RU2354806C1 - Method for well construction - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to oil industry and may find application in construction of wells. Provides for increased reliability of well annular space cementing. In process of well construction drilling, lowering of casing string equipped with devices for collar cementing in the form of rubber-fabric material collars faced upwards and cementing of annular space of casing string. At least three devices of collar cementing are installed in well, the upper one - above payout oil beds under upper water-bearing beds, lower one - under payout oil beds above top of lower water-bearing beds, medium one - between payout beds, difference of bed pressures in which is at least 2 MPa. In case there are several beds or groups of beds are available with differences of bed pressures of more than 2 MPa, several devices of collar cementing are installed between every such beds or groups of beds.

EFFECT: increased reliability of well annular space cementing.

2 cl, 1 ex, 1 dwg

Description

The invention relates to the oil industry and may find application in well construction.

A device for casing cementing of a casing is known, comprising a housing, injection cementing holes, and a sealing collar. The device contains protective removable centralizers and a safety collar working for breaking, and the sealing sleeve is made in the form of a “tulip” with the possibility of opening (Publication number 99126102, published. 2001.09.20).

A device in the form of one element behind the casing, installed without reference to the properties of the reservoirs, is practically useless.

Closest to the proposed invention in technical essence is a method of opening a reservoir, according to which dynamically stressed zones are determined, a well is fastened by lowering a casing equipped with a packer and filters in the proposed zone of the reservoir and additional packers located at the boundaries of dynamically stressed zones between the filters cement the casing from the packer to the mouth (RF Patent No. 2154726, published. 2000.08.20 - prototype).

The known method does not allow you to create reliable annular cement bridges in the annulus and isolate annulus in the interval of productive formations from overflows of formation fluids from adjacent formations. Cementing from the packer and higher creates a large, uncemented interval in the well, which is prone to the manifestation of flows of formation fluids. Reliability of cementing the annulus of the well is insufficient.

The proposed invention solves the problem of improving the reliability of cementing annular space of the well.

The problem is solved in that in a method for constructing a well, including drilling, running a casing equipped with casing packers, and cementing the casing annulus, according to the invention, casing cementing devices are used as casing packers in the form of upward-facing cuffs of rubber material lowered into a well on a casing string, at least three lip-cementing devices are installed in the well, the upper one is above the productive oil-bearing strata under the upper and aquifers, the lower - under the productive oil strata above the roof of the lower aquifers, the middle - between the productive strata, the differential pressure of which is at least 2 MPa.

If there are several formations or groups of formations with reservoir pressure differences of more than 2 MPa, several cuff cementing devices are installed between each such formations or groups of formations.

SUMMARY OF THE INVENTION

A number of oil fields, such as, for example, the Romashkinskoye oil field, are multi-layer objects with zonal heterogeneity. The development of productive formations occurs unevenly, which leads to varying degrees of water cut in the formations. At the same time, reservoir pressures between productive formations can differ by more than 2 MPa due to uneven development of formations. In addition, above the terrigenous sediments in the section, there are highly permeable water-saturated carbonate rocks. Below are aquifers. During the cementing of the well, due to the pressure difference between the water-saturated carbonate reservoirs and also between the reservoirs themselves, fluid flows occur. These flows lead to poor cementation, as a result, water appears in the production of the well. Reliability of cementing remains low. The proposed invention solves the problem of improving the reliability of cementing annular space of the well. The problem is solved as follows.

During the construction of a well, a well is drilled, a casing string is equipped with lip-cementing devices in the form of upward-facing cuffs made of rubber material, and cementing the casing annulus. At least three lip-cementing devices are installed in the well. The upper one is set above the productive oil bearing strata under the upper aquifers, the lower one is placed under the productive oil strata above the roof of the lower aquifers, the middle - between the productive strata, the differential pressure of which is not less than 2 MPa.

If there are several formations or groups of formations with reservoir pressure differences of more than 2 MPa relative to each other, several cuff cementing devices are installed between each such formations or groups of formations.

Concrete example

Build an oil well. They drill a vertical wellbore to a depth of 1800 m, run a casing with a diameter of 146 mm, equipped with three lip-cementing devices. The well diagram is shown in the drawing.

The notation is used in the drawing: 1 - a highly permeable water-saturated carbonate reservoir, 2 - dense limestones, 3 - a reservoir with a reservoir pressure of 13 MPa, 4 - a reservoir with a reservoir pressure of 16 MPa, 5 - a flooded reservoir with a reservoir pressure of 13.5 MPa, 6 - upper cuff cementing device, 7 - middle cuff cementing device, 8 - lower cuff cementing device, 9 - casing string. The pressure difference between the upper and middle reservoir is 3 MPa, and between the middle and lower reservoir 2.5 MPa.

When cementing, the cement slurry is pumped along the casing 9 into the annulus past the lip-cementing devices 8, 7 and 6, which, under the pressure of the cement slurry, are bent and the cement slurry passes by themselves. Raise the cement to the wellhead. Technological exposure is carried out to wait for the cement to harden, during which the cement slurries down, bends the cuffs of the lip-cementing devices under its own weight, which overlap the cross section of the annulus of the borehole and create a reliable bridge in the cement cup of the annulus of the borehole. Migration of cement unhardened mortar and subsequently formation fluids in the annulus is completely eliminated. The reliability of cementing is increasing.

As a result, it is possible to completely eliminate the overflows in the annulus of the well.

The application of the proposed method will improve the reliability of cementing annular space of the well.

Claims (2)

1. A method of constructing a well, including drilling, running a casing equipped with casing packers, and cementing the casing annulus, characterized in that casing cementing devices are used in the form of casing packers in the form of upward-facing cuffs of rubber material that are lowered into the well on the casing at least three lip-cementing devices are installed in the well, the upper one is above the productive oil-bearing strata under the upper aquifers, n further, under productive oil strata above the roof of the lower aquifers, the average between productive strata, in which the pressure drop is not less than 2 MPa. 2. The method according to claim 1, characterized in that in the presence of several formations or groups of formations with differential pressure of more than 2 MPa, several cuff cementing devices are installed between each such formations or groups of formations.