RU2349743C1 - Method of extraction of high viscosity oil from carbonate collectors - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: according to method of extraction of high viscosity oil before pressurising of replacing agent into carbonate collector following is pumped: saturated water solution of ammonium chloride in volume 0.08 of void volume, then spacer fluid - 5% solution of sodium chloride in volume equal 2-3 m of height of pump-compressor pipes, after that 35-40% water solution of formalin in volume 0.07 of void volume is added, then solution of catalyst - sodium or potassium hydroxide at amount of 7% from volume of preliminary supplied liquid, which is pressurised into collector by means of acetate spacer in volume equal 2-3 m of height of pump-compressor pipes, then 30% hydrogen peroxide in volume of 0.1 of void volume, acetate spacer in volume equal 2-3 m of height of pump-compressor pipes, then 5% solution of manganese as catalyst of hydrogen peroxide pumped into formation with replacing agent supplied in volume equal to one volume of pump-compressor pipes; then holding is carried out and pumping of replacing agent is commenced with simultaneous withdrawal of oil from producing wells.

EFFECT: upgraded efficiency of method.

Description

The invention relates to the oil industry, in particular to the development of oil fields, namely deposits of high viscosity oils and bitumen in dense carbonate reservoirs using physico-chemical methods of exposure.

A known method of developing deposits of highly viscous oil or bitumen (RF patent No. 2286445, IPC EV 43/24, publ. 2006.10.27). When developing a highly viscous oil or bitumen deposit, horizontal wells are drilled with horizontal injection wells located above the producing horizontal wells, coolant is injected through the horizontal injection wells and reservoir fluids are taken through the producing horizontal wells. For the development of deposits take a deposit with a carbonate reservoir. Production horizontal wells are placed perpendicular to the direction of natural fracture of the carbonate reservoir. Horizontal injection wells are drilled from vertical wells located above horizontal trunks of production wells. Moreover, the horizontal wells of injection wells are drilled by erosion of the rock under fluid pressure with the formation of thin channels with a diameter of 30-70 mm. Thin channels are of different lengths with the predominant placement of longer channels in a direction close to the direction perpendicular to the direction of natural fracture of the carbonate reservoir, and shorter channels are predominantly placed in the direction of natural fracture of the carbonate reservoir. The disadvantage of this method is the low efficiency associated with insufficiently effective impact on a dense carbonate reservoir and a narrow scope.

A known method of developing an oil field with carbonate reservoirs of low productivity (RF patent No. 2227207, IPC EV 43/20, publ. 2002.06.19). The essence of the invention: according to the method in the bush have production, injection and water wells. Areal placement of wells is carried out according to a uniform triangular grid of 400 × 400 m. Injection of a working agent through injection wells is carried out according to a seven-point scheme in a cyclic mode. As a working agent, highly mineralized, thermal, produced water of the underlying horizons is used. The discharge pressure withstand 0.6 mountain. At the mouth of the injection wells, the pressure is maintained at 3.0-6.0 MPa. The intake and injection of produced water is carried out by electric submersible pumps in a cyclic mode with periodic injection of a microbiological composition based on dry activated sludge into the formation. As the production wells are flooded, the extra production of oil in the interwell space is carried out by drilling additional sidetracks from the flooded wells. The disadvantage of this method is the insufficient effect on the dense carbonate reservoir and the aggressiveness of the reagents supplied through the well, which leads to high corrosion wear of the tubing.

A known method of processing carbonate reservoirs, adopted as a prototype (RF patent No. 2094604, IPC EV 43/27, publ. 1997.10.27). The essence of the invention: inject 15% hydrochloric acid into the aluminum-containing composition in the ratio of 1:30, which leads to an increase in the start time of interaction with the carbonate rock due to the inhibition of the hydrolysis of aluminum chloride and reduces the possibility of gelation by 1.5-4.2 times As a result, the radius of the formation treatment is increased by 4-10 times compared with conventional acid treatments. The disadvantage of this method is the lack of impact on the dense carbonate reservoir and the aggressiveness of the reagents supplied through the well, which leads to high corrosion wear of the tubing.

