SU1677275A1 - Method for developing oil pool by water flooding - Google Patents

Abstract

The invention relates to mining. The goal is to increase oil recovery while maintaining the estimated volume of water injection. For this, prior to the placement of injection wells in the field, the clay content in the formations is determined and lines of its equal content are constructed. The placement of the injection wells is carried out taking into account the filtration of the injected water through formations with a clay content of 10-15 wt.%. A higher clay content in the reservoir does not lead to an increase in oil recovery, but only increases the displacement time. 1 tab., 2 Il.

Description

The invention relates to mining, in particular to the development of oil fields by flooding, whose formations contain clays.

The goal is to increase oil recovery while maintaining the estimated volume of water injection.

FIG. 1 shows the layout of the wells of the prototype; in fig. 2 - the same, according to the invention.

The essence of the invention is as follows.

On the basis of the experimental studies carried out, it was established that when water is filtered through a clayed porous medium, water changes its physicochemical properties. The change in water properties contributes to a better displacement of oil from the reservoir and thereby increases the final coefficient of oil recovery.

The mechanism for enhanced oil recovery when filtering injected water through reservoirs containing clay is as follows.

Water, in contact with clay particles, is exposed to magnetic fields and under the action of them changes its physicochemical properties. In addition, water, a solution in itself of the smallest particles with magnetic properties, also changes its physicochemical properties. It is known that water subjected to magnetic fields improves the displacement of oil from the porous medium. The most optimal mode of displacement is observed when the clay content in the reservoir is 10–15 wt.%. Large values of clay content in the reservoir do not lead to an increase in oil recovery compared with clay content values of 10-15 wt.%, But only increase the displacement time, which is associated with a decrease in phase permeability for water when the clay content in the reservoir is more than 15 wt. % (when the content of clay in the reservoir

cl

with

about

Xi

Xi

N) XI SL

up to 15 wt.%, it practically does not affect the phase permeability for water). A decrease in the phase permeability of water with a clay content of more than 15 wt.% Leads to a decrease in the injectivity of injection wells, respectively, to a decrease in the efficiency of the flooding process. When filtering the injected water through reservoir areas with a clay content in the reservoir of less than 10 wt.%, Oil recovery is observed. Based on the above, it is proposed to place injection wells behind the oil-bearing circuit so that before the injected water enters the oil-bearing formation, the water is filtered through areas of the reservoir, the layers of which contain 10-15 mas.% Clay. At the same time, with the new arrangement of injection wells, the estimated volume of water injection introduced into the reservoir, which is selected according to the prototype (according to the project), should be maintained in order to maintain the pressure in the reservoir at the required level,

Experiments were conducted on artificially created models. At the same time, the porous medium of the marginal part of the reservoir model consisted of a mixture of quartz sand and montmorillonite clay, and the oil per zone - only of quartz sand. Before the experiments, the quartz sand and clay were dried in a drying cabinet at 378 K, after which they were divided into fractions by sieving through a sieve. Experimental studies were carried out on a specially assembled installation. The reservoir models for the marginal and oil zones were placed in two core carriers (KD), connected in series with each other. Metal pipes with an internal diameter of 0.04 and a length of 0.8 m were used as CDs. Concentration of clay and quartz sand along the sample was ensured in each experiment by preliminarily mixing clay with quartz sand. The concentration of clay in the porous medium was created by the weight method.

In order to completely remove air from the first space to saturate with liquid, both porous media were evacuated with a vacuum pump (HV) for 3 hours. After queuing, both rock samples were saturated with liquid from VS and HC vessels under pressure from a high-pressure cylinder. pressure (BVD). At the same time, one of the porous media (KD2) was saturated with the displaced, and the other (KD1) - with the displacing liquid. Oil with a dynamic viscosity of 15 mPa С and specific gravity of 0.88 g / cm was used as the displaced fluid. Water was used as a displacing agent, containing 2.5% salt and forming surface tension at the boundary with oil 27. N / m.

During the experiments, the volume of the liquid (oil and water) coming out of the porous medium was periodically measured. Process

Displacement proceeded to 100% watering of products leaving the porous medium (KD2). The experiments were carried out at different clay contents in a water-saturated porous medium (KD1), and

5 namely: 0; five; 7; ten; 15; 25; thirty%.

