Method for evaluating effective storage space of buried hill gas storage

Abstract

The invention belongs to the technical field of oil-gas exploration, and discloses a buried hill gas storage effective reservoir space evaluation method. The method comprises the following steps: describing a buried hill fracture development condition by using rock core observation to obtain main parameters; analyzing the development characteristics of cracks and corrosion pores under microscopic conditions, and determining the buried hill reservoir space type and the internal cause relation thereof; a single-well buried hill fracture system and a matrix system are divided by using core scale logging and combining gas logging production data, and reservoir logging response characteristics are determined; and by utilizing an effective reservoir space calculation formula, logging response characteristics and related parameters of the divided fracture system and the effective matrix system are substituted, the total pore volume of the reservoir and the pore volume of the invalid reservoir are calculated, and the final effective reservoir space is determined as the effective reservoir space of the buried hill database building. According to the method, the invalid storage space calculation problem is deducted, the calculation accuracy is improved, and a basis is provided for subsequent storage capacity calculation and related research.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploration, relates to a gas storage space evaluation technology for underground gas storage reservoirs, and specifically relates to an effective storage capacity evaluation method for buried-hill gas storage reservoirs. Background Art

[0002] Underground gas storage is one of the important links in the natural gas industry chain and has become a strategic infrastructure to ensure safe and stable gas supply. As the proportion of natural gas in my country's energy consumption increases year by year, underground gas storage has become a key link in my country's natural gas safety supply in recent years. Submerged hill oil and gas reservoirs are one of the hottest exploration and development targets at home and abroad. They have large reserves and excellent sealing conditions, and have good value for gas storage construction.

[0003] Due to the complex and diverse lithology and lithofacies of the buried hill reservoir, the large vertical and horizontal changes, the relatively complex lithology identification, and the large changes in the reservoir pore structure, the existing calculation method of the gas storage space of the buried hill gas storage does not take into account the loss of the effective reservoir after dissolution filling, which leads to a larger calculation result of the effective gas storage space of the buried hill, and then leads to a higher calculation result of the storage capacity. Therefore, it is urgent to invent a method for evaluating the effective storage capacity of the gas storage. Summary of the invention

[0004] In order to better cope with the reconstruction of underground gas storage from buried hill oil and gas reservoirs, it is necessary to establish an effective and applicable method for calculating the effective storage capacity of buried hills as soon as possible. Therefore, deducting the invalid storage space formed by weak dissolution from the final storage space is of great significance for the calculation of the storage capacity of buried hill reservoirs and the subsequent deployment of injection and production wells.

[0005] The purpose of the present invention is to provide a method for solving the problem of the accuracy of calculation of total reservoir space due to dissolution of buried hill reservoirs, and a method for correcting the calculation influence.

[0006] To achieve the above-mentioned purpose, the present invention provides a method for predicting the effective storage space of buried-hill gas storage reservoirs based on well logging, gas logging and lithofacies analysis theory, which mainly includes:

[0007] The purpose of the present invention can be achieved by the following steps:

[0008] Step 1: Use core observation to describe the development of buried-hill fractures and obtain the main parameters such as the number of fractures, density, and aperture.

[0009] Step 2: Use casting thin sections, scanning electron microscopy and other data to analyze the development characteristics of fractures and dissolution pores under microscopic conditions, and clarify the types of buried hill reservoir space and their internal genetic relationships;

[0010] Specifically, fractures are channels for the migration of hydrothermal fluids inside the buried hill, and they play an important role in controlling the formation of dissolution pores. Dissolution will produce secondary pores such as intercrystalline pores and dissolution pores, which are easy to form favorable reservoirs; at the same time, secondary minerals produced by alteration will fill the reservoir space and form invalid reservoirs.

[0011] Step 3: Use core calibration logging and combine gas logging production data to divide the single well buried hill fracture system and matrix system to determine the reservoir logging response characteristics.

[0012] The matrix system is further divided into two categories: effective matrix system and ineffective matrix system.

