Chemical flooding oil well lifting process

Abstract

The invention belongs to the field of oil production engineering, and discloses a chemical flooding oil well lifting process. And the oil well lifting process is determined according to the liquid production capacity, the maximum pump descending depth, the content of sand bodies with the sand body particle sizes smaller than or equal to the sand-carrying particle sizes in discharged sand in the liquid production capacity, the particle size median of the part with the sand body particle sizes larger than the sand-carrying particle sizes in the discharged sand, the fine particle content of the particle size median in different ranges, the separation coefficient, the permeability, the well section length and the maximum gap. The method has high field applicability, is suitable for chemical flooding production wells, and has wide application prospects. By means of the technology, which lifting mode is adopted can be accurately judged, and technical support is provided for oil production engineering scheme design.

Description

Technical Field

[0001] The invention belongs to the field of oil production engineering and relates to a chemical flooding oil well lifting process. Background Art

[0002] Converting to chemical flooding is the primary method for increasing crude oil production in oilfields. The effectiveness of chemical flooding plays a key role in whether an oilfield can achieve stable production of tens of millions of tons. After converting to chemical flooding, production wells gradually begin to see the effects of chemical flooding, but increased viscosity of produced fluids and sand production are common issues.

[0003] In response to the above situation, corresponding measures were taken on site based on experience. With the increase in overall planning and deployment, it is necessary to conduct qualitative analysis on which lifting technology to adopt for oil wells to provide a theoretical basis for the precise design of lifting technology for chemical flooding production wells. Summary of the Invention

[0004] To address the challenges of existing technologies, this invention fully considers the production characteristics of oil wells after conversion to chemical flooding and develops methods for optimizing lifting processes for different chemical flooding production wells. These include methods for optimizing lifting processes that increase the viscosity of produced fluids after effective recovery and for optimizing lifting processes for oil wells experiencing sand production after effective recovery. This method accurately determines which lifting process to use, providing technical support for oil production project design.

[0005] 1. Calculation ideas

[0006] (1) Determination of pump depth

[0007] Design the pump depth based on the known IPR curve.

[0008] (2) Determination of produced fluid viscosity

[0009] 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.

[0010]

[0011] Where: μ 剪 --shear viscosity, mPa·s;

[0012] Φ--porosity, %;

[0013] K r -- radial permeability, mD;

[0014] N--fluidity index, dimensionless;

[0015] K--consistency coefficient, mPa·sn .

[0016] It can be assumed that the viscosity ratio is N de The relationship is:

[0017]

[0018] Where c and m are constants that depend on the geometric complexity of the reservoir pore media. γ is the shear rate.

[0019] According to formula (1) and formula (2), we have

[0020] μ 有效 =μ 剪 +μ 弹 =(1+c * γ m )μ (3)

[0021] By weighted average of water content, the comprehensive viscosity of formation fluid is expressed as:

[0022]

[0023] Where: μ--comprehensive viscosity of formation fluid, mPa·s;

[0024] μ 弹 --elastic viscosity, mPa·s;

[0025] μ 有效 --Effective viscosity of the polymer solution in the formation, mPa·s;

[0026] μ o --Oil viscosity, mPa·s;

[0027] S w --Average water saturation, %.

[0028] (3) Determination of critical sand-carrying particle size

[0029] ① Determination of flow state

[0030] The critical Reynolds number (Re c =2100) as the criterion for Newtonian fluid: when Re≤2100, the fluid flow state is laminar flow; when Re≥2100, the fluid flow state is turbulent flow

[0031] Among them, the expression of the Reynolds number Re of Newtonian fluid is:

[0032]

[0033] Where u l —Average flow rate of wellbore liquid, m / s

[0034] d t2 —Oil pipe diameter, m

[0035] μ—formation fluid viscosity, mPa.s

[0036] ②Drag coefficient C d Determination of:

[0037] C d is the solid particle Reynolds number (Re) s A single-valued function of :

[0038] (a) Laminar flow region ((Re) s ≤1):

[0039]

[0040] (b) Transition region (1<(Re) s ≤1000)

[0041] Using the Allen formula

[0042] C d =30(R e ) s -0.625 (7)

[0043] (c) Turbulent zone (1000<(Re) s ≤2×10 5 )

[0044] C d =0.45 (8)

[0045] Among them, the solid particle Reynolds number (Re) s Calculation:

[0046]

[0047] Where: ρ l --Fluid density, Kg / m 3 ;

[0048] μ is the comprehensive viscosity of the formation fluid, mPa·s;

[0049] d s --Sand grain diameter, mm;

[0050] u0--the terminal free settling velocity of solid particles, m / s.

