RU2018629C1 - Method for well completion - Google Patents

Abstract

FIELD: well completion. SUBSTANCE: method includes drilling-in, running casing into well, and injection of cement mortar. Injected between portions of cement mortar is portion of viscoelastic compound with stable properties. It is provided above producing formation under condition that hydrostatic pressure of columns of overlying portion of cement mortal and portion of viscoelastic compound exceeding formation pressure is transmitted to lower elevation of viscoelastic compound. EFFECT: higher efficiency due to provision of improved sealing of casing string-borehole annulus.

Description

 The invention relates to drilling equipment and well construction technology, in particular to their completion.

 A known method of well completion, including opening the reservoir, lowering the casing string, installing a packing element, introducing cement into the pipe string, securing the packer in the well with the possibility of its subsequent separation from the column [1].

 The disadvantage of this method is that it does not prevent the formation of migration channels in the annulus and therefore does not provide reliable sealing.

 Closest to the proposed one is a method of well completion, which includes opening a producing formation, lowering a casing string, injecting a cement slurry and a portion of a viscoelastic composition (CCL) between portions of a cement slurry [2].

 The disadvantage of this method is the low tightness of annular space due to the properties used by the method of WCS and the lack of back pressure from the WCS to the reservoir pressure.

 The aim of the invention is to increase the efficiency of the method by ensuring the tightness of annular space.

 This goal is achieved by the fact that in the method of completion of the wells, including opening the reservoir, casing, pumping cement and portions of viscoelastic composition between portions of cement, a composition with stable properties is used as a viscoelastic composition and placed over the reservoir with the condition of transfer to the lower mark of the viscoelastic composition of the hydrostatic pressure of the columns of the overlying portion of the cement mortar and the portion of the viscoelastic composition exceeding the reservoir howl pressure.

 The viscoelastic composition located between the upper and lower portions of the cement mortar during the initial period of hydration under the action of hydrostatic pressure of the overlying suspension due to its elastic properties is compressed and adheres tightly to the walls of the wellbore and casing. When a gas or other formation fluid passes through the lower interval of the cement stone and due to the high ultimate shear stress, the viscoelastic composition penetrates into the formed channels, seals the annular space and prevents further fluid advancement.

 The method is as follows.

 An autopsy of the reservoir is carried out. Then the casing is lowered, cement mortar is pumped. Between portions of the cement slurry, a portion of the viscoelastic composition is pumped. As a viscoelastic composition, a composition with stable properties is used, i.e. ensuring its stability after hardening of cement mortar for the required period when tightness of annular space is required. It is important that the WCS does not decompose due to temperature and other physical and mechanical influences. The HCS is placed above the reservoir with the condition that the hydrostatic pressure of the columns of the overlying portion of the cement slurry and the portion of the HCS itself exceeding the reservoir pressure is transferred to the bottom mark of the HCS.

PRI me R. The reservoir was opened in the range of 4000-4200 m. The technical string was lowered in the range of 0-3900 m. The internal diameter of the technical string was 22, 24 cm. The production string was lowered in the range of 0-4200 m. The outer diameter of the production string was 16.83 cm. The diameter of the wellbore in the range of 3900-4200 m is 21.5 cm. After the production casing is launched, the cementing process begins. Inject the first portion of the cement mortar, equal to the volume of annular space to a height of H ₁ .

(D $\genfrac{}{}{0ex}{}{\text{2}}{\text{в}}$ - D $\genfrac{}{}{0ex}{}{\text{2}}{\text{н}}$ ) Н₁ = 0,785 (22,24² - 16,83²) 3725 = 61,8 м³.V ₁ =

(D $\genfrac{}{}{0ex}{}{\text{2}}{\text{at}}$ - D $\genfrac{}{}{0ex}{}{\text{2}}{\text{n}}$ ) H ₁ = 0.785 (22.24 ² - 16.83 ² ) 3725 = 61.8 m ³ .

Then pumped VUS equal to the volume of annular space to a height of H ₂ .

(D_в ² - D_н ²) Н₂ = 0,785 (22,24² - 16,83²) 75 = 1,245 м².V ₂ =

(D _in ² - D _n ² ) H ₂ = 0.785 (22.24 ² - 16.83 ² ) 75 = 1.245 m ² .

Next, the remainder of the cement mortar is pumped into the annular space to a height of H ₃ + H ₄ .

(D_в ² - D_н ²) Н₂ + (D_с ² - D_н ²) Н₄ = 0,785 (22,24² - 16,83²) 100 + (21,5² - 16,83²)х х300 = 5,9 м³.V ₃ =

(D _in ² - D _n ² ) H ₂ + (D _s ² - D _n ² ) H ₄ = 0.785 (22.24 ² - 16.83 ² ) 100 + (21.5 ² - 16.83 ² ) x x300 = 5.9 m ³ .

 Then the cement mortar and viscoelastic composition is pressed into the annular space to obtain a "Stop".

Hydrostatic pressures at the cement mortar – HSS interface, HEM — cement slurry and back pressure on the formation are determined by the following formulas
for H ₁ = 3725, P _g.s. = ρ _c.p x H ₁ = 1.820 x 3725 = 67.8 MPa, for H ₂ = 3800, P _g.p. = ρ _c.p. x H ₂ + ρ _v.u.s. x H ₂ = 3785 + 1,040 x 75 = 67.8 + 0.8 = 68.6 MPa, for H ₄ = 4200, P _g.p. = ρ _pr x H ₁ + ρ _vc x H ₂ + ρ _pr (H ₃ + H ₄ ) = 1.820 x 3725 + 1.040 x 75 + + 820 x 400 = 67.8 + 0.8 + 7, 3 = 75.9 MPa.

Since the value of the WCS column can be different, for the initial data it is possible to take the compression pressure of the latter along the overlying column of cement, which in this case is 68.6 MPa. The reservoir pressure of the reservoir Р _pl = 63.0 MPa, i.e. The WCS, compressed to 68.6 MPa, serves as an impenetrable barrier to formation fluid.

Claims (1)

 METHOD FOR FINISHING WELLS, including opening a producing formation, lowering a casing string, injecting a cement slurry and a portion of a viscoelastic composition between portions of a cement slurry, characterized in that, in order to increase the efficiency of the method by increasing the tightness of the annular space, a composition with stable properties and place it over the reservoir with the condition of transferring to the lower mark the viscoelastic composition of the hydrostatic pressure of the columns of the overlying portions of the cement slurry and portions of the viscoelastic proper composition exceeding the reservoir pressure.