RU2245993C1 - Well cluster operation method - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes full raising of cement in behind-pipe space up to mouth, sectioning wells by electro-isolating compounds from oil transporting system or bed pressure support system and use of cathode protection plant as cathode protection station with current controller. For each well time needed for completing cathode polarization of well is determined as well as time for well depolarization, during which potentials on well of cluster are lowered to minimal protective values. On each cluster well cyclic mode of cathode protection plant is performed: cathode polarization during completion of cathode well polarization and well depolarization during lowering potential on well to minimal protective values. During depolarization of one well cathode polarization of other cluster well is performed.

EFFECT: higher effectiveness.

1 ex

Description

The invention relates to the oil industry and may find application in the operation of oil producing and injection wells.

A known method of protecting underground metal multi-pipe pipelines from electrochemical corrosion and a device for its implementation. The device contains three single-phase DC voltage sources, input power rails, plus and minus output load rails, plus and minus rails of measuring circuits connected in a certain way to each other (RF Patent No. 2204626, class C 23 F 13/22, publ. 2003.05. 20). The device supplies cathodic protection current in a constant mode.

The disadvantage of this method is the high power consumption.

Closest to the invention in technical essence is a method of electrochemical protection of wells, comprising cementing the annular space of the casing of the well and equipping each individual well with cathodic protection devices or constructing cathodic protection for 2-3 wells. At the same time, cathodic protection installations ensure uninterrupted cathodic polarization of well casing throughout the entire operational period (Instruction for joint cathodic protection of casing and flow lines of wells. RD 153-39.0-238-02. Bugulma, TatNIPIneft, 2002).

The known method of electrochemical protection of wells involves the installation of cathodic protection devices for each well individually or the construction of cathodic protection for 2-3 wells. In this case, the cathodic protection installations according to the requirements for electrochemical protection must ensure uninterrupted cathodic polarization of the structure during the entire operational period, which leads to unjustified energy costs.

The proposed invention solves the problem of providing energy savings during electrochemical protection of casing strings introduced from drilling wells with a minimum number of cathodic protection installations and during their cyclic operation.

The problem is solved in that in a method of operating a well cluster, including raising cement in the annulus to the wellhead, partitioning wells with electrical insulating connections from an oil transport system or reservoir pressure maintenance system, using a cathodic protection unit with a current controller as a cathodic protection station, according to the invention, determination of the completion time of the cathodic polarization cycle of the well, determination of the time of depolarization of the wells at which the potentials at the wells are lower wives to the minimum protective values, conducting a cyclic mode of operation of the cathodic protection installation: cathodic polarization during the completion time of the cathodic polarization cycle of the well and depolarization of the well during the time of lowering the potential at the well to the minimum protective values, while cathodic polarization of the other is carried out at the moment of depolarization of one well well bush.

The features of the invention are:

1) raising cement in the annulus to the mouth;

2) sectioning wells with electrical insulating compounds from the oil transport system or reservoir pressure maintenance system;

3) the use of a cathodic protection unit with a current controller as a cathodic protection station;

4) determining the completion time of the cathodic polarization cycle of the well;

5) determination of the time of depolarization of wells, at which the potentials in the wells are reduced to the minimum protective values;

6) the cyclic mode of operation of the cathodic protection installation: cathodic polarization during the completion time of the cathodic polarization cycle of the well and depolarization of the well during the time that the potential in the well decreases to the minimum protective values;

7) at the time of depolarization of one well, conducting cathodic polarization of another well in the bush.

Signs 1-3 are common with the prototype, signs 4-7 are the salient features of the invention.

SUMMARY OF THE INVENTION

Electrochemical protection of casing of wells against corrosion is carried out by cathodic protection units, which ensure a continuous cathodic polarization of the structure with a rated protection current of 5 A and allow a break in the operation of each installation of the electrochemical protection system for no more than 80 hours per quarter (GOST R 51164-98 “Pipelines steel trunking. General requirements for corrosion protection Section 5. Requirements for electrochemical protection "). Such work requires the use of a cathodic protection installation for each well individually or the construction of cathodic protection for 2-3 wells and leads to unjustified energy costs. The proposed invention solves the problem of providing energy savings during electrochemical protection of casing strings introduced from drilling wells with a minimum number of cathodic protection installations and during their cyclic operation. To ensure reliable electrochemical protection of wells, it is planned to build one cathodic protection unit for several wells located on the same well. The electrochemical protection of the casing strings of a group of wells on one well is ensured by the installation of cathodic protection with a controller that allows, after a certain time, to selectively connect one or another well to the cathodic protection system.

