RU2527419C2 - Development method for oil and gas wells - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is referred to oil and gas industry. In the method for development of oil and gas wells, which includes treatment of the bottomhole zone by emulsified acid injection and process aging, displacing fluid, parting fluid of high viscosity and emulsified acid are injected in sequence to the well equipped with flow column; at that foamed acid is used as emulsified acid and it is prepared by aeration of the design volume of foam-forming emulsion equal to the well volume at drilling-in interval. The foam-forming emulsion contains (wt %): diesel fuel 25.0; salt KCl 10.0; neonol surfactant AF 9-12 1.0-1.5; hydrochloric acid HCl 10.0, water - the remaining part. Aeration degree of the foam-forming emulsion is regulated on the basis of maximum permitted depression at the roof depth of the productive stratum. Foamed acid is injected through tubular annulus to the drilling-in interval, then foamed acid is flushed to the productive stratum by displacing fluid, at that between supplies of displacing fluid and foamed acid the parting fluid is supplied with high viscosity of at least 120 CP, thereafter excess pressure to the bottomhole zone is generated in tubular annulus of the well and tubing with periodicity ensuring creation of at least three cycles of depression and repression to the stratum, at that process aging takes at least three hours in each depression and repression cycles until influx of the reservoir fluid is obtained in depression cycle.

EFFECT: improving efficiency in development of oil and gas wells and increasing their productivity.

4 tbl, 1 dwg

Description

The invention relates to the oil and gas industry and can be used in the completion, repair and reconstruction of wells in fields and underground gas storages.

A known method of processing the bottom-hole zone with subsequent development of the well (RF patent No. 2196226, E21B 43/27, publ. 10.01.2003), including the descent of the tubing, delivery to the bottom of the acid, the removal of sludge and the flow of gas. Acid is delivered to the face, to the perforation zone, in a self-destructive container, which, corroding it or leaking through the bottom hole, reacts with waste at the face and carbonate rock in the formation, foaming the liquid and providing its removal. An unsupported packer is installed over the container in the tubing, which is unpacked over the perforation of the production string, providing a local effect of acid in the well. The disadvantage of this method is the decrease in well productivity, due to the need to kill the well for lowering the tubing with a packer. In addition, the delivery of acid to the bottom of the well in a self-destructive container is technically difficult.

The closest in technical essence to the claimed method is a method of processing the bottom-hole zone of the well (RF patent No. 2304710, E21B 43/27, publ. 08/20/2007), in which the annular space of the well is disconnected above the reservoir by the packer. Emulsions are sold when pressure and flow rise to the maximum permissible values. Upon reaching the maximum allowable pressure, the injection rate is reduced. Continue the injection until the injection pressure decreases. Close the well. Technological exposure is carried out for 20-30 hours with a closed well. Relieve pressure, tear off the packer, swab in the well until the fluid enters the well with a hydrogen indicator of the formation fluid. Washed and mastered the well. As an inverse oil acid emulsion, an emulsion is used containing, vol.%: As a dispersion medium, a solvent for petroleum paraffins - distillate 40-42, emulsifier "Yalan-E-1" 5-8, 22-24% aqueous solution of inhibited hydrochloric acid 50-55. The specified method provides an increase in the penetrating ability of the emulsion. A disadvantage of the known solution is the low efficiency when processing the bottom-hole zone of the well, because in this case, to completely cover the entire length of the exposed formation by exposure to acid, it is necessary to plug the well and lower the tubing with the packer to the bottom, which requires the use of expensive equipment. The need for holding for a long time (20-30 hours) also leads to a decrease in the effectiveness of this method. In addition, the acid emulsion used in the known solution does not contain a gas phase, i.e. is not an acidic foam, and will be absorbed by some of the most permeable layers of the reservoir, which will not allow to process the entire interval of opening the formation, especially when processing horizontal wells.

Known methods for developing wells when they are completed and repaired, in particular when opening low-permeability reservoirs, either do not provide the design flow rate, or require long development time, especially when completing and repairing horizontal wells, and also require the use of pipe lowering and lifting systems in well.

