RU2320856C1 - Injection well operation method - Google Patents

Abstract

FIELD: oil industry, particularly to operate injection wells.

SUBSTANCE: method involves insulating lower reservoir having high injectivity by installing cement-and-chalk bridge within interval of lower reservoir having high injectivity along with cement-and-chalk mix injection in said interval under pressure within time period enough for partial cement-and-chalk mix penetration in well zone through design depth; performing time-delay for cement-and-chalk mix setting and hardening; operating upper reservoirs after lower reservoir isolation by injecting working agent, namely water, therein. For secondary operation of lower reservoir having high-injectivity acid bath is arranged in well for cement-and-chalk bridge damage. Then new casing pipe having lesser diameter is lowered in well and cement mix is injected in space between old and new casing pipes. After that technological time-delay is carried out for cement mix setting and hardening and both casing pipes are perforated within productive interval reservoir for depth exceeding design depth of partial cement-and-chalk mix penetration into well zone.

EFFECT: possibility to keep producing ability of well.

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Description

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

A known method of completing oil and gas wells, including the formation in the reservoir of a network of cracks and channels using an explosive perforator, the creation in the bottomhole zone of the productive formation of an acid-destructible protective screen by injection of an acid-destructible solution under a pressure 10-15% higher than the calculated cementing pressure, well fixing, destruction of the acid-degradable protective shield and its removal by acid treatment of the formation in a hydro-pulse mode with periodic monitoring of the rate of decrease in pressure I, for a dramatic reduction which is judged on the end of the processing operation (RF patent №2225503, Cl. E 21 B 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.

Closest to the proposed invention in technical essence is a 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 cement bridge setting site and an acid solution is pumped until the cement bridge is destroyed (RF Patent No. 2164588, CL ЕВВ 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. Cement-chalk solution penetrates into the formation to a great depth and clogs the bottom-hole zone of the formation, reducing the productivity of the well.

The invention solves the problem of maintaining well productivity.

The problem is solved in that in a method of operating an injection well, which includes lowering a new casing of a smaller diameter, injecting a solution into the space between the old and new casing, installing a cement-chalk bridge, destroying the cement-chalk bridge with an acid solution, according to the invention, when isolating the lower highly accepting the formation, the cement-chalk bridge is installed in the interval of the lower highly accepting formation with the injection of the cement-chalk solution in the specified interval under pressure and during time, providing a partial flow of cement-chalk solution into the near-wellbore zone to the calculated depth, the upper layers are exploited, an acid bath is drilled in the well for re-operation of the lower highly-receiving formation, a cement-chalk bridge is drilled, a new casing string of a smaller diameter is launched, pumped into the space between old and new casing cement mortar and perforate both casing strings in the interval of the reservoir to a depth exceeding the calculated depth partial receipt at the cement-Cretaceous solution in the near-wellbore zone.

The features of the invention are:

1) the launch of a new casing of a smaller diameter;

2) injection into the space between the old and new casing strings of the solution;

3) installation of a cement-chalk bridge;

4) destruction of the cement-chalk bridge with an acid solution;

5) when isolating the lower highly accepting formation, the installation of a cement-chalk bridge in the interval of the lower highly-accepting formation with the injection of cement-chalk solution into the specified interval under pressure and for a time, providing a partial flow of cement-chalk solution to the near-wellbore zone at the estimated depth;

6) the operation of the upper layers;

7) for re-operation of the lower highly-receiving formation, the implementation of an acid bath in the well;

8) drilling a cement-chalk bridge;

9) launching a new smaller diameter casing;

10) injection into the space between the old and new casing strings of cement;

11) perforation of both casing strings in the interval of the reservoir to a depth exceeding the estimated depth of the partial flow of cement-chalk solution into the near-wellbore zone.

Signs 1-4 are common with the prototype, signs 5-11 are the essential distinguishing features of the invention.

SUMMARY OF THE INVENTION

During the operation of a well that has discovered a multilayer oil reservoir with formations of different injectivity, there is a need to temporarily shut off some intervals of the reservoir, most often highly accepting, developed, absorbing, etc. When connecting such intervals, it becomes necessary to install a new casing in the well. In such works, the bottomhole zone of the well is inevitably mated, and its injectivity is reduced. 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 maintaining well productivity. The problem is solved as follows.

During the operation of the injection well, the lower highly-receiving formation is isolated. To do this, install the cement-chalk bridge in the interval of the lower highly accepting formation with the injection of cement-chalk solution into the specified interval under pressure and for a time, providing a partial flow of the cement-chalk solution into the near-wellbore zone at the calculated depth.

