SU1758217A1 - Method of control of water flooding front in oil pools with non-uniform penetrability - Google Patents

Abstract

SUMMARY OF THE INVENTION: A clay slurry with a density of 1.02-1.08 kg / dm and an aqueous polymer solution, which uses 1-3% aqueous solution of cellulose ether (methyl, hydroxyethyl, carboxymethylcellulose) are sequentially pumped into the formation . 2 tab.

Description

The invention relates to the oil industry, namely to the method of enhancing oil recovery of a reservoir that is not uniform in permeability.

There is a method of enhanced oil recovery by pumping aqueous solutions of polyacrylamide into them.

The disadvantage of this method is that its use is effective only at an early stage of field development during the initial displacement of oil, and to regulate the water front of a reservoir that is not uniform in permeability if it has absorption zones at a late stage of development, the method is ineffective or ineffective.

Closest to the proposed method is to isolate the flow of water into the well. This method of isolating the inflow of water into a well is also applicable for the purpose of regulating the water front of a permeability non-uniform reservoir. It is carried out by injecting into the reservoir an initially aqueous solution of a partially hydrolyzed polyacrylamide of 0.001-0.05% concentration, and then

clay suspension with a density of 1.02-1.08 kg / dm3.

A disadvantage of the known method is the low control efficiency of the flooding front of a reservoir that is not uniform in permeability, due to the fact that, at the specified injection sequence, the polymer and clay slurry solution is filtered mainly into absorption zones (cracks, channels). As a result of this, a subsequent flooding encompasses an insignificant part of the reservoir.

The aim of the invention is to increase the efficiency of oil displacement from the formation.

This goal is achieved by the fact that according to the method of controlling the water front of heterogeneous permeability of an oil reservoir, including sequential injection into the formation of an aqueous polymer solution and clay suspension with a density of 1.02-1.08 kg / dm3, clay suspension with a density of 1.02-1.08 kg / dm3 is pumped before pumping an aqueous solution of the polymer, and the quality of the aqueous solution of the polymer is added (L

WITH

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Chipet 1-3% aqueous solution of cellulose ether.

At a late stage of field development, in the presence of absorption zones and / or highly permeable watered layers of clay, the suspension, as well as the polymer solution, is filtered predominantly into the absorption zones with little coverage of the layers (subsequent flooding. This is aloof to the joint simultaneous injection of clay slurry and polymer solution and sequential injection, when the polymer solution is initially pumped, and then the clay slurry. Initially, the clay suspension is filtered into the absorption zones and then plugged. Then, when a 1-3% solution of cellulose ether is pumped, it is filtered into highly permeable watering formations, followed by a sharp decrease in the permeability of such formations. by connecting low-permeable oil-saturated formations into the development. Thus, the proposed injection sequence and cellulose ether concentrations are both Sintering the direction and distribution of the flow of filter solutions (clay powder and polymer) throughout the thickness of the productive layers, depending on their heterogeneity in permeability.

The method of controlling the water front of a non-uniform permeability oil reservoir is carried out as follows.

Preparatory work is preliminarily carried out: an experimental plot is selected at the field, an injection volume (injection well) is selected, and production wells connected to it are determined hydrodynamically; conduct a complex of standard hydrodynamic Vi geophysical studies at wells to determine the current state of wells, the profile of the injectivity of the formations, the degree of production of productive formations. The injection of reagents at the well is performed according to the following process flow diagram: water jet pump (ejector) of the AN type -700 - well. Initially, a clay slurry with a density of 1.02– 1.08 kg / dm3 is pumped, which is prepared either on stationary aluminae and delivered to the well by tank trucks, or directly to the well by dosing in

dry mud blast pump. The technological process of pumping is controlled by the suppression of injection, determined by the gauge of the pump unit. how

shows the field practice of pumping chemical reagents, when the injection pressure increases by 30-50% from the initial injection pumping unit of the AN-700 type, the absorption zones are blocked and disconnected; therefore, increasing the pressure by this amount stops injection of the clay slurry and injects polymer aqueous solution with

5 concentration of 1-3%, depending on the type of cellulose ether. After the completion of polymer injection, water injection into the well is resumed.

In the proposed method injected

0 clay suspension with a density of 1.02– 1.08 kg / dm3, which corresponds to a concentration of bentonite clay powder in a suspension of 5–12%. According to the results of laboratory studies, the amount of injected clay suspension is 3-8% of the pore volume of the formation model. The polymer solution is pumped at a concentration of 1–3%, depending on the type of cellulose ether and its viscosity chosen.

0 properties As laboratory studies show, in order to effectively reduce the permeability of highly permeable wetting formations, the viscosity of cellulose ether solutions in the interval of 100-500 MPa is necessary. c, which corresponds to the concentration of the polymer in the proposed method. As practice shows the injection of polymer compositions, the required amount of the injected solution of ether

0 pulp depends on the degree of production of productive formations and is 10% of the pore volume of the formations.