The technical result of the invention is to increase the efficiency of the method through the use of complex thermogasdynamic effects on a dense carbonate reservoir using low aggressive reagents to prevent premature corrosion wear of tubing.

The technical result is achieved in that in a method for producing highly viscous oil from carbonate reservoirs, including drilling injection and production wells from a surface on a specific grid, installing tubing in them, pumping a displacing agent and taking oil from production wells, according to the invention, before pumping a displacing agent in a carbonate reservoir pump saturated aqueous solution of ammonia in a volume of 0.08 pore volume, then the buffer liquid is a 5% solution of sodium chloride in a volume equal to 2- 3 m in height of the tubing, after which a 35-40% aqueous formalin solution is supplied in a volume of 0.07 pore volume, after which a catalyst solution is injected - sodium hydroxide or potassium hydroxide, in the amount of 7% of the volume of previously supplied liquid which is pressed into the collector using an acetate buffer in a volume equal to 2-3 m in height of the tubing, then 30% hydrogen peroxide is fed in a volume of 0.1 pore volume, an acetate buffer in a volume equal to 2-3 m in height of the tubing, then a 5% solution of ma Rhana as a catalyst of hydrogen peroxide, injected into the reservoir by a displacing agent supplied in a volume equal to one volume of the tubing, withstand and resume the injection of the displacing agent with simultaneous extraction of oil from the producing wells.

The application of the proposed method in comparison with the prototype will improve its efficiency through the use of complex thermogasdynamic effects on a dense carbonate reservoir using low aggressive reagents to prevent premature corrosion wear of the tubing.

With the use of thermal technologies for the processing of oil from dense carbonate reservoirs, the following limit values for the extraction of highly viscous oil are established: with heat and steam and in-situ combustion - 0.3 units; with steam-cyclic treatments of the bottom-hole zones of wells - 0.5 units When developing viscous heavy oils in dense carbonate reservoirs, oil recovery under natural conditions does not exceed 0.08-0.12 unit units. When using the proposed method of oil production from dense carbonate reservoirs using thermogasdynamic effects, this value can be increased to 0.7-0.8 units. The main components of high-viscosity oil - paraffins, resins and asphaltenes - have high viscosity, crystallization and the ability to "drop out" (condensation) at temperatures of 25-30 ° C. This leads to poor filtration and reduced oil recovery. The attenuation coefficient of the filtration of heavy paraffinic oils is: at 60 ° C - 1; at 45 ° C - 2.1; at 30 ° C -2.5; at 15 ° C - 5. The attenuation coefficient of the filtration is reversible and increases with increasing temperature and disappears at t = 60-65 ° C for most oils.

In order to influence the bottom-hole zone of a formation in rocks containing more than 20% carbonates or in sandy rocks with a cementing material consisting of calcium or magnesium carbonates, acids are widely used, the main of which is HCl. Hydrochloric acid has a high corrosivity and affects almost all metals included in the design of ground and underground equipment during the processing operation. Various inhibitors are used to reduce the corrosive activity of hydrochloric acid, but their use does not solve all the problematic issues to prevent corrosion, especially when stimulating deep wells. In order to increase the efficiency and safety of operations with the simultaneous intensification of oil production, it is advisable to generate hydrochloric acid directly in the reservoir.

The method of formation in the collector of hydrochloric acid consists in pumping aqueous solutions of ammonia and formalin into it:

4NH ₄ Cl + 6CHNO → C ₆ H ₁₂ N ₄ + 4HCl + 6H ₂ O

To prevent the reaction of the formed hydrochloric acid with the formed hexamethylenetetramine (C ₆ H ₁₂ N ₄ ), an excessive amount of ammonia must be used.

