Method for evaluating fracturing property of sandstone reservoir

Abstract

The invention relates to the field of oil and gas development, in particular to a sandstone reservoir fracturing performance evaluation method which comprises the following steps: step 1, determining a plurality of fracturing performance evaluation indexes of a sandstone reservoir; 2, analyzing the influence rule of each factor on the fracture form; 3, obtaining a weight coefficient of the fracturing performance evaluation index; 4, defining a sandstone fracturing index, and determining a comprehensive fracturing coefficient of the sandstone reservoir; and 5, calculating a fracturing index and guiding fracturing well selection and layer selection. According to the method, a plurality of fracturing performance evaluation indexes of the sandstone reservoir are determined by utilizing a rock broken sample of the sandstone reservoir, different fracture forms are obtained by changing parameters such as rock elasticity modulus, fracture energy and minimum horizontal ground stress, and the fracturing performance of the sandstone reservoir is evaluated through micro-earthquake and volume fracturing data regression of a fractured well. The weight coefficients of the multiple fracturing performance evaluation indexes of the compact sandstone reservoir are obtained, so that the brittle interlayer is accurately judged, and the position of the fracturing perforation cluster is optimized conveniently.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas development, and in particular to a method for evaluating the fracturing performance of a sandstone reservoir. Background Art

[0002] With the rapid economic growth and the improvement of living standards, energy demand has increased dramatically, and the contradiction between supply and demand of oil and gas resources has become prominent. my country is rich in sandstone oil and gas resources, which can serve as an important energy source in the future. Sandstone reservoirs are usually treated with large-scale volume fracturing.

[0003] However, the brittleness of rock is an important factor affecting the formation of fracture networks. The existing brittleness evaluation model has certain limitations and cannot accurately judge the brittle barrier, which makes the optimization of fracturing perforation cluster locations unsuccessful. Therefore, it is necessary to propose a method for evaluating the fracturability of sandstone reservoirs. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a sandstone reservoir fracturing evaluation method, which has the advantages of comprehensive analysis of multiple fracturing evaluation indicators and various factors, and solves the above problems.

[0006] (II) Technical solution

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0008] A method for evaluating the fracturability of a sandstone reservoir comprises the following steps:

[0009] Step 1: Determine multiple fracturing evaluation indicators of sandstone reservoirs;

[0010] Step 2: Analyze the influence of various factors on crack morphology;

[0011] Step 3: Obtaining the weight coefficient of the fracturing evaluation index;

[0012] Step 4: Define the sandstone fracturing index and determine the comprehensive fracturing coefficient of the sandstone reservoir;

[0013] Step 5: Calculate the fracturing index and guide the selection of wells and layers for fracturing.

[0014] Preferably, the step 1 uses rock samples of the sandstone reservoir to determine multiple fracturing evaluation indicators of the sandstone reservoir.

[0015] Preferably, in step 2, different crack morphologies are obtained by changing parameters such as rock elastic modulus, fracture energy, minimum horizontal ground stress, and the like, and the influence of these factors on the crack geometry (such as crack length, width, etc.) is tested.

[0016] Preferably, the step three obtains weight coefficients of multiple fracturing evaluation indicators of tight sandstone reservoirs by regressing microseismic and volume fracturing data of fractured wells.

[0017] Preferably, in step 4, the comprehensive fracturing coefficient of the sandstone reservoir is determined according to different fracturing evaluation indicators of the sandstone reservoir and the weight coefficients of the different fracturing evaluation indicators, and the sandstone fracturing index is defined as Fracsand = 100 × E a / σh (where Fracsand is the fracturability index of the sandstone reservoir; E is the elastic modulus of the material; a is a constant between 1 / 6 and 2 / 3, usually close to 1 / 6; σh is the minimum horizontal ground stress of the reservoir rock).

[0018] Preferably, the step five calculates the reservoir fracturing index according to given reservoir parameters (or logging data), which plays a certain guiding role in the selection of wells and layers for fracturing.

[0019] (III) Beneficial effects

[0020] Compared with the prior art, the present invention provides a method for evaluating the fracturability of sandstone reservoirs, which has the following beneficial effects:

[0021] The present invention utilizes rock samples of sandstone reservoirs to determine multiple fracturing evaluation indices of sandstone reservoirs, obtains different fracture morphologies by changing parameters such as rock elastic modulus, fracture energy, and minimum horizontal ground stress, obtains weight coefficients of multiple fracturing evaluation indices of tight sandstone reservoirs by regressing microseismic and volume fracturing data of fractured wells, determines a comprehensive fracturing coefficient of sandstone reservoirs according to different fracturing evaluation indices of sandstone reservoirs and weight coefficients of different fracturing evaluation indices, calculates the fracturing index of the reservoir according to given reservoir parameters (or logging data), and plays a certain guiding role in fracturing well and layer selection, thereby accurately judging brittle interlayers and facilitating the optimization of fracturing perforation cluster positions. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention relates to a method for evaluating the fracturability of a sandstone reservoir, comprising the following steps:

[0024] Step 1: Determine multiple fracturing evaluation indicators of sandstone reservoirs;

[0025] Using rock samples from sandstone reservoirs, multiple fracturing evaluation indicators of sandstone reservoirs are determined. These indicators are related to the characteristics of sandstone reservoirs forming complex fracture networks.

