

[0040] Where K is the light hydrocarbon correction factor, dimensionless; S KD is the theoretical movable hydrocarbon content, mg / g; S 1总 =S 1-1 +S 1-2 , S 1-1 is the light oil content, S 1-2 is the light medium oil content, S 1总 Light hydrocarbon content.

[0041] S4. According to the light hydrocarbon correction coefficient obtained in S3, the corrected light hydrocarbon content, i.e., the maximum movable amount S 1总 (S 1－1 +S 1－2 ) and the original total oil content S TOL (S 1－1 +S 1－2 +S 2-1 ).

[0042] The calculation expression of the corrected light hydrocarbon content of shale oil is:

[0043] S 轻烃 =KS 1总 +S 1总 (3)

[0044] The calculation expression of the corrected original total oil content is:

[0045] S TOL =KS 1总 +S 1总 +S 2-1 (4)

[0046] In the formula, S 2-1 It is light and heavy oil content.

[0047] In a specific embodiment, taking a high gas-oil ratio shale oil reservoir as an example, the present invention is used to correct the original total oil volume of the shale oil reservoir, specifically comprising the following steps:

[0048] 1. The formation fluid data of the target well is obtained, as shown in Table 1;

[0049] Table 1 Fluid property data of target shale reservoir

[0050] Pressure(MPa) Temperature (K) <![CDATA[Gas-oil ratio (m 3 / m 3 )]]> Coefficient of variation 30 362.15 1000 1.1129

[0051] 2. The viscosity of the sample fluid is 0.256mPa·s, and the density of the condensate oil is 0.8024g / cm 3 . The composition of the sample preparation fluid is calculated as shown in Table 2;

[0052] Table 2 Well Flow Composition

[0053]

[0054] 3. The basic data of the core tested are shown in Table 3:

[0055] Table 3 Core basic data table

[0056]

[0057] 4. Calculate the movable hydrocarbon volume S of shale core KD ;

[0058] Based on different cores, the movable hydrocarbon volume S of shale core is calculated according to formula (1): KD The calculation results are shown in Table 4.

[0059] Table 4 Calculation results of movable hydrocarbon content in different cores

[0060] serial number 1 2 3 4 5 6 7 8 9 10 <![CDATA[S KD ]]> 0.465 0.88 0.471 0.582 0.33 0.33 0.706 1.065 0.366 0.739

[0061] 5. Perform segmented pyrolysis on common core samples to establish a theoretical shale movable hydrocarbon content S KD Compared with ordinary shale staged pyrolysis S 1总 Total light hydrocarbon correction model;

[0062] The core was subjected to a staged pyrolysis experiment, and the light hydrocarbon correction coefficient was calculated according to formula (2). The calculation results are shown in Table 5.

[0063] Table 5 Results of staged pyrolysis and light hydrocarbon correction

[0064]

[0065] 6. Calculate the original total oil content S TOL ;

[0066] According to formula (3), the total oil content is corrected and the calculation results are shown in Table 6;

[0067] Table 6 Corrected total oil content results

[0068] serial number 1 2 3 4 5 6 7 8 9 10 <![CDATA[S TOL ]]> 3.072 1.024 3.829 3.989 5.869 5.26 3.788 1.359 4.327 1.962

[0069] like Figure 2 - Figure 3 As shown in the figure, the theoretical movable hydrocarbon content and total oil content are compared with the experimental test values, and it is found that the calculated results and the measured results have a good correlation, and the correlation coefficient R2 >0.9, indicating that this method can be effectively used to correct the amount of movable hydrocarbons in shale oil with a high gas-oil ratio.

[0070] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for correcting the amount of movable hydrocarbons in high gas-oil ratio shale oil based on phase state and rock pyrolysis, characterized in that: The following steps are involved: S1. According to the formation fluid properties of the target block, simulate and prepare the fluid under the original formation conditions; S2. Perform PVT experiment and fluid physical property test on the fluid configured in S1 to obtain the well flow composition and deviation coefficient; S3. Establish a theoretical shale movable hydrocarbon amount prediction model to calculate the theoretical shale movable hydrocarbon amount and light hydrocarbon correction coefficient; The theoretical shale movable hydrocarbon amount prediction model is: In the formula, S KD is the theoretical movable hydrocarbon content, mg / g; P p is the formation pressure, MPa; V b is the core volume, m 3 ; is the porosity, %; S O is the oil saturation, %; M is the relative molecular mass, dimensionless; Z is the deviation coefficient, dimensionless; R is the molar gas constant, 0.008314; T p is the formation temperature, K; m b is the core weight, g; The calculation expression of the light hydrocarbon correction coefficient is: Where K is the light hydrocarbon correction factor, dimensionless; S KD is the theoretical movable hydrocarbon content, mg / g; S 1总 =S 1-1 +S 1-2 , S 1-1 is the light oil content, S 1-2 is the light medium oil content, S 1总 is the total amount of light hydrocarbons; S4. Determine the light hydrocarbon content and the original total oil content of the recovered shale oil based on the light hydrocarbon correction coefficient obtained in S3.

2. The method for correcting movable hydrocarbons in high gas-oil ratio shale oil based on phase state and rock pyrolysis according to claim 1, characterized in that: The formation fluid properties of the target block in S1 include formation temperature, formation pressure, gas-oil ratio, and deviation coefficient.

3. The method for correcting movable hydrocarbons in high gas-oil ratio shale oil based on phase state and rock pyrolysis according to claim 1, characterized in that: In S4, the calculation expression of the light hydrocarbon content of the recovered shale oil is: S 轻烃 =KS 1总 +S 1总 (3) The calculation expression of the original total oil content after recovery is: S TOL =KS 1总 +S 1总 +S 2-1 (4) In the formula, S 2-1 It is light and heavy oil content.

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