Indoor core test and calculation evaluation method for reservoir sand production critical production pressure difference

Abstract

The invention belongs to the technical field of oil and gas exploitation engineering in the petroleum and natural gas development industry, and particularly relates to an indoor rock core testing and calculation evaluation method for reservoir sand production critical production pressure difference. The method comprises the following steps: S1, determining an experimental rock core confining pressure used in a reservoir rock core sand production displacement test; s2, determining core displacement initial flow and step flow increment used in the reservoir core sand production displacement test; s3, determining reservoir core sand production critical pressure difference based on a reservoir core sand production displacement test; and S4, calculating the actual reservoir sand production critical pressure difference according to the reservoir core sand production critical pressure difference. According to the method, the long-standing key problem that unreasonability and even errors are caused when the sand production critical condition obtained by a rock core test is directly and mechanically equivalent to the reservoir sand production critical condition and is used for reservoir production system design in the past is solved; the method has important significance and value for improving efficient sand production control of an oil and gas reservoir easy to produce sand and improving mining benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas production engineering in the petroleum and natural gas development industry, and specifically relates to an indoor core test and calculation evaluation method for critical production pressure difference of reservoir sand production. Background Art

[0002] Oil reservoirs prone to sand production are widely distributed at home and abroad, and the sand production problem has plagued their normal development. In the optimization of the exploitation policy and system of such oil reservoirs, it is necessary to accurately obtain the critical production pressure difference or output of reservoir sand production, that is, the production pressure difference or output when the reservoir begins to show obvious sand production during the oil production process, as the critical condition for judging the sand production of the reservoir, which is an important basis for on-site production control and production system optimization, and provides a key basis for the decision-making of sand control measures and the optimization of sand control parameter design.

[0003] At present, the methods for obtaining the critical production pressure difference of reservoir sand production at oil fields mainly include numerical simulation prediction method and core test experiment method (as shown in the patent document with announcement number CN205135616U). The latter uses reservoir cores to conduct sand displacement simulation experiments, which has better credibility than numerical calculation methods and has become the main technical approach to obtain the critical production pressure difference of reservoir sand production.

[0004] However, the current technology for obtaining the critical production pressure difference of sand production through reservoir core testing has the following key problems: (1) There is a lack of standardized and effective indoor experimental test methods for the critical pressure difference of reservoir core sand production. The existing core test methods are difficult to obtain accurate critical conditions for sand production. The lack of effective test methods makes it difficult to obtain accurate production pressure difference data. The general experimental method is to conduct core displacement experiments based on the reservoir flow rate of reservoir conditions. The experimental data obtained can determine whether the core has sand production, but the critical pressure difference or critical conditions for core sand production cannot be obtained.

[0005] (2) The critical production pressure difference of sand production obtained by small-scale reservoir core testing is not the critical condition of sand production under actual reservoir production conditions, and there is currently no conversion evaluation method. Directly equating the critical condition of sand production in the core with the critical condition of sand production in the reservoir will result in great errors or even mistakes. Since the core scale is very different from the actual reservoir, the experimental method adopts a unidirectional flow core displacement experiment, and the reservoir fluid flows to the wellbore in a radial flow manner. Therefore, the critical displacement pressure difference of sand production in the core obtained by the experiment is not the critical pressure difference of sand production in the actual reservoir (such as the attached Figure 1 As shown in (a) and (b), Figure 1 In (a), L0 is usually more than 100 meters). There is no calculation and evaluation method for converting the critical displacement pressure difference of core sand production into the critical production pressure difference of reservoir sand production. Instead, the critical condition of core sand production is directly equated with the critical condition of reservoir sand production to guide reservoir development and production policies and systems, which has great errors or even mistakes. Summary of the invention

[0006] In view of the key problems of lack of standardized and effective indoor experimental testing and conversion methods for the critical pressure difference of sand production from cores of reservoirs, and the huge error in directly equating the critical conditions of sand production from cores with the critical conditions of sand production from reservoirs, the present invention provides an indoor core testing and calculation evaluation method for the critical production pressure difference of sand production from oil reservoirs. One of its purposes is to provide a standardized experimental procedure for obtaining accurate critical flow rate and pressure difference conditions for sand production from cores, so as to solve the problem that the critical conditions for sand production from cores cannot be accurately obtained due to the lack of experimental methods; the second purpose is to provide a conversion method for converting the critical pressure difference for sand production obtained from core testing to obtain the critical production pressure difference for sand production under actual oil layer production conditions, so as to solve the problem that the critical conditions for sand production from cores are currently directly equated with the critical conditions for sand production from reservoirs, which is used to guide reservoir development and production policies and systems, and there is a huge error or even mistake.

