RU2307145C1 - Method for controlling hardening speed of cement solutions - Google Patents

Abstract

FIELD: oil and gas industry, in particular, cementation materials used during reinforcement of oil and gas wells.

SUBSTANCE: for controlling solidification of cementing solutions, solidification accelerator is injected into dry cement, placed in protective cover, with dissolves during hydration of clinker minerals of cement.

EFFECT: prevented premature solidification of cementing solution, shorter time between end of cementing operation and solidification of solution, prevented complications during cementing.

1 tbl, 5 ex

Description

The invention relates to the oil and gas industry, specifically to cement grouting materials used in the fastening of oil and gas wells.

For fastening oil and gas wells, the most effective material is cement Portland cement, which, when mixed with water, forms a cement grout, which is pumped into the well and, after hardening, turns into cement stone.

The most significant drawback of cement, as a grouting material, is the difficulty of regulating its hardening rate. A suspension of cement in water, forming a cement slurry, has a setting time of 4 to 10 hours [1]. Moreover, in the cement slurry, which is at rest in the well for 2-6 hours, sedimentation processes occur that lead to the formation of fluid-conducting channels in the forming cement stone [2]. It was during this period that the wells most often experienced complications in the form of annular gas and oil manifestations, often turning into open fountains [3].

The regulation of cement hardening using reagents of hardening accelerators [4], introduced into the mixing fluid or into dry Portland cement, leads to premature thickening of the cement slurry and complications during cementing of wells [5].

Therefore, it is necessary to minimize the time between the end of the cementing operation and the hardening of the solution with its transformation into a cement stone.

The closest technical solution to the proposed method is a method for controlling the hardening of cement mortars by adding additives to dry cement cement [6].

The disadvantage of this method is the low efficiency of the use of hardening reagents-regulators (accelerators), leading to premature thickening of the cement slurry and, as a result, to the occurrence of complications.

The technical task of the present invention is the ability to eliminate these disadvantages.

This problem is solved by the fact that in the method of regulating the hardening of cement grouting mortar by introducing a hardening accelerator into dry cement, a hardening accelerator is used, which is placed in a protective shell that dissolves during hydration of clinker cement minerals.

Thus, in the present invention, a new technology for introducing additives into the grouting composition is used, which gives grounds to assert that the proposed solution meets the criterion of "novelty."

The invention consists in the following. The additive of the hardening accelerator is placed in a special shell, which dissolves at a given speed in an alkaline medium formed during the hydration of clinker cement minerals. The dissolution rate is set due to a certain thickness and composition of the protective layer, selected taking into account the pH of the medium, temperature in the well and the duration of the cementing process. Thus obtained additive is introduced in the estimated amount into dry cement, which is closed in a liquid and pumped into the well. Since cement does not come into contact with the addition of a hardening accelerator during the injection and sale of grouting mortar due to the protective sheath, the properties of the mortar do not change at this stage of the cementing process, which eliminates the complications of this operation. At the same time, hydration and structure formation processes proceed at the usual rate. In the process of pumping and pouring cement grout into the well, the shell dissolves in the alkali solution formed by hydration of clinker cement minerals, and therefore the additive begins to react with cement only after the cement slurry is delivered to the desired location in the well. In this case, the cement mortar quickly hardens.

In the scientific and technical literature, the use of drugs enclosed in soluble shells is known. As a rule, these are water- or acid-soluble shells. However, it is not known from the scientific and technical literature the use of soluble alkaline additives to control the rate of hardening of cement slurries used in well fixing.

This indicates the compliance of the invention with the criterion of "inventive step".

An example implementation of the method.

It is necessary to prepare a cement grout for cementing wells, and the duration of the operation is 3 hours.

Example 1. A grouting mortar prepared from grouting portland cement PCT-1-50 with a water-cement ratio (W / C) of 0.5 at a temperature of 22 ° C had the properties shown in the table (experiment No. 1).

Example 2. As an additive to the hardening accelerator, water-soluble sodium silicate (water glass) was used in an amount of 2%, which was previously dissolved in a mixing liquid (fresh water).

The resulting cement slurry had the indicators shown in the table (experiment No. 2).

