Method for determining sand production critical gas production speed of water-containing loose sandstone reservoir

Abstract

The invention belongs to the field of oil and gas field development, and particularly relates to a method for determining the sand production critical gas production speed of a water-containing loose sandstone reservoir. The problem of sand production caused by unreasonable gas production speed of the existing water-containing loose sandstone reservoir is solved; according to the technical scheme, the method comprises the following steps: acquiring basic physical properties of a rock sample in a sandstone reservoir, carrying out a rock shear failure experiment to obtain cohesive force and an internal friction angle of the rock sample, carrying out a rock mechanics experiment, measuring tensile strength of the rock sample under different water saturations, and measuring the diameter of rock sample particles and the gas density in the reservoir. A reservoir sand production critical gas production speed calculation model is obtained by considering the dragging force of actual reservoir gas on rock sample particles and the resistance of the rock sample particles, and a curve graph of the relation between the water saturation and the reservoir sand production critical gas production speed is drawn; according to the novel method, the reasonable gas production speed of the gas reservoir can be controlled, damage to production caused by sand production is avoided, and the maximum productivity benefit is achieved.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas field development, and particularly relates to a method for determining a critical gas production rate of sand production in a water-containing loose sandstone reservoir. Background Art

[0002] In the field of oil and gas extraction, especially when developing water-contaminated loose sandstone gas reservoirs, sand production is a critical challenge. Water-contaminated loose sandstone gas reservoirs have weak bonding between rock particles, high porosity, and contain a large amount of fluid (including natural gas and water). During the exploitation of such gas reservoirs, the rock structure is easily destroyed due to the reduction of formation pressure, resulting in sand particles being produced along with the production fluid. Sand production not only blocks the wellbore and damages production equipment, but also reduces the conductivity of the gas well. Therefore, avoiding sand production in loose sandstone reservoirs is the basis for their efficient development.

[0003] After extensive research, it is found that the determination of the critical gas production rate of sand production in traditional reservoirs usually relies on empirical formulas or numerical simulations. However, numerical simulations need to consider multiple parameters and complex geological conditions. Model establishment and parameter setting are subject to certain subjectivity and uncertainty, which may lead to errors in simulation results. Empirical formulas are usually based on historical data and experience summaries. Their applicability is limited by factors such as reservoir type and geological conditions, and they cannot accurately predict the critical gas production rate of sand production in specific reservoirs. These methods have their own limitations. Therefore, it is very important to study a method for determining the critical gas production rate of sand production in water-rich loose sandstone reservoirs to ensure the stable and safe production of water-rich loose sandstone gas reservoirs and improve the efficiency of natural gas resource extraction. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of sand production caused by unreasonable gas production rate in water-rich loose sandstone reservoirs. The present invention adopts a combination of experimental and theoretical means to obtain the basic physical properties of rock samples in sandstone reservoirs, conduct rock shear failure experiments, obtain the cohesion and internal friction angle of rock samples, conduct rock mechanics experiments, measure the tensile strength of rock samples at different water saturations, measure the diameter of rock sample particles and the gas density in the reservoir, consider the drag force of actual reservoir gas on rock sample particles and the resistance of rock sample particles themselves, obtain a calculation model for the critical gas production rate of sand production in the reservoir, and then draw a water saturation and sand critical gas production rate chart, so as to determine the critical gas production rate of sand production in sandstone reservoirs at different production stages. The calculation is simple and the scalability is strong.

