阅读说明：本技术 基于孔喉半径适配性的驱油用二元复合体系配方优化方法 (Oil displacement binary composite system formula optimization method based on pore throat radius adaptability ) 是由 施雷庭 曾志伟 陈灿 王睿麒 张玉龙 朱珊珊 叶仲斌 于 2021-08-11 设计创作，主要内容包括：本发明公开了一种基于孔喉半径适配性的驱油用二元复合体系配方优化方法,步骤为：S1、配制一系列不同聚合物浓度和表面活性剂/碱浓度的聚合物-表面活性剂/碱二元复合体系溶液,测定各复合体系的水动力学半径R-(h)；S2、根据架桥理论确定步骤水动力学半径R-(h)所匹配的最小孔喉半径R-(m),并绘制聚合物浓度-表活剂浓度/碱浓度-最小孔喉半径图版；S3、对不同的聚合物绘制聚合物浓度-表活剂浓度/碱浓度-最小孔喉半径图版；S4、根据目标油藏孔喉半径大小,对照聚合物浓度-表活剂浓度/碱浓度-最小孔喉半径图版,兼顾复合体系黏度,优选出聚合物-表面活性剂/碱复合体系配方。该方法能够快速有效的实现表面活性剂/碱与聚合物最佳配方的优选。(The invention discloses a pore throat radius adaptability-based oil displacement binary composite system formula optimization method, which comprises the following steps: s1, preparing a series of polymer-surfactant/alkali binary composite system solutions with different polymer concentrations and surfactant/alkali concentrations, and measuring hydrodynamic radius R of each composite system h (ii) a S2, determining step hydrodynamic radius R according to bridging theory h Matched minimum throat radius R m Drawing a polymer concentration-surfactant concentration/alkali concentration-minimum pore throat radius chart; s3, drawing a polymer concentration-surfactant concentration/alkali concentration-minimum pore throat radius chart for different polymers; s4, according to the radius of the pore throat of the target oil reservoir, comparing a polymer concentration-surfactant concentration/alkali concentration-minimum pore throat radius chart, giving consideration to the viscosity of the composite system, and preferably selecting a formula of the polymer-surfactant/alkali composite system. The method can rapidly haveEffectively realizing the optimization of the optimal formula of the surfactant/alkali and the polymer.)

1. A binary composite system formula optimization method for oil displacement based on pore throat radius adaptability is characterized by comprising the following steps:

s1, selecting a certain polymer from multiple alternative polymers to prepare a series of polymer solutions with different concentrations, adding an auxiliary agent with different concentrations under each polymer concentration to prepare a series of binary composite system solutions with different auxiliary agent concentrations, and respectively measuring hydrodynamic radius R of each binary composite system solution_hThe adjuvant is alkali or surfactant;

s2, determining each hydrodynamic radius R in the step S1 according to the bridging theory_hMatched minimum throat radius R_m，R_m＝R_h0.46, drawing a polymer concentration-adjuvant concentration-minimum pore throat radius chart by taking the polymer concentration as an abscissa and the adjuvant concentration as an ordinate;

s3, selecting other polymers from the multiple alternative polymers respectively, and repeating the steps S1 and S2 to obtain polymer concentration-adjuvant concentration-minimum pore throat radius charts of the different polymers;

s4, determining a corresponding polymer-adjuvant binary composite system in each polymer concentration-adjuvant concentration-minimum pore throat radius chart according to the average pore throat radius of the target oil reservoir, and determining the binary composite system with the maximum viscosity in all the obtained polymer-adjuvant binary composite systems as the optimal polymer-adjuvant binary composite system formula.

2. The optimization method of the binary composite system formula for oil displacement based on the pore throat radius suitability of claim 1, wherein the specific method in the step S1 is as follows:

s11, preparing a binary composite system solution by using distilled water, stirring to fully dissolve a polymer, firstly measuring the initial viscosity of each binary composite system solution, then filtering by using microporous filter membranes with different pore diameters under constant pressure, and measuring the viscosity of a filtrate;

s12, in a rectangular coordinate system, taking the aperture size of the microporous filter membrane as a horizontal coordinate and the relative viscosity of the composite system as a vertical coordinate, and drawing a change curve of the relative viscosity of the composite system filtrate along with the aperture of the filter membrane; the relative viscosity of the composite system is equal to the viscosity of the filtrate of the composite system/the initial viscosity of the solution of the composite system;

s13, in the change curve of the relative viscosity of the composite system filtrate along with the aperture of the filter membrane, finding out the inflection point of the change curve by making the intersection point of the tangents of the change curve before and after the change of the relative viscosity, wherein the abscissa value corresponding to the inflection point is the hydrodynamic radius of the two composite systems.

