Method for calculating dosage of temporary plugging agent for fracturing based on reservoir fracture comprehensive evaluation

Abstract

The invention relates to a method for calculating the dosage of a temporary plugging agent for fracturing based on reservoir fracture comprehensive evaluation, and belongs to the technical field of fracturing. The method comprises the following specific steps: determining the number of cracks; determining the dynamic fracture height of the fractured interval; the crack width and the temporary plugging agent laying thickness are determined; and calculating the temporary plugging agent dosage under the condition of the thicknesses of the multiple fractured reservoirs. Compared with the prior art which excessively depends on indoor data and fracturing simulation software, the method has the advantages that the field effectiveness is highlighted, the opening number of single-well fractures is obtained through a pre-fracturing test means, the temporary plugging agent dosage under the thickness of an opened fractured reservoir is calculated by combining the relationship between the laying thickness of the temporary plugging agent and the width of the fractures, and dynamic monitoring in the fracturing process is carried out; and real-time adjustment is carried out according to the pressure fluctuation condition, opening and extending of multiple fractures are continuously promoted, a complex fracture net is formed, the purpose of increasing the transformation size is achieved, and effective utilization of a compact oil and gas reservoir is achieved.

Description

Technical Field

[0001] The present invention relates to a method for calculating the dosage of a temporary plugging agent for fracturing based on the comprehensive evaluation of reservoir fractures, and belongs to the technical field of fracturing. Background Art

[0002] With the increasing reduction of conventional oil and gas resources, unconventional oil and gas reservoirs have gradually become the focus of current exploration and development. The temporary plugging and diversion fracturing technology is one of the effective means for increasing production and tapping potential in unconventional oil and gas reservoirs. This technology involves injecting a temporary plugging agent one or more times during the fracturing operation. By utilizing the temporary plugging effect of the temporary plugging agent, the net pressure in the fracture is increased, promoting the opening and extension of secondary fractures and microfractures, forming a complex three-dimensional fracture network, and increasing the single-well stimulation volume to a greater extent. However, the temporary plugging mechanism of the temporary plugging agent in the fracture is a complex process. Whether the dosage design of the temporary plugging agent is reasonable is the key to the formation of a complex fracture network and directly affects the stimulation effect of the fractured well. If the dosage of the temporary plugging agent is too small, the degree of plugging is insufficient, resulting in limited permeability and pressure-bearing capacity of the temporary plugging layer, limited formation range of the branched fracture network, and failure to achieve the goal of increasing the stimulation volume. If the dosage of the temporary plugging agent is too large, it will not only cause waste of construction costs, but also increase the construction difficulty and operation time on site. Initially, the dosage of the temporary plugging agent was determined based on subjective experience, and there was no unified calculation method due to various factors such as regional geological conditions, reservoir temperature, reservoir thickness, and rock mechanical parameters.

[0003] Through literature retrieval, in the prior art, the patent application number is CN2018111247646, which discloses a method for controlling the dosage of a temporary plugging agent for temporary plugging and diversion fracturing. This method calculates the dosage of the temporary plugging agent based on the single-well geological data and the production dynamic data of adjacent wells, combined with the simulation of fracturing construction parameters using fracturing software. This method relies too much on indoor data and fracturing simulation software. Summary of the Invention

[0004] The present invention discloses a method for calculating the dosage of a temporary plugging agent for fracturing based on the comprehensive evaluation of reservoir fractures. This method highlights on-site effectiveness. By obtaining the number of single-well fracture openings through pre-fracture testing means, combining the relationship between the placement thickness of the temporary plugging agent and the fracture width, calculating the dosage of the temporary plugging agent under the thickness of the fractured reservoir with opened fractures, carrying out dynamic monitoring during the fracturing process, and making real-time adjustments based on the pressure fluctuation situation, continuously promoting the opening and extension of multiple fractures, forming a complex fracture network, achieving the goal of increasing the stimulation volume, and realizing the effective exploitation of tight oil and gas reservoirs.

[0005] The technical solution adopted by the present invention is as follows: A method for calculating the dosage of a temporary plugging agent for fracturing based on the comprehensive evaluation of reservoir fractures, and the specific steps are as follows:

[0006] Step 1: Determine the number of fractures;

[0007] Step 2: Determine the dynamic fracture height of the fracturing interval;

[0008] Step 3: Determine the crack width and the placement thickness of the temporary plugging agent;

[0009] Step 4: Calculate the amount of the temporary plugging agent for the case of multiple fracture reservoir thicknesses.