[0005] To achieve the above object, the present invention provides a method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, the method comprising the following steps:

[0006] The first step is to obtain the basic physical properties of rock samples in sandstone reservoirs, conduct rock shear failure experiments, and obtain the cohesion and internal friction angle of rock samples;

[0007] The second step is to saturate the dry rock samples with formation water, conduct rock mechanics experiments, and measure the tensile strength of the rock samples at different water saturations;

[0008] The third step is to measure the diameter of the rock sample particles and the gas density in the reservoir;

[0009] The fourth step is to consider the drag force of the actual reservoir gas on the rock sample particles and the resistance of the rock sample particles themselves, establish a calculation model for the critical gas production rate of reservoir sand production, and calculate the critical gas production rate of sandstone reservoir sand production;

[0010] The fifth step is to select the maximum diameter of the rock sample particles according to the size distribution of the rock sample particles and the critical diameter of the rock sample particles for instability, calculate and determine the critical gas production rate of sand production, and establish a relationship curve between water saturation and the critical gas production rate of sand production in the reservoir. Under different water saturations, the actual gas production rate of the reservoir needs to be less than the critical gas production rate of sand production so that the reservoir will not produce sand.

[0011] In the above method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, the step of obtaining the basic physical properties, cohesion and internal friction angle of the rock sample is:

[0012] The first step is to collect representative sandstone samples from the target reservoir, wash and dry them, and measure the length, diameter, weight, porosity and permeability of each dry rock sample;

[0013] The second step is to carry out rock shear failure experiments, record the shear stress experimental data during the experiment, and derive the cohesion and internal friction angle of the rock sample based on the experimental data;

[0014] In the above method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, the step of saturating the rock sample with formation water and obtaining the tensile strength of the rock sample at different water saturations is:

[0015] In the first step, the dry rock sample is saturated with formation water and the water saturation of the rock sample is calculated by weighing method;

[0016] In the second step, when the water saturation of the rock sample reaches 20%, 40%, 60% and 80%, rock mechanics experiments are carried out respectively to measure the tensile strength of the rock sample at different water saturations and obtain the relationship curve between the tensile strength of the rock sample and the water saturation;

[0017] In the above method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, the step of obtaining the diameter of the rock sample particles and the gas density in the reservoir is:

[0018] The first step is to crush the representative rock sample into rock sample particles of different diameters, and use a laser particle size analyzer to obtain the diameter size distribution of the rock sample particles;

[0019] The second step is to calculate the density of gas in the reservoir under the actual reservoir temperature and pressure conditions using the Lee model, an empirical formula for gas density.

[0020] In the above method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, the step of calculating the critical gas production rate of sand production in the sandstone reservoir is:

[0021] The first step is to consider that when the gas is continuously flowing in the reservoir pores, the gas will generate a drag force on the rock particles around the pore wall. The greater the gas velocity and the diameter of the rock particles, the greater the drag force, and the easier it is for the rock particles to fall off the pore wall. A calculation model for the drag force of rock particles can be established.

[0022]

[0023] Where F1 is the drag force of rock sample particles, unit is N; r g is the density of the gas, in kg / m 3 ; C D is the drag force coefficient, unit is dimensionless; v g is the gas velocity, in m / s; d0 is the diameter of the rock sample particles, in m;

[0024] In the second step, the drag force of the gas on the rock sample particles is the driving force for the movement of the rock sample particles. Considering that the rock sample itself has cohesion, tensile strength and static friction, these three forces are the resistance to the movement of the rock sample particles. A calculation model for the resistance of the rock sample particles is established.

[0025]

[0026] Among them, F2 is the resistance of rock sample particles, in N; d0 is the diameter of rock sample particles, in m; c is the cohesion of rock sample, in Pa; R0 is the tensile strength of dry rock sample, in Pa; S w is the water saturation, in %; e is the base of the natural logarithm, in dimensionless units; N is the radial stress, in Pa; M is the internal friction angle, in degrees; A is the tensile strength correction factor, in dimensionless units; B is the cohesion correction factor, in dimensionless units; Z is a constant, in dimensionless units;

[0027] In the third step, when the drag force of the rock sample is greater than the resistance of the rock sample, the rock sample particles migrate and fall off, and the reservoir begins to produce sand. Otherwise, the reservoir does not produce sand. When the rock sample particles of different diameters are in a critical instability state, the drag force of the rock sample and the resistance of the rock sample reach a two-force balance, and the two are equal. The calculation model of the drag force of the rock sample particles and the calculation model of the resistance of the rock sample particles can be combined to obtain the calculation model of the critical gas production rate of the reservoir sand.

