Rapid compressibility evaluation method for tight sandstone gas reservoir horizontal well section

Abstract

The invention discloses a tight sandstone gas reservoir horizontal well section compressibility rapid evaluation method, which comprises the following steps: (1) establishing a three-dimensional reservoir quality model, and obtaining the reservoir quality category of a horizontal well section; (2) constructing a brittleness index model of adjacent vertical well mineral components; (3) obtaining the brittleness index of the well section of the horizontal well; and (IV) integrating the reservoir types of the horizontal well section and the normalized brittleness index to form a compressibility rapid evaluation chart, and rapidly dividing compressibility types of the horizontal well section. According to the method, the reservoir quality type and the brittleness index of the horizontal well section are obtained on the basis of the relation among the adjacent vertical well productivity, the mineral component experiment and the natural gamma logging curve, the compressibility rapid evaluation chart is formed, and reference is provided for horizontal well rapid fracturing segmented optimization and fracturing effect improvement.

Description

Technical Field

[0001] The invention belongs to the technical field of geological exploration, and in particular relates to a method for quickly evaluating the compressibility of a horizontal well section in a tight sandstone gas reservoir. Background Art

[0002] Tight sandstone gas reservoirs have the characteristics of poor physical properties, complex pore structure, and strong heterogeneity. The reservoirs need to be broken up during exploitation. In order to significantly increase the reserve utilization rate and single well production capacity of tight gas reservoirs, horizontal well staged fracturing is often used.

[0003] Compressibility evaluation is the basis for selecting the optimal fracturing interval for tight sandstone gas reservoirs, the key to the success of fracturing scheme design, and an important factor affecting the effect of fracturing transformation. Compressibility is affected by factors such as reservoir physical properties, oil and gas content, mineral composition, rock mechanical properties, and geostress. Therefore, compressibility evaluation needs to comprehensively consider both geological sweet spots and engineering sweet spots to ensure that effective fractures are formed during fracturing while obtaining better production capacity.

[0004] Geological sweet spots refer to areas where oil and gas are relatively rich. Evaluation parameters are usually reservoir properties, thickness, oil and gas content, etc. Engineering sweet spots refer to the difficulty of reservoir fracturing transformation. Evaluation parameters are usually rock brittleness, fracture toughness, stress difference coefficient, etc. These evaluation parameters are generally obtained through three methods: one is downhole coring and experimental analysis. The second is to have complete logging data and conduct logging interpretation and evaluation. The third is seismic data and conduct seismic interpretation and evaluation (the research accuracy of this method is limited by the quality of seismic data). Therefore, it has been fully utilized in the evaluation of vertical well compressibility.

[0005] Compared with vertical wells, horizontal wells are more difficult to construct, have strong reservoir heterogeneity, and are more expensive. As a result, in actual work, horizontal wells are often not cored, and logging data are incomplete or missing (only natural gamma curves are available). If the quality of seismic data is poor, the parameters that can be obtained in geological sweet spots and engineering sweet spots are limited, and the accuracy of the parameters is difficult to guarantee. How to conduct compressibility evaluation of horizontal well sections and improve accuracy under the condition of limited data is a difficult problem currently faced. Summary of the invention

[0006] The present invention is proposed to solve the problem in the prior art that it is difficult to implement compressibility evaluation of horizontal wells due to limitations in coring and logging data collection. Its purpose is to provide a method for rapid evaluation of the compressibility of horizontal well sections in tight sandstone gas reservoirs, so as to provide a reference for rapid segmentation optimization of horizontal well fracturing and improving fracturing effects.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for quickly evaluating the compressibility of a horizontal well section in a tight sandstone gas reservoir comprises the following steps:

[0009] (I) Establishment of three-dimensional reservoir quality model (Z 模型 ), obtain the reservoir quality category (Z) of the horizontal well section

[0010] (i) Based on the production characteristics and formation conditions of tight sandstone gas reservoirs, combined with the gas well open flow rate (10 4 m 3 / dm) and porosityф(%), and the gas well types are classified;

[0011] This part is determined based on the patent "202110604813.1-Method and device for determining the production capacity of tight gas reservoirs"

[0012] The gas well types are divided into Class I gas wells, Class II gas wells and Class III gas wells;