[0010] Further, the specific content of the Step 1 is to conduct a small-scale pre-fracturing test construction on site to determine the number of fractures.

[0011] Further, after conducting the small-scale pre-fracturing test construction in the Step 1, the G-function analysis is carried out by using the FracproPT software to determine the number of fractures.

[0012] Further, the specific content of the Step 2 is to import the logging data into the in-situ stress profile software, obtain the in-situ stress profile diagram, and determine the dynamic fracture height of the fracturing interval.

[0013] Further, the logging data in the Step 2 includes natural gamma, density, and acoustic wave data.

[0014] Further, the specific content of the Step 3 is to determine the crack width and the placement thickness of the temporary plugging agent according to the fitting result of the relationship between the placement thickness (H) of the temporary plugging agent and the crack width (W) under the condition that the pressure bearing capacity of the indoor temporary plugging agent filter cake is ≥ 40 MPa.

[0015] Further, the specific content of the Step 4 is to calculate the amount of the temporary plugging agent for the case of multiple fracture reservoir thicknesses through the formula (1).

[0016] Q = 2(H × h × W) × n × ρ 视 × S (1)

[0017] In the formula: Q—the weight of the temporary plugging agent, kg; h—the dynamic fracture height, m; H—the placement thickness of the temporary plugging agent, mm; W—the crack width, cm; n—the number of fractures; ρ 视 —the apparent density of the temporary plugging agent, g / cm 3 , S—the safety factor, dimensionless (1.2 - 1.4).

[0018] The present invention discloses a method for calculating the amount of the temporary plugging agent for fracturing based on the comprehensive evaluation of reservoir fractures. Its beneficial effect is that compared with the prior art which overly relies on indoor data and fracturing simulation software, this method highlights the on-site effectiveness. By means of pre-fracturing test, the number of fractures opened in a single well is obtained, combined with the relationship between the placement thickness of the temporary plugging agent and the crack width, the amount of the temporary plugging agent for the fractured reservoir thickness that has been opened is calculated, dynamic monitoring is carried out during the fracturing process, and real-time adjustment is made according to the pressure fluctuation situation, continuously promoting the opening and extension of multiple fractures to form a complex fracture network, achieving the purpose of increasing the stimulation volume and realizing the effective development of tight oil and gas reservoirs. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 The following shows the schematic diagram of the small-scale test G-function analysis curve of Well YS306-3 in Embodiment 1;

[0021] Figure 2 The following shows the schematic diagram of the in-situ stress profiles of the first and second sections of Well YS306-3 in Embodiment 1;

[0022] Figure 3 The following shows the schematic diagram of the in-situ stress profiles of the third and fourth sections of Well YS306-3 in Embodiment 1;

[0023] Figure 4 The following shows the relationship diagram between the fracture width and the placement thickness of the temporary plugging agent of Well YS306-3 in Embodiment 1. Detailed implementation manners

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, rather than all, embodiments of the present invention.

[0026] The following description of at least one exemplary embodiment is merely illustrative and in no way restrictive of the present invention or its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. Embodiment 1

[0027] In this embodiment, taking Well YS306-3 in a certain oilfield as an example, this well is an exploration well, the target formation is the Yingcheng Formation, the exploited layer thickness is 165 meters, and it is fractured in four sections; a calculation method for the dosage of the temporary plugging agent for fracturing based on the comprehensive evaluation of reservoir fractures is provided, and the specific steps are as follows:

[0028] Step 1: Conduct a small-scale test construction before fracturing on site. As Figure 1 shown, use FracproPT software for G-function analysis to determine the number of fractures n;

[0029] Step 2: Import well logging data including natural gamma, density, acoustic wave, etc. into the in-situ stress profile software, such as Figure 2 and 3Obtain the in-situ stress profile as shown, and determine the dynamic fracture height h of the fracturing interval;

[0030] Step 3: According to the fitting result of the relationship between the placement thickness (H) and the fracture width (W) of the temporary plugging agent under the condition that the pressure-bearing capacity of the indoor temporary plugging agent filter cake ≥ 40 MPa, as Figure 4 shown, determine the fracture width W and the placement thickness H of the temporary plugging agent. For example, when the fracture width is 15 mm and the pressure-bearing capacity ≥ 40 MPa, the placement thickness of the temporary plugging agent is 400 mm;

[0031] Step 4: Calculate the dosage of the temporary plugging agent in the case of multiple fracture reservoir thicknesses through formula (1).