[0028]

[0029] Among them, v g is the gas velocity, in m / s; d0 is the diameter of the rock sample particles, in m; c is the cohesion of the rock sample, in Pa; R0 is the tensile strength of the dry rock sample, in Pa; S w is the water saturation, in %; e is the base of the natural logarithm, in dimensionless units; N is the radial stress, in Pa; M is the internal friction angle, in degrees; r g is the density of the gas, in kg / m 3 ; C D is the drag force coefficient, unit is dimensionless; A is the tensile strength correction factor, unit is dimensionless; B is the cohesion correction factor, unit is dimensionless; Z is a constant, unit is dimensionless;

[0030] In the above-mentioned method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, the step of determining the critical gas production rate of sand production is to select the maximum diameter of the rock sample particles according to the size distribution of the rock sample particle diameters and the critical diameter of the rock sample particles for instability, calculate and determine the critical gas production rate of sand production, and establish a relationship curve between water saturation and the critical gas production rate of sand production in the reservoir. Under different water saturations, the reservoir will not produce sand only when the actual gas production rate of the reservoir is less than the critical gas production rate of sand production.

[0031] In the above method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, the weighing method step for calculating the water saturation of the rock sample is:

[0032]

[0033] Among them, S w is the water saturation of the rock sample, in %; m2 is the weight of the wet rock sample, in g; m1 is the weight of the dry rock sample, in g; y is the porosity of the rock sample, in %; r w is the formation water density, in g / m 3 ; D is the diameter of the rock sample, in cm; L is the length of the rock sample, in cm.

[0034] Compared with the prior art, the present invention has the following beneficial effects: (1) the method has strong adaptability and a wider scope of application; (2) the method is convenient and effective, and the work efficiency is high; (3) the calculation results are highly accurate due to the comprehensive calculation of multiple factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the attached picture:

[0036] Figure 1 It is the overall technical roadmap of the method.

[0037] Figure 2 It is a curve diagram showing the relationship between the tensile strength of rock samples and water saturation.

[0038] Figure 3 It is a curve diagram showing the relationship between reservoir water saturation and critical gas production rate of sand production. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the embodiments and accompanying drawings;

[0040] The present invention provides a method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir. Figure 1 It is the overall technical roadmap of the method, which includes the following steps:

[0041] The first step is to obtain the basic physical properties of rock samples in sandstone reservoirs, conduct rock shear failure experiments, and obtain the cohesion and internal friction angle of rock samples;

[0042] The second step is to saturate the dry rock samples with formation water, conduct rock mechanics experiments, and measure the tensile strength of the rock samples at different water saturations;

[0043] The third step is to measure the diameter of the rock sample particles and the gas density in the reservoir;

[0044] The fourth step is to consider the drag force of the actual reservoir gas on the rock sample particles and the resistance of the rock sample particles themselves, establish a calculation model for the critical gas production rate of reservoir sand production, and calculate the critical gas production rate of sandstone reservoir sand production;

[0045] The fifth step is to select the maximum diameter of the rock sample particles according to the size distribution of the rock sample particles and the critical diameter of the rock sample particles for instability, calculate and determine the critical gas production rate of sand production, and establish a relationship curve between water saturation and the critical gas production rate of sand production in the reservoir. Under different water saturations, the actual gas production rate of the reservoir needs to be less than the critical gas production rate of sand production so that the reservoir will not produce sand.