3. The optimization method of the formulation of binary complex system for flooding based on the suitability of pore throat radius of claim 2, wherein in step S1, the constant pressure during the microfiltration membrane filtration is 0.2 MPa.

4. The method for optimizing the formulation of the binary complex system for flooding based on the suitability of pore throat radius according to claim 2, wherein in step S1, the size of the microporous membrane is in the range of 0.10 μm to 3.00 μm.

5. The optimization method of the formulation of the binary composite system for oil displacement based on the pore throat radius suitability of claim 2, wherein in the step S1, the concentration range of the polymer is 500-3000 mg/L, the concentration of the surfactant is 500-3000 mg/L, and the concentration range of the alkali is 0.2-1.2% by mass.

Technical Field

The invention relates to the technical field of oilfield development, in particular to a formula optimization method of a polymer-surfactant or polymer-alkali binary composite system for oil displacement based on pore throat radius adaptability.

Background

Binary composite flooding is a new technology for enhanced oil recovery developed in 80 s of 20 th century, and is an oil displacement technology compounded by alkali or a surfactant and a polymer. The binary combination flooding has more chemical agent types, and the appropriate chemical agent needs to be selected according to the actual characteristics of a target oil reservoir.

At present, the research of a binary composite system is rapidly developed, and based on the synergistic effect of chemical agents, the water-oil fluidity ratio is reduced and the swept volume is enlarged by adding a high molecular weight water-soluble polymer solution with a certain concentration. The water-oil interfacial tension can be reduced by adding a certain amount of surfactant, and the oil displacement efficiency is improved; the adsorption of the chemical agent can be effectively reduced by adding a certain amount of alkali. The binary composite flooding technology has the characteristics of small dosage of the surfactant, high oil displacement efficiency and the like, and can greatly reduce the dosage of the surfactant. A large number of indoor experiments and domestic and foreign mine field test effects show that the recovery ratio of binary compound flooding can be improved by more than 20% on the basis of water flooding, and the technology is an important technical guarantee for realizing stable production or even high production of developed old oil fields in China.

The oil displacement effect of the composite system is greatly influenced by the rock structure and the fluid property. Therefore, in designing the scheme, a composite system suitable for adapting to the formation conditions must be selected. In order to ensure the smooth operation of the binary combination flooding and obtain reasonable economic benefit, the injectability problem of a composite system must be considered so as to avoid the situation of difficult injection or even no injection. Research shows that when the matching performance of a composite system and the oil layer condition is poor, the oil displacement efficiency is greatly influenced, and the matching performance of the composite system and the oil layer condition mainly refers to the matching relation between the hydrodynamic radius of the system and the pore throat radius of the oil layer.

Both indoor experimental research and oilfield and mining field practice show that when binary combination flooding is carried out, a composite system matched with the oil layer condition is selected as a precondition for ensuring the success of binary combination flooding. The stratum conditions of different oil fields are generally different, different formulations are selected and optimized according to actual conditions when binary composite oil displacement is carried out, when the permeability of an oil layer is low, and if a polymer with large molecular weight and high concentration is selected, the oil-water fluidity ratio can be well improved, but the stratum is also seriously blocked and is not paid for. Therefore, the key point for ensuring the binary combination flooding is to select a proper composite system according to the actual formation conditions. However, in the current optimization of the formulation design of the binary composite system, the formulation optimization method between the surfactant/alkali and the polymer is still lack of an effective and rapid means.

At present, the indoor experimental research aiming at the suitability of the pore throat radius is less in the research of a binary system, most of the research of the binary system is limited to the situation in a unitary system (namely a single polymer flooding system), and the injection experimental steps for evaluating the suitability of the pore throat radius are complex, the consumption of manpower and material resources is high, the evaluation result has no universality, and the large-scale application in an oil field site is inconvenient. Therefore, it is necessary to research a formula optimization method of a polymer-surfactant and polymer-alkali binary composite system, and provide technical guidance for the design of an oil displacement system of the binary composite system.

Disclosure of Invention

The invention aims to provide a pore throat radius adaptability-based oil displacement binary composite system formula optimization method.

The invention provides a pore throat radius adaptability-based oil displacement binary composite system formula optimization method, which comprises the following steps of:

s1, selecting a certain polymer from multiple alternative polymers to prepare a series of polymer solutions with different concentrations, adding an auxiliary agent with different concentrations under the concentration of each polymer to prepare a series of binary composite system solutions with different concentrations of the auxiliary agent, and respectively measuring each solutionHydrodynamic radius R of binary composite system solution_h. The adjuvant is alkali or surfactant.

