Analysis method for sand-carrying capacity of chemical flooding well

Abstract

The invention belongs to the field of oil production engineering, and discloses a method for analyzing the sand-carrying capacity of a chemical flooding oil well, which comprises the following steps of: on the basis of calculating the viscosity of formation fluid in different stages of a polymer flooding production well, establishing a sand production quantity model of an oil well for producing liquid with the viscosity and a critical sand-carrying particle size model under the output liquid quantity; and judging whether the oil well has sand-carrying capacity or not through sand particle size analysis, sand content calculation and sand burying time of the pump cylinder. The method has high field applicability, can predict whether the chemical flooding production well can carry sand to produce oil or not in advance in the oil reservoir deployment stage, clearly determines which sand prevention and sand carrying lifting process mode is adopted, provides theoretical guidance for oil production engineering block scheme design, and improves the oil production efficiency. And meanwhile, technical support is provided for adjustment of a single-well sand prevention and sand carrying lifting process in different production and polymer concentration stages of the converted chemical flooding production well.

Description

Technical Field

[0001] The invention belongs to the field of oil production engineering and relates to an analysis method for the sand carrying capacity of a chemical flooding oil well. Background Art

[0002] Chemical flooding is the primary method for increasing crude oil production in oilfields. Its effectiveness plays a key role in ensuring a stable production of tens of millions of tons. Currently, several chemical flooding blocks experience varying degrees of sand production. After transitioning to chemical flooding, the increased viscosity of the produced fluid exacerbates sand production in the formation. Based on field experience, appropriate sand control and sand-carrying lift measures have been implemented, achieving some success. With the increasing number of planned deployments, a qualitative analysis of the sand-carrying capacity of oil wells in each chemical flooding block is required to provide a theoretical basis for lift technology design in these blocks.

[0003] Currently, there is no analytical method for the sand-carrying capacity of chemical flooding wells at home and abroad. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention calculates the viscosity of formation fluids at different stages in polymer flooding production wells, establishes a sand production model for oil wells with liquid production at this viscosity, and a critical sand-carrying particle size model under the produced liquid rate. The sand production particle size analysis, sand content calculation, and sand buried pump barrel time are used to determine whether the oil well has the sand-carrying capacity.

[0005] The present invention can predict in advance whether a chemical flooding production well can carry sand for oil production during the reservoir deployment stage, clarify which sand control + sand carrying lifting process to adopt, provide theoretical guidance for the design of oil production project block schemes, and also provide guidance for the adjustment of single-well lifting technology of chemical flooding production wells in different production and accumulation stages as the chemical flooding continues to be developed.

[0006] 1. Calculation ideas

[0007] (1) Determination of flow state

[0008] The critical Reynolds number (Re c =2100) as the criterion for Newtonian fluid:

[0009] When Re≤2100, the fluid flow state is laminar flow

[0010] When Re≥2100, the fluid flow state is turbulent

[0011] Among them, the expression of the Reynolds number Re of Newtonian fluid is:

[0012]

[0013] Where u l —Average flow rate of wellbore liquid, m / s

[0014] d t2 —Oil pipe diameter, m

[0015] μ--formation fluid viscosity, mPa.s

[0016] (2) Drag coefficient C d Calculation:

[0017] C d is the solid particle Reynolds number (Re) s A single-valued function of :

[0018] (a) Laminar flow region ((Re) s ≤1):

[0019]

[0020] (b) Transition region (1<(Re) s ≤1000)

[0021] Using the Allen formula

[0022] C d =30(R e ) s -0.625 (3)

[0023] (c) Turbulent zone (1000<(Re) s ≤2×10 5 )

[0024] C d =0.45 (4)

[0025] Among them, the solid particle Reynolds number (Re) s Calculation:

[0026]

[0027] Where: ρ l --Fluid density, Kg / m 3 ;

[0028] μ--comprehensive viscosity of formation fluid, mPa·s;

[0029] d s --Sand grain diameter, mm;

[0030] u0--the terminal free settling velocity of solid particles, m / s.

[0031] (3) Calculation of formation fluid viscosity

[0032] The polymer solution in the produced fluid of polymer flooding wells is a typical viscoelastic fluid. Therefore, the effective viscosity of the solution μ 有效 From shear viscosity μ 剪 and elastic viscosity μ 弹 composition.

[0033]

[0034] Where: μ 剪 --shear viscosity, mPa·s;

[0035] Φ--porosity, %;

[0036] K r -- radial permeability, mD;

[0037] N--fluidity index, dimensionless;

[0038] K--consistency coefficient, mPa·s n .