[0013] (ii) determining the reservoir quality parameter limits of each type of gas well based on the reservoir quality calibration parameters;

[0014] The reservoir quality calibration parameter porosity ф;

[0015] The reservoir quality parameter limits of each type of gas well are specifically as follows:

[0016] The limit of reservoir quality parameters for Class I gas wells is porosity ф ≥ a;

[0017] The limit of reservoir quality parameters for type II gas wells is a≥porosityф≥b;

[0018] The limit of reservoir quality parameters for Class III gas wells is b≥porosityф≥c

[0019] Among them: a, b, and c are the lower limits of porosity of three types of gas wells determined by the classification and evaluation of gas wells in tight sandstone gas reservoirs in the study area;

[0020] a, b, and c in this application are data determined after regular analysis based on known data; gas well classification and evaluation belongs to the prior art, and this application obtains a, b, and c based on the document "Li Tiantai, Mou Maoyuan, Zhang Xin, Li Wenpeng, Ye Xiaochuang, Li Chunxia, ​​"Horizontal Well Classification and Evaluation Method Based on Dynamic Data - Taking Su 14 Block as an Example", Journal of Xi'an Shiyou University (Natural Science Edition), Vol. 30, No. 5, September 2015, pp. 31-36";

[0021] (iii) Using three-dimensional porosity ф 模型 Based on the reservoir quality calculation formula, the three-dimensional reservoir quality model Z is established by calculation in the geological modeling software. 模型 ;

[0022] The three-dimensional porosity ф 模型Based on the porosity interpretation results of adjacent vertical wells, the property modeling function of the commercial petrel geological modeling software of the conventional oil industry was used to establish the model;

[0023] The reservoir quality calculation formula is: Z = IF (ф ≥ a, 3, IF (ф ≥ b, 2, IF (ф ≥ c, 3, 1))),

[0024] Where: a, b, c are the lower limits of porosity of three types of gas wells determined by the classification and evaluation of tight sandstone gas reservoirs in the study area, %;

[0025] The three-dimensional reservoir quality model Z 模型 The calculation expression of Z is: 模型 =IF(ф 模型 >a,3,IF(ф 模型 >b,2,IF(ф 模型 >c,1,0))),

[0026] Where: a, b, c are the lower limits of the porosity of three types of gas wells determined by the classification and evaluation of gas wells in the tight sandstone gas reservoirs in the study area, respectively; 3 represents the reservoir quality development area of ​​type I gas wells, 2 represents the reservoir quality development area of ​​type II gas wells, 1 represents the reservoir quality development area of ​​type III gas wells, and 0 represents the reservoir development area with ineffective fracturing;

[0027] (iv) Based on the three-dimensional reservoir quality model (Z 模型 ), in the three-dimensional reservoir quality model Z 模型 Extract the reservoir category (Z) along the horizontal well trajectory;

[0028] (II) Constructing a brittleness index model for the mineral components of adjacent vertical wells;

[0029] (i) Calculate the quartz brittle mineral content BI based on the mineral composition analysis results of the adjacent vertical well core 石英 (%);

[0030] The quartz brittle mineral content BI 石英 The calculation expression of (%) is:

[0031]

[0032] (ii) Using core calibration logging technology, applying the natural gamma curve G R Linear fitting of quartz brittle mineral content BI 石英 (%) calculation expression,

[0033] Quartz brittle mineral content BI after fitting 石英 (%) Expression is BI 石英 =eG R+ f,

[0034] Where: e and f are fitting values;

[0035] (iii) Using the natural gamma curve G of the adjacent vertical well R， Substitute the quartz brittle mineral content BI after fitting 石英 Calculate the expression to determine the brittleness index BI of the mineral components of the adjacent vertical wells;

[0036] (iv) Calculate the rock brittleness index BI of a single well based on the vertical and shear wave velocity and density curves of adjacent vertical wells 测井 ; The method is based on references: Qin Hao, Yang Xiaolei, "Research on Brittle Well Logging Interpretation Methods for Tight Reservoirs", Well Logging Technology, October 2019, Vol. 43, No. 5, pp. 509-513, 530;

[0037] (III) Obtaining the brittleness index of the horizontal well section;

[0038] (i) Comparison of the brittleness index (BI) of the mineral components of adjacent vertical wells with the rock mechanics brittleness index (BI) of a single well 测井 If the two trends are consistent, the constructed quartz brittle mineral content BI 石英 The calculation expression is applied to calculate the brittleness index of the horizontal well section in the study area;

[0039] (ii) Based on the mineral component brittleness index interpretation model, the brittleness index BI of the horizontal well section is obtained.

