SU1479620A1 - Method of cementing casings - Google Patents

Abstract

The invention relates to the drilling of wells. used in their cementing. The goal is to improve the quality of cementing the lower part of the casing, while reducing the time for its cementing. Buffer fluid, cement mortar, squeezing fluid is pumped in, then cement mortar is forced into the annulus, leaving a portion of the cement slurry in the bottom of the casing. After that, the last one is supplied with a retarder setting the cement mortar, which is placed in destructible containers. Non-adherent cement slurry is washed out through specially drained casting pipes. The method permits the deliberately inflated volumes of cement mortar to remain in the column, which eliminates the likelihood of overstocking of the cement slurry behind the casing.

Description

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

The aim of the invention is to improve the quality of cementing the lower part of the casing while reducing the time for its cementing.

The method is carried out as follows.

Conducting preparatory and final works for cementing, then proceed with cementing itself. In this case, a buffer fluid, a cement slurry, a squeeze fluid is pumped. Then, the cement slurry is pushed into the annulus. At the same time, a portion of the cement slurry is left in the bottom of the casing.

After all the operations have been completed, the flow area of the casing is restored.

Additionally, after the cement slurry is pumped, the retarder is set in the lower part of the casing to set the cement slurry, which is placed in destructible containers. At the same time, the restoration of the casing through passage section is carried out by washing out the cement slurry.

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The essence of the method lies in the fact that, when cementing casing strings without cementing plugs, there is a potential danger of either leaving a large volume of cement slurry in the casing, which requires long-term costs of drilling the cement stone which reduces the tightness of the column space.

Using this method, a cementing scheme can be adopted, leaving in the column a deliberately overestimated amount of cement mortar, eliminating the entire likelihood of selling the cement slurry behind the casing. But even with such a cementing scheme, the time spent on restoring the casing casing section is minimal, since it involves the removal of only the liquid phase (drilling is excluded).

Sugar, dextrin, carboxymethylcellulose, tartaric, boric and nitrilotrimethylphosphonic acid can be used as chemical reagents (cement retarders).

Destructible containers, which are high-pressure vessels, can be delivered to the bottom by dropping into pipes, where they will be moved by gravity or lowered on the logging cable. Then, the displacement of the chemical agent from the container or its destruction can be carried out with the help of an explosion, and the mixing of the chemical agent with the cement mortar through the translational movements of the cable. The shape of the container and its dimensions and materials for manufacture may vary.

When dextrin chips were added to a clean cement solution in a volume of 0.2%, the setting time was increased to 30-36 hours, and when 0.2% nitrilotrimethylphosphonic acid was introduced into the solution, it did not thicken and after 72 hours it was enough for priming well (tubing) and scrubbing loose cement slurry.

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Example. A stepped column of 146 mm is lowered into a well with a depth of 2500 m. The Stop ring is located at a depth of 2490 m. According to the plan, leave a Stop cemented glass 25 m high (volume 0,012, 3 m) above the Stop ring. Nitrilotrimethylphosphonic acid is used as a moderator.

Entering 0.2% acid by volume is sufficient to slow down the setting of the cement slurry. Then the required volume of acid is 0.3 0.002 0.0006 m (0.6 l). The volume is increased to 1 l and, for a larger volume, the acid is diluted with water to 3 l and placed in degradable containers (paraffin capsules). In a perforated .pigugunnuyu pipe with a diameter of 73 mm, with a die, capsules are placed and thrown into the well. When the intake is reached, the paraffin melts, the tightness of the capsules is broken, the acid leaves the container and, because it is lighter than the solution, it floats. In this case, the cement slurry will be mixed with the retarder. Bubbling will also contribute to paraffin surfacing. Thus, mixing the cement slurry with the retarder will be provided.

Claims (1)

Invention Formula A method of cementing casing strings, which includes pumping buffer fluid, cement slurry, flushing fluid, pushing cement slurry into the annulus, leaving a portion of the cement slurry in the bottom of the casing and restoring the casing through passage, characterized in improving the quality of cementing the lower part of the casing while reducing the time for its cementing, after dispatching the cement slurry is served in the lower part of the casing 3 The cement slurry setting block, which is placed in destructible containers, and the restoration of the casing flow section is carried out by washing out the cement slurry.