[0039] It can be assumed that the viscosity ratio is N de The relationship is:

[0040]

[0041] Where c and m are constants that depend on the geometric complexity of the reservoir pore media, and γ is the shear rate.

[0042] According to formula (6) and formula (7), we have

[0043] μ 有效 =μ 剪 +μ 弹 =(1+c * γ m )μ (8)

[0044] By weighted average of water content, the comprehensive viscosity of formation fluid is expressed as:

[0045]

[0046] Where: μ is the comprehensive viscosity of the formation fluid, mPa·s;

[0047] μ 弹 is the elastic viscosity, mPa·s;

[0048] μ 有效 is the effective viscosity of the polymer solution in the formation, mPa·s;

[0049] μ o is the viscosity of the oil, mPa·s;

[0050] S wis the average water saturation, %.

[0051] (4) A certain volume concentration C S The terminal settling velocity of solid particles

[0052] In the actual oil well production process, the wellbore fluid carries a certain concentration of solid particles. In this case, the influence of concentration must be taken into account when calculating its terminal settling velocity.

[0053] When low-concentration solid particles settle, due to the interaction between particles and between particles and the surrounding medium, the difference between their settling velocity and the free settling velocity of a single particle is a random variable with a non-zero average value. A large number of experimental statistics show that for a certain volume concentration C S The final settling velocity u of solid particles S0 The following formula can be used for calculation:

[0054] u s0 =u0(1-6.55c s ) (10)

[0055] The above formula is applicable to the case where the volume concentration CS is less than 0.05, which also basically covers the sand-carrying concentration value of the well fluid during actual oil well production.

[0056] (5) Calculation of the free settling velocity of solid particles corrected by the shape irregularity coefficient:

[0057] u α =αu0 (11)

[0058] Where: u α --free settling velocity of sand particles corrected by shape irregularity coefficient, m / s;

[0059] u0--free settling velocity of particles, m / s;

[0060] A--Shape coefficient of irregular solid particles.

[0061] Table 1 Shape coefficients of irregular solid particles Shape coefficients of irregular solid particles

[0062] Particle shape Form Factor Sphericity coefficient (sphericity) spherical 1 1 spherical 1～0.8 0.91～0.75 polygon 0.8～0.65 0.82～0.67 Long strip 0.65～0.50 0.71～0.58 flat shape ＜0.50 0.58～0.47

[0063] (6) Given the critical sand production pressure difference and reservoir production allocation under different water content and static pressure, calculate the critical sand production flow rate Q1 and critical sand production time T0 using the oil production binomial equation (known)

[0064] (7) Calculation of sand production

[0065] Calculate the sand production amount within 1 day (T=1) starting from the critical sand production time T0 (T0=0):

[0066]

[0067] Where, h is the perforation thickness;

[0068] φ--porosity;

[0069] x--expansion index;

[0070] r e --Oil layer supply radius;

[0071] r s -Sand production radius at the bottom of the well;

[0072] r w --Wellbore radius;

[0073] △q1--Flow rate exceeding the critical liquid production;

[0074] k o -- formation permeability;

[0075] P w -- Bottom hole flowing pressure, MPa;

[0076] P wcl --Critical pressure of sand production at the bottom of the well, MPa.

[0077] (8) Calculation of critical sand-carrying particle size

[0078]

[0079] Where, u0 is the terminal velocity of free settling of solid particles, m / s;

[0080] C d --Drag coefficient;

[0081] g--gravitational acceleration;

[0082] d s --Sand grain diameter, mm;

[0083] ρ l --Fluid density, Kg / m 3 ;

[0084] ρ s --Particle density, Kg / m 3 .

[0085] (9)u α Calculation of the free settling velocity of sand particles corrected for shape irregularity coefficient: The normalized equation obtained from the fluid sand carrying test is:

[0086] u' α =u α -0.2988ul (14)

[0087] Where: u′ α --Settling velocity of sand produced from oil well in well fluid, m / s;

[0088] U α --free settling velocity of sand particles corrected by shape irregularity coefficient, m / s;

[0089] U l --Average flow velocity of wellbore fluid, m / s.

[0090] When u′ α =0, the minimum flow rate required to carry sand of a certain particle size and concentration out of the wellbore can be calculated.

[0091] (10) Average wellbore fluid velocity u at a certain production rate l Calculation:

[0092] The movement of fluid in the wellbore of an oil pumping well can be calculated in three sections:

[0093]

[0094] (a) Oil layer-bottom of oil pipe

[0095]

[0096] Where Q t is the liquid production of the oil well, m 3 / d;

[0097] u l1 is the flow velocity of the fluid in the wellbore from the oil layer to the bottom of the oil pipe, m / s;

[0098] d ci is the inner diameter of the casing, m.