The problem to which the invention is directed, is to develop a method for developing oil and gas wells by foam-acid treatment of a productive formation, which allows to reduce the time of well development, including directional and horizontal wells.

The technical result, the achievement of which the present invention is directed, is to increase the efficiency of development of oil and gas wells and increase their productivity.

The specified technical result is achieved due to the fact that in the proposed method for the development of oil and gas wells, which includes treatment of the bottomhole zone of the well by injecting an acid emulsion into the well and holding the process, the sequentially injected into the well equipped with a column of lift pipes, squeezing fluid, highly viscous separation fluid and acid emulsion. As the acidic emulsion, an acidic foam is used, which is prepared by carbonating the calculated volume of the foaming emulsion, equal to the volume of the well in the interval of opening the reservoir, and the foaming emulsion contains, wt.%: Diesel fuel - 25.0; KCl salt - 10.0; surfactant neonol AF 9-12-1.0-1.5; HCl acid - 10.0 and water - the rest. The degree of carbonation of the foaming emulsion is regulated based on the maximum allowable depression at the depth of the roof of the reservoir. The injection of acid foam is carried out through the annulus of the well in the interval of opening of the reservoir. Then the acid foam is forced into the reservoir with a squeezing liquid, and a high-viscosity separation liquid with a nominal viscosity of at least 120 s is introduced between the squeezing liquid and the acid foam. Then, in the annulus of the well and the lift pipes, overpressure is created through the squeezing fluid through the bottomhole formation zone with a frequency that ensures the creation of alternating at least three cycles of depression and repression on the formation, while the well is technologically aged for at least three hours in each from cycles of depression and repression to an influx of reservoir fluid in the cycle of depression.

The drawing shows a diagram of the placement in the well of acid foam, squeezing fluid and highly viscous separation fluid in the lift pipes and annulus during the development of the well by the proposed method.

Table 1 shows the results of a study of the effect of the concentration of diesel fuel in the composition of the foaming emulsion on the parameters of acid foam.

Table 2 shows the results of a study of the effect of surfactant concentration in the composition of a foaming emulsion on the parameters of acid foam.

Table 3 shows the results of a study of the effect of salt concentration in the composition of the foaming emulsion on the parameters of acid foam.

Table 4 shows the results of a study of the effect of acid concentration in the composition of a foaming emulsion on the parameters of acid foam.

The method is as follows.

Squeezing fluid is pumped into the well through the annulus 1 between the cemented production string 2 and the lift pipes 3, which is either water or a polymer solution or an aqueous solution of salts. Squeezing fluid displaces drilling fluid, oil or gas (if the well is not plugged) from the well through lift pipes 3. Then, in order to separate the squeezing liquid and the acid foam, to prevent their mixing, a highly viscous separation liquid 4 (not more than 0.5 m) is introduced into the well, which acts as a liquid packer, which is used as a polymer liquid with a nominal viscosity of at least 120 s. Then acid foam is pumped, while the level of acid foam will be located above the roof of layer 5. After that, the highly viscous separation liquid 4 is again pumped (not more than 0.5 m ³ ). Acid foam is squeezed by squeezing liquid into the opening interval of the reservoir and then into the lift pipes 3. As a result, the lift pipes 3 and the annular space 1 of the well at the same depth h _pr (drawing) are filled with the squeezing liquid, below which there is a highly viscous separation liquid of height h _in (drawing ), and even lower - acid foam. Acid foam enters into chemical interaction with a sludge dune 6, the walls of an open wellbore 7 of the well and the zone of mudding 8 of the bottomhole formation zone (PZP). Acidic foam is prepared on the surface by pumping a foaming emulsion (POE) and an inert gas (or gas from an adjacent well) through a foam generator. In some cases, acid foam can be obtained by self-generation by heating the POE at the bottom of the well, which occurs at a temperature of the formation above 75 ° C. Acid foam is prepared from the estimated volume of POE equal to the volume of the well in the opening interval of the reservoir (the internal volume of production casing 2 minus the volume of metal lowered into the interval of the lift pipes 3). For the preparation of acid foam using POE of the following composition, wt.%:

