SU759704A1 - Borehole cementing method - Google Patents

Description

Union of Soviet

Socialist

Republics

USSR State Committee for Inventions and Discoveries

O P I S A N I E

Inventions

TO AUTHOR'S CERTIFICATE (61) Additional To author. certificate-wu - (22) Declared 22.08.78 (21) 2594534 / 22-03 with the addition of application No. - (23) Priority -

Published on August 30.80. Bulletin No. 32 Date of publication of the description 10.099.80 (P) (51) M. Cl. ³ Е 21 В 33/13 (53) UDC 622.245. .42 (088.8) (72) The inventors B.N. Isaev, A.A. Tsybin, A.A. Gaivoronsky and G.A. Pakhmurin

All-Union Order of the Red Banner of Labor (71) Applicant Research Institute of Drilling Equipment (54) METHOD OF CEMENTING SK & AZHIN

The invention relates to the field of well drilling, in particular to methods for cementing wells.

A known method of cementing wells by pumping cement slurry in portions with various additives that regulate the time of its setting in depth and reduce the permeability of cement stone in the annulus [1].

The disadvantages of the method are the low efficiency of isolation of zones with abnormally high reservoir pressures, characterized by gas and oil manifestations, as well as the complexity of the preparation and injection into the well of cement slurry with various additives.

Closest to the invention is a method of cementing wells by pumping cement slurry into the casing, pushing it into the annulus, leaving the glass in the column and creating pressure in the annulus when the grout hardens [2].

A disadvantage of the known method is the low reliability of preventing oil and gas manifestations due to non-optimal compensation of the loss of hydrostatic pressure of the cement slurry during its hardening.

The aim of the invention is to increase the reliability of preventing gas-oil-water manifestations by providing constant back pressure on the developing layers during the entire hardening of the cement slurry.

This goal is achieved by the fact that the pressure in the annulus at ¹⁰ hours of cementing of the grouting mortar is increased in steps in accordance with the drop in the hydrostatic pressure of the grouting column.

The method is carried out as follows, ₅ zom.

According to the calculation, cement slurry is pumped into the well in the normal mode of its punching. The last 100-150 m of grouting cement is pressed through with short-term (5-10 min) stops for 20 determining the beginning of setting of grouting grout. The cementing process is completed due to the impossibility of further selling, (increase in pressure on the aggregates without the availability of production 759704). At the same time, a cement cup is left in the casing.

Immediately after the completion of cementing, an annular pressure is created, the value of which is periodically increased in time in such a way that in _{5 the} pressure in the annular space on the gas-oil and water-producing strata does not change 'with a decrease in back pressure from the side of the cement slurry column due to its structure formation (setting ) Yu

After the time of the OZC, the pressure 'at the mouth of the annulus is relieved.

An example of the implementation of the proposed method.

In a field with abnormally high formation pressures, ¹⁵ wells with a depth of 2500 m are drilled under an intermediate casing with a diameter of 245 mm. In the process of drilling in the range of 1800-2000 m, formations with abnormally high pressures are opened, the density of the drilling fluid, on which _{20 a} well is drilled, is 2.20 g / cm ³ . The expected pressure in the range of the above formations is about 420 kgf / cm ² .

The well is cemented to the mouth with grouting mortar with a density of 2.25 g / cm ^3. Mixing of the solution is carried out on brine with a density of ^{25 with a} density of 1.18 g / cm ³ . The cementing process is controlled according to the RCC diagrams (cementing control station).

According to the proposed method in the final stage cementing pro- crush ₃₀ carried by one unit with stops for 5-10 min. With a sharp increase in pressure to 170-190 kgf / cm ² and the absence of flow rate of the squeezing fluid, according to the RCC data, the moment of coverage of the cement slurry is determined and the cementing process is completed 35.

After that, the preventer is closed, the discharge line of the unit is connected to the annulus and periodically at certain intervals increase the pressure in it.

The pressure created by the column of cement slurry, decreases in the first 40 minutes of the period of the WPC to the hydrostatic pressure created by the column of brine with a density of 1.18 g / cm ³ . Moreover, if in the first 10 minutes pressure is reduced by an amount corresponding to a decrease in the density of the solution by 0.320 g / cm ³ , then in the next 30 mts, the pressure decreases every 5 minutes by an amount corresponding to a decrease in the density of the solution by 0.125 g / cm ³ .

Therefore, so that the back pressure created by the column of cement slurry does not decrease on the developing strata in the interval 1800–2000 m, the annular pressure is increased periodically every 21 minutes every 5 minutes to 215 kgf / cm ² . Moreover, in the first 10 minutes the pressure is increased to 65 kgf / cm ² , and then every 5 minutes thereafter 25 kgf / cm ² .

The minimum value of pressure created in the annulus of the well to prevent manifestations after cementing should be equal to the difference between the expected reservoir pressure and the hydrostatic pressure created on the AVPD layers by a column of brine or water, therefore the pressure created in the annulus should be not less than = 185 kgf / cm ² . ,

Claims (1)

Claim A method of cementing wells by injecting grouting mortar into the casing and pushing it into the annulus with leaving the nozzle in the string and creating pressure in the annulus during solidification of the grout, characterized in that, in order to increase the reliability of preventing oil and gas occurrences by providing constant back pressure on the layers during the entire time of hardening of the cement slurry, the pressure in the annulus is increased in steps in accordance with by the hydrostatic pressure of the column of cement slurry.