Ammonium chloride - NH ₄ Cl, colorless crystals. Nitrogen fertilizer (up to 25% N) for neutral and alkaline soils for crops that are poorly responsive to excess chlorine (sugar beets, rice, corn). They are also used in the production of dry galvanic cells, in soldering and tinning, in medicine, as a smoke generator. To obtain an aqueous solution of ammonia, you can use ammonium chloride, which is in solid crystalline form. Ammonium chloride is readily soluble in water; at 20 ° C, a saturated solution contains 37 g of ammonia per 100 cm ^{3 of} water.

Formalin is an aqueous solution containing 37-40% formaldehyde and 6-15% methyl alcohol (stabilizer). During storage it becomes cloudy, because a white precipitate (paraformaldehyde) precipitates. Source of formaldehyde disinfectant and deodorizing agent; solution for the preparation of anatomical preparations and tanning of the skin. Formalin necessary for the implementation of the method is in the form of an aqueous solution with a concentration of 35-40%.

When using the proposed method, the effects of thermodynamic and hydrodynamic effects (thermogasdynamic effects) are simultaneously superimposed. It is known that at a calcination temperature of 800-1000 ° C, carbonate rocks undergo significant physical and chemical changes. There is an increase in porosity and permeability of the reservoir. Porosity increases several times, and permeability increases by an order of magnitude and higher (according to the heat treatment of the Artinskian stage of the Perm deposits of Bashkiria). When exposed to high temperature, up to 800-1000 kg of CO ₂ can be released from 1 m ^{3 of} carbonate rock. In this case, the released volume of CO ₂ causes a significant increase in the oil recovery of the reservoir. The decomposition of CaCO ₃ occurs at a temperature of 649-815 ° C:

CaCO ₃ → CaO + CO ₂

At the upper limit, the sample turns into CaO. Thus, the carbonate reservoir may become fragile when exposed to high temperatures. According to studies by domestic and foreign authors, the characteristics of CO ₂ at high temperatures change:

- the mass of the studied samples is reduced by 20-40%. This is due to the shrinkage (sintering) of clay impurities with the evaporation of hydrated water;

- the effective porosity of the samples increases by 140-160%;

- the permeability of the sample increases significantly: from 120 to 220 md ~ 90%; from 30 to 107 md ~ 250%.

During the experiments, the breed changed from solid, well cemented to relatively fragile. The lack of cementation is associated with burning clay and free carbon.

When applying the proposed method, in addition to the above processes, the elastic energy supply increases due to the manifestation of a gas-pressure effect. The dissolution of CO ₂ in oil leads to a decrease in its viscosity. A positive aspect of the change in gas equilibrium is the volume expansion of oil. When a dense carbonate reservoir is heated, thermal expansion of formation fluids and a decrease in their viscosity occur. Capillary forces are the main reason holding oil in a heterogeneous porous medium (reservoir). They determine the residual oil saturation, and with increased water saturation of the bottom-hole zone, they prevent the flow of oil. With increasing temperature, capillary processes are practically eliminated by reducing viscosity and decreasing interfacial tension to 0.01 mN / m, which allows for almost complete oil displacement.

In a dense carbonate reservoir, as the reactants are fed, reactions of the following type occur, accompanied by the formation of hydrochloric acid directly in it:

4NH ₄ Cl + 6CHNO → C ₆ H ₁₂ N ₄ + 4HCl + 6H ₂ O

To obtain 1 mole of HCl, you must:

- NH ₄ Cl - 1 mol;

- NSNO - 1.5 moles.

To obtain 1 kmol of HCl, you must:

- NH ₄ Cl - 1 kmol or 53.5 kg, because the molar mass of NH ₄ Cl is 53.5 g / mol;

- НСОО - 1.5 kmol or 45.045 kg, because the molar mass of НСОО is 30.03 g / mol or in volume units of 33.6 m ³ (under normal conditions).

As a result of the reaction 4NH ₄ Cl + 6CHNO → C ₆ H ₁₂ N ₄ + 4НСд + 6Н ₂ О, 53.5 kg of NH ₄ Cl and 45.045 kg of HCNO react in the carbonate reservoir to produce 71 kg of hydrochloric acid HCl.