[0046] Furthermore, the step of obtaining the basic physical properties, cohesion and internal friction angle of the rock sample is:

[0047] The first step is to collect representative sandstone samples from the target reservoir, wash and dry them, and measure the length, diameter, weight, porosity and permeability of each dry rock sample;

[0048] The second step is to carry out rock shear failure experiments, record the shear stress experimental data during the experiment, and derive the cohesion and internal friction angle of the rock sample based on the experimental data;

[0049] Furthermore, the steps of saturating the rock sample with formation water and obtaining the tensile strength of the rock sample at different water saturations are:

[0050] In the first step, the dry rock sample is saturated with formation water and the water saturation of the rock sample is calculated by weighing method;

[0051] In the second step, when the water saturation of the rock sample reaches 20%, 40%, 60% and 80%, rock mechanics experiments are carried out respectively to measure the tensile strength of the rock sample at different water saturations and obtain the relationship curve between the tensile strength of the rock sample and the water saturation;

[0052] Furthermore, the step of obtaining the diameter of the rock sample particles and the gas density in the reservoir is:

[0053] The first step is to crush the representative rock sample into rock sample particles of different diameters, and use a laser particle size analyzer to obtain the diameter size distribution of the rock sample particles;

[0054] The second step is to calculate the density of gas in the reservoir under the actual reservoir temperature and pressure conditions using the Lee model, an empirical formula for gas density.

[0055] Further, the step of calculating the critical gas production rate of sand production in the sandstone reservoir is:

[0056] The first step is to consider that when the gas is continuously flowing in the reservoir pores, the gas will generate a drag force on the rock particles around the pore wall. The greater the gas velocity and the diameter of the rock particles, the greater the drag force, and the easier it is for the rock particles to fall off the pore wall. A calculation model for the drag force of rock particles can be established.

[0057]

[0058] Where F1 is the drag force of rock sample particles, unit is N; r g is the density of the gas, in kg / m 3 ; C D is the drag force coefficient, unit is dimensionless; v g is the gas velocity, in m / s; d0 is the diameter of the rock sample particles, in m;

[0059] In the second step, the drag force of the gas on the rock sample particles is the driving force for the movement of the rock sample particles. Considering that the rock sample itself has cohesion, tensile strength and static friction, these three forces are the resistance to the movement of the rock sample particles. A calculation model for the resistance of the rock sample particles is established.

[0060]

[0061] Among them, F2 is the resistance of rock sample particles, in N; d0 is the diameter of rock sample particles, in m; c is the cohesion of rock sample, in Pa; R0 is the tensile strength of dry rock sample, in Pa; S w is the water saturation, in %; e is the base of the natural logarithm, in dimensionless units; N is the radial stress, in Pa; M is the internal friction angle, in degrees; A is the tensile strength correction factor, in dimensionless units; B is the cohesion correction factor, in dimensionless units; Z is a constant, in dimensionless units;

[0062] In the third step, when the drag force of the rock sample is greater than the resistance of the rock sample, the rock sample particles migrate and fall off, and the reservoir begins to produce sand. Otherwise, the reservoir does not produce sand. When the rock sample particles of different diameters are in a critical instability state, the drag force of the rock sample and the resistance of the rock sample reach a two-force balance, and the two are equal. The calculation model of the drag force of the rock sample particles and the calculation model of the resistance of the rock sample particles can be combined to obtain the calculation model of the critical gas production rate of the reservoir sand.

[0063]

[0064] Among them, v g is the gas velocity, in m / s; d0 is the diameter of the rock sample particles, in m; c is the cohesion of the rock sample, in Pa; R0 is the tensile strength of the dry rock sample, in Pa; S w is the water saturation, in %; e is the base of the natural logarithm, in dimensionless units; N is the radial stress, in Pa; M is the internal friction angle, in degrees; r g is the density of the gas, in kg / m 3 ; C D is the drag force coefficient, unit is dimensionless; A is the tensile strength correction factor, unit is dimensionless; B is the cohesion correction factor, unit is dimensionless; Z is a constant, unit is dimensionless;

[0065] Furthermore, the step of determining the critical gas production rate of sand production is to select the maximum diameter of the rock sample particles according to the size distribution of rock sample particle diameters and the critical diameter of rock sample particle instability, calculate and determine the critical gas production rate of sand production, and establish a curve diagram of the relationship between water saturation and the critical gas production rate of sand production in the reservoir. Under different water saturations, the reservoir will not produce sand only when the actual gas production rate of the reservoir is less than the critical gas production rate of sand production.

