RU2184212C2 - Process of pressure grouting of wells - Google Patents

Abstract

FIELD: hole drilling, pressure grouting of casing string. SUBSTANCE: hole in clay roof is completed. Sump of smaller diameter is made. Casing string with shoe is run into hole. Shoe is fitted with container carrying reagent-cement mortar setting accelerator. Shoe is placed above sump before pressure grouting. Cement mortar is injected. It is injected in portions having different time of setting. Finish of setting of one portion is start of setting of next portion. Separator and forcing fluid are injected till "stop" pressure is achieved. Casing string is forced into sump. Container is open. Reagent-cement mortar setting accelerator is injected into portion of cement mortar in zone of shoe. Process secures tightness of hole clearance and insulation of pools up to well-head, if necessary. EFFECT: higher efficiency of process. 1 cl

Description

 The present invention relates to the field of well drilling, and more specifically to the fastening of wells, in particular to methods of cementing a casing string.

 A known method of cementing wells, including the installation of hydraulic packers in the annulus [1, 2].

 However, due to cavern formation, pressure reduction in the sealing sleeve, ledges and bends of the wellbore, it is not possible to achieve tightness of the annulus with the packer (the success rate does not exceed 70%).

 A known method of cementing wells, including lowering the casing without bearing on the bottom, pumping a spacer, cement slurry, squeezing fluid until a stop signal is received, leaving the well for the period of setting and hardening of cement stone [3].

 The disadvantage of this method is that in the presence of such unavoidable factors as mixing zones, incomplete replacement of the drilling fluid with cement, etc., the tightness of the annulus with the appearance of overflows, pressures in the annulus is not ensured.

 The closest in technical essence and the achieved result is a method of cementing wells, including completion of a well in a clay roof with a smaller diameter with a sump, lowering the casing with a shoe into the well, crushing the shoe into the sump by 1.5-2 m [4].

 The disadvantage of this method is the low height of the grouting and the inability to isolate overlying formations. All this does not ensure the tightness of the annulus and the isolation of all layers, if necessary, to the wellhead.

 The aim of the invention is to ensure the tightness of the annulus and the isolation of the layers, if necessary, to the wellhead.

 This goal is achieved by the fact that in the known method of cementing wells, including completing a well in a clay roof with a smaller diameter with a sump, lowering the casing with a shoe into the well, pumping a spacer, cement, grouting fluid until a stop signal is received and leaving the well on the period of setting and hardening of cement stone (OZZ). According to the invention, the casing shoe is additionally equipped with a container with a cement mortar setting accelerator reagent, which is placed above the sump before cementing; after the cement mortar is pressed into the annulus, the casing with the shoe is lowered into the sump with force, and the setting accelerator is injected into the sump from the container a portion of cement mortar in the area of the shoe before leaving the well at the OZZ. After slipping the shoe with the casing string into the sump, the last axial force is removed from the sump. In addition, the cement slurry is pumped into the well in portions having different setting times.

 The method of cementing a well is as follows.

 At the end of drilling, in a clay roof above the reservoir, the wellbore is made with a diameter less than the diameter of the main well (sump), but not more than the outer diameter of the casing. The casing shoe is equipped with a container with a cementing agent setting accelerator reagent. Cementation of the annulus is carried out with the shoe position above the sump, all operations are carried out to pump cement into the casing, push it into the annulus and receive a stop signal, after which the casing shoe is lowered with force, while providing reagent injection accelerator setting in cement mortar. Shoe, crushing, expanding the rock in the sump, seals the annulus. After slipping the shoe with the casing string, to eliminate bending, the axial force is removed from the latter and the casing string is left on the baffle plate. During casing, several portions of cement mortar different in time of setting are pumped into the annulus during cementing. The setting time, starting from the bottom, is selected so that the setting of one portion of the cement mortar determines the start time of the thickening of the next portion, etc. Thus, they provide hydrostatic pressure on the cement mortar during its thickening and setting, which prevents the formation of channels for the movement of fluids from the reservoirs.

 Example.

 Well drilling is carried out according to standard known technology and lead to the roof of the project horizon and stopped in clay deposits up to 20-5 m from the roof of the reservoir. Drill a sump 2-3 m in diameter 240-243 mm, then lower the casing with a diameter of 245 mm with a shoe with a diameter of 270 mm, equipped with a container with a reagent-accelerator setting cement and equipment (centralizers, turbulators, etc.). At a distance of 0.5-1 m from the sump, cementing of the casing string begins, pumping a separator, cement mortar, squeezing fluid into it, and the cement mortar is pumped in portions with different setting times. After the pumping fluid has been pumped in and the stop signal has been received, the casing shoe is lowered into the sump with force, and the setting accelerator reagent is injected into the cement mortar from the container. Then they pressurize, check the tightness of the shoe, remove the load from the casing and leave it on the OZZ.

 Using the present invention will allow for reliable sealing of annular space, to avoid breakthrough of fluid from the reservoir into the overlying horizons and the surface. This invention will improve the quality and reliability of the well, as a capital construction. At the underground gas storage (UGS), by installing the shoe of the intermediate column in the roof of the gas-bearing horizon according to the proposed method, overflow can be avoided and the service life of the wells can be extended under such conditions.

Sources of information
1. Bulatov A.I. A guide to fixing oil and gas wells. M .: Nedra, 1977, p. 204-207.

 2. Bulatov A.I. Theory and practice of well completion. M .: Nedra, 1977, v. 3, p. 266-276.

 3. Bulatov A.I. Handbook for fixing oil and gas wells. M .: Nedra, 1977, p. 132-138.

 4. Balyshek S.M. etc. Drilling of wells. M .: Nedra, 1990, p. 402-403.

Claims (2)

 1. A method of cementing wells, including completing a well in a clay roof with a smaller diameter with a sump, lowering the casing with a shoe into the well, pumping a spacer, cement, squeezing fluid to a stop pressure, characterized in that the casing shoe is equipped with a container with the reagent-accelerator setting the cement mortar, place them over the sump before cementing, the casing after pumping the required volume of cement mortar, squeezing fluid is lowered with a mustache or in the sump, while opening the container and injecting the accelerator reagent into a portion of cement mortar in the area of the shoe.  2. The method according to p. 1, characterized in that the cement mortar is pumped into the well in portions having different setting times, the end of setting of one portion is the beginning of the subsequent thickening.