SU1501597A1 - Method of mining oil seams with non-uniform penetration - Google Patents

Abstract

The invention relates to the oil industry and is intended to increase oil recovery of water-penetrated reservoirs that are not uniform in permeability. The purpose of the invention is to increase the sweep coverage of watered layered heterogeneous oil reservoirs. A suspension of a water-soluble polymer is pumped into the formation in a non-swelling fluid. The injection is made by fringes, a series with water. The concentration of the polymer in the suspension is in the range of 20.0-0.01 wt.%. In each subsequent portion of the suspension it is less than the previous one. The suspension first of all gets into the high-permeable interlayers, swells under the action of water and covers the high-permeable zones. Subsequently, under the action of water, the swollen particles dissolve, forming high-viscous low-mobility rims. 1 tab.

Description

The invention relates to the oil industry, in particular, to enhanced oil recovery of wort formations that are not uniform in permeability.

The aim of the invention is to increase the sweep coverage of watered layered heterogeneous productive oil reservoirs.

In this method of developing an oil reservoir, which involves pumping a polymer suspended in a non-swelling fluid into a producing formation, a water-soluble polymer is used as the suspended particles, and the suspension is pumped in portions, the concentration of each subsequent portion being less than the previous one and falling in the interval from 20% doO, 01%, and between portions of the polymer suspension, portions of water are pumped.

Using a suspension of water-soluble polymer, which in an inert carrier fluid enters first of all into watered high-permeability zones, where its particles first swell and cover these zones, and later under the influence of water in the reservoir, the swollen particles dissolve and as a result Slag sedentary rim of soluble polymer, which moves through the reservoir to the zone with

about

El VI VI

personal permeability. This process in a porous medium is very long and takes years to complete. To level the permeability of layered heterogeneous formations, the suspension is pumped in portions with a decrease in polymer concentration in each subsequent batch, whereby the suspension enters lower permeability zones, where the polymer also dissolves and forms a viscous but mobile rim, and so on. Between portions of the suspension, water is injected into the layers so that the volume of the injected suspension is completely in contact with water, forming solutions. The polymer particles in the oil medium do not dissolve and, if they enter it, are extracted together with the oil.

Thus, reservoir heterogeneity in permeability is reduced by distances far from the wellbore zone. This leads to an increase in the enrollment rate of the reservoir with water-flooding, which, ultimately, will provide enhanced reservoir recovery.

The polymer is pumped in the form of a homogeneous suspension and additional mixing is not necessary; it takes place in the reservoir for a long time due to hydrodynamic flows. The solid particles of the polymer absorb water from the suspension and the reservoir, swell, increase in volume and clog the washed flooded high-permeability zones, thereby solving the problem posed.

The method is carried out in the following sequence.

1. In a selected area with a reservoir that is not uniform in permeability, having injection and production wells that are hydrodynamically interconnected, a complex of hydrodynamic and geological and physical studies is carried out, on the basis of which the volume V of the formation zones is to be injected.

2. As a polymer, water-soluble polymers are used that have the ability to swell before dissolving, increasing in volume several times, for example, carboxymethylcellulose polyoxyethylene, hydroxyethylcellulose, hydroxyethylcellulose, polyacrylamide and others.

H. As a carrier fluid, diesel fuel, anhydrous oil, distillate, salt solutions with high mineralization, and others are used.

4. The calculation of the volume of the suspension, according to the research by the formula

 (D - D V -N p

where Di is the radius of the element of the area where the blocking rim should be obtained, m;

D2 is the radius of the element of the area, less the thickness of the rim, m; H is the thickness of the layers, m: n is the porosity, in units of x. 5. The concentration of the polymer in the suspension and the number of portions are calculated taking into account the injectivity of the layers and its heterogeneity by permeability. Depending on the quality of the polymer, it is taken into account that the viscosity of the low-concentrated fringe is not lower than 10 MPa «s and not higher than 500. for highly concentrated in the dissolved state.

6. The amount of polymer is determined by the formula

P VrCi-t-V2-C2 + ... + VnCn.

where Vi, V2 ... Vn - the volume of suspensions,

Ci, C2 ... Cn - polymer concentration in

suspensions, fractions of a unit.

7. Between portions of the suspension, portions of water are pumped in a volume of at least 50-70% of the volume of water that can be absorbed

Popmer before dissolving. The selected polymer absorbs 5 volumes of water, therefore, portions of water will correspond to 100 m. The polymer will absorb the remainder of the water from the reservoir.

The suspension is prepared directly.

prior to injection into the formation, using jet pumps for this purpose. From a tank of no more than 500-1000 l {so that the suspension does not settle) the finished suspension is pumped into the injection well by a pump unit. The same unit pumps a portion of water between portions of the suspension into the well. An example of a specific implementation. Plot on which there are three

production wells are affected by a single injection well. From producing wells receive a liquid that is flooded more than 80%. The reservoir porosity is average - 0.20, thickness -3 m,

the distance between the producing and injection wells is on average 500-600 m, the injection capacity of the injection well is 800. It is necessary to obtain a rim 1 m wide in the formation at a distance of 200 m.