[0026] Step 2: Analyze the influence of various factors on crack morphology;

[0027] By changing parameters such as rock elastic modulus, fracture energy, and minimum horizontal ground stress, different fracture morphologies are obtained, and the influence of these factors on fracture geometry (such as fracture length and width, etc.) is tested. For example, the larger the rock elastic modulus, the smaller the normal displacement of the fracture wall under the same stress, and the fracture becomes flat and long; the smaller the fracture energy, the smaller the fracture width and the larger the fracture length; the larger the minimum horizontal ground stress, the significantly smaller the fracture length and the larger the fracture width;

[0028] Rock elastic modulus: The higher the elastic modulus, the better the fracturability of the reservoir;

[0029] Minimum horizontal geostress: The smaller the minimum horizontal geostress, the better the fracturability of the reservoir;

[0030] Step 3: Obtaining the weight coefficient of the fracturing evaluation index;

[0031] The weight coefficients of multiple fracturing evaluation indicators of tight sandstone reservoirs are obtained through regression of microseismic and volume fracturing data of fractured wells.

[0032] The indicator weights include the original logging parameters: moderate weights, including resistivity, density, acoustic wave time difference, etc.;

[0033] Well logging interpretation parameters: moderate weights, including porosity, permeability, saturation, etc.;

[0034] Geomechanical parameters: with higher weights, including elastic modulus, Poisson's ratio, minimum horizontal ground stress, etc.;

[0035] Fracturing process parameters: moderate weight, including fracturing fluid type, proppant type, pumping mode, etc.;

[0036] By collecting data of various parameters, pre-processing the collected data to ensure the accuracy and consistency of the data;

[0037] Step 4: Define the sandstone fracturing index and determine the comprehensive fracturing coefficient of the sandstone reservoir;

[0038] According to the different fracturing evaluation indexes of sandstone reservoirs and the weight coefficients of different fracturing evaluation indexes, the comprehensive fracturing coefficient of sandstone reservoirs is determined, and the sandstone fracturing index is defined as Fracsand = 100 × E a / σh (where Fracsand is the fracturability index of the sandstone reservoir; E is the elastic modulus of the material; a is a constant between 1 / 6 and 2 / 3, usually close to 1 / 6; σh is the minimum horizontal ground stress of the reservoir rock). This method fully and comprehensively considers multiple fracturing evaluation indicators that affect the formation of complex fracture networks in tight sandstone reservoirs. The constructed comprehensive brittleness evaluation model can better reflect the comprehensive ability of tight sandstone reservoirs to form complex fracture networks during volume fracturing.

[0039] Step 5: Calculate the fracturing index and guide the selection of wells and layers for fracturing;

[0040] The reservoir fracturing index is calculated based on the given reservoir parameters (or logging data), which plays a certain guiding role in the selection of wells and layers for fracturing. The reservoir fracturing ability is evaluated by the size of the fracturing index (such as color representation, the redder the color, the stronger the fracturing ability of the sandstone; the bluer the color, the lower the fracturing ability of the sandstone).

[0041] The present invention utilizes rock samples of sandstone reservoirs to determine multiple fracturing evaluation indices of sandstone reservoirs, obtains different fracture forms by changing parameters such as rock elastic modulus, fracture energy, and minimum horizontal ground stress, obtains weight coefficients of multiple fracturing evaluation indices of tight sandstone reservoirs by regressing microseismic and volume fracturing data of fractured wells, determines a comprehensive fracturing coefficient of sandstone reservoirs according to different fracturing evaluation indices of sandstone reservoirs and weight coefficients of different fracturing evaluation indices, calculates the fracturing index of the reservoir according to given reservoir parameters, and plays a certain guiding role in fracturing well and layer selection, thereby accurately judging brittle interlayers and facilitating the optimization of fracturing perforation cluster positions.

[0042] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating the fracturability of a sandstone reservoir, characterized in that: The following steps are involved: Step 1: Determine multiple fracturing evaluation indicators of sandstone reservoirs; Step 2: Analyze the influence of various factors on crack morphology; Step 3: Obtaining the weight coefficient of the fracturing evaluation index; Step 4: Define the sandstone fracturing index and determine the comprehensive fracturing coefficient of the sandstone reservoir; Step 5: Calculate the fracturing index and guide the selection of wells and layers for fracturing.

2. A sandstone reservoir fracturability evaluation method according to claim 1, characterized in that: The first step uses rock samples of the sandstone reservoir to determine multiple fracturing evaluation indicators of the sandstone reservoir.

3. A sandstone reservoir fracturability evaluation method according to claim 1, characterized in that: The second step is to obtain different crack shapes by changing parameters such as rock elastic modulus, fracture energy, minimum horizontal ground stress, etc., and test the influence of these factors on the crack geometry.

4. A sandstone reservoir fracturability evaluation method according to claim 1, characterized in that: The step three obtains weight coefficients of multiple fracturing evaluation indicators of tight sandstone reservoirs by regressing microseismic and volume fracturing data of fractured wells.

5. The method for evaluating the fracturability of a sandstone reservoir according to claim 1, characterized in that: In step 4, the comprehensive fracturing coefficient of the sandstone reservoir is determined according to different fracturing evaluation indicators of the sandstone reservoir and the weight coefficients of different fracturing evaluation indicators, and the sandstone fracturing index is defined as Fracsand = 100 × E a / σh (where Fracsand is the fracturability index of the sandstone reservoir; E is the elastic modulus of the material; a is a constant between 1 / 6 and 2 / 3, usually close to 1 / 6; σh is the minimum horizontal ground stress of the reservoir rock).

6. A sandstone reservoir fracturability evaluation method according to claim 1, characterized in that: The step five calculates the reservoir fracturing index according to the given reservoir parameters (or logging data), which plays a certain guiding role in the selection of wells and layers for fracturing.