Diesel fuel 25.0 KCl salt 10.0 Surfactant 1.0-1.5 HCl Acid 10.0 Water Rest

Neonol AF 9-12 (TU 2483-077-05766801-98) is used as a surfactant. The technological parameters of POE are determined in a laboratory way by comparing the multiplicity (K _p ) and stability (V _p ) for foams prepared by carbonation of various POE compositions. The multiplicity of acid foam is defined as the ratio of the volume of the foam (V _p ) to the volume of POE. The stability of the acid foam is determined by the reciprocal of the outflow time of 50% of the volume of POE from the film frame of the foam. The optimal composition of POE is considered, from which foam is obtained with the values: K _p from 2.4 to 3.7; At _n from 4.0 ° 10 ^-2 to 5.68 ° 10 ^-2 (1 / s). Acid foam is pressed into the reservoir by squeezing fluid, which is shared with acid foam by a highly viscous separation fluid 4. They create a depressive effect on the reservoir (ΔP _dep ), which is not more than 15% of the value of skeletal stresses (the difference between the mountain and reservoir pressures), by choosing the required densities of acid foam, squeezing and viscoelastic separation fluids.

$$\Delta R_{deP}=(R_{Pl}-R_{s\mathrm{but}b})=0.10(R_{g\mathrm{about}R}-R_{Pl})÷0.15(R_{g\mathrm{about}R}-R_{Pl}),(\mathrm{one})$$

where P _PL , P _Zab , P _gore respectively reservoir, bottomhole, rock pressure, measured at the depth of the roof 5 of the reservoir. The choice of the value of depression pressure is carried out in accordance with the requirements of the Safety Rules in the oil and gas industry (PB 08-624-03). The shutters 9 and 10 are closed at the wellhead in the lift pipes 3 and in the annulus 1, respectively, and technological exposure is carried out, for which the well is kept in a static state for at least 3 hours to obtain an inflow of formation fluid. In the absence of inflow, which is determined by the constant excess pressure at the mouth in the annulus 1 and the lift pipes 3, create a repression effect on the reservoir. The specified effect is created by injection into the annular space 1 and the elevator pipes 3 of an additional squeezing fluid until the pressure at which the acid foam penetrates into the PPP is reached. After reducing the pressure at the wellhead, which indicates the penetration of acid foam into the bottomhole formation zone, the injection fluid is pumped back into the annulus 1 and the lift pipes 3 until the initial overpressure is reached and the excess wellhead pressure is stabilized at the initial level. The establishment of a constant pressure of the squeezing fluid at the wellhead indicates the completion of the process of penetration of acid foam into the bottomhole formation zone. The valves 9 and 10 are opened and the wellhead pressure is released to atmospheric pressure by releasing the squeezing fluid into the collection tank. Thus, depression on the PPP is gradually created due to the expansion of the acid foam. The increase in overpressure at the wellhead indicates the influx of formation fluid. In the absence of an influx, alternating cycles of depression and repression are created several times (usually no more than three times), while the technological exposure is increased to 6 hours for a longer exposure to acid foam on the PPP. After the development of the well through the holes of the filter-shank 11, the reaction products of the sludge with acid foam are carried to the surface through the valves 9 and 10.

The proposed method does not require the use of non-standard technological equipment and can be implemented using commercially available units, including for overhaul and maintenance of wells with tubing lowered into them, in the presence of a pumping unit, nitrogen-compressor station and receiving tanks.

An example implementation of the method.

They mastered a directional gas well at an underground gas storage facility having the following parameters:

The depth of the roof of the reservoir (N _cr ) 814 m Reservoir pressure 10.8 MPa Mountain pressure 22.0 MPa Reservoir temperature (T _PL ) 26 ° C

Well Design:

- production casing ⌀ 168.3 mm - to the depth of the formation roof (along the length of 1026 m);

- lift pipes ⌀ 114.0 mm - to the depth of the formation roof;

The volume of the well in the interval of opening the reservoir - 3.74 m ³ ;

The opening interval of the reservoir (length) 814 ÷ 1026 m;

Static repression to the reservoir at its opening in accordance with the requirements of PB 08-624-03 for wells with a depth of up to 1200 m should be not less than 10% higher than the reservoir pressure.

