SU1303702A1 - Method of cementing casings of deep wells - Google Patents

Abstract

The invention relates to the field of drilling. The goal is to improve the quality of cementing due to the possibility of pumping cement mortar (CR) in the mode of counteracting the discontinuity of the CR flow continuity. The casing (OK) is lowered below the absorption zone. OK is then cemented. Cementation of the lower part of the OC to the absorption zone is carried out through the internal section of the OC. Cementation of the upper part of the OK in the upper absorption zone is carried out through the annular space. During the cementation of the upper part of the OK, the first portion of CR is mixed with an aqueous solution of aluminum sulfate at a concentration of the latter of 50 wt.%. In this case, the mixing volumes of the CR and the aluminum sulfate solution are taken in a ratio of 1:: (O, 5-1.0), respectively. The volume of the first portion of the CR containing the aluminum sulphate solution is assumed to be not less than the volume of the annular space in the interval of the absorbing formation. Injection and injection of the entire volume of the CR to fill the annulus from the mouth to the bottom of the absorbing formation is performed under pressure. 1 tab. With S (L I

Description

BACKGROUND OF THE INVENTION The invention relates to drilling: down holes, in particular, to methods for cementing them.

The aim of the invention is to improve the quality of cementing due to the possibility of pumping cement in the mode of countering the discontinuity of the cement slurry.

The method is carried out as follows.

The casing is lowered below the absorption zone, after which cementation is carried out. The cementation of the bottom part of the casing to the absorption zones is carried out via an internal section of the column, and the cementation of the upper part of the casing Bbmie of the absorption zone is carried out through the annulus.

During the cementation of the upper part of the casing, the first portion of the cement slurry is mixed with an aqueous solution of aluminum sulphate at a concentration of 50% by weight of the latter. Before this, the mixing volumes of cement mortar and aluminum sulphate solution are taken in a ratio of 1: (0.5-1.0), respectively. The volume of the first portion of the cement slurry containing aluminum sulphate solution is assumed to be not less than the volume of the zirconium space in the interval of the absorbing formation.

As a result of laboratory studies (see table), it was found that when mixing cement mortar with an aqueous solution of aluminum sulphate, the mixture quickly forms. The beginning of the setting of such a mixture with a ratio of the volumes of the components to be mixed 1: 0.5 is 5 minutes, with a ratio of the volumes of 1: 1 - 7 minutes. A distinctive feature of the mixture, having a thick pass structure, is that, when forces are applied, it retains its mobility and pumpability for a long time (more than 15 minutes) without setting and in a state of rest quickly gains structure, turning into a dense non-flowing mass after 1 min, and begins to seize after 5-7 minutes.

When the ratios of the volumes of the mixed solutions are larger and smaller than the indicated ones, as well as when adding aluminum sulphate solution with the concentration

0

five

five

five

0 5 0 5

0

With less than 50%, the start and end times for setting the mixture are noticeably longer, so mixtures with these ratios of components are not recommended for use.

When moving a mixture of cement - mortar and aluminum sulphate solution at a volume ratio of 1:: (0.5-1) in the behind-the-casing. high resistance arises in space, which prevents the development of high velocity of the cement mortar column behind the column and the discontinuity of its flow.

Following the first portion of the cement slurry containing aluminum sulphate solution, cement slurry is pumped into the annulus without additives or with additives in the form of gel cement, aerated cement slurry, etc. The first portion of the cement slurry in the form of a thick mass is injected under pressure and due to the occurrence of high resistance forces during the movement of this portion after the column development is high. the speed of movement of the cement mortar column under the action of gravity does not occur. Injection of cement slurry is therefore carried out under pressure. Ultimately, by the end of cementing the second stage, the solutions in the annulus occupy a position in which a cement slurry with the addition of aluminum sulphate solution is located above the absorbing formation and slightly above the top of the wellhead - the cement slurry.

The advantage and significant difference of the proposed method from the known one is that the injection of and injection of the entire volume of cement mortar to fill the annulus from the mouth to the bottom of the absorbing reservoir is produced by pressure - pressure. At the same time, hydraulic fracturing and the withdrawal of a large volume of cement slurry into the absorbing reservoir, the development of high velocity of the cement slurry column behind the column, the inflow of formation water, the discontinuity of the cement slurry behind the column, and the underrun of the cement solution are prevented.

To implement the proposed method, a small consumption of aluminum sulfate is required. Powdery

3.13

aluminum sulphate or its saturated solution with a concentration of 50% (ppm) is a waste from the production of oil refineries.

Example. A casing string with a diameter of 146 mm was lowered into a well with a diameter of 215.9 mm and a depth of 2500 m. In the section of the well, there is an absorbing formation in the range of 1000-1030 m.

The first stage of the casing due to the ratio of the volumes of the components is intervented directly with the base of the absorbing or conductive layer through the wellbore, the open end of the pipe string or the hydronium of the cement slurry in the interval of 2500- 1030 m.

The annular space of the well in the range of the absorbing reservoir, taking into account cavernosity, is 1 m, and in the range of 0-1000 m - 21 m.

Exodus from the depth of jazheni por15

mechanical packer.

Claims (1)

Invention Formula A method for cementing deep wells casing, comprising 20 formations of the casing below the zone of the total volume of cement mortar dp, cementing the second stage, the ratio of the volumes of the mixed cement solution and aluminum sulphate solution of 50% concentration take 1: 1. The volume of the first portion of the cement slurry with the addition of aluminum sulphate solution with the possibility of entering a small portion of the cement slurry into the absorbing reservoir, some of its rise above the top of the absorbing reservoir is 3 m. To obtain this mixture with such a volume in the well for 25 thirty cementing the lower part of the casing through its internal section to the absorption zone and cementing the upper part of the casing through its annular space above the absorption zone, characterized in that, in order to improve the quality of cementing due to the possibility of pumping cement in the mode of countering the flow continuity during the cementing of the upper part of the casing, the first portion of the cement is bored out at the same time as the cement rast-35 of the thief is mixed with a saline solution a thief with a volume of 1.5 m and a solution of aluminum sulfate with a volume of 1.5 m. Following the first batch of cement mortar containing aluminum sulphate aluminum sulphate solution at a concentration of the last 50% by weight, the mixing volumes of cement mortar and aluminum sulphate solution are taken into the annulus well in a ratio of 1: (0.5-1 , 0) the corresponding pumped 20 m cement cement. solution and a well under pressure in. annulus 25-30 kgf / cm left on RFQ. The proposed method is recommended to be used also to isolate zones of absorption and water intake of high intensity during the drilling of a well by pumping a plug-in mixture of the indicated compositions and with mechanical packer. Invention Formula A method for cementing deep wells casing, comprising five 0 cementing the lower part of the casing through its internal section to the absorption zone and cementing the upper part of the casing through its annular space above the absorption zone, characterized in that, in order to improve the quality of cementing due to the possibility of pumping cement in the mode of countering the flow continuity during the cementing of the upper part of the casing, the first portion of the cement aluminum sulphate at a concentration of the last 50 wt. volume volumes of mixing cement mortar and aluminum sulphate solution. Compiled by, Grishanov Tehred M.Morgental - Proofreader A.Obruchar Order 1284/33 Circulation 533 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 Table continuation