RU2170333C1 - Process correcting defects of casing strings - Google Patents

Abstract

FIELD: oil and gas production industry. SUBSTANCE: process can also be employed to conduct insulation operations during hole drilling under conditions of intensive water manifestation and absorption. Technical objective of invention lies in increased reliability of insulation while correcting lack of tightness of casing string in intervals of well located above productive zone, in enhanced quality of grouting thanks to increase of amount of cement mortar pumped beyond casing string and in maintenance of productivity of well. Process correcting defects of casing strings consists in pumping of aqueous solution containing calcium chloride, cement mortar into well through tubing string. Packer-plug is installed below defects of casing strings before pumping, then 10-15% solution of calcium chloride, water, 15-50% solution of potassium or sodium naphthenate or their mixture, water are pumped through tubing string in sequence in amount of 0.5-5.0 cu m per running meter of defects in cement mortar with water-to-cement ratio 0.5-0.8 with addition of 20-50-% of volume of cement mortar of 20-50% sodium or potassium naphthenate or their mixture with subsequent forcing of entire mass with stratal water into well at rate of 1.0-2.0 cu m per 1.0 m of thickness of pool till technological screen is formed. EFFECT: increased reliability of insulation while correcting lack of tightness of casing string.

Description

 The invention relates to the oil and gas industry, in particular, it can be used to eliminate defects in casing strings, as well as for conducting insulation work while drilling a well in conditions of intense water development and absorption.

 A known method of restoring the tightness of the casing string [1]. The essence of the method is as follows: the insulating composition is pumped into the annulus of the well, and before the insulating composition is pumped into the leak, it is aerated in the wellbore by cyclically changing the gas flow through the insulating composition by periodically opening and closing the annulus. Then the insulating composition is pumped into the casing leakage point, for which the annular space is opened to a free exit, creating a pressure differential across the production casing. The presence of a gaseous phase in the sealing composition increases its mobility. This ensures its penetration into the most minor violations. After the cessation of the flow of gas or liquid from the annulus, the sealant is removed from the well.

 This method allows to eliminate annular space leakage, but it is ineffective when used in fractured reservoirs and formations composed of weakly cemented sandstones and having extremely high permeability.

A known method of repairing microholes in a cement stone of a well [2]. The method consists in sealing a hole in a cement stone, filling the annular gap between the casing and the wall of the well, determine the location of the hole. At this point, the casing is perforated and the cavity is insulated around the hole. The required amount of cement slurry is injected into this cavity through the perforated section of the casing to form a hard cement plug in the specified hole after hardening. The injected solution is an aqueous mixture taken in a ratio of about 0.5-5 l / kg cement. The particle size of the cement should not exceed 30 microns, and the fineness of the grinding should not be less than 6,000 cm ² / g The cement used refers to Portland cement or slag Portland cement.

 The disadvantages of this method are the low reliability of the insulation and leakage of the casing, since there is mixing of the cement mortar and squeezing fluid.

 A known method of repair work in a production well [3]. The essence of this method is to pump a viscoelastic composition and cement mortar into the well through a tubing (tubing). This process is carried out with open annular space of the well. The viscoelastic composition is located below the lower boundary of the casing leakage. Before the injection of the cement solution, the tubing string is raised to locate its end at the level of casing leakage. After injection, the tubing string also rises above the upper boundary of the cement mortar. Before pumping cement mortar do technological exposure. Then pumping fluid is pumped with a closed annular space of the well. The amount of this liquid is equal to one and a half times the volume of the part of the tubing string in the cement solution.

 This method allows to reduce the consumption of cement mortar and to increase the reliability of insulation while eliminating leaks in the casing in the intervals of the production well located above the productive zone. However, this technical solution does not allow to fully carry out the sealing of production casing in the interval of occurrence of aquifers.

 The closest analogue is the "Method of restoring the tightness of production casing" [4], ie elimination of casing string defects, which consists in injecting liquid glass and an aqueous solution of calcium chloride into the leakage interval of the production casing strings; these reagents are injected simultaneously separately, then a blocking rim is created by Product 119-204 with subsequent cement cement fixation.