The specific method comprises the following steps:

s11, preparing a binary composite system solution by using distilled water, stirring to fully dissolve a polymer, firstly measuring the initial viscosity of each binary composite system solution, then filtering by using microporous filter membranes with different pore diameters under constant pressure, and measuring the viscosity of a filtrate;

s12, in a rectangular coordinate system, taking the aperture size of the microporous filter membrane as a horizontal coordinate and the relative viscosity of the composite system as a vertical coordinate, and drawing a change curve of the relative viscosity of the composite system filtrate along with the aperture of the filter membrane; the relative viscosity of the composite system is equal to the viscosity of the filtrate of the composite system/the initial viscosity of the solution of the composite system;

s13, in the change curve of the relative viscosity of the composite system filtrate along with the aperture of the filter membrane, finding out the inflection point of the change curve by making the intersection point of the tangents of the change curve before and after the change of the relative viscosity, wherein the abscissa value corresponding to the inflection point is the hydrodynamic radius of the two composite systems.

S2, determining each hydrodynamic radius R in the step S1 according to the bridging theory_hMatched minimum throat radius R_m，R_m＝R_hAnd/0.46, plotting polymer concentration-adjuvant concentration-minimum pore throat radius chart with polymer concentration as abscissa and adjuvant concentration as ordinate.

S3, selecting other polymers from the multiple alternative polymers respectively, and repeating the steps S1 and S2 to obtain polymer concentration-adjuvant concentration-minimum pore throat radius charts of different polymers.

S4, determining a corresponding polymer-adjuvant binary composite system in each polymer concentration-adjuvant concentration-minimum pore throat radius chart according to the average pore throat radius of the target oil reservoir, and determining the binary composite system with the maximum viscosity in all the obtained polymer-adjuvant binary composite systems as the optimal polymer-adjuvant binary composite system formula.

Preferably, in the step S1, the polymer concentration is in the range of 500-3000 mg/L. The concentration of the surfactant is 500-3000 mg/L. The alkali concentration range is 0.2-1.2% by mass.

Preferably, in step S1, the constant pressure during the microfiltration membrane filtration is 0.2 MPa.

Preferably, in step S1, the size of the microporous filter membrane is in the range of 0.10-3.00. mu.m.

Further preferably, the size of the microfiltration membrane is 0.10, 0.20, 0.30, 0.45, 0.65, 0.80, 1.00, 1.20, 1.50, 2.00, 3.00 μm.

Compared with the prior art, the invention has the advantages that:

the invention relates to the selection of the proportion of a binary complex system for oil displacement under different oil reservoir conditions, and measures and draws a polymer concentration-surfactant concentration-minimum pore throat radius relation chart or a polymer concentration-alkali concentration-minimum pore throat radius relation chart by utilizing an established polymer-surfactant binary complex system or a polymer-alkali binary complex system.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a graph showing the relative viscosity of filtrate of a composite system as a function of the pore size of a filter membrane according to an example of the present invention.

FIG. 2 is a plot of polymer concentration-surfactant concentration-minimum pore throat radius in example 1 of the present invention.

FIG. 3 is a plot of polymer concentration-sodium carbonate concentration-minimum pore throat radius in example 2 of the present invention.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

Example 1

In this example, the polymer used was partially hydrolyzed polyacrylamide having a molecular weight of 700, 1000, 1500, 1900, 2300 ten thousand, respectively, and the surfactant was sodium dodecylbenzenesulfonate.

The binary composite system formula optimization method comprises the following steps:

step S1, preparing a binary composite system solution with the molecular weight of 700 ten thousand and the concentrations of the partially hydrolyzed polyacrylamide of 500, 1000, 1500, 2000, 2500 and 3000mg/L, and the corresponding concentrations of the sodium dodecyl benzene sulfonate of 500, 1000, 1500, 2000, 2500 and 3000mg/L under each polymer concentration, and measuring the hydrodynamic radius R of each binary composite system_hThe method comprises the following specific steps:

firstly, preparing various binary composite system solutions by using distilled water, stirring by using an electric stirrer to fully dissolve a polymer, measuring the initial viscosity of the binary composite system solution, then filtering by using microporous filter membranes with the pore diameters of 0.45, 0.65, 0.80, 1.00, 1.20 and 1.50 mu m under the constant pressure of 0.2MPa, and measuring the viscosity of various filtrates.

Secondly, in a rectangular coordinate system, the pore size of the microporous filter membrane is taken as a horizontal coordinate, the relative viscosity of the composite system filtrate (namely the viscosity of the composite system filtrate/the initial viscosity of the composite system solution) is taken as a vertical coordinate, and a curve of the relative viscosity of the binary composite system filtrate along with the change of the pore size of the filter membrane is drawn, as shown in fig. 1.