[0066] Further, the weighing method steps for calculating the water saturation of the rock sample are:

[0067]

[0068] Among them, S w is the water saturation of the rock sample, in %; m2 is the weight of the wet rock sample, in g; m1 is the weight of the dry rock sample, in g; y is the porosity of the rock sample, in %; r w is the formation water density, in g / m 3 ; D is the diameter of the rock sample, in cm; L is the length of the rock sample, in cm.

[0069] Taking a water-filled loose sandstone reservoir as an example, the basic physical properties of the rock samples were obtained, and the rock samples were saturated with formation water to obtain rock samples with different water saturations, as shown in Table 1. According to the on-site production sand state, the correction coefficient was given, as shown in Table 2. Through rock shear failure experiments and rock mechanics experiments, the cohesion, internal friction angle and tensile strength of the rock samples at different water saturations were measured. With the increase of water saturation, the tensile strength of the rock samples gradually weakened, as shown in Table 2. Figure 2 , the critical gas production rate of sand production is calculated through the calculation model of the critical gas production rate of reservoir sand production, see Table 3.

[0070] Table 1 Water saturation calculation results

[0071]

[0072] Table 2 Correction coefficients and constant values

[0073] Tensile strength correction factor A Cohesion correction factor B Constant Z <![CDATA[1.0×10 -16 ]]> <![CDATA[2.2×10 -13 ]]> 0.017 <![CDATA[1.0×10 -16 ]]> <![CDATA[2.2×10 -13 ]]> 0.017 <![CDATA[1.0×10 -16 ]]> <![CDATA[2.2×10 -13 ]]> 0.017 <![CDATA[1.0×10 -16 ]]> <![CDATA[2.2×10 -13 ]]> 0.017 <![CDATA[1.0×10 -16 ]]> <![CDATA[2.2×10 -13 ]]> 0.017

[0074] Table 3 Calculation results of critical gas production rate for sand production

[0075]

[0076] Draw a curve of the relationship between water saturation and critical gas production rate of reservoir sand production, see Figure 3 , according to the reservoir at different water saturations, the critical gas production rate of sand production in the reservoir can be quickly determined. When the actual gas production rate of the reservoir is less than the critical gas production rate of sand production, the reservoir will stop producing sand.