[0051] ③Calculation of the terminal velocity of free settling of solid particles

[0052]

[0053] Where, u0 is the terminal velocity of free settling of solid particles, m / s;

[0054] C d --Drag coefficient;

[0055] g--gravitational acceleration;

[0056] d s --Sand grain diameter, mm;

[0057] ρ l --Fluid density, Kg / m 3 ;

[0058] ρ s --Particle density, Kg / m 3 .

[0059] (4) Determination of sorting coefficient

[0060] The particle size composition cumulative distribution curve can be used to express the mass percentage of particles of different particle sizes in the total particles.

[0061]

[0062] Where, d 25 --The particle diameter corresponding to 25% on the cumulative distribution curve, mm;

[0063] d 75 --The particle diameter corresponding to 75% on the cumulative distribution curve, mm;

[0064] According to Trask's convention: S = 1-2.5 is good sorting; S = 2.5-4.5 is medium sorting; S>4.5 is poor sorting.

[0065] Table 1 Classification of particle size

[0066]

[0067] (5) Determination of maximum gap

[0068] ① Determination of theoretical displacement

[0069]

[0070] Where: Q--theoretical displacement, m 3 / d;

[0071] S--pump stroke, m;

[0072] N--strokes, times / minute;

[0073] D--pump diameter, m.

[0074] ② Determination of maximum leakage

[0075]

[0076] Where: η--average pump efficiency, %;

[0077] Q--theoretical displacement, m 3 / d;

[0078] q--leakage, m 3 / s.

[0079] ③Determination of maximum gap

[0080]

[0081] Where: q--leakage, m 3 / s;

[0082] D--pump diameter, m;

[0083] δ--single-side clearance, m;

[0084] μ--dynamic viscosity, Pa·s;

[0085] L-- plunger length, m;

[0086] Δp--pressure difference between the upper and lower parts of the plunger, Pa.

[0087] Compared with the prior art, the present invention has the following beneficial effects:

[0088] The present invention relates to a method for optimizing the lifting process for chemical flooding oil wells. This method has high field applicability and is suitable for converting chemical flooding production wells, with broad application prospects. This process can accurately determine which lifting method to use, providing technical support for oil production project design. DETAILED DESCRIPTION

[0089] 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.

[0090] Example 1

[0091] The specific embodiments of the present invention are described in detail below with reference to Table 2.

[0092] 1. Data preparation:

[0093] Well production allocation, reservoir thickness, permeability (obtained from reservoir interpretation), porosity, well section length (the difference between the upper and lower boundaries of the perforation section), produced liquid volume, crude oil viscosity, average pump efficiency, etc.

[0094] 2. Calculation steps:

[0095] S1. Design the pumping depth based on the known IPR curve.

[0096] S2. Measured sand production from oil wells.

[0097] S3. Calculate the viscosity of the produced fluid using formulas (1)-(4).

[0098] S4. Analyze the particle size of the formation sand body according to the actual situation on site and obtain the content of sand of each particle size.

[0099] S5. Calculate the critical sand-carrying particle size using formulas (5)-(10).

[0100] S6. Determine the critical sand-carrying particle size based on the cumulative distribution curve of particle size composition and determine the median particle size D of the part of the sand body that is larger than the sand-carrying particle size. 中 , determine the fine sand content of the median particle size in different ranges.

[0101] S7. Use formula (11) to determine the sorting coefficient of the median particle size in different ranges.

[0102] S8. Calculate the maximum leakage using formulas (12)-(14) to determine the maximum pump clearance.

[0103] S9. Determine the oil well lifting technology based on the liquid production, maximum pumping depth, the content of sand bodies with a particle size less than or equal to the sand-carrying particle size in the sand production, the median particle size of the sand body with a particle size greater than the sand-carrying particle size in the sand production, the fine particle content and sorting coefficient of the median particle size in different ranges, permeability, well section length, and maximum gap.

[0104] Create the template as follows:

[0105] Table 2 Optimal lifting method diagram for chemical flooding sand production wells

[0106]

[0107]

[0108] The above is a schematic description of the present invention and its embodiments. This description is not restrictive and only illustrates one embodiment of the present invention. 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 structures and embodiments similar to this technical solution without creatively designing them, they shall fall within the scope of protection of the present invention.