[0007] Therefore, the indoor core test and calculation evaluation method of the critical production pressure difference of oil reservoir sand production of the present invention includes the following two parts: Part 1: Provide an experimental test method for critical pressure difference of reservoir core sand production; The method is based on a core displacement experimental device. First, a basic method for determining the confining pressure is proposed. Then, a method for determining the initial flow rate of step flow displacement and a method for determining the step flow increment are given. Two characteristic phenomena of initial slight sanding and obvious sanding and a method for determining the corresponding critical pressure difference conditions are proposed. The step flow method proposed in the present invention can accurately determine the critical pressure difference corresponding to the initial slight sanding and obvious sanding of the reservoir core through experiments.

[0008] Part 2: Provide a method for calculating the critical production pressure difference of sand production in the actual reservoir based on the critical pressure difference of sand production in the core; This method takes into account the differences between the confining pressure conditions of the core test and the actual reservoir confining pressure conditions, the differences between the physical properties of the core test fluid and the reservoir fluid, and the differences between the core scale and the scale of the sand production area of ​​the near-wellbore reservoir, and converts the critical pressure difference for sand production obtained from the reservoir core test into the critical pressure difference for sand production under actual reservoir conditions.

[0009] Based on this, the specific technical solution of the present invention is as follows: An indoor core test and calculation evaluation method for critical production pressure difference of reservoir sand production includes the following steps: S1. Determine the experimental core confining pressure used in the reservoir core sand displacement test: The present invention proposes an experimental confining pressure determination method which refers to the uniaxial compressive strength of a core and aims at finitely simulating reservoir stress conditions while avoiding core wall seepage and core extrusion and crushing.

[0010] S11. Calculate the minimum experimental confining pressure: Whether the fluid flows in the gap between the core holder and the core depends on the flow driving pressure and the confining pressure. According to the pressure balance principle, the critical confining pressure to prevent the core wall from flowing can be obtained. In order to ensure that the wall does not flow during the entire experiment, the present invention proposes that the minimum confining pressure is 1.25 times the critical confining pressure of the flow: (Ⅰ) In formula (I), s min is the minimum experimental confining pressure, MPa; s l is the critical confining pressure of core wall flow, MPa; m is the displacement fluid viscosity, mPa·s; L is the core length, m; Q max is the maximum displacement flow rate of the experiment, m 3 / s; m c The friction coefficient is generally 0.3~0.5 according to the rock type and the surface roughness of the core. For dense rock or core with relatively smooth surface, the value is 0.3; for loose sandstone or core with relatively rough surface, the value is 0.5; b is the gap height between the core holder and the core, m; d is the core diameter, m; S12. Calculate the maximum experimental confining pressure: The core holder has axial support stress. To ensure that the core is not squeezed and damaged during the experiment, the upper limit of the confining pressure is set according to the uniaxial compressive strength of the core. s max : (Ⅱ) In formula (II), s max is the maximum experimental confining pressure, MPa; α It is an empirical coefficient, generally ranging from 1.5 to 3.0. For weakly cemented loose sandstone, a value of 3.0 is recommended, for moderately consolidated sandstone, a value of about 2.0 is recommended, and for strongly consolidated sandstone, a value of about 1.5 is recommended. s c is the uniaxial compressive strength of the core, MPa; S13. Determine the experimental core confining pressure: The experimental setting confining pressure should be [ s min , s max] are selected. The actual reservoir rock is under the ground stress environment condition, and the rock of any unit in the reservoir is under the surrounding rock stress condition. In order to simulate the formation stress condition in the core displacement experiment, the present invention proposes to determine the experimental core confining pressure used according to the following method: (III) (IV) In formula (III), s ve is the finite formation vertical stress value simulated by the experimental confining pressure, and the recommended value is 20% of the original vertical principal stress of the reservoir, MPa; s v is the original vertical principal stress of the reservoir; r r is the average density of reservoir rock, kg / m 3 ; g is the acceleration due to gravity, which is 9.8N / kg; h is the vertical depth of the reservoir, m; In formula (IV), s w It is the recommended reasonable value of experimental confining pressure, i.e. experimental core confining pressure, MPa.