[0077] Compared with the prior art, the present invention has the following beneficial effects: Compared with the prior art, the present invention has the following beneficial effects: (1) The method has strong adaptability and a wider scope of application; (2) The method is convenient and effective, and the work efficiency is high; (3) Multi-factor comprehensive calculation has high accuracy of calculation results.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir, characterized in that: The method comprises the following steps: S100, the steps of obtaining the basic physical properties of rock samples in sandstone reservoirs, carrying out rock shear failure experiments, and obtaining the cohesion and internal friction angle of rock samples are as follows: S101, collect representative sandstone samples from the target reservoir, wash and dry them, and measure the length, diameter, weight, porosity and permeability of each dry rock sample; S102, conduct rock shear failure experiments, record shear stress experimental data during the experiment, and derive rock sample cohesion and internal friction angle based on the experimental data; S200, saturate dry rock samples with formation water, carry out rock mechanics experiments, and measure the tensile strength of rock samples at different water saturations. S201, saturate the dry rock sample with formation water and calculate the water saturation of the rock sample by weighing method; S202, when the water saturation of the rock sample reaches 20%, 40%, 60% and 80%, rock mechanics experiments are carried out respectively to measure the tensile strength of the rock sample at different water saturations, and obtain the relationship curve between the tensile strength of the rock sample and the water saturation; S300, the steps of measuring the diameter of rock sample particles and the gas density in the reservoir are: S301, crushing a representative rock sample into rock sample particles of different diameters, and using a laser particle size analyzer to obtain the diameter distribution of the rock sample particles; S302, under actual reservoir temperature and pressure conditions, using the Lee model, an empirical formula for gas density, to calculate the density of the gas in the reservoir; S400, considering the drag force of the actual reservoir gas on the rock sample particles and the resistance of the rock sample particles themselves, the steps of calculating the critical gas production rate of sandstone reservoir are: S401, when the gas is continuously flowing in the reservoir pores, the gas will generate drag force on the rock particles around the pore wall. The greater the gas velocity and the diameter of the rock particles, the greater the drag force, and the easier it is for the rock particles to fall off the pore wall. A calculation model for the drag force of rock particles can be established. Where F1 is the drag force of rock sample particles, in N; r g is the density of the gas, in kg / m 3 ; C D is the drag force coefficient, dimensionless; v g is the gas velocity, in m / s; d0 is the rock particle diameter, in m; S402, the drag force of the gas on the rock sample particles is the driving force of the rock sample particle movement. Considering that the rock sample itself has cohesion, tensile strength and static friction, these three forces are the resistance to the movement of the rock sample particles. A rock sample particle resistance calculation model is established. Among them, F2 is the resistance of rock sample particles, in N; d0 is the diameter of rock sample particles, in m; c is the cohesion of rock sample, in Pa; R0 is the tensile strength of dry rock sample, in Pa; S w is the water saturation, in %; e is the base of the natural logarithm, in dimensionless units; N is the radial stress, in Pa; M is the internal friction angle, in degrees; A is the tensile strength correction factor, in dimensionless units; B is the cohesion correction factor, in dimensionless units; Z is a constant, in dimensionless units; S403, when the drag force of the rock sample is greater than the resistance of the rock sample, the rock sample particles migrate and fall off, and the reservoir begins to produce sand. Otherwise, the reservoir does not produce sand. When the rock sample particles of different diameters are in a critical instability state, the drag force of the rock sample and the resistance of the rock sample reach a two-force balance, and the two are equal. The calculation model of the drag force of the rock sample particles and the calculation model of the resistance of the rock sample particles are combined to obtain the critical gas production rate calculation model of the reservoir sand production. Among them, v g is the gas velocity, in m / s; d0 is the diameter of the rock sample particles, in m; c is the cohesion of the rock sample, in Pa; R0 is the tensile strength of the dry rock sample, in Pa; S w is the water saturation, in %; e is the base of the natural logarithm, in dimensionless units; N is the radial stress, in Pa; M is the internal friction angle, in degrees; r g is the density of the gas, in kg / m 3 ; C D is the drag force coefficient, unit is dimensionless; A is the tensile strength correction factor, unit is dimensionless; B is the cohesion correction factor, unit is dimensionless; Z is a constant, unit is dimensionless; S500, according to the distribution of rock sample particle diameters and the critical diameter of rock sample particle instability, the maximum diameter of rock sample particles is selected, the critical gas production rate of sand production is calculated and determined, and a curve diagram of the relationship between water saturation and the critical gas production rate of sand production in the reservoir is drawn. Under different water saturations, the reservoir will not produce sand only when the actual gas production rate of the reservoir is less than the critical gas production rate of sand production.

2. The method for determining the critical gas production rate of sand production in a water-containing loose sandstone reservoir according to claim 1, characterized in that: The weighing method formula for calculating the water saturation of the rock sample is: Among them, S w is the water saturation of the rock sample, in %; m2 is the weight of the wet rock sample, in g; m1 is the weight of the dry rock sample, in g; y is the porosity of the rock sample, in %; r w is the formation water density, in g / m 3 ; D is the diameter of the rock sample, in cm; L is the length of the rock sample, in cm.

Images