RU2172810C1 - Method of isolation of lost-circulation formations - Google Patents

Abstract

FIELD: well drilling, particularly, isolation of zones of lost-circulation and fractures of hydrofracturing of formation in string cementing. SUBSTANCE: method includes supply of calculated volume of grouting mortar with filler. Said volume is determined by formula Vp=Va+DwxL/a, where Va is volume of annular space with consideration of cavernosity, cu.m; Psp is specific pressure with consideration of relationship of opening of fractures of lost circulation and well pressure, Mpa; Dw is well diameter with consideration of cavernosity, m; L is well length in zone of minimum hydrofracturing gradient, m; a is hydrofracturing gradient of rocks of slightly consolidated bed, Mpa/m. EFFECT: provided rise of grouting mortar to planned height.

Description

 The invention relates to drilling wells, in particular to the isolation of absorption zones and hydraulic fractures during cementing of columns.

 A known method of isolating absorbent layers, including the descent of the column, mixing and pumping light and cement slurries into the well, into which up to 10% inert filler is introduced in the amount necessary to close the interval from the absorbing layer to the design height of the grout. [Krylov V.I. Isolation of absorbing formations in deep wells. - M .: Nedra, 1980, p. 127-128].

 The disadvantage of this method is the low guarantee of raising the cement slurry to the planned height with a small gradient of hydraulic fracturing of the rocks.

There is also known a method of isolating absorbing formations, in which, after lowering the columns before cementing, 15-20 m ^{3 of} clay mud with a filler is prepared and pumped into the well, and then cement slurry. (Ibid., Pp. 127 and 128).

 The disadvantage of this method is also the low guarantee of raising the cement slurry to the planned height with a small gradient of hydraulic fracturing of the rocks.

 The problem to which the invention is directed is to increase the insulation efficiency of absorbing formations and hydraulic fractures.

 The technical result achieved by the invention is the provision of lifting the cement slurry to the planned height with a low hydraulic fracturing gradient.

где V_зп - объем затрубного пространства с учетом кавернозности, м³;
P_уд - удельное давление поглощения или раскрытия трещин гидроразрыва, МПа;
D_скв - диаметр скважины с учетом кавернозности, м;
L - длина скважины в зоне наименьшего градиента гидроразрыва, м;
α_грп - градиент гидроразрыва пород слабого пласта, МПа/м.The specified technical result is achieved by the fact that in the known method of isolation of absorbing formations, including the injection into the well of a cement slurry with a filler, the feature is that the volume of injected solution with a filler is determined by the formula

where V _zp - the volume of the annulus taking into account cavernousness, m ³ ;
P _beats - specific pressure of absorption or opening of fractures, MPa;
D _SLE - well diameter taking into account cavernousness, m;
L is the length of the well in the zone of the smallest fracturing gradient, m;
α _fracturing - fracturing gradient of weak formation rocks, MPa / m.

 The hydraulic fracturing gradient in a well is determined experimentally by running the packer and pressing the wellbore or according to statistics for other wells during hydraulic fracturing during various operations, or by calculation using existing methods. The length of the well in the interval of a weak formation is determined identically. If this is difficult to do, you can take the interval from the bottom to the shoe of the previous column.

 The proposed method is as follows.

After determining the smallest hydraulic fracturing gradient in the well and the length of the interval of the well with this gradient, the volume of grouting mortar with a filler is determined. For example, for a well with a depth of 1300 m with a conductor lowered to a depth of 550 m, the interval length is taken from the bottom to the conductor shoe L = 1300 - 550 = 750 m; the diameter of the well, taking into account cavernousness in this interval, is 0.23 m; the volume of the annular space, taking into account cavernousness, is 25 m ³ ; hydraulic fracturing gradient was determined during hydraulic fracturing in a neighboring well, α _fracturing is equal to 0.0161 MPa / m; column with a diameter of 0.168 m; specific pressure, taking into account the dependence of the opening of hydraulic fractures or absorption on the pressure in the well, is equal to 0.001 MPa.

С учетом этого затаривают смесители расчетным количеством тампонажной смеси с наполнителем.Then the volume of cement slurry will be equal to

With this in mind, mixers are packed with the estimated amount of cement mixture with filler.

 The column is lowered and cemented using conventional technology. In the process of bursting during absorption and hydraulic fracturing, cracks and absorption zones are plugged with a cement composition with a filler, which guarantees the rise of the cement slurry to the wellhead.

 The use of the claimed invention improves the efficiency of insulation work without changing the existing technology of fastening, time and additional work on the isolation of absorption zones and hydraulic fractures.

Claims (1)

A method of isolating absorbent layers, including the injection into the well of a cement slurry with a filler, characterized in that the volume of injected cement slurry with a filler is determined by the formula

where V _zp - the volume of the annulus taking into account cavernousness, m ³ ;
P _beats - specific pressure of absorption or opening of fractures, MPa;
D _SLE - well diameter, taking into account the trickiness, m;
L is the length of the well in the zone of the smallest fracturing gradient, m;
α _fracturing - hydraulic fracturing gradient of weak formation rocks, MPa / m.