[0013] Based on the identification of alteration characteristics, the response characteristics of invalid reservoirs and effective reservoirs of clay-altered alteration on conventional logging are further determined. The clay produced by alteration often contains a large amount of crystalline water, which fills the pores and cracks of the rock, causing the neutron logging value to increase, the density logging value to decrease, and the resistivity to decrease, showing good reservoir characteristics, but the actual seepage characteristics are poor, which means it is a non-reservoir or a poor reservoir. Combined with the characteristics of the gas logging curve, the alteration characteristic curve is selected as the compensated neutron, deep lateral resistivity and total hydrocarbon curve.

[0014] The specific parameters are as follows:

[0015] The compensation neutron is greater than 15% and the density is less than 2.8g / cm 3 , as the limit of the sensitive parameters of the logging curve of clay alteration characteristics, the sensitive parameters are used to establish the identification indicator factors of invalid reservoirs and effective reservoirs caused by alteration. When the index factor is greater than 10, it is an invalid reservoir, and less than 10 is an effective reservoir:

[0016] Φ=DEN*CNL*e

[0017] Where: CNL is compensated neutron logging, %; DEN is neutron density, g / cm 3 ; e is the difference of gas measurement curve.

[0018] Step 4, using the calculation formula for effective reservoir space as shown below, the logging response characteristics and related parameters of the divided fracture system and effective matrix system are brought into the calculation to calculate the total pore volume of the reservoir and the pore volume of the invalid reservoir, wherein the total pore volume is the sum of the fracture system and the matrix system;

[0019] Specific: V 有效 =A*(H 总 -H 无效 )*Φ e *S o

[0020] Where: V 有效 -Effective gas storage space, 10 6 m3 ; A-oil-bearing area, km 2 ;H 总 -Total effective reservoir thickness, m; H - Ineffective reservoir thickness, m; Φe - Porosity (fractures + matrix), decimal; So - Oil saturation, decimal.

[0021] Step 5, determine the final effective storage space, which is the effective storage space for buried hill reservoir construction.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] By carrying out research on the calculation method of storage space of gas storage rebuilt from buried hill oil and gas reservoirs, the present invention eliminates the problem of invalid storage space calculation, improves the calculation accuracy, and provides a basis for subsequent storage capacity calculation and related research. DETAILED DESCRIPTION

[0024] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0025] Example 1

[0026] Take the calculation of effective pore volume of buried hill reservoir in MG block of a certain oil field as an example:

[0027] In the first step, the core of Well MG1-1 was observed to obtain the macroscopic fracture characteristics. The main parameters are as follows: 2 fracture groups, 16 fractures, density 26 fractures / m, opening 0.2-0.5 mm, inclination 30-90°, and filling degree from semi-filled to unfilled.

[0028] The second step is to analyze the main reservoir space of the buried hill as fractures and dissolution pores based on the results of the impact of dissolution and alteration on the reservoir by using different core thin section analysis and other relevant data.

[0029] The dissolution pores are mainly distributed along the fractures, indicating that there is an intrinsic genetic connection between the two formations, and the degree of fracture development controls the distribution of dissolution pores; the dissolution alteration characteristics show that alteration has an important controlling effect on the formation of buried hill reservoirs, and the alteration zone is mainly along the fracture direction, within the range of 10-50m below the fracture zone.

[0030] In addition, the dissolution effect is mainly manifested in the following ways: dissolution will produce secondary pores such as intercrystalline pores and dissolution pores, which are easy to form favorable reservoirs; on the contrary, the secondary minerals produced by alteration will fill the reservoir pores and cracks, reduce the effectiveness of the reservoir pores, and the dissolution pores will be filled with a large amount of secondary minerals to form invalid reservoirs.

[0031] The third step is to use core calibration logging and combine gas logging production data to divide the single well buried hill fracture system and matrix system to determine the reservoir logging response characteristics.

[0032] The matrix system is further divided into two categories: effective matrix system and invalid matrix system. The 4567.8-4579.3m interval of the MG1-1 well caused the neutron logging value to increase, the density logging value to decrease, and the resistivity to decrease, showing reservoir characteristics. However, the well produced 0.06 cubic meters of water per day after fracturing, and the oil test conclusion was that it was a dry layer with poor seepage characteristics, which was a non-reservoir or a poor reservoir.