[0040] (iii) Perform positive normalization on the horizontal well section brittleness index BI to obtain the normalized brittleness index BI n , the calculation formula is:

[0041]

[0042] Where: B min is the minimum brittleness index, B max is the maximum brittleness index;

[0043] (IV) The reservoir type of the horizontal well section and the normalized brittleness index are integrated to form a rapid evaluation chart for compressibility, and the compressibility type of the horizontal well section is quickly classified.

[0044] The compressibility types specifically include:

[0045] Good compressibility A1: Z = 3 and BI n ≥0.5;

[0046] Good compressibility A2: Z=3and BI n ≤0.5 or Z=2and BI n ≥0.5;

[0047] Medium compressibility B1: Z = 2 and BIn ≤0.5;

[0048] Compressibility is generally B2: Z = 1 and BI n ≥0.5;

[0049] Compressibility difference C: Z = 1 and BI n ≤0.5.

[0050] The beneficial effects of the present invention are:

[0051] The present invention provides a method for rapid evaluation of the compressibility of horizontal well sections in tight sandstone gas reservoirs, which can obtain the reservoir quality type and brittleness index of the horizontal well section based on the relationship between the production capacity of adjacent vertical wells, mineral composition experiments, and natural gamma logging curves, and form a rapid evaluation chart for compressibility, thereby providing a reference for rapid fracturing segmentation optimization of horizontal wells and improving fracturing effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a flow chart of the method of the present invention;

[0053] Figure 2 is a schematic diagram of the three-dimensional porosity model in Example 1 of the present invention;

[0054] Figure 3 Schematic diagram of reservoir quality parameter boundaries of three types of gas wells in Example 1 of the present invention;

[0055] Figure 4 is a schematic diagram of a three-dimensional reservoir quality model in Example 1 of the present invention;

[0056] Figure 5 It is a schematic diagram of a calculation model for the brittleness index of mineral components by fitting the brittle mineral content of quartz with a natural gamma curve in Example 1 of the present invention;

[0057] Figure 6 It is a schematic diagram of trend comparison between the brittleness index of mineral components and the brittleness index of rock mechanics in Example 1 of the present invention;

[0058] Figure 7 It is the horizontal well compressibility classification chart in Example 1 of the present invention;

[0059] Figure 8 It is a schematic diagram of the compressibility evaluation of the horizontal well section in Example 1 of the present invention.

[0060] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0062] Example 1

[0063] Take the compressibility evaluation scenario of a horizontal well in the T gas layer of an onshore L gas field as an example.

[0064] The L gas field belongs to the developed block. There are 8 vertical wells in the block for fracturing production (including 1 exploration well and 7 development wells). One horizontal well (H well, only natural gamma curve is measured) is pre-drilled. Only the exploration well (A well) has P-wave and S-wave logging data and core experimental mineral component analysis results. Other vertical wells have conventional logging series data and porosity interpretation results. The seismic quality in the work area is poor, and the reliability of reservoir inversion results is poor. According to the following Figure 1 The process shown is used to quickly evaluate the compressibility, specifically:

[0065] S1. Based on the production characteristics and formation conditions of 8 wells in tight sandstone gas reservoirs, combined with the gas well meter open flow rate Q(10 4 m 3 / dm) and porosityф(%), the gas wells are divided into three categories, the reservoir parameter porosityф is selected as the reservoir quality calibration parameter, and the reservoir quality parameter limits of the three types of gas wells are determined by analysis, such as Figure 3 As shown in the figure, the reservoir quality of Class I gas wells is ф≥12, the reservoir quality of Class II gas wells is 12≥ф≥10, and the reservoir quality of Class III gas wells is 10≥ф≥8. Due to the poor seismic quality of the block, a three-dimensional porosity model ф was established based on the porosity interpretation results of 8 vertical wells and the attribute modeling function of the geological modeling software. 模型 ( Figure 2 ), based on the reservoir quality calculation formula: Z=IF(ф≥a,3,IF(ф≥b,2,IF(ф≥c,3,1))), calculate in the geological modeling software to establish a three-dimensional reservoir quality model Z 模型 ,like Figure 4 As shown,