[0011] S2. Determine the core displacement starting flow rate and step flow rate increment used in the reservoir core sand displacement test experiment: In order to accurately test the critical pressure difference of core sand production by gradually increasing the flow rate in steps, it is necessary to determine the core displacement starting flow rate and step flow rate increment used in the displacement experiment. Q 0 and Δ Q Represent the experimental core flooding starting flow rate and step flow rate increment respectively, requiring Q 0 must be lower than the critical minimum flow rate that causes sand production in the core (the critical sand production state is the target state to be tested in the experiment), and Δ Q Should be as small as possible to ensure more accurate testing; however, too small Δ Q It will increase the test time and complexity, and it is necessary to select a reasonable Δ Q value.

[0012] The present invention proposes a method for calculating the experimental core displacement starting flow rate according to the production and sand production of oil and gas wells in the target work area (oil and gas block or reservoir) where the experimental core is sourced. Q 0 and step flow increment Δ Q The method is divided into three situations for calculation: Situation 1: There are no wells with obvious sand production under the production conditions of the target work area (all wells do not produce sand) The situation Q 0, Δ Q The specific calculation steps are as follows: S21. Calculate the characteristic volume liquid production intensity: Sort all the wells in the target area by their fluid production intensity from high to low, and select the top N Wells are taken as typical wells ( N Select 3-5 wells or 1 / 10 of the total number of wells in the target work area), select typical production conditions for each typical well (typical production conditions refer to the key dynamic parameter combination that is commonly present in reservoir development and affects the risk of sand production, such as bottom hole flowing pressure, fluid properties, production system, etc.) n i Daily production report ( n i Take 15 to 30 days), divide the bottom hole volume production data in the daily production report by the production layer thickness to get the liquid production intensity, and then calculate the characteristic volume liquid production intensity according to the following formula: (V) (VI) In formula (V), For the i Average characteristic volumetric fluid production intensity of typical wells, m 3 / d / m, i The value is 1,2.. N ; n i For the i The number of daily production days for a typical well; q ij For the i A typical well j Volumetric liquid production intensity per day (obtained by dividing the bottom hole volumetric production by the production layer thickness), m 3 / d / m, j The value is 1,2… n i ; In formula (VI), q a is the characteristic volumetric liquid production intensity of the target work area (the characteristic volumetric liquid production intensity in case 1 is q a Specifically refers to the characteristic volume production intensity of sand production), m 3 / d / m; N is the typical number of wells calculated; S22, according to the characteristic volume liquid production intensity q a , calculate the corresponding core displacement flow rate under the same flow rate conditions: (VII) In formula (VII), Q ais the velocity equivalent core displacement flow rate (the velocity equivalent core displacement flow rate in case 1 Q a Specifically, it refers to the flow rate equivalent to the core displacement flow rate corresponding to the characteristic volume production intensity without sand production), L / min; d is the core diameter, m; d w for N Average borehole diameter of typical wells, m; S23. Determine the core displacement starting flow rate and step flow rate increment in the target work area: (VIII) (IX) In this case, the core displacement starting flow rate is calculated according to the flow rate equivalent core displacement flow rate. Q a 0.9 times of the selected, the step flow increment is based on Q 0.5 times of 0, that is x The value is 0.9. y The value is 0.5.

[0013] Situation 2: Some wells have produced sand or are producing sand under production conditions in the target area (other wells do not produce sand) The situation Q 0, Δ Q The specific calculation steps are as follows: S21. Calculate the characteristic volume production intensity: Sort the wells in the target area that do not produce sand by the intensity of liquid production from high to low, and select the top N Wells are taken as typical wells ( N Take 3-5 wells or 1 / 10 of the total number of wells that do not produce sand in the target area), select each typical well under typical production conditions n i Daily production report ( n i Take 15 to 30 days), divide the bottom hole volume production data in the daily production report by the production layer thickness to get the liquid production intensity, and then calculate the characteristic volume liquid production intensity according to formula (V) and (VI): Characteristic volumetric liquid production intensity in case 2 q a Specifically, it refers to the liquid production intensity of the characteristic volume without sand production; S22, according to the characteristic volume liquid production intensity q a , according to formula (VII) to calculate the corresponding core displacement flow rate under the same flow rate conditions: Velocity equivalent core displacement flow in case 2 Q aSpecifically, it refers to the equivalent core displacement flow rate corresponding to the fluid production intensity of the characteristic volume without sand production; S23. Determine the core displacement starting flow rate and step flow rate increment of the target work area according to formula (VIII) and (IX): In this case, the core flooding start flow rate Q 0 Equivalent core displacement flow rate according to flow velocity Q a 0.75 times of the selected, the step flow increment is based on Q 0.25 times of 0, that is x The value is 0.75. y The value is 0.25.

