SU1609967A1 - Plugging composition - Google Patents

Abstract

The invention relates to drilling. The purpose of the invention is to increase the insulating properties by reducing blurriness while maintaining the setting time. The composition contains components in the ratio, parts by weight: Portland cement 100

polyacrylamide 0.05-0.15

potassium chromate or bichromate 0.2-0.5

water 53.29-59.85. The composition is prepared by mixing the cement with an aqueous solution of polyacrylamide, then an aqueous solution of chromate is added. The composition has an initial plastic strength of 2.2-4.8 kPa, which is maintained at the same level for a long time, then increases dramatically. The composition can be used to isolate zones of absorption and water inflow at great depths at 40-100 ° C. 1 tab.

Description

The invention relates to the drilling of wells and can be used in the oil and gas industry and mining to isolate zones of intensive water flows and acquisitions.

The purpose of the invention is to increase the insulating properties by reducing erosion while maintaining the setting time.

The cement composition contains Portland cement, polyacrylamide, potassium chromate or dichromate and water in the following ratio of components, wt.h .:

Portland Cement100

Polyacrylamide 0.05-0.15

Potassium chromate or bichromate 0.2-0.5

Water53.29-59.85

The interaction of cement with a solution of potassium chromate or dichromate followed by the addition of polyacrylamide at the indicated ratios ensures high

insulating and structural-mechanical properties at the time of setting necessary for carrying out technological operations for isolating the zones of interstates, water inflows, and absorption at great depths.

The mechanism of paste formation can be explained by the formation of new stable bonds between polyacrylamide molecules and the products of cementation cementation. Crystals of complex salts, forming the EU in the interaction of cement and chromates, contribute to the strengthened / zo structure.

It has been established experimentally that a composition having a plastic strength of 0.2 kPa is eroded by water; with a plastic strength of 6.4 kPa, the composition is not pumped through the pipes.

The above composition has an initial plastic strength of 2.2-4.8 kPa, which, due to the introduction of potassium dichromate (chromate) for a long time

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kept on par. This allows the solution to be pumped to a predetermined depth, after which a sharp increase in the plane strength occurs and a seizure of the solution occurs.

Example. The preparation of the cement composition in the laboratory,

The following substances were used to obtain the composition: cement (portland cement) cement for elevated temperatures (PCT); polyacrylamide (white powder); potassium chromate (yellow powder): potassium bichromate (orange powder): tap water with a total hardness of 5-6 mg-eq / l.

First, a 1.5% aqueous solution of polyacrylamide was prepared in a separate container. To do this, in 3.29-9.85 ml of water at 40-60 ° C, 0.05-0.15 g of dry polyacrylamide was dissolved (the powder was poured into the water gradually, with constant stirring).

A solution of a salt of chromic or two-chromic acid was prepared in another container, for which 0; 2-0.5 g of salt was dissolved in 50 ml of water. On the resulting salt solution, cement was closed (at the rate of 1W g of cement per 50 ml of water) and a previously prepared 1.5% polyacrylamide solution was added to it. Then the whole mixture was stirred with a laboratory stirrer for 1 min at a speed of 90–100 rpm, as a result of which an insulating composition was obtained,

During laboratory tests, the structural and mechanical properties of the resulting composition were determined, namely: spreadability, thickness, plastic strength, washability, setting time.

Under production conditions, the composition is obtained in the following manner.

In the measuring section of one cementing unit, a 1.5% polyacrylamide solution is prepared according to the calculation; in the measurement section of another unit, an aqueous solution of potassium chromate (dichromate) is used at the rate of 0.2-0.5% of salt and 50% of water of the required weight. cement. The cement is then shut in an aqueous solution of chromate at a water-cement ratio of 0.5. The resulting cement slurry is pumped into pipes. In parallel, another unit serves 1.5% polyacrylamide solution prepared previously. When mixing solutions in drill pipes, a composition is obtained which is forced into the absorption zone. Data on the properties of the cement composition are given in the table.

Experimental data indicate that the content of polyacrylamide in the cement composition in an amount of from 0.05 to 0.15 May, h. gives the composition a high structural-mechanical properties (experiments 3-12 tabl). A further increase in the content of polyacrylamide entails an increase in the amount of water and the composition loses the necessary structural and mechanical properties (Table 13-15 experiments). A decrease in the content of polyacrylamide with a minimum content of chromates also leads to a decrease in the structural and mechanical properties of the composition, increasing blurring.

Optimum up to; for the polymer, above which the deterioration of the structure formation process begins, depends little on the amount of chromate (Tables 7–9), but with other doses of polymer, the content of chromates affects not only the setting time (Experiments 4 and 5, 10-12 tab.). A significant increase in chromates (experiments 15, 16 tab.) Does not achieve the goal. The addition of chromates in small doses from 0.2 to 0.5 parts per hour. acts as a time delay setting. An increase in the setting time is not always proportional to an increase in the dose of 5 chromate (experiments 4 and 5, 7–9, 10 and 11, 15 and 16 tabl.).

The water content in the cement composition exceeds the traditional by 20-30%. Due to this, a slight decrease in the strength of cement stone is possible,

The density of the cement composition during the tests had a value in the range of 1670-1730 kg / m.

The setting time of the composition is within 5 limits, h-min:

The beginning of the setting is 3-20 - 5-00. The temperature limits for the use of the composition are due, on the one hand, to a long setting time (at t 40 ° C) and, on the other hand, to a decrease in the effectiveness of polyacrylamide (at t 100 ° C).

The use of cement composition 5 allows to qualitatively eliminate the intensive water inflows and removals in large porous fractured rocks when drilling deep and ultra-deep wells in the temperature range of 40-100 ° C,

Claims (1)

Claims of the cement composition comprising Portland cement, polyacrylamide, chromate 55 or potassium bichromate and water, characterized in that, in order to increase the insulating properties by reducing the erosion while maintaining the setting time, it contains the components in the following ratio, May. including: Portland Cement Polyacrylamide 100 0.05-0.15 Potassium chromate or bichromate 0.2-0.5 Water53.29-59.85 Composition and properties of cement slurry Table continuation