RU2320854C1 - Well operation method - Google Patents

Abstract

FIELD: oil production, particularly to operate well drilling in stacked pool including reservoirs with different injectivities.

SUBSTANCE: method involves injecting cement-and-chalk mix in well; casing well and performing acid well treatment. Cement-and-chalk mix has volume and is injected in hole annuity under pressure, which provide cement-and-chalk ring creation in hole annuity for partial perforation orifice of productive interval mudding. For well casing cement bridge of plugging cement is arranged in well opposite to lower reservoir having high injectivity. Acid treatment is performed in productive reservoir intervals not covered with cement. The cement-and-chalk mix includes cement and chalk with ratio of 1:(0.1-0.4).

EFFECT: possibility to create isolation screen, which may be easily removed during well development with the use of acid solution along with well deliverability keeping.

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Description

The invention relates to the oil industry and may find application in the operation of a well that has uncovered a multilayer oil reservoir with formations of different injectivity.

A known method of operating a well equipped with an old casing string. A new smaller diameter casing is lowered into the well. The cavities are separated by injection into the space between the old and new casing strings of the anticorrosive fluid and the volume of the cement mortar that can be destroyed in an acid - cement-chalk solution. A cement bridge of cement-chalk solution is installed above the perforation interval and above the bottom of a new casing string. If it is necessary to replace a new casing string, a new casing string is perforated at the place of setting up the cement bridge and the acid solution is pumped until the cement bridge is destroyed (RF Patent No. 2164588, class E21B 43/00, published 2001.03.27).

The known method provides the elimination of fluid loss through the casing and maintainability of the well. However, the method is complex, requires the use of a new smaller diameter casing, which negatively affects the productivity of the well.

Closest to the proposed invention in technical essence is a method of completing oil and gas wells, including the formation in the formation of a network of cracks and channels using an explosive perforator, the creation in the bottom-hole zone of the productive formation of an acid-destructive protective screen by injection of an acid-destructible solution under pressure, exceeding 10-15 % design cementing pressure, well fixing, destruction of the acid-degradable protective shield and its removal by acid treatment of the formation in droplet mode with periodic monitoring of the rate of pressure reduction, by a sharp decrease in which they judge the end of the processing operation (RF Patent No. 2225503, CL EV 43/11, publ. 2004.03.10).

The disadvantage of this method is that the acid-destroying protective shield penetrates into the formation to a greater depth and clogs not only high-permeability zones, but also low-permeability zones that open under high pressure, where it is not possible to remove it when injecting an acid solution under a typical treatment pressure. An acid-degradable protective shield reduces the permeability of the bottom-hole zone and, consequently, the productivity of the well.

The invention solves the problem of creating an insulating screen of the reservoir, easily removed during the development of the acid solution while maintaining the productivity of the well.

The problem is solved in that in the method of operating the well, including the injection of cement-chalk solution into the annulus, fixing the well and acid treatment, according to the invention, the injection of cement-chalk solution is carried out in volume and under pressure, ensuring minimal penetration of the cement-chalk solution into non-insulated productive layers, when attaching the well, put in the well a cement bridge made of classic cement cement opposite the lower highly accepting layer, and acid treatment with wire Yat uncovered cement bridge productive intervals of the formation.

The features of the invention are:

1. injection into the annulus of the cement-chalk solution;

2. well fastening;

3. acid treatment;

4. injection of cement-chalk solution in volume and under pressure, ensuring minimal penetration of cement-chalk solution in non-insulated productive formations;

5. installation in the well of a cement bridge made of classic cement cement opposite the lower highly receiving formation;

6. acid treatment of reservoir intervals not closed by a cement bridge.

Signs 1-3 are common with the prototype, signs 4-6 are the salient features of the invention.

SUMMARY OF THE INVENTION

When operating a well that has discovered a multilayer oil reservoir with formations of different injectivity, it becomes necessary to shut off some intervals of the reservoir, most often highly accepting, developed, absorbing, etc. The installation of a cement bridge leads to isolation of the interval, however, cement easily penetrates into the working intervals of the reservoir and reduces their productivity. The use of cement-chalk solution as an acid-degradable protective screen does not always allow maintaining the permeability of working intervals. The deep penetration of the cement-chalk solution into the reservoir leads to the impossibility of its destruction by acid treatment. Applicable grouting injection volumes are of the order of 1 m ^{3 /} pm. of the productive interval create a significant colmatized zone in the reservoir, which is not always possible to destroy by acid treatment.

