RU2152507C1 - Method of insulating water-development strata - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: invention can be applied when performing insulation operations in borehole by installation of cement bridging by balance technique. Method consists in exposing water-development stratum, washing hole, injecting specified volume of grouting mortar, forcing it into casing string-borehole annulus, and removing extra grouting mortar, while simultaneously expanding borehole. Grouting mortar is prepared by adding to cement mortar a special plasticizing reagent or water-treatment station waste. During cement hardening wait state, counterpressure on the bed to be insulated is exposed. EFFECT: improved reliability and quality of insulation due to improved adhesion of grouting material to stratum rock. 3 dwg, 1 tbl

Description

 The invention relates to the mining and oil and gas industries and can be used when conducting insulation work in the well by installing cement bridges in a balanced way.

 A known method of installing cement bridges, including the descent into the installation interval of casting pipes equipped with a tool to create an expansion zone and the injection of cement slurry. Moreover, the expansion of the wellbore is carried out in a grouting medium with the subsequent formation of a dividing bridge (SU 1615333, class E 21 B 33/13, dated 23.12.90).

 The disadvantage of this method is that it allows you to install a bridge of only a limited length due to the danger of sticking the pipe string with cement mortar, in the medium of which the borehole is expanded, since this is due to the thickening time and the beginning of cement mortar setting, which is only 1.5 -2 hours from the moment it was pumped into the well. For this reason, its use with the aim of simultaneously expanding the wellbore and combating absorption or water manifestations is not possible.

 There is also known a method of isolating a formation by installing a cement bridge, which includes lowering a pipe string equipped with centralizers to the bottom of the formation, flushing the well, pumping the estimated volume of cement, pushing it into the annulus, raising the pipe string to the roof of the formation, and cutting off the excess portion of the cement to the daytime surface. At the same time, during the cutting and until the cement mortar has set, the pouring column is continuously mixed and then the filling pipes are lifted into the safe zone until the cement mortar hardens (SU 1836542, E 21 B 33/13, from 08.23.93).

 The disadvantage of this method is the low efficiency of the insulating work, since when drilling a cement bridge or other work with pressure, under the action of alternating loads, the cement ring formed around the wellbore after drilling the bridge gradually collapses, access to the formation fluids into the well is opened, which necessitates conducting repeated insulating work.

 The aim of the present invention is to increase the reliability and quality of insulating work by improving the adhesion of the cement material with the formation rock and ensuring durability.

 The technical result of the method of isolating water-producing strata by installing a cement bridge is achieved by including drilling a water-developing stratum by drilling, lowering a pipe string into the well to the bottom of the formation, flushing the well, pumping the estimated volume of grout, pumping it into the annulus, raising the pipes to the roof of the formation and removal of excess cement slurry. At the same time, an excess portion of the cement slurry is cut using a high-density drilling fluid that provides back pressure on the water-developing formation for the time of the WOC, and the water-developing formation is opened simultaneously with the expansion of the wellbore in the forecast water-developing interval with the formation of a variable cross-section; plasticized cement is used as grouting mortar solution. In this case, for example, Sepacall CE-5381 or waste water treatment plants are used as a plasticizer.

 A comparative analysis of similar technical solutions allows us to conclude that in the proposed method there are no identical and equivalent features in comparison with similar features of known methods i.e. on the conformity of the claimed technical solution to the criterion of "novelty."

In FIG. 1 shows a water-producing layer of a well with a bridge installed after preliminary expansion of the wellbore in the indicated interval, using an erosion control device, section;
in FIG. 2 - the same, after drilling a cement bridge, section,
in FIG. 3 is a view I in FIG. 1.

 The method is carried out in the following sequence.

 The opening of the water-developing layer, determined according to the forecast, is carried out using conventional bits 1.