[0066] The calculation expression of reservoir quality model is: 模型 =IF(ф 模型 >12,3,IF(ф 模型 >10,2,IF(ф 模型 >8,1,0))), where the three-dimensional reservoir quality model Z 模型 The value of 1 is the development area of ​​Class I gas well reservoir quality. The three-dimensional reservoir quality model Z 模型 The value of 2 is the development area of ​​Class II gas well reservoir quality. The three-dimensional reservoir quality model Z 模型 The area with a median value of 3 is the area with Class III gas well reservoir quality development.

[0067] According to the three-dimensional reservoir quality model Z 模型 , extract the reservoir category Z along the horizontal well trajectory.

[0068] S2. Calculate the quartz brittle mineral content BI based on the mineral composition analysis results of the core of the adjacent A vertical well 石英 (%), the calculation expression is: BI 石英 = quartz content / (quartz content + clay mineral content + carbonate mineral content) × 100%: using core calibration logging technology, applying natural gamma curve G R Linear fitting method was used to establish the calculation model of mineral component brittleness index ( Figure 5 ), the expression is BI 石英 =eG R+ f, where e and f are fitting values ​​of -0.4554 and 106.88 respectively. The calculation model is used to determine the brittleness index BI of the mineral components of vertical well A; the rock mechanics brittleness index BI of a single well is obtained based on the longitudinal and transverse wave velocity and density curves of the adjacent vertical well A. 测井 ; The mineral component brittleness index BI and rock mechanics brittleness index BI of the adjacent vertical well A 测井 contrast( Figure 6 ), the trends are consistent, indicating that the constructed mineral component brittleness index model can be applied in the study area.

[0069] Based on the mineral component brittleness index interpretation model, BI = BI 石英 =-0.4554G R+ 106.88, calculate the brittleness index BI of the horizontal well section, and use the positive normalized brittleness index BI n , the calculation formula is: BI n＝ (BI-B min ) / (BI max -B min ), where B min The minimum brittleness index is 30, B max The maximum brittleness index is 90.

[0070] S3. Comprehensive reservoir category Z and brittleness index BI along the horizontal well trajectory n , forming a quick evaluation chart for compressibility and classifying compressibility ( Figure 7 , 8 ):

[0071] Good compressibility A1: Z = 3 and BI n ≥0.5

[0072] Good compressibility A2: Z=3and BI n ≤0.5 or Z=2and BI n ≥0.5

[0073] Medium compressibility B1: Z = 2 and BI n ≤0.5

[0074] Compressibility is generally B2: Z = 1 and BI n ≥0.5

[0075] Compressibility difference C: Z = 1 and BI n ≤0.5

[0076] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for rapid evaluation of the compressibility of horizontal well sections in tight sandstone gas reservoirs, characterized by: (I) Establish a three-dimensional reservoir quality model to obtain the reservoir quality category of the horizontal well section; (II) Constructing a brittleness index model for the mineral components of adjacent vertical wells; (III) Obtaining the brittleness index of the horizontal well section; (IV) The reservoir type of the horizontal well section and the normalized brittleness index are integrated to form a rapid evaluation chart for compressibility, and the compressibility type of the horizontal well section is quickly classified.

2. The method for rapid evaluation of horizontal well section compressibility of tight sandstone gas reservoir according to claim 1, characterized in that: The specific method of step (I) is: (i) Classify gas well types based on the production characteristics and formation conditions of tight sandstone gas reservoirs and the positive correlation between the gas well's unimpeded flow rate per meter and porosity ф; (ii) determining the reservoir quality parameter limits of each type of gas well based on the reservoir quality calibration parameters; (iii) using the three-dimensional porosity and the reservoir quality calculation formula to calculate in geological modeling software to establish a three-dimensional reservoir quality model; (iv) Based on the three-dimensional reservoir quality model (Z 模型 ), extract the reservoir category (Z) along the horizontal well trajectory.

3. The method for rapid evaluation of horizontal well section compressibility of tight sandstone gas reservoir according to claim 2, characterized in that: The gas well types are divided into Class I gas wells, Class II gas wells and Class III gas wells.