The table shows the results of experimental studies

As can be seen from the table, the final recovery rate increases with

0 increase in clay content of O

up to 10-15% inclusive. Then, start with

clay content values over 15

wt.%, oil recovery coefficient is not measured. Considering the fact that the content

5 clay in the reservoir up to 15 wt.% Inclusive, practically does not affect the phase permeability of the reservoir for water, and the oil recovery coefficient does not increase beyond the clay content in the reservoir 10-15 wt.%,

0 optimal for an effective process of oil displacement by water should be considered the clay content in the reservoir in the range of 10-15 wt.%.

Example. On the development map is built

5 lines of equal containing clay in the reservoir. The sections of the deposit with clay content in the reservoir are 10-15 wt.% (Shaded areas in Fig. 1). Inject the injection wells in such a way that

0 so that before the injected water enters the oil-saturated formation, the water is filtered through areas of the reservoir, the formations of which contain 10-15 May. % clay.

5 In FIG. 1 shows the layout of the injection wells of the prototype, and FIG. 2 on the proposed method. K - power circuit; A - injection well; O - production well. Shaded

0 area - the area of the reservoir with a clay content of 10-15 wt.%.

At the field site, the estimated volume of water injection into the reservoir through a series of injection wells is 3,000.

5 m / day. As can be seen from FIG. 1, in the layout of injection wells of the prototype, three injection skooshes (No. 1, 2 and 3) are randomly positioned so that the injected water is filtered through a portion of the deposit with clay content of 10-15 wt.%. Rest

4 wells did not get to the area required by this method.

In this method it is necessary to place wells 5, 6 and 7 in the area of the deposit with clay content of 10-15 wt.% (See Fig. 2). Well No. 4 can be left in place if, due to physical conditions, it does not have a place on the outlined area of the reservoir (i.e. as many as possible wells should be located on the section of the reservoir with clay content of 10-15 wt.%). Note that the arrangement of injection wells here means the setting of points for drilling injection wells in sections of the reservoir with clay content of 10-15 wt.% Or, if the injection wells are selected from among the former producers, it is indicated which wells need to be converted into injection so that water is filtered through areas of deposits with the required clay content, i.e. the placement of injection wells according to the proposed method should be reflected in the design of the flooding. Before the implementation of the aquifer flooding process, a project is made with the arrangement of injection wells according to the prototype and according to this method, after which the efficiency is compared and the implementation begins.

So, according to the proposed method, wells 5, 6 and 7 are placed in such a way that the injected water is filtered through areas of the deposit with clay content of 10-15 wt.% (See Fig. 2). This section is 100m farther from the production well line (compared to the prototype), which can lead to an increase in the outflow of injected water into the boundary area according to the theory of boundary flooding. Suppose, in this case, the leakage (outflow) of the injected water is 20% of the total injection volume. Then, if the prototype (estimated injection volume) had to pump 700 m3 of water per day into wells 5, 6 and 7, then using the proposed method, to compensate for the leakage (i.e., to maintain the estimated amount of injection water that is injected into the oil-saturated formation ), it is necessary to pump water 20% more into injection wells 5,6 and 7, i.e. 840

m / day. In this case, the condition for maintaining the estimated volume of injected water that is embedded in the oil-saturated formation is preserved.

Thus, the advantages of the method

the following.

The oil recovery coefficient reaches a maximum value when water is filtered through the rock with a clay content of up to 10-15 wt.%, Inclusive, and with a further increase in clay content, it does not change.

The permeability of the reservoir (i.e., its conductivity for the injected water) is not affected by the clay content up to 10-15 wt.%

inclusive. When the clay content in the reservoir is more than 15 wt.%, Its permeability drops sharply (i.e., the resistance of the filtering water increases).

In this connection, the placement of injection wells in front of sections of the reservoir with a clay content of up to 10-15 wt.%, Inclusively, leads to an increase in the final oil recovery coefficient.

Claims (1)

Invention Formula A method for developing an oil field by flooding, including the placement of injection wells in a field, the formations of which contain clay, pumping a calculated volume of water through injection wells and withdrawing oil through producing wells, characterized in that, in order to increase oil recovery while maintaining the estimated volume of water injection, prior to the placement of injection wells at the field, the clay content in the formations is determined and lines of equal clay content in the formations are constructed, and the distribution is injection wells carried out with the filtering the injected water through the layers with clay content of 10-15 wt.%. The clay content in the reservoir, wt.% O 5 7 10 15 25 30 The final rate of oil recovery,% 55 60 65 70 70 70 70 1 ABOUT about f f T 3 oh oh / d l oh oh