Water-soluble polymer hydroxyethylcellulose (OEC). According to the injectivity profile, the formation is taken in the range of 3 m (100 m, 300 m, 400 m and 1 m). Hydroxyethylcellulose viscosity of 0.5% solution - 11 MPa-s, 1.0% - 138 MPa-s, 2.0% - 500 MPa-s.

Payment:

1. Volume of suspension

V

iJ5bPli ..

4 i2 op2

 3.14 (201 2000 3x0.2 189 m

2. Plastics are the same thickness. The whole volume is divided equally into 3 portions (189: 3 63 m.

3. The amount of polymer

R BZHO, 02x + 63x0.01 + 63x0.005 2.21 tons,

4.0xyethylcellulose does not dissolve in diesel fuel, therefore it was chosen as a carrier fluid.

5. The volume of water pumped between portions of slurry 35-45 m.

The effectiveness of this method in comparison with the known was investigated in laboratory conditions on reservoir models.

When testing were used the following materials.

1. Hydroxyethylcellulose, carboxymethylcellulose with a particle size of from 0.1 to 30 microns.

2. As a carrier fluid: diesel fuel, mineralized water with a density of 1.20 g / cm.

Z.V quality of oil - oil model (oil: kerosene - 1: 1) with a density of 0.798 g / cm, viscosity 6.1 MPa C.

The experiments were carried out on artificial models of the formation, which represent a system of elements, which were used as glass tubes with a diameter of 2 cm and a length of 28 cm, which were filled with quartz sand. In the model, two tubes were taken, with the change in the fraction of sand, the permeability of the elements was 300 μm and 1080 μm.

Experiments were performed in the following sequence:

1. The porous medium of each element was individually saturated with oil, then they were connected through a common entrance to the model.

2. Went out the displacement of oil from the model to the complete water cut of both elements.

H. At the entrance a suspension of the polymer was fed in an inert solvent (diesel fuel, saline water) and pushed with water into a porous medium, the operation was performed four times with a sequential decrease of the polymer in the dispersion.

4. After the suspension was sent to the reservoir model, exposure was given for up to 30 days (since

:

the length of the reservoir model and the distance between wells is incommensurable).

5. The replacement of oil by water has been renewed.

56. Processing of experimental results

carried out according to the formulas:

AK K2 -Ki

V2 Vo

100:

K2

 V1 Vo

Vi -I-V2

Ki -5,100;

Vo

Vc

where L K is the increase in the displacement coefficient,%:

Ki, K2 - primary and secondary displacement coefficients,%:

Vi is the volume of oil displaced by primary water, cm;

V2 is the volume of oil displaced after treatment, cm: Vo is the volume of oil in a porous medium, see

The results of the experiments are given in the table.

thirty

35

40

45

50

55

tse

As can be seen from the table, as a result of the injection of polymer suspended in an inert solvent, the coefficient of displacement from low-permeable zones significantly increases (by an average of 50%), and in general, the increase in the model is 28.2% compared to the known.

The upper limit of the concentration of the polymer is determined by its filtering ability in a porous medium (from slow-moving or stationary in the washed highly permeable zones), controlled by viscosity.

The lower concentration limit of the subsequent portions is limited by the viscosity of the displaced oil, i.e. must not be lower than the displaced oil.

Claims (1)

Invention Formula A method for developing non-uniform permeability of oil reservoirs, including pumping a polymer suspended in a non-causing swelling fluid into a producing formation, characterized in that a water-soluble polymer is used as a suspended polymer to increase coverage by displacing flooded layered heterogeneous oil reservoirs. with the suspension of water-soluble polymer being pumped into the formation in portions, in a series of water, and in each the subsequent portion of the concentration of water-soluble polymer in the suspension is reduced, while the concentration of the polymer in the suspension is equal to 20.0-0.01 wt.%, 59.0 Offered, 3 61, 0 60.0 15,037,00,8 carboxy-66,021 solution, 56.5 unstable but swollen deed I "ode - 0.5 cm P, ;; 37,0 Hydroxy ethyl cellulose 63.0 V3, O73.036.5 in mineralized veda (density 1.19 g / cm) with concentration; U - 1.5 s “0.11 - 1.6 cm Carbonsimethylphenolloe in diesel with K1 and centering: 22, ЬИ, 5101 - 2.0 cm 61, В61), О62,921, ll 1.0–1.3 cm of hydroxylcelluloseenergic water (porosity 1.19 g / cm) with noncentration; O, OH - .5 cm Carbocsilscellosis with a concentration of 19.0.39.520 -1.5 m 61., 578.071,232.7 28.2