Claims

1. A chemical flooding oil well lifting process, characterized in that: The following steps are involved: S1. Design the pumping depth based on the known IPR curve; S2. Measured sand production of oil wells; S3. Calculate the viscosity of the produced fluid; S4. Analyze the particle size of the formation sand according to the actual situation on site to obtain the content of sand of each particle size; S5. Calculate the critical sand carrying particle size; S6. Determine the critical sand-carrying particle size based on the cumulative distribution curve of particle size composition and determine the median particle size D of the part of the sand body that is larger than the sand-carrying particle size. 中 , determine the fine sand content of the median particle size in different ranges; S7. Determine the sorting coefficient of the median particle size under different ranges; S8. Calculate the maximum leakage and determine the maximum clearance of the pump; S9. Determine the oil well lifting technology based on the liquid production, maximum pumping depth, the content of sand bodies with a particle size less than or equal to the sand-carrying particle size in the sand production, the median particle size of the sand body with a particle size greater than the sand-carrying particle size in the sand production, the fine particle content and sorting coefficient of the median particle size in different ranges, permeability, well section length, and maximum gap.

2. The chemical flooding well lifting process according to claim 1, characterized in that: The calculation method of the produced fluid viscosity is: the effective viscosity of the solution μ 有效 From 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 (1) and formula (2), we have: 有效 =μ 剪 +μ 弹 =(1+c * γ m )μ(3); By weighted averaging of water content, the comprehensive viscosity of formation fluid is expressed as: Where: μ--comprehensive viscosity of formation fluid, mPa·s; μ 弹 --elastic viscosity, mPa·s; μ 有效 --Effective viscosity of the polymer solution in the formation, mPa·s; μ o --Oil viscosity, mPa·s; S w --Average water saturation, %.

3. The chemical flooding well lifting process according to claim 1, characterized in that: The determination of critical sand carrying particle size includes: flow state judgment, resistance coefficient C d Determination of, calculation of the terminal free settling velocity of solid particles, determination of the sorting coefficient, and determination of the maximum gap.

4. The chemical flooding well lifting process according to claim 3, characterized in that: The flow state is judged by the critical Reynolds number. When Re≤2100, the fluid flow state is laminar flow; when Re≥2100, the fluid flow state is turbulent flow. In the formula, u l —Izutsu liquid average flow velocity, m / s; d t2 —Oil pipe diameter, m; μ—formation fluid viscosity, mPa.s.

5. The chemical flooding well lifting process according to claim 3, characterized in that: Drag coefficient C d The determination is divided into the following three situations: (a)When(Re) s When ≤1, it is laminar flow area: (b) When 1<(Re) s When ≤1000, it is the transition zone: C d =30(R e ) s -0.625 ; (c) When 1000 < (Re) s ≤2×10 5 When , it is the turbulent zone: C d ＝0.45； in, Where: ρ l --Fluid density, Kg / m 3 ; μ is the comprehensive viscosity of the formation fluid, mPa·s; d s --Sand grain diameter, mm; u0--the terminal free settling velocity of solid particles, m / s.

6. The chemical flooding well lifting process according to claim 3, characterized in that: Terminal free settling velocity of solid particles 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 .

7. The chemical flooding well lifting process according to claim 3, characterized in that: The sorting coefficient is expressed by the cumulative distribution curve of particle size composition, which is the mass percentage of particles of different particle sizes in the total particles. Where, d 25 --The particle diameter corresponding to 25% on the cumulative distribution curve, mm; d 75 --The particle diameter corresponding to 75% on the cumulative distribution curve, mm.

8. The chemical flooding well lifting process according to claim 3, characterized in that: The determination of the maximum clearance includes the determination of the theoretical displacement, the determination of the maximum leakage, and the determination of the maximum clearance.

9. The chemical flooding well lifting process according to claim 8, characterized in that: Theoretical displacement Where: Q--theoretical displacement, m 3 / d; S--pump stroke, m; N--strokes, times / minute; D--pump diameter, m.

10. The chemical flooding oil well lifting process according to claim 8, characterized in that: Maximum leakage Where: η--average pump efficiency, %; Q--theoretical displacement, m 3 / d; q--leakage, m 3 / s.

11. The chemical flooding well lifting process according to claim 8, characterized in that: Maximum gap Where: q--leakage, m 3 / s; D--pump diameter, m; δ--single-side clearance, m; μ--dynamic viscosity, Pa·s; L-- plunger length, m; Δp--pressure difference between the upper and lower parts of the plunger, Pa.

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