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Low permeability oil reservoir polymer injectivity evaluation method

A technology of injection ability and evaluation method, which is applied in the field of polymer injection ability evaluation of low permeability reservoirs, can solve the problem of not considering polymer injection ability, etc., and achieves the effect of good shear resistance, good application prospect and good viscosity increase.

Active Publication Date: 2020-01-21
PETROCHINA CO LTD
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This application involves a method for evaluating the injection capacity of multi-reservoir polymer injection wells considering the viscoelasticity of polymers. It mainly solves the injection capacity by establishing a polymer seepage mathematical model, and does not consider how to evaluate the polymer injection capacity under real reservoir conditions.

Method used

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  • Low permeability oil reservoir polymer injectivity evaluation method
  • Low permeability oil reservoir polymer injectivity evaluation method
  • Low permeability oil reservoir polymer injectivity evaluation method

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Experimental program
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Effect test

no. 1 approach

[0064] The first embodiment of the present invention relates to a method for evaluating the injection capability of polymers in low-permeability reservoirs, comprising the following steps:

[0065] S1 Construction polymer injection ability evaluation index

[0066] Through the physical simulation experiment of polymer injection in low-permeability reservoirs, the corresponding evaluation indexes of polymer injection capability in low-permeability reservoirs are constructed, including polymer injection pressure, viscosity retention rate, drag coefficient, residual drag coefficient, plugging capacity and injection curve feature;

[0067] S2 classifies each evaluation index

[0068] According to the results of the polymer injection physical simulation experiment in step S1, combined with the actual reservoir development, the classification basis for each evaluation index described in step S1 is determined one by one, and each evaluation index is divided into one type, two types ...

no. 2 approach

[0077] On the basis of the above embodiments, it should be noted that in the step S2, the basis for the classification of the polymer injection pressure is as follows: according to the requirements of reservoir development, the polymer injection pressure P cannot exceed 90% of the formation fracture pressure, preferably at 60% or less, so 60% and 90% of the maximum allowable pressure (that is, the formation fracture pressure) are used as the cut-off point of the polymer injection pressure, and the polymer injection pressure ≤ 60% of the maximum allowable pressure is divided into one category; 60% of the maximum allowable pressure %90% of the maximum allowable pressure is divided into three categories.

[0078] Further, the viscosity retention rate η is the ratio of the viscosity of the produced liquid to the viscosity of the formulated polymer solution when the injection pressure is stable. A high retention rate proves that polymer molecules can effectively pass through pores a...

no. 3 approach

[0089] On the basis of the above embodiment, further, in the step S3, the weight of each evaluation index is determined, and the gray correlation method is used to process the data, and the processing process is as follows:

[0090] Step 1: Determine the reference sequence and compare the sequence

[0091] Taking each group of cores to improve oil displacement efficiency range as a reference sequence, taking polymer injection pressure, viscosity retention rate, residual resistance coefficient, injection curve characteristics, plugging capacity and resistance coefficient as a comparison sequence;

[0092] Step 2: Dimensionless data processing

[0093] let x 0 ={x 0 (k)|k=1, 2,..., m} is the reference sequence, x i ={x i (k)|k=1, 2,..., m} (i=1, 2,..., n) is a comparison sequence; due to the different dimensions of each parameter, in order to make it comparable, the formula is used for each term Parameters are dimensionless:

[0094] x i (k)'=[x i (k)-min x i (k)] / [max ...

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Abstract

The invention provides a low permeability oil reservoir polymer injectivity evaluation method, comprising the following steps: by performing polymer injectivity physical simulation experiments under different oil reservoir conditions, obtaining six parameters, namely plugging capability, a polymer injection pressure, a resistance coefficient, a residual resistance coefficient, a viscosity retention rate and injection curve characteristics, further calculating an influence factor of each parameter by utilizing a gray correlation coefficient method, determining weight of each parameter, determining a score of each class of each parameter, and then determining a polymer injectivity evaluation standard, thus polymer injectivity is simply, effectively and quantitatively evaluated, polymers applicable to oil reservoir conditions and with good viscosifying capability, good shearing resistance, good injectivity and good stability under oil reservoir conditions are selected according to the standard, and oil displacement effect of polymer flooding and binary flooding is improved.

Description

technical field [0001] The invention belongs to the technical field of oilfield exploitation, and in particular relates to a method for evaluating the injection capacity of polymers in low-permeability oil reservoirs. Background technique [0002] With the prolongation of water flooding time, the oil field gradually enters the medium-high water-cut development stage, especially for reservoirs with serious horizontal and vertical heterogeneity, polymer flooding can change the oil-water mobility ratio, expand the swept volume, and improve the oil displacement efficiency. Polymer flooding, as the main tertiary oil recovery technology for oil field development or production increase, has been widely used at home and abroad. The oil increase per ton of polymer reaches 80-150 tons, which is 6%-12% higher than water flooding recovery. The effect of polymer flooding depends on many factors, one of the most important factors is the injection capacity of polymer, which directly determ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N33/26
CPCG01N33/26Y02A10/40
Inventor 李兆国袁国伟李文宏张晓斌张永强杜朝锋李建霆杨金龙冯春艳王丽莉王胜华
Owner PETROCHINA CO LTD
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