RU2109128C1 - Method of injecting into wells - Google Patents

Abstract

FIELD: oil and gas production industry. SUBSTANCE: this is used for increasing oil recovery from oil bed. According to method, after opening of oil bed, casing string is lowered into well. Prior to that, casing string is provided with hydraulic giant nozzles which are plugged by stoppers soluble in acids. Then casing string is cemented with isolation of productive part of bed from cement slurry. Stoppers are dissolved and effected is hydraulic jet perforation. This is performed through hydraulic giant nozzles. Preliminarily space inside casing string is subjected to packing. EFFECT: higher efficiency. 4 dwg

Description

 The invention relates to the oil industry and can be used when completing wells in the late stages of field development.

 A known method of selective isolation of the reservoir when cementing the production string of pipes in the well, implemented in the device of the same name. The method involves the installation of packing devices, rigidly mounted on the body, located under the sole and above the roof of the reservoir, flushing with drilling fluid and sealing the annulus by opening the packing devices with subsequent pumping of grouting mortar into the annulus through the annular channel of the housing [1]. However, when using the method, cumulative perforation of the uncemented part of the casing string is required, the oscillations of which increase the likelihood of depressurization of the packing elements and the destruction of the cement stone.

 A known method of opening productive formations by hydro-jet perforation, including opening a formation, cementing a casing string, lowering tubing with a hydraulic perforator inside the casing, installing it opposite the productive formation and hydro-jet perforation of the required perforation interval [2].

 However, the known method has significant disadvantages. Firstly, it is associated with a significant expenditure of energy necessary for the destruction of the casing string body. Secondly, due to the large hydraulic resistances during perforation of the holes in the casing, the supplied hydraulic power is sharply lost, which does not allow to significantly increase the drainage area by erosion and, consequently, increase the oil recovery, which is especially important in the conditions of the late stage of field development.

 The objective of the invention is the creation of an energy-intensive and effective method of completion in a late stage of development of hard-to-recover formations.

 The proposed method is solved by the proposed method of well completion, which includes opening the casing, cementing the casing, waterjet perforation of the productive part of the formation and developing the well, in which, according to the invention, before casing, the casing is equipped with hydromonitor nozzles closed with acid-soluble plugs opposite the productive formation, then cemented of the productive part of the reservoir from cement mortar, dissolve acid-soluble plugs and carry out a water-jet perf radio well through jet nozzle into the isolated portion of the formation with a pre-packer space inside the casing to be subjected to hydroentangling perforation.

 In FIG. 1-4 schematically depicts the stages of implementation of the above method. Figure 1 shows the device installed in front of the reservoir before the cementing process, Figure 2 shows the tubing run with a packer with a further acid bath to dissolve the plugs after cementing, Figure 3 shows the hydro-jet perforation through nozzles after the packet 3a has been activated, in the case when the lower the aquifers are far, 3b - through the upper nozzles in the case of a close location of the lower aquifers. Scheme 4 - development through tubing.

 The method is as follows. After the formation is opened, the casing is equipped with hydromonitor nozzles closed with acid-soluble plugs and installed with the equipped part opposite the productive formation (Fig. 1). Then the string is cemented to isolate the productive part of the formation from the cement mortar (for example, using the device [1], lower the tubing with a packer and carry out an acid treatment of the casing string to dissolve the plugs (Fig. 2). a space above a certain number of hydraulic nozzles for effective erosion of the rock and carry out hydro-jet perforation of the well (treatment of the formation), as a result of which caverns 3a are formed in its lower part. true in the roof of the treated formation pack the annular space below a certain number of nozzles, and the fluid is injected into the annular space for hydro-jet perforation (Fig. 3b) .After completion of the hydro-jet perforation (processing of the formation), the well is developed.

 1. The initial data for the calculation of the process.

The well is inclined, vertical H _well = 1400 m.

 The production casing is lowered to a depth of 1800 m. A productive formation with a capacity of 10 m has a roof at a depth of 1750 m, a sole of 1760 m. There is an impenetrable bridge with a capacity of 2 m between the reservoir and the lower water head. The diameter of the well (bit) is 216 mm, the outer diameter columns 146 mm, inner 130 mm.

 The bottom equipment of the column is as follows: BK-146 shoe 1800 m, TsKOD at a depth of 1870 m, USIP (device for selective formation isolation) 1750-1760 m [1].

The column pre-pressed to 20.0 MPa is cemented with a pure cement mortar with a density of 1850 kg / cm ² , the clay solution in the well has a density of 1200 kg / cm ² . Selling cement mortar is made clay.

 The equipment of the bottom of the tubing during perforation and development is as follows: tubing string 1770 m, packer 1756 m, outer diameter of tubing 73 mm, inner diameter 62.0 mm, nozzles with a diameter of 7 mm 3 pcs, per 1 meter in USIP.