[0014] Situation 3: All wells have produced sand or are producing sand under production conditions in the target area The situation Q 0, Δ Q The specific calculation steps are as follows: S21. Calculate the characteristic volume liquid production intensity: Sort all the wells in the target work area by sand production from mild to severe, and select the top N Wells are taken as typical wells ( N Select 3-5 wells or 1 / 10 of the total number of wells in the target area), select each typical well under typical production conditions n i Daily production report ( n i Take 15 to 30 days), divide the bottom hole volume production data in the daily production report by the production layer thickness to get the liquid production intensity, and then calculate the characteristic volume liquid production intensity according to formula (V) and (VI): Characteristic volumetric liquid production intensity in case 3 q a Specifically refers to the characteristic volumetric liquid production intensity of slight sanding; S22, according to the characteristic volume liquid production intensity q a , according to formula (VII) to calculate the corresponding core displacement flow rate under the same flow rate conditions: Velocity equivalent core displacement flow in case 3 Q a Specifically, it refers to the flow rate equivalent to the core displacement flow corresponding to the characteristic volume production intensity of slight sanding; S23. Determine the core displacement starting flow rate and step flow rate increment of the target work area according to formula (VIII) and (IX): In case 3, the core flooding initial flow rate Q 0 Equivalent core displacement flow rate according to flow velocity Q a 0.5 times of the selected, the step flow increment is based on Q0.15 times of 0, that is x The value is 0.5. y The value is 0.15.

[0015] S3. Use the step-by-step flow rate method to test the critical conditions for slight sanding and obvious sanding of the core According to the selected core flooding starting flow rate Q 0 and step flow increment Δ Q , the step-by-step flow rate method was used to conduct sand displacement experiments. It is proposed to use the following two sand production states and the critical pressure difference under these states to characterize the critical pressure difference of sand production in the reservoir core: Slight sanding state and its critical pressure difference condition: The initial slight sanding state is defined as the experimental fluid flowing out of the core begins to become obviously turbid compared with the original inlet fluid, or muddy fine sand particles begin to appear on the filter medium (usually filter paper). At this time, it can be determined that the core begins to produce slight sand, and the core displacement pressure difference at this time is the critical pressure difference for initial slight sanding of the core. Obvious sanding state and its critical pressure difference condition: Obvious sanding state is defined as the state when obvious sand deposition begins to be observed on the filter medium with the naked eye. At this time, it is determined that the core begins to show obvious sanding phenomenon. At this time, the core displacement pressure difference is the critical pressure difference for obvious sanding of the core.

[0016] According to the attached Figure 3 The experimental process shown, the specific experimental test method: a. Set the core confining pressure to s w , the experimental fluid used high-mineralization water with the same composition as that of the actual reservoir.

[0017] b. Q 0 was used as the initial experimental displacement flow rate, and the constant flow was used for 30 min; c. Based on the previous displacement flow, increase the flow rate by Δ Q , constant flow displacement for 30 minutes; observe the state and color of the core output fluid during the experiment; take out the sand retaining filter paper after each displacement and observe the filtering state of the filter paper.

[0018] d. When slight sanding occurs, record the critical pressure difference and flow rate of slight sanding at this time, which are denoted as Δ P c1 and Q c1 .

[0019] e. After a slight sanding state occurs, the incremental flow rate of each flow change is reduced to 0.5Δ Q , that is, the flow rate increases by 0.5Δ each time Q, constant flow displacement for 30 minutes; observe the state and color of the core output fluid during the experiment; take out the sand retaining filter paper after each displacement and observe the filtration state of the filter paper.

[0020] f. When obvious sand production occurs, record the critical pressure difference and flow rate of obvious sand production at this time, which are recorded as Δ P c2 and Q c2 . Then end the experiment.