Depression on the formation was determined during well development according to the requirements of PB 08-624-03:

ΔP _dep = 0.10 (P _mountains -P _pl ) ÷ 0.15 (P _mountains -P _pl ) = (0.10 ÷ 0.15) _· (22.0-10.8) ≈1.12 ÷ 1.68 MPa, i.e. to create cycles of depressions, it is necessary to create an acid foam pressure on the formation roof from 9.12 MPa to 9.68 MPa. For further calculations, the minimum calculated depression was chosen: ΔР _dep = 1.12 MPa.

Pumped into the well through the annular space squeezing liquid whose density ρ _w = 1460 kg / m ^3. This density allows you to provide a specified 10% back pressure at the depth of the roof of the reservoir. After obtaining circulation from the elevator pipes, 0.5 m ^{3 of} high viscosity separation liquid was pumped into the annulus of the well, which was used as an aqueous polymer solution with a nominal viscosity of at least 120 s.

At the wellhead (since the formation temperature is 26 ° C), acid foam was prepared. Used foaming emulsion of the following composition, wt.%:

Diesel fuel 25 KCl salt 10 Surfactant neonol AF 9-12 1,5 HCl Acid 10 Process water Rest

The volume of POE required to process the PPP in the interval of opening the horizontal trunk is 3.74 m ³ . The degree of _{aeration of the} foaming emulsion α _poet was assumed to be 20. Acid foam was prepared by supplying nitrogen by pumping with a nitrogen compressor unit of the TGA-10/251 type manufactured by TEGAS company (Krasnodar). The nitrogen flow rate is 10 m ³ / min at an injection pressure of 25 MPa. The consumption of POE for the production of acid foam is 0.5 m ³ / min.

3.74 m ^{3 of} acidic foam was pumped through the annulus into the well in a volume of foaming emulsion, after which 0.5 m ^{3 of} viscoelastic separation fluid was pumped. Acid foam was squeezed into the opening interval of the reservoir by squeezing fluid, and the total volume of squeezing fluid and viscoelastic fluid was 14.0 m.Then the annulus and lift pipes were closed and the borehole was subjected to technological exposure to establish the static equilibrium of the liquid columns in the lift pipes and annulus. Spent three technological excerpts for three hours. Then they mastered the well. After the pressure in the elevator pipes increased, which indicated the flow of formation fluid, gas was pumped from the neighboring well into the annulus and displaced the squeezing and viscoelastic separation fluid into the receiving tank, and the acid foam into another receiving tank. We tested and tested the well in five modes, after which it was put into operation.

The degree of well development was determined by the value of the specific productivity of the well before and after its processing. Specific productivity is productivity related to one meter of the uncovered thickness (length) of the reservoir:

, $${\mathrm{TO}}_{PR\mathrm{about}d}=\frac{Q}{(P_{Pl}^2-P_{s\mathrm{but}b}^2)\cdot L_{PR}}$$

,

where K _prod - specific productivity coefficient;

Q is the flow rate of the well;

R _PL and R _Zab - reservoir and bottomhole pressure, respectively; L _ave - tampering thickness (length) of the producing formation.

Implementation of the proposed method on this directional gas well allowed to increase specific productivity by more than 4 times.

The proposed method allows to increase the efficiency of development of oil and gas wells by reducing the time of exposure of acid foam to the reservoir and by eliminating the need for the use of expensive equipment, as well as increasing the productivity of wells by increasing the processing interval, including in directional and horizontal wells.