[0099] (b) Oil pipe bottom end - pump suction inlet section (tail pipe)

[0100] Lever pump:

[0101]

[0102] Screw pump:

[0103]

[0104] Where u l2 is the average flow velocity of the wellbore fluid from the bottom of the tubing to the pump suction port, m / s;

[0105] d t1 is the inner diameter of the oil well pump tail pipe, m.

[0106] (c) Pump outlet - ground section

[0107] Lever pump:

[0108]

[0109] Screw pump:

[0110]

[0111] Where u l3 -- Pump outlet - average flow velocity of wellbore fluid in the surface section, m / s;

[0112] d t2 --Inner diameter of the oil pipe, m;

[0113] D r --Sucker rod diameter, m.

[0114] (11) Calculation of critical time of sand buried pump barrel

[0115]

[0116] Where: T--critical time of sand buried pump barrel, d;

[0117] V1--the volume of sediment particles, m 3 ;

[0118] V2--The volume from the pump base to the bottom of the artificial well, m 3 .

[0119] Among them, the calculation of the volume of sediment particles is:

[0120]

[0121] Where: m2--the sediment mass obtained by particle size analysis and combining with the critical sand carrying particle size;

[0122] ρ s --Particle density, Kg / m 3 ;

[0123] Calculation of volume from pump base to artificial well bottom:

[0124]

[0125] Where, d0--inner diameter of casing, m;

[0126] h--the depth from the pump base to the bottom of the artificial well, m.

[0127] Compared with the prior art, the present invention has the following beneficial effects:

[0128] The calculation method involved in the present invention has high field applicability. Through this method, it is possible to predict in advance whether chemical flooding production wells can carry sand for oil production during the reservoir deployment stage, clarify which sand control + sand carrying and lifting process to adopt, provide theoretical guidance for the design of oil production project block plans, and at the same time provide technical support for the adjustment of single-well sand control + sand carrying and lifting processes at different production concentration stages of chemical flooding production wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0129] Figure 1 This is a calculation flow chart of the present invention. DETAILED DESCRIPTION

[0130] The present invention is implemented in the following examples. Unless otherwise specified, the experimental methods used in the present invention are conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0131] Example 1

[0132] The following combination Figure 1 Specific embodiments of the present invention will be described in detail.

[0133] 1. Data preparation:

[0134] Reservoir thickness, permeability, porosity, produced fluid volume, polymer concentration, crude oil viscosity, critical sand production pressure difference under different water content and static pressure, reservoir production allocation, and the binomial equation for oil production.

[0135] 2. Calculation steps:

[0136] S1. Calculate the formation fluid viscosity using formulas (6) to (9).

[0137] S2. Calculate the critical sand production flow rate and critical sand production time based on the critical sand production pressure difference and reservoir production allocation under different water content and static pressure, and the oil production binomial equation.

[0138] S3. Use formula (12) to calculate the amount of sand produced within one day starting from the critical sand production time T0.

[0139] S4. Make corrections based on actual site conditions, analyze the particle size of the formation sand, and obtain the content of sand of each particle size.

[0140] S5. Calculate the average flow velocity of the fluid in the wellbore using formulas (15) to (20).

[0141] S6. Based on the normalized equation obtained from the fluid sand carrying test, the final free settling velocity of particles at the critical sand settling velocity is obtained using formulas (10), (11), and (14).

[0142] S7. Calculate the critical sand-carrying particle size using formulas (1) to (5) and formula (13).

[0143] S8. Perform particle size analysis to obtain the particle size and amount of sediment.

[0144] S9. Calculate the critical time of the sand buried pump using formulas (21) to (23).

[0145] S10. Determine whether the sand buried pump time is greater than the pump inspection cycle. If so, proceed to the next step of determination. If not, proceed to step S3 before taking measures.

[0146] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs a structure and embodiment similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A method for analyzing the sand carrying capacity of a chemical flooding well, characterized in that: The following steps are involved: S1. Calculate formation fluid viscosity; S2. Calculate the critical sand production flow rate and critical sand production time based on the critical sand production pressure difference and reservoir production allocation under different water content and static pressure, and the oil production binomial equation; S3 calculates the critical sand production time T0 starting time within 1 day of sand production; S4. Make corrections based on actual site conditions and analyze the particle size of the formation sand to obtain the content of sand of each particle size; S5. Calculate the average flow velocity of the fluid in the wellbore; S6. Obtain the terminal free settling velocity of particles at the critical sand settling velocity based on the normalized equation obtained from the fluid sand carrying test; S7. Calculate the critical sand carrying particle size; S8. Perform particle size analysis to obtain sediment particle size and sediment amount; S9. Calculate the critical time of the sand buried pump using formulas (21) to (23); S10. Determine whether the sand buried pump time is greater than the pump inspection cycle. If so, proceed to the next step of determination; if not, proceed to step S3 before taking measures.

2. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: The viscosity of the formation fluid is determined by the shear viscosity μ 剪 and elastic viscosity μ 弹 composition, Where: μ 剪 --shear viscosity, mPa·s; Φ--porosity, %; K r -- radial permeability, mD; N--fluidity index, dimensionless; K--consistency coefficient, mPa·s n ; Assuming that the viscosity ratio is N de The relationship is: Where: c, m are constants, γ is the shear rate; According to formula (6) and formula (7), we have: m 有效 =μ 剪 +m 弹 =(1+c * c m )m (8) By weighted averaging of water content, the comprehensive viscosity of formation fluid is expressed as: Where: μ is the comprehensive viscosity of the formation fluid, mPa·s; μ 弹 is the elastic viscosity, mPa·s; μ 有效 is the effective viscosity of the polymer solution in the formation, mPa·s; μ o is the viscosity of the oil, mPa·s; S w is the average water saturation, %.

3. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: The method for calculating the amount of sand produced within one day starting from the critical sand production time T0 is: Where, h is the perforation thickness; φ--porosity; x--expansion index; r e --Oil layer supply radius; r s -Sand production radius at the bottom of the well; r w --Wellbore radius; △q1--Flow rate exceeding the critical liquid production; k o -- formation permeability; P w -- Bottom hole flowing pressure, MPa; P wcl --Critical pressure of sand production at the bottom of the well, MPa.

4. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: The average flow velocity of the fluid in the wellbore is calculated in three sections: (a) Oil layer-bottom of oil pipe Where Q t is the liquid production of the oil well, m 3 / d; u l1 is the flow velocity of the fluid in the wellbore from the oil layer to the bottom of the oil pipe, m / s; d ci is the inner diameter of the casing, m; (b) Oil pipe bottom end - pump suction inlet section (tail pipe) Lever pump: Screw pump: Where u l2 is the average flow velocity of the wellbore fluid from the bottom of the tubing to the pump suction port, m / s; d t1 is the inner diameter of the oil well pump tail pipe, m; (c) Pump outlet - ground section Lever pump: Screw pump: Where u l3 -- Pump outlet - average flow velocity of wellbore fluid in the surface section, m / s; d t2 --Inner diameter of the oil pipe, m; D r --Sucker rod diameter, m.

5. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: A certain volume concentration C S Final settling velocity of solid particles u S0 Use the following formula to calculate, which is applicable to volume concentration CS < 0.05: u s0 =u0(1-6.55c s ) (10)。 6. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: Calculation of the terminal free settling velocity of solid particles corrected by the shape irregularity coefficient: in α =αu0 (11) Where: u α --free settling velocity of sand particles corrected by shape irregularity coefficient, m / s; u0--free settling velocity of particles, m / s; Α--Shape coefficient of irregular solid particles.

7. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: Calculation of free settling velocity of sand particles corrected by shape irregularity coefficient: The normalized equation obtained from the fluid sand carrying test is and' α =and α -0.2988u l (14) Where: u′ α --Settling velocity of sand produced from oil well in well fluid, m / s; U α --free settling velocity of sand particles corrected by shape irregularity coefficient, m / s; U l --Izutsu fluid average flow velocity, m / s.

8. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: Critical sand-carrying particle size Where, u0 is the terminal velocity of free settling of solid particles, m / s; C d --Drag coefficient; g--gravitational acceleration; d s --Sand grain diameter, mm; ρ l --Fluid density, Kg / m 3 ; ρ s --Particle density, Kg / m 3 .

9. The method for analyzing the sand carrying capacity of a chemical flooding well according to claim 1, wherein: The calculation method of the critical time of the sand buried pump is as follows: Where: T--critical time of sand buried pump barrel, d; V1--the volume of sediment particles, m 3 ; V2--The volume from the pump base to the bottom of the artificial well, m 3 ; Among them, the calculation of the volume of sediment particles is: Where: m2--the sediment mass obtained by particle size analysis and combining with the critical sand carrying particle size; ρ s --Particle density, Kg / m 3 ; Calculation of volume from pump base to artificial well bottom: Where, d0--inner diameter of casing, m; h--the depth from the pump base to the bottom of the artificial well, m.

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