[0021] g. If no slight or obvious sand production is observed until the maximum flow rate of the displacement condition, it means that under the current maximum experimental conditions, there is no corresponding sand production in the core. You can replace the displacement pump with a larger flow rate (because the core cannot fully reflect the actual reservoir and there are differences with the actual reservoir, there may be no sand production under the maximum displacement flow rate condition, so you can replace the displacement pump with a larger flow rate at this time), or terminate the test.

[0022] S4, calculating the actual reservoir sand production critical pressure difference according to the reservoir core sand production critical pressure difference obtained in step S3, specifically comprising the following steps: S41. Calculate the correction coefficient for the difference between the experimental core size and the actual reservoir size To convert the critical pressure difference of sand production of small-scale cores to the actual reservoir, the difference between the core size and the actual reservoir size needs to be considered. According to the phenomenon and principle of the reservoir near-wellbore pressure drop funnel, the oil well production pressure difference (the difference between the reservoir boundary pressure and the bottom hole flowing pressure, as shown in the attached figure) is the difference between the core size and the actual reservoir size. Figure 3 ) Most of the pressure is consumed in a limited range near the wellbore. The present invention proposes to use the equivalent pressure consumption radius R c As an indicator of the actual reservoir size, R c The meaning and selection principle are: from the wellbore radius to R c In the area, the flow pressure drop accounts for the total production pressure difference Δ P According to the reservoir radial seepage mechanics principle and Darcy's law, Rc Use the following formula to calculate: (Ⅹ) In formula (X), R c is the equivalent pressure loss radius representing the reservoir scale, m; r w is the wellbore radius, m; r e is the radius of the reservoir outer boundary, m; The flow of the experimental core is unidirectional linear flow, and the flow within the equivalent pressure loss radius of the actual reservoir is radial flow. It is proposed to calculate the correction coefficient of the difference between the experimental core scale and the actual reservoir scale based on the principle that the average pressure drop gradient of the reservoir radial flow is equivalent to the pressure drop gradient of the core. β 1: (Ⅺ) In formula (XI), L is the core length, m.

[0023] S42. Calculate the correction coefficient of the difference between the physical properties of the fluid tested in the indoor core and the physical properties of the actual reservoir fluid The definition of viscosity index is proposed to characterize the product of fluid density and viscosity to the zth power, as shown in the following formula: (Ⅻ) (XIII) In formula (XII), λ1 is the viscosity index of the fluid in the indoor experiment; is the density of the indoor experimental fluid, kg / m 3 ; is the viscosity of the experimental fluid in the room, Pa·s; z It is an empirical index, and 0.5 is recommended; In formula (XIII), λ2 is the actual reservoir fluid viscosity index; is the actual reservoir fluid density, kg / m 3 ; is the actual reservoir fluid viscosity, Pa·s; The viscosity index is used to characterize the effect of fluid on sand production conditions and sand carrying in porous media. The larger the viscosity index (i.e., the greater the fluid viscosity or density), the easier it is for the reservoir to produce sand, and the smaller the critical production pressure difference for sand production.

[0024] Proposed correction coefficients for differences between laboratory experimental fluid properties and actual reservoir fluid properties β 2 is the viscosity index of the indoor experimental fluid l 1 and the viscosity index of the actual reservoir fluid l 2, as shown below: (XIV) When calculating the density and viscosity of the reservoir oil-water mixture fluid, the density and viscosity of oil and water are used respectively, and the water content weighted average method is used to calculate the result.

[0025] S43, calculate the correction coefficient of the difference between the indoor core test confining pressure (stress) and the actual reservoir stress conditions Propose a correction coefficient for the difference between the confining pressure (stress) of the indoor core test and the actual reservoir stress conditions β3 is the ratio of the core experimental confining pressure to the actual reservoir minimum in-situ principal stress, as shown in the following formula: (XV) In formula (XV) ,s v is the original vertical principal stress of the reservoir, MPa; s h is the original minimum horizontal principal stress of the reservoir, MPa.