To do this, during drilling, a complete lift of cement in the annulus to the wellhead is carried out, which ensures isolation of the well from the rock. Then, wells are partitioned (separated) by electrical insulating compounds from the oil transport system or the reservoir pressure maintenance system. In this case, the aim is to minimize energy losses. As a cathodic protection station, a cathodic protection installation with a current controller is used, which allows connecting a well to polarization in a given mode. The time for completing the cathodic polarization of each well is determined, during which the protective potential of the well grows to the operating value. Determine the depolarization time of each well (with the power supply turned off), at which the potential at the well decreases to the minimum protective value. A cyclic operation mode of the cathodic protection installation is carried out at each well in the cluster: cathodic polarization during the completion time of the cathodic polarization cycle of the well and depolarization of the well during the time that the potential in the well decreases to the minimum protective value. Moreover, at the time of depolarization of one well, cathodic polarization of another well in the bush is carried out.

An example of a specific implementation of the method

On the bush of the group metering unit 44c of the oil and gas production workshop No. 2 of the Almetyevneft oil and gas production department, four production wells were put into operation after drilling with a full rise of cement to the wellhead after drilling.

In order to prevent leakage of cathodic protection current, dielectric insulating inserts of the TIS type are mounted on all pipelines of flow lines of the wells, inserted at the joints of the metal pipes. As a cathodic protection installation, a cathodic protection converter with a current controller of the KSKZ type is used.

For each well, the time for completion of the cathodic polarization of the well is determined after the start of the cathodic protection current supply to the casing string of 5 A before the current protective potential of more than 0.9 V appears and the time of depolarization of the well after the cathodic protection current supply to the casing string is stopped, when where the potential at the well decreases to a minimum protective value of 0.9 V. At each well in the bush, a cyclic mode of operation of the cathodic protection installation is carried out: cathodic field polarization during the time of completion of the cathodic polarization of the well and depolarization of the well during the time that the potential in the well decreases to the minimum protective value. In this case, mainly at the time of depolarization of one well, cathodic polarization of another well in the bush is carried out.

The duration of completion of the cathodic polarization of the wells was 5 days for wells No. 32955, 25349 and 32706 and 6 days for well No. 3098d.

The duration of well depolarization, at which the potentials at the wells were reduced to the minimum protective values of 0.9 V, was: 3 days for well No. 3098d, 4 days for well No. 3295, 6 days for well No. 25439 and 8 days for well No. 32706.

Assign a mode in which at the time of depolarization of one well conduct cathodic polarization of another well of the bush.

Instead of the design 2 cathodic protection installations according to the prototype with 4 anode grounding conductors, according to the proposed method, one cathodic protection installation with one anode grounding is used, equipped with a controller, which after 3 to 8 days turns on the current from the cathodic protection installation for the period of casing polarization of the wells during 5-6 days. The operating mode of the controller is selected so that mainly at the time of depolarization of one well, cathodic polarization of another well in the bush occurs.

The application of the proposed method will save energy and provide electrochemical protection of the casing of the wells during cyclic installation of cathodic protection.

Claims (1)

A method of operating a well cluster, including raising cement in the annulus of wells to the wellhead, partitioning wells with electrical insulating compounds from an oil transport system or reservoir pressure maintenance system, using a cathodic protection unit with a current controller as a cathodic protection station, characterized in that each well is carried out determining the completion time of the cathodic polarization of the well and determining the time of depolarization of the wells, at which the potential at the well is reduced to of the minimum protective value, a cyclic mode of operation of the cathodic protection unit is carried out at each well in the cluster: cathodic polarization during the time of completion of the cathodic polarization of the well and depolarization of the well during the time of lowering the potential at the well to the minimum protective value, while at the time of depolarization of one well, cathodic polarization another well of the bush.