 2. Calculation of the cementing process.

a) the volume of cement slurry to be pumped into the casing in one step is determined as follows
V _tsp = V ₁ + V ₂
where V ₁ = 0.785 • (D $\genfrac{}{}{0ex}{}{\text{2}}{\text{SLE}}$ -d $\genfrac{}{}{0ex}{}{\text{2}}{\text{n}}$ ) - the volume of the solution to fill the annulus to the wellhead;
V ₁ = 0.785 (0.216 ² - 0.146 ² ) 1800 = 36.7 m ³ ,
and taking into account the coefficient of cavernosity of the wellbore k = 1, 2
V ₁ = 1.2 • 36.7 m ³ ≈44.2 m ³ ;
V ₂ = 0.785 • d $\genfrac{}{}{0ex}{}{\text{2}}{\text{VK}}$ • (l _SLE - l _ccode ) = 0.785 • 0.13 ² • 20 = 0.3 m ³ - the volume of the solution below the TsKOD check valve until the bottom of the well inside the column, then
V = V ₁ + V ₂ = 44.2 + 0.3 = 44.5 m ^{3 of the} solution.

a) Pressure at the mouth at the end of cementing at the time the cork fits on the “stop ring”
P = P ₁ + P ₂
where P ₁ = 0,1 (γ • H _{ts.r. borehole} -γ _gl.r. • H _rms) = 0,1 • 1400 • 0,65 = 91 bar - the pressure drop caused by the difference of the densities of the cement and the mud .

P ₂ = 0.01 • l _SLE = 0.01 • 1800 = 18 atm — pressure to overcome hydraulic resistance in the well.

P = 18 atm + 91 atm = 110 atm
After receiving the pressure "stop" P _stop = 150 atm, the pressure inside the column is vented to zero and left to wait for the cement to solidify (T _OZZ = 24 hours);
c) After the time of the OZZ run the tubing with a packer. To dissolve the acid-soluble plugs of the USIP, a 15% solution of hydrochloric acid (HCl) is pumped into the well. The required volume of Hcl solution is determined from the following expression
V _HCl = V ₁ + V ₂
where V ₁ = 0.785 • d $\genfrac{}{}{0ex}{}{\text{2}}{\text{ext.}}$ • l _SLE = 0.785 • 0.062 ² • 1800 = 5.4 m ³ - the volume of solution required to fill the tubing string;
V ₂ = 0.785 (D $\genfrac{}{}{0ex}{}{\text{2}}{\text{vn}}$ count d $\genfrac{}{}{0ex}{}{\text{2}}{\text{nar}}$ Tubing) • (l _SLE - l _roofs ) = 0.785 (0.13 ² - 0.073 ² ) • (1800 - 17500) = 0.46 m ³ ≈0.5 m ³ - the volume of the solution required to fill the annulus with overlap reservoir interval.

Then V = 5,4 + 0,5≈ 6 m ³
The dissolution time of the plugs t _min = 2 h
3. Calculation of the process of hydraulic washing.

 After dissolving the plugs and pressing the solution of unreacted acid into the reservoir, a packer is installed under pressure in the interval 1756-1758 m and this space is sealed. Below the packer, in the range of 1758-1760 m, 6 jetting nozzles remain open for the outflow of jets, and above, in the range of 1750-1756 m, 18 nozzles acting as circulation holes for washing out the rock to the surface. The required clay flow rate and pressure loss for effective perforation are determined.

 For 6 jet nozzles with a diameter of 7 mm, the maximum flow rate is 23 m / s, and the pressure loss for clay mud is 13.4 MPa at an effective flow rate of 100 m / s from each nozzle.

 According to RD-39-R-0135648-001-89, it is found that the U8-6M mud pump with a sleeve diameter of 150 mm is suitable for washing cavities and expanding the conditional diameter of the well. Next, the lower part of the reservoir is eroded by pumping a clay solution inside the tubing string.

 We will take the rock erosion time with the U8-6M pump equal to the hydroperforation time of 70 minutes.

 To perforate the upper part of the formation, a packer is installed in the interval 1752-1754 m and this interval is sealed in the space between the tubing and the casing. Above the packer there are 6 hydraulic nozzles, and below - 18. The mode of the process is defined in section a). The upper part of the reservoir is eroded by pumping a clay solution in the annulus between the tubing and the casing.

 The invention allows to increase oil recovery while isolating the production interval along the wellbore from lower and overlying nearby aquifers in the late stage of development of fields with hard to recover oil reserves. In addition, the proposed method is less energy intensive and more reliable when used.

Claims (1)

 A method of completing wells, including drilling a hole, cementing a casing string, waterjet perforation of a productive part of a formation, and developing a well, characterized in that prior to cementing, a casing string is equipped with hydraulic monitor nozzles closed with acid-soluble plugs opposite the production interval, then cemented with isolation of the productive part of the formation dissolve acid-soluble plugs and carry out hydro-jet perforation of the well through hydraulic nozzles in zolirovannoy portion of the formation with a pre-packer space inside the casing to be subjected to hydroentangling perforation.

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