Thirdly, in the figure 1, the inflection point of the change curve is found by making the intersection point of the tangent lines of the change curve before and after the change of the relative viscosity, and the value of the abscissa corresponding to the inflection point is the hydrodynamic radius R of the composite system_h。

Step S2, determining a series of hydrodynamic radiuses R of the composite system in the step S1 according to the bridging theory_hMatched minimum throat radius R_m(R_h＝0.46R_m) Concentration of surfactant on the abscissaAnd (4) drawing a polymer concentration-surfactant concentration-minimum pore throat radius chart according to the degree ordinate.

And S3, adopting 1000 ten thousand, 1500 ten thousand, 1900 ten thousand and 2300 ten thousand of partially hydrolyzed polyacrylamide respectively, and repeating the steps S1 and S2 to obtain polymer concentration-surfactant concentration-minimum pore throat radius charts of polymers with different molecular weights.

And S4, measuring the average pore throat radius of the target oil reservoir to be 1.25 mu m, determining a corresponding polymer-surfactant binary composite system in each polymer concentration-surfactant concentration-minimum pore throat radius chart, and determining the binary composite system with the maximum viscosity in all the obtained polymer-surfactant binary composite systems to be the optimal polymer-surfactant binary composite system formula. As shown in FIG. 2, the present example finally determines that the binary composite system with the maximum viscosity, the molecular weight of 1500 ten thousand, the concentration of the partially hydrolyzed polyacrylamide is 1500mg/L, and the concentration of the sodium dodecylbenzenesulfonate is 2000mg/L, which is the optimized formulation of the binary composite system for flooding.

Example 2

The polymer used in this example was a partially hydrolyzed polyacrylamide having a molecular weight of 700, 1000, 1500, 1900, 2300 ten thousand and the base was sodium carbonate.

The binary composite system formula optimization method comprises the following steps:

step S1, preparing a binary composite system solution with the concentration of the partially hydrolyzed polyacrylamide of 500, 1000, 1500, 2000, 2500 and 3000mg/L and the concentration of sodium carbonate of 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 percent (by mass) corresponding to the concentration of each polymer by adopting the partially hydrolyzed polyacrylamide with the molecular weight of 700 million, and measuring the hydrodynamic radius R of each composite system_hThe method comprises the following specific steps:

firstly, preparing various binary composite system solutions by using distilled water, stirring by using an electric stirrer to fully dissolve a polymer, measuring the initial viscosity of the binary composite system solution, then filtering by using microporous filter membranes with the pore diameters of 0.45, 0.65, 0.80, 1.00, 1.20 and 1.50 mu m under the constant pressure of 0.2MPa, and measuring the viscosity of various filtrates.

And secondly, in a rectangular coordinate system, drawing a change curve of the relative viscosity of the binary composite system filtrate along with the aperture of the filter membrane by taking the aperture size of the microporous filter membrane as a horizontal coordinate and the relative viscosity of the composite system filtrate (namely the viscosity of the composite system filtrate/the initial viscosity of the composite system solution) as a vertical coordinate.

Finding out the inflection point of the curve by making the intersection point of the tangent lines of the curve before and after the change of the relative viscosity, wherein the value of the abscissa corresponding to the inflection point is the hydrodynamic radius R of the composite system_h。

Step S2, determining a series of hydrodynamic radiuses R of the composite system in the step S1 according to the bridging theory_hMatched minimum throat radius R_m(R_h＝0.46R_m) And drawing a polymer concentration-sodium carbonate concentration-minimum pore throat radius chart by taking the polymer concentration as an abscissa and taking a sodium carbonate concentration as an ordinate.

And S3, adopting 1000 million, 1500 million, 1900 million and 2300 million of partially hydrolyzed polyacrylamide respectively, and repeating the steps S1 and S2 to obtain polymer concentration-sodium carbonate concentration-minimum pore throat radius charts of polymers with different molecular weights.

And S4, measuring the average pore throat radius of the target oil reservoir to be 1.25 mu m, determining a corresponding polymer-sodium carbonate binary composite system in each polymer concentration-sodium carbonate concentration-minimum pore throat radius chart, and determining the binary composite system with the maximum viscosity in all the obtained polymer-sodium carbonate binary composite systems as the optimal polymer-sodium carbonate binary composite system formula. As shown in FIG. 3, the binary composite system with the maximum viscosity, the concentration of 1900 ten thousand partially hydrolyzed polyacrylamide being 1500mg/L and the concentration of sodium carbonate being 0.8% is finally determined as the optimized formulation of the binary composite system for oil displacement.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.