According to the calculation, R is set - the depth of the cement-chalk solution flow into the near-wellbore zone, which should be no more than the depth of the future perforation. The volume of the near-wellbore zone V is determined by the product of the area πR ² by the height h of the near-wellbore zone

V = πR ² h,

where V is the volume of the near-wellbore zone, m ³ ;

R - the depth of the cement-chalk solution in the near-wellbore zone, m;

h is the height of the near-wellbore zone, m;

π = 3.14.

The volume of crushed cement-chalk solution V _ce , m ³ is defined as the product of the volume of the near-wellbore zone and porosity

V _ce = V m,

m - porosity of the reservoir in the near-wellbore zone, d.

Delivering cement-chalky solution in the lower reservoir interval and is forced into the borehole zone in a volume V _CEM. Carry out technological exposure for setting and hardening of the cement-chalk solution. After isolation of the lower highly accepting layer, the upper layers are exploited by pumping a working agent (water) into them.

For re-exploitation of the lower highly-receiving formation, an acid bath is created in the borehole to destroy the cement-chalk bridge, a cement-chalk bridge is drilled, a new casing string of smaller diameter is launched, cement mortar is pumped into the space between the old and new casing strings, technological exposure is carried out for setting and hardening of cement mortar and perforate both casing strings in the interval of the productive formation to a depth exceeding the estimated depth of the partial supply of c element-chalk solution in the near-wellbore zone. If necessary, acid treatment of the perforated interval is carried out.

The ratio of cement and chalk in the cement-chalk solution is 1: (0.1-0.4).

The presence of a small crust of cement-chalk stone in the near-wellbore zone prevents cement from entering the near-wellbore zone when attaching a new casing string, and the shallow depth of the crust allows restoration of permeability during perforation or acid treatment.

Concrete example

They operate an injection well that has uncovered a multilayer oil reservoir. The lower layer with a thickness of h = 2 m and a porosity of 0.2 should be turned off as highly accepting and absorbing almost the entire volume of the working agent pumped into the well - water. Isolate the lower highly reservoir. To do this, install the cement-chalk bridge in the interval of the lower highly accepting formation with the injection of cement-chalk solution into the specified interval under pressure and for a time, providing a partial flow of the cement-chalk solution into the near-wellbore zone at the calculated depth. The ratio of cement to chalk in cement-chalk solution is 1: 0.3. Set the depth of the cement-chalk solution in the near-well zone R, which should be 0.2 m. From the formula

V = πR ² h

find

V = 3.14 · 0.2 ² · 2 = 0.25 m ³ .

Hence, the amount of crushing of cement-Cretaceous solution V _CEM, m ³ is defined as the product of the volume of the near-wellbore area and porosity

V _ce = V m = 0.25 · 0.2 = 0.05 m ³ .

The cement-chalk solution is delivered to the interval of the lower layer and forced into the near-well zone in the volume of 0.05 m ³ . Carry out technological exposure for setting and hardening of the cement-chalk solution. After isolation of the lower highly accepting layer, the upper layers are exploited by pumping a working agent (water) into them.

For re-exploitation of the lower highly-receiving formation, an acid bath is created in the borehole to destroy the cement-chalk bridge, a cement-chalk bridge is drilled, a new casing string of smaller diameter is launched, cement mortar is pumped into the space between the old and new casing strings, technological exposure is carried out for setting and hardening of cement mortar and perforate both casing strings in the interval of the productive formation to a depth exceeding the estimated depth of the partial supply of c element-chalk solution in the near-wellbore zone. Cumulative perforation with a perforation depth of 0.6 m is used. If necessary, acid treatment of the perforated interval is carried out.

The presence of a small crust of cement-chalk stone in the near-wellbore zone prevents cement from entering the near-wellbore zone when attaching a new casing string, and the shallow depth of the crust allows restoration of permeability during perforation or acid treatment.

Claims (1)

A method of operating an injection well, including lowering a new casing of a smaller diameter, injecting a solution into the space between the old and new casing, installing a cement-chalk bridge, destroying the cement-chalk bridge with an acid solution, characterized in that the cement is installed during isolation of the lower highly-receiving formation Cretaceous bridge in the interval of the lower highly accepting formation with the injection of cement-chalk solution in the specified interval under pressure and for a time providing the flow of cement-chalk solution into the near-wellbore zone to the calculated depth, the upper layers are exploited, an acid bath is drilled in the well for re-exploitation of the lower highly-receiving formation, a cement-chalk bridge is drilled, a new casing string of a smaller diameter is lowered, pumped into the space between the old and new casing cement mortar and perforate both casing strings in the interval of the reservoir to a depth exceeding the estimated depth of the partial inflow of c element-chalk solution in the near-wellbore zone.