[0026] S44. Calculate the actual critical pressure difference of reservoir sand production based on the critical pressure difference correction of indoor core test According to the reservoir scale difference correction coefficient β 1. Correction coefficient for reservoir fluid property differences β 2 and reservoir stress difference correction coefficient β 3. Calculate and correct the critical pressure difference of actual reservoir sand production: (XVI) (XVII) Where Δ P 1 is the critical pressure difference of slight sand production in actual reservoir, MPa; Δ P 2 is the critical pressure difference of the actual reservoir for obvious sand production, MPa. The critical pressure difference of the actual reservoir for obvious sand production is calculated by Δ P 1. Δ P 2 Characterization.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) The experimental test method for the critical pressure difference of reservoir core sanding provided by the present invention can simply and quickly determine the confining pressure conditions and the step displacement flow conditions, and carry out displacement according to the step-up flow method, and accurately test and obtain the critical pressure difference corresponding to the initial slight sanding and obvious sanding. The method is simple and convenient, has good operability, and solves the problem that the critical conditions of core sanding cannot be accurately obtained due to the lack of standardized experimental methods.

[0028] (2) The method provided by the present invention for calculating the critical production pressure difference of sand production in the actual reservoir based on the critical pressure difference of sand production in the reservoir core fully considers the difference between the test conditions in the core laboratory and the actual reservoir production conditions (including the difference between the confining pressure conditions in the core experimental test and the actual reservoir confining pressure conditions, the difference between the physical properties of the fluid in the core test and the physical properties of the reservoir fluid, and the difference between the scale of the core and the scale of the sand production area in the near-well reservoir). The critical production pressure difference of sand production obtained by the core test can be easily and quickly converted to the critical production pressure difference of sand production under the actual oil and gas reservoir production conditions, and the indoor test results can be converted into the actual reservoir conditions, so that the results are more accurate and reliable. (3) The indoor core test and calculation evaluation method of the critical production pressure difference of reservoir sanding provided by the present invention includes both an experimental operation method and a conversion evaluation method for experimental data processing; it is applicable to both oil wells and gas wells, and builds a bridge between indoor core testing and actual reservoir production conditions to achieve rapid conversion. It solves the long-standing problem of mechanically equating the critical sanding conditions obtained from core testing with the critical sanding conditions of the reservoir (in fact, the two are completely different), which leads to unreasonable or even wrong key problems in the design of reservoir production systems. It is of great significance and value for improving the efficient sanding control of oil and gas reservoirs prone to sanding and improving mining efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of reservoir, where (a) is the actual reservoir schematic diagram, (b) is the reservoir rock schematic diagram used in the experiment; Figure 2 Schematic diagram of the experimental device for reservoir core sand displacement test; Figure 3 Schematic diagram of the correction principle of core size and actual reservoir near-wellbore range scale.

[0030] 1-data acquisition system, 2-liquid storage tank, 3-liquid pump, 4-core holder, 5-sand collection device. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0032] Taking a block of an oil field as an example for conversion analysis, all wells in the reservoir have sand production. The natural core depth of the main reservoir of the oil field is 1608m, and the basic data are shown in Table 1 below.

[0033] Table 1 Case basic data

[0034] According to step S1, the reservoir is a loose sandstone reservoir, and according to the rock type and core compressive strength, s c is 19.61MPa; according to the crossflow drive theory, s min It is 11.13MPa, and the final experimental confining pressure is determined to be 15.37MPa.

[0035] According to step S2, all wells in the reservoir have produced sand. According to the average liquid production of the selected wells and the reservoir conditions, the method of situation three is used to determine that the starting flow rate of core flooding is 0.288 ml / min and the flow gradient is 0.043 ml / min.

[0036] in, NFor three typical wells, each typical well n i The values ​​are all taken as 20 days, and the q ij They are obtained by dividing the bottom hole production data in the daily production report by the thickness of the production layer.

[0037] According to step S3, using Figure 2 The experimental setup shown is used for testing. Figure 2 The experimental device for the reservoir core sand displacement test shown in the figure includes a data acquisition system 1, a liquid storage tank 2, a liquid pump 3, a core holder 4 and a sand collecting device 5. Figure 2 The arrow in the middle indicates the flow direction of the fluid during the experiment, and the data acquisition system 1 is used to collect the experimental data. The critical pressure difference results of the core test are shown in Table 2.