[0033] Select characteristic sensitive logging curves to compensate for neutrons and neutron density. Through research and analysis, the neutrons with a density greater than 15% and a density less than 2.8g / cm 3 , the parameters are used to establish the identification indicator factor between the invalid reservoir and the effective reservoir caused by alteration. If the factor is greater than 17, it is an invalid reservoir.

[0034] In the fourth step, the total pore volume of the reservoir and the pore volume of the ineffective reservoir were calculated using the logging response characteristics of the divided effective reservoir and ineffective reservoir, which were 1550.7×10 6 m 3 and 254.8×10 6 m 3 The invalid storage space accounts for 16.43%, and the final gas storage space after deducting the invalid reservoir is 1295.9×10 6 m 3 .

[0035] Step 5: The final effective storage space of the MG block is 1295.9×10 6 m 3 .

[0036] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating the effective storage capacity of a buried-hill gas storage reservoir, characterized in that: The following steps are involved: Step 1: Use core observation to describe the development of buried hill fractures and obtain the main parameters; Step 2: Analyze the development characteristics of fractures and dissolution pores under microscopic conditions, and clarify the types of buried hill reservoir spaces and their intrinsic genetic relationships; Step 3, using core calibration logging and combining gas logging production data to divide the single well buried hill fracture system and matrix system, and determine the reservoir logging response characteristics; Step 4, using the calculation formula for effective reservoir space, the logging response characteristics and related parameters of the divided fracture system and effective matrix system are brought in to calculate the total pore volume of the reservoir and the pore volume of the invalid reservoir, wherein the total pore volume is the sum of the fracture system and the matrix system; Step 5, determine the final effective storage space, which is the effective storage space for buried hill reservoir construction.

2. The method for evaluating the effective storage capacity of a buried-hill gas storage reservoir according to claim 1, characterized in that: The main parameters in step 1 include the number, density and opening of cracks.

3. The method for evaluating the effective storage capacity of a buried-hill gas storage reservoir according to claim 1, characterized in that: The analysis method in step 2 is to use casting thin sections, scanning electron microscopy and other data.

4. The method for evaluating the effective storage capacity of a buried-hill gas storage reservoir according to claim 1, characterized in that: In step 2, the cracks are the hydrothermal migration channels inside the buried hill, which control the formation of dissolution pores.

5. The method for evaluating the effective storage capacity of a buried-hill gas storage reservoir according to claim 1, characterized in that: In step 2, the alteration is within 10-50m below the fracture zone.

6. The method for evaluating the effective storage capacity of a buried-hill gas storage reservoir according to claim 1, characterized in that: In step 3, the matrix system is divided into two categories, one is the effective matrix system and the other is the ineffective matrix system.

7. The method for evaluating the effective storage capacity of a buried-hill gas storage reservoir according to claim 1, characterized in that: The specific parameters of reservoir logging response characteristics determined in step 3 are as follows: the compensation neutron is greater than 15%, the density is less than 2.8g / cm 3 , as the limit of the sensitive parameters of the logging curve of clay alteration characteristics, the sensitive parameters are used to establish the identification indicator factors of invalid reservoirs and effective reservoirs caused by alteration. When the index factor is greater than 10, it is an invalid reservoir, and less than 10 is an effective reservoir: Φ=DEN*CNL*e, Where: CNL is compensated neutron logging, %; DEN is neutron density, g / cm 3 ; e is the difference of gas measurement curve.

8. The method for evaluating the effective storage capacity of a buried-hill gas storage reservoir according to claim 1, characterized in that: The calculation formula for the effective reservoir space in step 4 is: V 有效 =A*(H 总 -H 无效 )*Φ e *S o , where: V 有效 -Effective gas storage space, 10 6 m 3 ; A-oil-bearing area, km 2 ; H 总 -Total effective reservoir thickness, m; H - Ineffective reservoir thickness, m; Φe - Porosity (fractures + matrix), decimal; So - Oil saturation, decimal.