The justification of the injection sequence and polymer concentration was carried out on linear bulk reservoir models filled with quartz sand (model length 0.5 m, cross-sectional area 6.4-). The reservoir model consisted of three metal tubes with a common inlet.

0 Quartz sand was selected for a specific fraction for each tube in such a way as to simulate reservoirs with a large permeability heterogeneity. First tube (part) of the reservoir model

5 modeled the absorption zone, the second part of the model is a high-permeable formation, a third part is a low-permeable formation.

After evacuation, the model was saturated with fresh water and water permeability was determined. Then, into the model

clay slurry or polymer solution was pumped. The sequence of injection compositions presented in table. 1. After injection of each of the compositions, water permeability was determined. The blocking capacity of the clay suspension or polymer solution was determined by the formula

Ki

x 100%

where Ki is the initial water permeability, microns;

K2 - water permeability after injection of a clay suspension or polymer solution, μm.

In all experiments, the pressure differential between the ends of the formation model is 0.05 MPa

In the experiments, the following polymers were used: Acacterol (Japan) polyacrylamide, MMC-BTR (TU 39-08-047-74) methylcellulose, TYLOSE ENM (HPM) hydroxyethylcellulose (Germany), CMC 85/700 carboxymethylcellulose ( OST 6-05-386-80).

As shown in experiments 1-3, the proposed injection sequence and cellulose ether concentration is highly effective for controlling flooding of a heterogeneous reservoir. Initially, after the injection of a clay slurry, the absorption zone is blocked (plugged), and then after the injection of the polymer, there is a sharp decrease in the permeability of the highly permeable formation (blocking capacity -88%)

For comparison, experiment 4 was conducted with the concentrations and sequence of injection of the compositions described in the prototype. When the solution of polyacrylamide is initially injected, the solution is filtered through all parts of the formation model, especially into the absorption zone. At the same time, the permeability decreases in different parts of the model by 11-20 % Then, during the injection of the clay suspension, the absorption zone is plugged, however, the clay suspension is not filtered into the high and low permeable portions of the formation. The subsequent injected water is filtered only into the highly permeable part of the formation, and the low permeable part remains unconnected to the development. As a result, the reservoir coverage does not increase by flooding, therefore. The prototype injection sequence is ineffective.

From the results of experiments 5-8 it follows that the largest (100%) clogging

The ability of the absorption zones is possessed by a clay suspension with a density of 1.02-1.08 kg / dm3.

The results of experiments 1-3, 9-11 show that the optimal concentrations of the injected solution of cellulose ether are concentrations in the range of 1-3%. The polymer solution with a concentration of less than 1% (test 9. 10) is filtered into all parts 10 of the reservoir model with a slight decrease in their permeability. The polymer solution with a concentration of more than 3% (test 11) is filtered only into the absorption zone and has a low blocking capacity, 15 is also a solution polymer with a concentration of more than 3% is impractical to use from a technological and economic point of view.

Evaluation of the effectiveness of the proposed control method was carried out on a three-layer linear model of an inhomogeneous permeability reservoir with isolated layers. After evacuation, the model was successively saturated with water and oil. The oil recovery coefficient of the reservoir when oil was displaced by water. Then, the clay slurry was pumped until the injection pressure was increased to a value greater than 0 initial 1.5 times (initial pressure at which oil was displaced with water of 0.1 MPa). Then, an aqueous solution of cellulose ether with a volume equal to 10% of the first 5 volume of the reservoir was injected. After the polymer was injected, the oil was extracted with water and an increase in the oil recovery coefficient was determined. The results of the experiments are presented in table. 2. The obtained results of experiments on reservoir models show the high efficiency of the regulation of the water front by the proposed method. As a result of an increase in the coverage of the reservoir-water flooding, the oil recovery ratio increased by 15-17%.

Claims (1)

The invention of the method of regulating the water front of inhomogeneous permeability of oil to a footplast, including 0 sequential injection into the reservoir of an aqueous solution of the polymer and clay slurry with a density of 1.02-1.08 kg / dm3, characterized in that, in order to increase the efficiency of displacing oil from the reservoir, clay slurry with a density of 1.02-1.08 kg / dm is injected before the injection of an aqueous solution of the polymer, and a 1-3% aqueous solution of cellulose ether is injected as an aqueous solution of the polymer. Table 2 Water displacement Clay suspension with a density of 1.05-1.06 kg / dm3 (5% of the pore volume of the formation) 1.5% solution of methylcellulose viscosity (1 C (10% of the pore volume of the reservoir) Additional displacement of oil by water Clay suspension with a density of 1.02-1.03 kg / dm3 (8% of the pore volume of the formation) 1% solution of hydroxyethylcellulose with a viscosity of 180 MPa s (10% of the pore volume of the formation) Oil displacement with water Clay suspension of density J, 07-1.08 kg / dm3 (3% of the pore volume of the formation) 3% solution of carboxymethylcellulose with viscosity of 260 mPa-s (10% of the pore volume of the formation) Oil displacement with water 72 50 nineteen 47 72 51 64 62 56 62 63 53 66 64