 However, this method has a very high consumption of components and has insufficient reliability of the resulting insulation.

 The technical result is to increase the reliability of isolation during the elimination of leaks in the casing string in the intervals of the well located above the productive zone, to improve the quality of cementing by increasing the amount of cement solution injected behind the casing string, and to preserve the productivity of the well.

The technical result is achieved by the fact that in the method of eliminating defects in the casing strings, which consists in pumping a tubing of calcium chloride, an cement solution through a tubing tubing into the well, a packer plug or any other current pipe is installed below the casing defects in the well before pumping slaughter, then 10–15% solution of calcium chloride, water, 15–50% solution of sodium or potassium naphthenate, or mixtures thereof, water, 0.5-5 m ³ per 1 meter of solution defects are pumped sequentially through the tubing cement with a water-cement ratio of 0.5-0.8 with the addition of 20-50% of the volume of the cement solution of 20-50% sodium or potassium naphthenate, or a mixture thereof, followed by forcing the entire mass into the well with produced water at a rate of 1-2 m ³ at 1 m of reservoir power before creating a technological screen.

Percentage of main components:
10-15% calcium chloride solution,
10-50% solution of sodium or potassium naphthenate, or mixtures thereof.

 The method is as follows.

The well was cleaned to the bottom by flushing, then the 2PD-YAG packer was lowered onto the tubing and installed it 50-150 m above the casing string defects. We checked the tightness of its installation. The injectivity of the reservoir was determined. If there is a throttle response within the pressure range that allows the process to be carried out (P _max <0.8 P formation fracture), an impermeable layer is started.

The reagents were injected into the well according to the following scheme: initially, 2 m ^{3 of} 15% CaCl ₂ was pumped, then 0.5 m ^{3 of} water, followed by 2 m ^{3 of a} 4% sodium naphthenate solution, then again 0.5 m ^{3 of} water. This procedure was repeated at least three times, after which cement mortar (water-cement ratio 0.5), closed in water, was pumped in a volume of 0.5-2 m ³ per linear meter, specific gravity 1.82 g / cm ² with the addition of 20% - of sodium naphthenate and the whole mass was pushed into the well with produced water at the rate of 2 m ³ per 1 m of the formation capacity so that a cement cup of 30 m remained above the filter zone. Then the packer was raised to a height of 50-100 m, the well and the well were washed the wells were sealed, and then kept under pressure for 24 hours to harden clogging mass. Then the column was compressed. After the expiration of the time, the OZZ drilled the beaker to the required interval and the column was pressed again.

Sources of information
1. USSR author's certificate 1624127, E 21 В 33/13, 03/29/1991

 2. 2. U.S. Patent 5127473, E 21 B 33/13, 07/07/1992.

 3. RF patent "Method for repair work in a production well" RU N 212155901, 6 E 21 В 33/13, 02.22.1999, Mamedov B.A., Zazirny D.V., King P.V.

 4. RF patent "Method for restoring the tightness of production casing" RU N 2116432 C1, E 21 V 33/13, 11/20/1998 Komarov A.A., Bodryagin A.V. , Levitsky A.V., Levitsky V.I., Gashev A.A., Nikolaev A.Yu.

Claims (1)

A method for eliminating defects in casing strings, which involves pumping a tubing of tubing into a well of an aqueous solution containing calcium chloride, a cement mortar, characterized in that a packer plug or any other current bottom hole is installed below the casing stain defects before being pumped into the well 10–15% solution of calcium chloride, water, a 15–50% solution of sodium naphthenate, or potassium, or a mixture thereof, water, 0.5–5 m ³ per 1 meter of cement mortar defects are pumped sequentially through the tubing water-cement ratio 0.5-0.8 with the addition of 20-50% of the cement volume of 20-50% sodium or potassium naphthenate, or a mixture thereof, followed by forcing the entire mass into the well with produced water at a rate of 1-2 m ³ per 1 m of formation power before creating a technological screen.