Table 1 No. p / p The composition of the POE, wt.% Acid Foam Parameters V _p cm ³ K _{p P} , 1 / s one 20% DT + 10% KCl + 1.5% surfactant + 10% HCl + 58.5% water 420 2.1 6.16 · 10 ^-2 2 25% DT + 10% KCl + 1.5% surfactant + 10% HCl + 53.5% water 480 2,4 5.68 · 10 ^-2 3 30% DT + 10% KCl + 1.5% surfactant + 10% HCl + 48.5% water 460 2,3 3.32 · 10 ^-2 four 35% DT + 10% KCl + 1.5% surfactant + 10% HCl + 43.5% water 435 2.18 2.97 · 10 ^-2 5 40% DT + 10% KCl + 1.5% surfactant + 10% HCl + 38.5% water 400 2.0 1.9810 ^-2

table 2

No. p / p The composition of the POE, wt.% Acid Foam Parameters V _p cm ³ K _{p P} , 1 / s one 0.5% surfactant + 25% DT + 10% KCl + 10% HCl + 54.5% water 550 2.75 5.8810 ^-2 2 1.0% surfactant + 25% DT + 10% KCl + 10% HCl + 54% water 740 3.70 4.0 · 10 ^-2 3 1.5% surfactant + 25% DT + 10% KCl + 10% HCl + 53.5% water 680 3.40 4.6110 ^-2 four 2.0% surfactant + 25% DT + 10% KCl + 10% HCl + 53% water 430 2.15 1.13 · 10 ^-2

Table 3 No. p / p The composition of the POE, wt.% Acid Foam Parameters V _p cm ³ K _p y _p , 1 / s one 6.0% KCl + 25% DT + 1.5% surfactant + 10% HCl + 57.5% water 476-710 2.38-3.55 (4.0-5.27) 10 ^-2 2 8.0% KCl + 25% DT + 1.5% surfactant + 10% HCl + 55.5% water 430-620 2.15-3.1 (3.9-5.38) 10 ^-2 3 10.0% KCl + 25% DT + 1.5% surfactant + 10% HCl + 53.5% water 480-740 2.4-3.7 (4.0-5.68) · 10 ^-2 four 12.0% KCl + 25% DT + 1.5% surfactant + 10% HCl + 51.5% water 370-520 1.85-2.6 (3.7-4.92) · 10 ^-2

Table 4 No. p / p The composition of the POE, wt.% Acid Foam Parameters V _p cm ³ K _p y _p , 1 / s one 5.0% HCl + 25% DT + 10% KCl + 1.5% Surfactant + 58.5% Water 520-670 2.6-3.35 (4.3-5.63) · 10 ^-2 2 10% HCl + 25% DT + 10% KCl + 1.5% surfactant + 53.5% water 480-740 2.4-3.7 (4.0-5.68) · 10 ^-2 3 15% HCl + 25% DT + 10% KCl + 1.5% Surfactant + 48.5% Water 410-570 2.05-2.85 (3.7-5.43) · 10 ^-2

Claims (1)

A method for developing oil and gas wells, including treating the bottomhole zone of the well by injecting an acid emulsion into the well and holding a process shutter, characterized in that the sequentially injected into the well equipped with a lift pipe string, a squeezing fluid, a high viscosity separation fluid and an acidic emulsion emulsions use acidic foam, which is prepared by carbonating the calculated volume of the foaming emulsion, equal to the volume of the well in the interval ytiya producing formation, wherein the foaming emulsion contains, by weight%: Diesel - 25.0;. KCl salt - 10.0; surfactant neonol AF 9-12 - 1.0-1.5; HCl acid - 10.0 and water - the rest, the degree of aeration of the foaming emulsion is regulated based on the maximum allowable depression at the depth of the roof of the reservoir, the acid foam is injected through the annulus of the well into the opening interval of the reservoir, then the acid foam is forced into the reservoir of the vending a highly viscous separation fluid with a nominal viscosity of at least 120 s is introduced between the squeezing fluid and the acid foam, and then in the annulus e wells and elevator pipes create, by means of a squeezing fluid, excess pressure on the bottom-hole zone of the formation with a periodicity that ensures the creation of alternating at least three cycles of depression and repression on the formation, while conducting technological exposure of the well for at least three hours in each of the cycles of depression and repression to receive the influx of reservoir fluid in the cycle of depression.

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