[0038] Table 2 Core sand production results data table

[0039] Using the S4 method: Calculate the correction coefficient for the difference between the indoor core size and the actual reservoir near the wellbore range:

[0040] Calculate the difference correction coefficient between the physical properties of the fluid tested in the indoor core and the physical properties of the actual reservoir fluid:

[0041] Calculate the correction coefficient for the difference between the indoor core test confining pressure (stress) and the actual reservoir stress conditions:

[0042] Calculate the critical production pressure difference Δ of the actual reservoir with slight sand production P 1:

[0043] Calculate the critical production pressure difference Δ for obvious sand production in the actual reservoir P 2:

Claims

1. An indoor core test and calculation evaluation method for critical production pressure difference of reservoir sand production, characterized in that: The steps include: S1. Determine the experimental core confining pressure used in the reservoir core sand displacement test; Based on the critical confining pressure of core wall channeling, the minimum experimental confining pressure is calculated. Based on the uniaxial compressive strength of the core, the maximum experimental confining pressure is calculated. Based on the minimum experimental confining pressure, the maximum experimental confining pressure and the original vertical principal stress of the reservoir, the experimental core confining pressure is determined. σ w ; S2. Determine the core displacement starting flow rate and step flow rate increment used in the reservoir core sand displacement test; Based on the sand production situation of the target reservoir area to be predicted, the characteristic volume production intensity of the target area is calculated. Based on the characteristic volume production intensity, the velocity equivalent core displacement flow rate is calculated. Based on the velocity equivalent core displacement flow rate, the core displacement starting flow rate of the target area is determined. Q 0 and step flow increment Δ Q ; S3. Determine the critical pressure difference of reservoir core sanding based on the reservoir core sanding displacement test; The experimental core confining pressure is set to σ w , the core displacement starting flow rate is Q 0, based on Δ Q Set the incremental flow rate and use the step-by-step incremental flow rate method to conduct sand displacement test to determine the critical pressure difference of slight sand production Δ P c1 and critical pressure difference of obvious sand production Δ P c2 ; S4, calculating the actual reservoir sand production critical pressure difference according to the reservoir core sand production critical pressure difference obtained in step S3; (XVI) (XVII) In formula (XVI), Δ P 1 is the critical pressure difference of slight sand production in the actual reservoir, dimensionless; β 1 is the reservoir scale difference correction coefficient, dimensionless; β 2 is the correction coefficient for reservoir fluid property differences, dimensionless; β 3 is the reservoir stress difference correction coefficient, dimensionless; In formula (XVII), ΔP 2 is the critical pressure difference for obvious sand production in the actual reservoir; The actual critical pressure difference of reservoir sand production is Δ P 1. Δ P 2 Characterization.

2. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 1 is characterized in that: Step S1 is specifically as follows: S11. Calculate the minimum experimental confining pressure: (Ⅰ) In formula (I), σ min is the minimum experimental confining pressure, MPa; σ l is the critical confining pressure of core wall flow, MPa; μ is the displacement fluid viscosity, mPa·s; L is the core length, m; Q max is the maximum displacement flow rate of the experiment, m 3 / s; μ c is the friction coefficient, dimensionless; b is the gap height between the core holder and the core, m; d is the core diameter, m; S12. Calculate the maximum experimental confining pressure: (Ⅱ) In formula (II), σ max is the maximum experimental confining pressure, MPa; α is the empirical coefficient, dimensionless; σ c is the uniaxial compressive strength of the core, MPa; S13. Determine the experimental core confining pressure: (Ⅲ) (Ⅳ) In formula (III), σ ve is the vertical stress value of the finite formation simulated by the experimental confining pressure, MPa; σ v is the original vertical principal stress of the reservoir, MPa; ρ r is the average density of reservoir rock, kg / m 3 ; g is the acceleration due to gravity, which is 9.8N / kg; h is the vertical depth of the reservoir, m; In formula (IV), σ w is the experimental core confining pressure, MPa.

3. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 1 is characterized in that: In step S2, the sand production situation of the target work area of ​​the reservoir to be predicted is divided into: situation 1, there is no obvious sand production well under the production conditions of the target work area; situation 2, some wells have produced sand or have sand production under the production conditions of the target work area; situation 3, all wells have produced sand or have sand production under the production conditions of the target work area; Step S2 is specifically as follows: S21. Select the target area of ​​the reservoir to be predicted. N Typical wells, each of which is selected under typical production conditions n i Daily production report for the day, calculate the characteristic volume production intensity: (Ⅴ) (Ⅵ) In formula (V), For the i Average characteristic volumetric fluid production intensity of typical wells, m 3 / d / m, i The value is 1,2.. N ; n i For the i The number of daily production days for a typical well; q ij For the i A typical well j Volumetric liquid production intensity per day, m 3 / d / m, j The value is 1,2… n i In formula (VI), q a is the characteristic volumetric liquid production intensity, m 3 / d / m; Among them, when the sand production situation of the target work area of ​​the reservoir to be predicted is situation one or situation two, a typical well is selected based on the liquid production intensity, and the characteristic volume liquid production intensity obtained by formula (VI) is the characteristic volume liquid production intensity of no sand production; when the sand production situation of the target work area of ​​the reservoir to be predicted is situation three, a typical well is selected based on the degree of sand production, and the characteristic volume liquid production intensity obtained by formula (VI) is the characteristic volume liquid production intensity of slight sand production; S22, calculate the equivalent core displacement flow rate: (Ⅶ) In formula (VII), Q a is the flow rate equivalent to the core displacement flow, L / min; d is the core diameter, m; d w for N Average borehole diameter of typical wells, m; S23. Determine the starting flow rate of core flooding in the target work area and step flow increment Δ Q : (Ⅷ) (Ⅸ) Among them, when the sand production situation of the target reservoir area to be predicted is situation 1, x The value is 0.

9. y The value is 0.5; when the sand production situation of the target area of ​​the reservoir to be predicted is situation 2, x The value is 0.

75. y The value is 0.25; when the sand production situation of the target reservoir area to be predicted is situation 3, x The value is 0.

5. y The value is 0.

15.

4. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 1 is characterized in that: Step S3 is specifically as follows: a. Set the core confining pressure to σ w , the experimental fluid used high-mineralization water with the same composition as the actual reservoir formation sand; b. Q 0 was used as the initial experimental displacement flow rate, and the constant flow was used for 30 min; c. Based on the previous displacement flow, increase the flow rate by Δ each time Q , constant flow displacement for 30 minutes, observe the state and color of the core output fluid during the experiment, take out the sand filter paper after each displacement, and observe the filtering state of the filter paper; d. When slight sanding occurs, record the critical pressure difference Δ for slight sanding at this time. P c1 ; e. After slight sanding occurs, increase the flow rate by 0.5Δ each time Q , constant flow displacement for 30 minutes, observe the state and color of the core output fluid during the experiment, take out the sand filter paper after each displacement, and observe the filtering state of the filter paper; f. When obvious sand production occurs, the critical pressure difference for obvious sand production is recorded as Δ P c2 , and then end the experiment.

5. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 1 is characterized in that: In step S4, the actual reservoir scale difference correction coefficient β The calculation method of 1 is: (Ⅹ) In formula (X), R c is the equivalent pressure loss radius, m; r w is the wellbore radius, m; r e is the radius of the reservoir outer boundary, m; (Ⅺ) In formula (XI), L is the core length, m.

6. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 1 is characterized in that: In step S4, the actual reservoir fluid property difference correction coefficient β 2 is calculated as: (Ⅻ) (XIII) In formula (XII), λ1 is the viscosity index of the fluid in the indoor experiment; is the density of the indoor experimental fluid, kg / m 3 ; is the viscosity of the indoor experimental fluid, Pa·s; z is the experience index; In formula (XIII), λ2 is the actual reservoir fluid viscosity index; is the actual reservoir fluid density, kg / m 3 ; is the actual reservoir fluid viscosity, Pa·s; (XIV)。 7. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 1 is characterized in that: In step S4, the actual reservoir stress condition difference correction coefficient β The calculation method of 3 is: (XV) In formula (XV) , σ v is the original vertical principal stress of the reservoir, MPa; σ h is the original minimum horizontal principal stress of the reservoir, MPa; σ w is the experimental core confining pressure.

8. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 2 is characterized in that: In step S11, μ c The value range is 0.3~0.

5. For dense rocks or cores with relatively smooth surfaces, the value is 0.3; for loose sandstones or cores with relatively rough surfaces, the value is 0.

5.

9. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 2 is characterized in that: In step S12, α The value range is 1.5~3.0; for weakly cemented loose sandstone, the value is 3.0, for moderately consolidated sandstone, the value is 2.0, and for strongly consolidated sandstone, the value is 1.

5.

10. The indoor core testing and calculation evaluation method for critical production pressure difference of reservoir sand production according to claim 6, characterized in that: In step S4, z The value is 0.5.

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