Example 3. In accordance with the proposed method, liquid glass was placed in a shell of alkali-soluble glass, and the dissolution time of the shell was 3 hours, which was necessary for the preparation, injection and delivery of cement into the well. The resulting additive, a hardening accelerator, was added to dry cement, and the resulting mixture was sealed with water.

Thus obtained cement slurry had the indicators shown in the table (experiment No. 3).

Thus, the time between the end of the cementing process and the beginning of setting of the cement slurry was 30 minutes, whereas in experiment 1 this time was 4 hours 45 minutes.

The introduction of accelerator additives according to the prototype (experiment 2) led to the formation of a non-pumpable cement slurry that cannot be used for cementing wells.

Example 4. It is necessary to prepare a cement grout for cementing wells, and the duration of the operation is 3 hours, the temperature in the well 50 ° C.

As an additive to the hardening accelerator, calcium chloride was used in an amount of 8%, which was previously mixed with dry cement, and the resulting mixture was closed with fresh water. The resulting cement slurry had the indicators shown in the table (experiment No. 4).

Example 5. A solution was prepared for the same conditions as example 4.

In accordance with the proposed method, calcium chloride was placed in an alkali-soluble shell (carbonized water glass), and the dissolution time of the shell was, as in the previous example, 3 hours. The resulting curing accelerator additive was added to dry cement, and the resulting mixture was sealed with water.

The prepared cement slurry had the indicators shown in the table (experiment No. 5). Thus, the time between the end of the cementing process and the beginning of setting of the cement slurry was 45 minutes.

The introduction of the accelerator additive in cement according to the prototype (experiment 4) led to an acceleration of hardening and a reduction in pumpability, which was less than the duration of the cementing operation, i.e. obtaining cement grout, which cannot be used for cementing a well under given conditions.

By reducing the amount of additive for a given condition, you can prepare a solution with pumpability, the same as the solution prepared by the present method (3 hours 20 minutes), see table (experiment 6).

The table shows that in experiment 6, the time between the end of the cementing operation and the beginning of setting of the mortar was 1 hour 35 minutes, whereas in the proposed method only 40 minutes

In all cement grouting mortars prepared according to the proposed method, the time between the end of cementing and the beginning of setting of the cement slurry is reduced. It is this time period that is the most dangerous from the point of view of the occurrence of oil and gas manifestations and the formation of channels in the hardening cement grouting mortar. The specified example of the implementation of the method shows the compliance of the invention with the criterion of "industrial applicability".

Information sources

1. GOST 1581-96.

2. Gas manifestations in wells and the fight against them / A.I. Bulatov, V. I. Ryabchenko, I. A. Sibirko, N. A. Sidorov. - M: Nedra, 1969.

3. Malevanskiy V.D. Open gas fountains and the fight against them. - M .: Gostoptekhizdat, 1963 .-- 212 p.

4. Danyushevsky B.C., Aliyev P.M., Tolstykh I.F. Reference guide for cementing materials. - 2nd ed. M .: Nedra, 1987. p. 156.

5. Soloviev EM Well completion. M., Nedra, 1979.

6. Danyushevsky B.C., Aliyev P.M., Tolstykh I.F. Reference guide for cementing materials. - 2nd ed. M .: Nedra, 1987. p. 204.

Table Experience number Additive % Additive input method Temperature ° C Spreadability, cm after mixing, hour Setting time, h-min Pumpability of solution, h-min 0 one 2 2,5 3 Start end one Without additives - - 22 24 7-45 9-30 6-05 2 Liquid glass 2.0 Prototype 22 12 2-15 3-10 Not pumped 3 Liquid glass 2.0 According to the proposed method 22 24 22 19 eighteen 17 3-30 4-10 3-15 four Calcium chloride 8.0 Prototype fifty 25 twenty 16 fourteen 12 3-05 4-20 2-30 5 Calcium chloride 8.0 According to the proposed method fifty 24 21 twenty 19 17 3-40 4-30 3-20 6 Calcium chloride 3.0 Prototype fifty 25 23 21 19 eighteen 4-35 5-20 3-25

Claims (1)

A method of regulating the hardening of cement grouting mortars by introducing a hardening accelerator into dry cement, characterized in that they use a hardening accelerator placed in a protective shell that dissolves during hydration of clinker cement minerals.