RU2263777C1 - Method for bottom water isolation in producing well - Google Patents

Abstract

FIELD: oil industry, particularly to isolate bottom water in producing well.

SUBSTANCE: method involves arranging bottom of production string in center of interval to be treated; injecting thickened water and oil in hole annuity of the well by circulating thereof; forcing cement grout in production string until bottom thereof; injecting oil into formation through hole annuity and simultaneously injecting cement grout into formation through production string. Rate of above injection operations are equal and set so that liquids are injected at laminar flow regime.

EFFECT: increased reliability of bottom water isolation.

2 cl, 1 ex

Description

The invention relates to the oil industry and may find application in the isolation of bottom water in a producing well.

A known method of limiting bottom water and annular flows in production wells, including flushing the wells and batch injecting water, cement and calcium chloride into it, provides that calcium chloride solution is pumped into the wells through an open filter, then water is added, then a solution of sodium naphthenate or potassium or a mixture thereof, this procedure is repeated at least 3 times, after which a cement slurry mixed with water is pumped, the water-cement ratio of which is 0.2-0.6, in volume 0.5-2 m ³ per 1 m thick layer with addition in an amount of 0.5-10% by volume of the cement slurry further solution of sodium or potassium naphthenate or mixtures thereof with a ratio naphthenate: water 1: 2 followed by forcing the entire weight of the well formation water at the rate of 1-2 m ³ per 1 m of reservoir power, then the wells are washed, their mouths are sealed and kept under pressure for 24 hours (RF patent No. 2172825, class E 21 B 43/32, publ. 2001.08.27)

The known method does not allow to create a reliable isolation of water inflows, because the impact is directed both to the flooded and oil-saturated parts of the interval of the reservoir, which leads to a deterioration in the filtration properties of the oil-saturated part of the reservoir.

Closest to the invention in technical essence is a method of isolating bottom water in oil wells by pumping oil into the formation and subsequent cementing using substances that have good adhesion to the formation and column, providing sealing under the hydrophobic effect of oil and further opening of the upper part of the formation (patent RF №2079647, class E 21 43/32, publ. 1997.05.20 - prototype).

The known method allows better isolation of bottom water to the well through the use of immiscible fluids, such as oil and an aqueous cement solution, however, injection of solutions into the perforation interval reduces the effect of isolation of bottom water due to the ingress of cement into the oil-saturated part of the reservoir.

The proposed method solves the problem of increasing the reliability of isolation of bottom water in the producing well.

The problem is solved in that in the method of isolating bottom water in a producing well, including injecting oil and cement mortar into the formation, according to the invention, the bottom of the tubing string is preliminarily placed in the middle of the treated interval and the circulation is pumped into the annulus of the oil well, and into the column tubing to its shoe cement, the injection into the reservoir of oil is carried out through the annulus, at the same time, the injection of cement into the reservoir through Olona tubing, the injection is performed with the same productivity, to provide a laminar oil flow mode and the cement slurry.

Before pumping oil into the annulus, it is possible to pump a thickened aqueous solution.

The features of the invention are:

1) injection into the reservoir of oil;

2) injection into the reservoir of cement mortar;

3) preliminary placement of the bottom of the tubing string in the middle of the processed interval;

4) injection of oil into the annular space by circulation;

5) pumping circulation into the column of tubing to its shoe cement;

6) injection into the reservoir of oil through the annulus;

7) the simultaneous injection into the reservoir of cement mortar through the tubing string;

8) injection with the same capacity, providing a laminar flow regime of oil and cement;

9) before pumping oil into the annulus, injection of a thickened aqueous solution.

Signs 1 and 2 are common with the prototype, signs 3-8 are the salient features of the invention, sign 9 is a particular feature of the invention.

SUMMARY OF THE INVENTION

When oil is taken through production wells, water tongues break through to production wells and bottom water cones form in the near-wellbore zone. As a result of this, flooding of produced products occurs. Isolation of water inflows by known methods is ineffective, and the insulation created is unreliable. The proposed method solves the problem of increasing the reliability of isolation of water inflows in producing wells. The problem is solved as follows.

When bottom water is isolated in the producing well, the bottom of the tubing string is placed in the middle of the treated interval. When the annulus is open (the space between the tubing string and the casing), oil is pumped by circulation into the annulus of the well. In order to exclude the replacement of oil by water in the well before oil, it is possible to inject a volume of thickened water. The volume of thickened water is set 0.25-0.4 m ³ . Water is thickened with any thickener, for example 4-6% carboxymethyl cellulose, tulose, etc. The tubing string to the shoe is filled with cement mortar. After that, oil is simultaneously pumped into the reservoir through the annulus and cement mortar through the tubing string. For this, as a rule, two pumping units of the CA-320 type are used. Download performance support the same and providing a laminar flow regime of liquids. This eliminates the mixing of flows in the well and provides a layered arrangement of fluids in the reservoir. As a rule, a flow rate of not more than 3 l / s provides a laminar flow of liquids.

According to this scheme, oil from the annulus enters through the upper perforations into the upper oil-saturated part of the reservoir, fills it and prevents cement mortar from getting there. Cement mortar as a heavier fluid and a fluid related to water enters the lower flooded part of the reservoir. This is facilitated by the placement of the bottom of the tubing string, through which cement slurry is pumped, in the middle of the processed interval. Those. cement mortar is initially sent to the lower part of the reservoir.

After pumping the calculated volumes of fluids of the order of 1.5-2.0 m ³ / m of the treated interval, technological exposure is performed to harden the cement for at least 24 hours and the well is mastered.

Concrete example

Bottom water isolation is performed in an oil well. The perforation interval is located at depths of 968–972 m. The bottom of the tubing string is placed in the middle of the processed interval at a depth of 970 m. With an open annulus, 0.25 m ^{3 of a} 5% aqueous solution of carboxymethyl cellulose and 8 m ³ oil. The tubing string to the shoe is filled with cement mortar in a volume of 3 m ³ . Another 3 m ^{3 of} cement mortar is located in the cementing unit ЦА-320. After that, oil is simultaneously pumped into the reservoir through the annulus with one cementing unit CA-320 with a capacity of 3 l / s and cement slurry through a tubing string with another cementing unit with the same capacity of 3 l / s. The injection performance is maintained the same throughout the entire download period.

After pumping the calculated volumes of oil and cement mortar, technological exposure is performed to harden the cement within 24 hours and the well is mastered.

The water content of the extracted products before work was 99.7%, after - 3.9%, so A reduction of water cut of 95.8% was achieved. Performing work in similar conditions by the prototype method leads to a reduction in water cut by 15-20%.

During the year of operation of the well, the water cut of the produced products increased and amounted to 37.2% at the end of the year.

Application of the proposed method will improve the reliability of isolation of bottom water in production wells.

Claims (2)

1. A method of isolating bottom water in a producing well, comprising injecting oil and cement mortar into the formation, characterized in that the bottom of the tubing string is preliminarily placed in the middle of the treated interval and the circulation is pumped into the annular space of the oil well, and into the tubing string compressor pipes to its shoe of cement mortar, oil is injected into the reservoir through the annulus, at the same time, cement mortar is injected into the reservoir through the pump-compressor column pipes, while the injection is performed with the same capacity, providing a laminar flow of oil and cement mortar. 2. The method according to claim 1, characterized in that before the injection of oil into the annulus, the injection of a thickened aqueous solution is carried out.