4. The method for rapid evaluation of compressibility of horizontal well sections in tight sandstone gas reservoirs according to claim 2, characterized in that: The reservoir quality calibration parameter is porosityф.

5. The method for rapid evaluation of compressibility of horizontal well sections in tight sandstone gas reservoirs according to claim 2, characterized in that: The reservoir quality parameter limits of each type of gas well are specifically as follows: The limit of reservoir quality parameters for Class I gas wells is porosity ф ≥ a; The limit of reservoir quality parameters for type II gas wells is a≥porosityф≥b; The limit of reservoir quality parameters for Class III gas wells is b≥porosityф≥c Among them: a, b, and c are the lower limits of porosity of three types of gas wells determined by the classification and evaluation of gas wells in tight sandstone gas reservoirs in the study area.

6. The method for rapid evaluation of horizontal well section compressibility of tight sandstone gas reservoir according to claim 2, characterized in that: The three-dimensional porosity ф 模型 Based on the porosity interpretation results of adjacent vertical wells, the attribute modeling function of geological modeling software was used to establish the model; The reservoir quality calculation formula is: Z = IF (ф ≥ a, 3, IF (ф ≥ b, 2, IF (ф ≥ c, 3, 1))), Where: a, b, c are the lower limits of porosity of three types of gas wells determined by the classification and evaluation of tight sandstone gas reservoirs in the study area, %; The three-dimensional reservoir quality model Z 模型 The calculation expression of Z is: 模型 =IF(ф 模型 >a,3,IF(ф 模型 >b,2,IF(ф 模型 >c,1,0))), Where: a, b, c are the lower limits of porosity of three types of gas wells determined by the classification and evaluation of gas wells in the tight sandstone gas reservoirs in the study area, respectively; 3 represents the reservoir quality development area of ​​type I gas wells, 2 represents the reservoir quality development area of ​​type II gas wells, 1 represents the reservoir quality development area of ​​type III gas wells, and 0 represents the reservoir development area with ineffective fracturing.

7. The method for rapid evaluation of horizontal well section compressibility of tight sandstone gas reservoir according to claim 1, characterized in that: The specific method of step (II) is: (i) Calculate the quartz brittle mineral content BI based on the mineral composition analysis results of the adjacent vertical well core 石英 ; The quartz brittle mineral content BI 石英 The calculation expression is: (ii) Using core calibration logging technology, the natural gamma curve G R Linear fitting of quartz brittle mineral content BI 石英 The calculation expression of Quartz brittle mineral content BI after fitting 石英 The expression is BI 石英 =eG R+ f, Where: e and f are fitting values; (iii) using the calculation model, determine the brittleness index BI of the mineral components of the adjacent vertical wells; (iv) Calculate the rock brittleness index BI of a single well based on the longitudinal and transverse wave velocities and density curves of adjacent vertical wells 测井 .

8. The method for rapid evaluation of horizontal well section compressibility of tight sandstone gas reservoir according to claim 1, characterized in that: The specific method of step (III) is: (i) Comparison of the brittleness index (BI) of the mineral components of adjacent vertical wells with the rock mechanics brittleness index (BI) of a single well 测井 , if the trends of the two are consistent, the constructed mineral component brittleness index model will be applied to the calculation of the brittleness index of the horizontal well section in the study area; (ii) Based on the mineral component brittleness index interpretation model, the brittleness index BI of the horizontal well section is obtained; (iii) Perform positive normalization on the horizontal well section brittleness index BI to obtain the normalized brittleness index BI n , the calculation formula is: Where: B min is the minimum brittleness index, B max is the maximum brittleness index.

9. The method for rapid evaluation of horizontal well section compressibility of tight sandstone gas reservoir according to claim 1, characterized in that: The compressibility types in step (IV) specifically include: Good compressibility A1: Z = 3 and BI n ≥0.5; Good compressibility A2: Z=3and BI n ≤0.5 or Z=2and BI n ≥0.5; Medium compressibility B1: Z = 2 and BI n ≤0.5; Compressibility is generally B2: Z = 1 and BI n ≥0.5; Compressibility difference C: Z = 1 and BI n ≤0.5.

Images