[0032] Q = 2(H×h×W)×n×ρ 视 ×S (1)

[0033] In the formula: Q—the weight of the temporary plugging agent, kg; h—the dynamic fracture height, m; H—the placement thickness of the temporary plugging agent, mm; W—the fracture width, cm; n—the number of fractures; ρ 视 —the apparent density of the temporary plugging agent, g / cm 3 , S—the safety factor, dimensionless (1.2 - 1.4).

[0034] As shown in Table 1, in order to verify the effectiveness of the calculation formula of the present invention, a comparative test was carried out. In the comparative test, the dosage of the temporary plugging agent put in the first stage was given according to conventional experience, and 200 kg of the temporary plugging agent was put in for in-fracture temporary plugging. After fracturing, it was found that the pressure before and after putting the temporary plugging agent at the same displacement not only did not increase but decreased by 2.1 MPa, indicating that the temporary plugging was ineffective. And the analysis result of the small-scale test G function before fracturing in this embodiment shows that the minimum number of fractures is 5. The 200 kg of the temporary plugging agent put in the first stage can only plug 2 or 3 fractures, and there is an obvious shortage of the amount of the temporary plugging agent.

[0035] Applying the calculation method of the present invention, timely adjust the dosage of the temporary plugging agent for the remaining three stages. It is found that the construction pressure at the same displacement before and after putting the temporary plugging agent increases by 3.0 - 8.0 Mpa, indicating that in-situ temporary plugging diversion within a certain range is achieved, the fracture rupture angle increases, the transformation range increases, and a complex fracture network is formed. The calculation method of the present invention is simple and reliable, and can effectively guide the design of the single-well fracturing plan.

[0036] Table 1: Pressure increase situation before and after putting the temporary plugging agent in Well Yingshen 306 - 3

[0037]

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A calculation method for the dosage of temporary plugging agent used in fracturing based on comprehensive evaluation of reservoir fractures, characterized in that, it includes the following steps: Step 1: Determine the number of fractures; Step 2: Determine the dynamic fracture height of the fracturing interval; Step 3: Determine the fracture width and the placement thickness of the temporary plugging agent; Step 4: Calculate the dosage of the temporary plugging agent in the case of multiple fracture reservoir thicknesses.

2. The calculation method for the dosage of temporary plugging agent used in fracturing based on comprehensive evaluation of reservoir fractures according to claim 1, characterized in that, Step 1 is specifically to carry out a small-scale pre-fracturing test construction on site to determine the number of fractures.

3. The calculation method for the dosage of temporary plugging agent used in fracturing based on comprehensive evaluation of reservoir fractures according to claim 2, characterized in that, After carrying out the small-scale pre-fracturing test construction in Step 1, the G-function analysis is carried out using FracproPT software to determine the number of fractures.

4. The calculation method for the dosage of temporary plugging agent used in fracturing based on comprehensive evaluation of reservoir fractures according to claim 1, characterized in that, Step 2 is specifically to import well logging data into the in-situ stress profile software, obtain the in-situ stress profile diagram, and determine the dynamic fracture height of the fracturing interval.

5. The calculation method for the dosage of temporary plugging agent used in fracturing based on comprehensive evaluation of reservoir fractures according to claim 4, characterized in that, The well logging data in Step 2 includes natural gamma, density, and acoustic data.

6. The calculation method for the dosage of temporary plugging agent used in fracturing based on comprehensive evaluation of reservoir fractures according to claim 1, characterized in that, Step 3 is specifically to determine the fracture width and the placement thickness of the temporary plugging agent according to the fitting result of the relationship between the placement thickness (H) of the temporary plugging agent and the fracture width (W) under the condition that the pressure-bearing capacity of the indoor temporary plugging agent filter cake ≥ 40 MPa.

7. The calculation method for the dosage of temporary plugging agent used in fracturing based on comprehensive evaluation of reservoir fractures according to claim 1, characterized in that, Step 4 is specifically to calculate the dosage of the temporary plugging agent in the case of multiple fracture reservoir thicknesses through formula (1); Q = 2(H×h×W)×n×ρ 视 ×S (1) Where: Q—the weight of the temporary plugging agent, kg; h—the height of the dynamic fracture, m; H—the laying thickness of the temporary plugging agent, mm; W—the width of the fracture, cm; n—the number of fractures; ρ 视 —the apparent density of the temporary plugging agent, g / cm 3 , S—the safety factor, dimensionless (1.2 - 1.4).

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