The invention solves the problem of creating an insulating screen of the reservoir, easily removed during the development of the acid solution while maintaining the productivity of the well. The problem is solved as follows.

When operating a well that has uncovered a multilayer oil reservoir with formations of different injectivity, if necessary, disconnect the lower highly accepting formation, cement-chalk mortar is injected into the annulus (the space behind the casing string) and technological exposure for setting and hardening of the mortar. In this operation, the main thing is to create a cement-chalk ring in the near-borehole space. A side effect is the creation of a small layer (crust) of cement-chalk stone in the perforations of the upper productive intervals. The injection of cement-chalk solution is carried out in volume and under pressure, ensuring minimal penetration of the cement-chalk solution in the upper, non-insulated reservoir formations. Typically, the injection volume is calculated on the isolation of the lower highly receiving formation. The bottom of the tubing string is led to the roof or below the roof of the lower formation. The main part of the cement-chalk solution, which mainly enters the lower insulated reservoir, is pumped through the tubing string. Due to the circulation of fluid in the well, a small part of the cement-chalk solution enters the perforations of the upper intervals of the productive formations and sets and hardens in them. There is a complete isolation of the lower layer and isolation of perforations or a very small zone of the upper layers. The volume and pressure of the cement-chalk solution injection into the annulus of the well are selected experimentally on the basis of not only the creation of the cement-chalk ring in the annulus, but also of a very small partial colmatation of the perforation holes of the upper productive intervals. If any solidified cement-chalk solution remains in the wellbore, they are removed by drilling. After technological exposure for setting and hardening of the cement-chalk solution, a cement bridge made of classic cement cement is placed opposite the lower layer. Cement-chalk solution, penetrated into the perforations of the upper intervals of the productive formations, prevents the penetration of conventional cement slurry into these formations when setting up a cement bridge and, thereby, prevents the clogging of the upper formations. An acid treatment is carried out for the reservoir intervals not closed by the cement bridge. During acid treatment, the cement bridge is practically not destroyed, and a small crust of cement-chalk solution in the perforations of the upper layers is easily destroyed by acid. The permeability of the upper layers is maintained.

As a cement-chalk solution, use a solution with a volume ratio of cement and chalk as 1: (0.1-0.4).

Concrete example

They operate an injection well that has uncovered a multilayer oil reservoir with formations of different injectivity. The lower layer should be turned off as highly accepting and absorbing almost the entire volume of the working agent pumped into the well - water. A cement-chalk solution is injected into the annulus of the well with a cement to chalk ratio of 1: 0.3 in a volume of 2 m ³ and under pressure at the mouth of 6 MPa, which ensures a minimum penetration of the cement-chalk solution into non-insulated productive formations. The injection volume is calculated on the isolation of the lower highly receiving formation at the rate of 1 m ^{3 /} p.m. The bottom of the tubing string is led to the roof of the lower formation. Carry out technological exposure for setting and hardening of the cement-chalk solution. A cement bridge made of classic cement cement is placed opposite the lower layer. An acid treatment is carried out for the reservoir intervals not closed by the cement bridge. During acid treatment, the cement bridge is practically not destroyed, and a small crust of the cement-chalk solution is easily destroyed by acid. The permeability of the upper layers is maintained.

When performing operations on the prototype, the decrease in permeability and productivity of the well reaches 100%.

The application of the proposed method will solve the problem of creating an insulating screen of the reservoir, which is easily removed during the development of the acid solution while maintaining the well productivity.

Claims (1)

A method of operating a well, including injecting a cement-chalk solution into the annulus, fixing the well and acidizing, characterized in that the cement-chalk solution is injected into the annulus in volume and under pressure, creating a cement-chalk ring in the annulus and partial the mud of the perforation holes of the upper productive intervals, when fixing the well, put in the well a cement bridge of cement cement opposite the lower highly formation, and acid treatment is carried out not covered by a cement bridge of productive intervals of the formation, while a cement with a chalk-to-cement volume ratio of 1: (0.1-0.4) is used as a cement-chalk solution.