 Before the drill string 2 is lowered into the well 3, its bottom is provided with a bitwise expansion of hydraulic-mechanical action or side nozzles 4 on the sub, the diameter of the nozzles is selected based on ensuring the speed of the formed jet at least 70 m / s, for example, 15-15-18 ml for hydroerosive expansion of the walls of the well. Then they start drilling using natural aqueous suspensions. As the hole deepens with a chisel, the drilling fluid destroys the walls of the well, forming an extended section in the wellbore. The quality and reliability of insulating work is greatly increased if the extended section 5 is of variable cross section. For this, after sinking with a chisel every 2-3 m in depth, the tool is raised several times to this height and the trunk is additionally worked out at various speeds.

 At the same time, under the influence of a high-pressure jet, not only the wellbore expands, but also at the same time its compaction and blockage by drill cuttings particles of the most open water development channels. Then, after opening the entire interval of the water-producing formation, without lifting the tool, the calculated volume of the cement slurry is pumped into the drill pipe string and forced into the annulus to equilibrium. Next, the drill pipe string 2 is lifted with the calculation of installing the bottom of the string at the roof level of the extended section of the wellbore, after which excess cement slurry is removed by cutting. In this case, to create a backpressure on the formation, drilling fluid with increased density is used. Then the drill pipe string with a chisel is raised to the surface and the well is left alone while waiting for the cement to harden (OZZ). After the OZZ, the cement bridge is drilled and the further deepening of the face is continued.

 As a grouting material for the installation of a cement bridge, plasticized cement mortar is used, forming a non-shrinking low-permeability stone.

 As such a plasticizer, for example, Sepacall CE-5381 or waste water treatment plants are used.

Sepacall CE-5381 manufactured by BASF (Germany) is a dark brown liquid with a density of 1200 kg / m ³ at 23 ^o C. Chemically, it is a sodium salt of sulfonated naphthalene resins.

Using Sepacall CE-5381 reagent as a plasticizer, a normally pumped cement mortar with a density of up to 1940 kg / m ³ can be obtained. With a reduced water content and with a Sepacoll content of 0.5 wt. fractions, the solutions are characterized by increased density and sedimentation stability, reduced cement setting time and the formation of a non-shrink stone with increased strength and low permeability.

 Plasticizer Sepacall CE-5381 is not harmful to humans and the environment.

 When applying it, the usual precautions taken when working with chemicals should be observed - avoid inhalation of vapors, use work clothing, mittens and safety glasses.

 The table shows the results of laboratory tests of cement mortar with a plasticizer from waste water treatment plants (EIA). The cement was taken from cement in the Novoulyanovsk plant according to GOST 1581-91, which, when treated with sodium chloride, sharply reduces the spreadability.

 EIA is a pulp containing dispersed particles planted with flocculants and coagulants.

As can be seen from the table (see position 5), with a lower water content, i.e. in 35 wt. hours, although the density is high, but the solution becomes poorly pumped (spreadability 180 cm). The best performance is the composition when the water is taken in 40 wt. hours and 5 wt. including EIA, the density of the solution 1880 kg / m ³ has a higher strength - 4.6 MPa in bending after 48 hours, as well as low permeability.

 The technical and economic advantages of the proposal are as follows.

 Using this method allows to increase the success of the insulating work of water-producing strata due to the use of cement mortar forming a non-shrinking stone, which ensures the density of contact of the cement stone with the rocks. This leads to an increase in the efficiency of insulation work, repeated insulation work is eliminated, and trouble-free drilling of wells in complicated intervals is ensured. The application of the proposal for the isolation of complicated sections in wells will provide tangible economic benefits.

Claims (1)

 A method of isolating water-producing strata by installing a cement bridge, including opening a drilling water-producing stratum by drilling, flushing a well, pumping the estimated volume of grout, pumping it into the annulus and removing excess grout, characterized in that the water-producing stratum is opened simultaneously with the expansion of the wellbore, and as cement slurry, plasticized cement mortar is used with SEPACOLL CE-5381 reagent or waste water treatment structures, while waiting for the cement to harden in the well create backpressure on the insulated reservoir.

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