A method of producing high viscosity oil from carbonate reservoirs is as follows. Injection and production wells are drilled from the surface into the carbonate reservoir according to a specific grid, determined mainly by the geological structure of the reservoir. Mount tubing in the wells. Before injection of a displacing agent, for example water, is similar in composition to the formation, ammonia is pumped into the carbonate reservoir in the amount of 0.08 pore volume. Ammonium chloride serves as a reagent for the formation of hydrochloric acid in the reservoir. Injecting it in a volume of 0.08 from the pore allows you to conduct the most effective reaction of the formation of HCl in the reservoir. Then, a buffer liquid is fed into the well - a 5% sodium chloride solution in an amount equal to 2-3 m in height of the tubing. The volume of injection of the buffer fluid depends on the internal cross-sectional area of the tubing. For example, with an internal cross-sectional area of tubing of 0.1 m ^2, the injection volume will be 0.2-0.3 m ^3, respectively. Buffer fluid serves to separate ammonia from a formalin solution and prevent their reaction directly in the tubing. The injection of a 5% solution of sodium chloride in the amount of 2-3 m in height of the tubing allows us to guarantee a preliminary “flushing” of the tubing before formalin. Then served 35-40% aqueous formalin solution in the amount of 0.07 pore volume. Formalin is a reagent for the formation of hydrochloric acid, pumping it in a volume of 0.07 from the pore volume allows for the most complete reaction. After it, a catalyst solution is injected - sodium hydroxide or potassium hydroxide, in the amount of 7% of the volume of the supplied liquid. A catalyst is needed to increase the reaction temperature when hydrogen peroxide is fed. Pumping it in a volume of 7% of the volume of the supplied liquid allows us to provide the most effective reaction temperature. The catalyst is fed using the acetate buffer necessary to separate the catalyst from hydrogen peroxide in an amount equal to 2-3 m in height of the tubing, which will ensure that there is no reaction directly in the tubing. The acetate buffer injection volume depends on the internal cross-sectional area of the tubing. For example, with an internal cross-sectional area of tubing of 0.1 m ^2, the injection volume will be 0.2-0.3 m ^3, respectively. Then served 30% hydrogen peroxide, in the amount of 0.1 pore volume. Hydrogen peroxide - H ₂ O ₂ , a colorless viscous liquid; density 1.45 g / cm ³ , t _pl = 0.41 ° C, t _bale = 150.2 ° C. Easily decomposes into water and oxygen. They are used as an oxidizing agent, a polymerization initiator, for bleaching hair, fur, silk, and in medicine as an antiseptic, hemostatic and deodorizing agent. Available in the form of 30-90% aqueous solutions (30% solution is called perhydrol). The use of perhydrol will improve the security of operations of the method. A feed of 0.1 pore volume will allow the remaining pore volume of the dense carbonate reservoir to be drawn into the treatment. The main advantages of using 30% hydrogen peroxide are as follows: 1) There are no heat losses on the surface and in the wells, especially in horizontal wells with a long length; 2) Most of the heat is distributed through heat transfer. When using 30% hydrogen peroxide, you can create a temperature of at least 550 ° C, which allows for shrinkage of clays, to destroy carbonates and evaporate emulsions; 3) In the processing cycles, preheating is used, therefore, in multi-stage processing, an insignificant part of the heat is lost; 4) In the case of horizontal wells, hydrogen peroxide stimulation is the only possible way to heat-treat these horizontal sections. Then, the acetate buffer necessary for separating the catalyst and hydrogen peroxide is fed in an amount equal to 2-3 m in height of the tubing, which will ensure that there is no reaction directly in the tubing. The acetate buffer injection volume depends on the internal cross-sectional area of the tubing. For example, with an internal cross-sectional area of tubing of 0.1 m ^2, the injection volume will be 0.2-0.3 m ^3, respectively. Then a 5% solution of manganese is fed as a catalyst, injected into the formation by squeezing liquid, supplied in a size equal to one volume of tubing. After exposure, the injection of the displacing agent (water) is resumed with the simultaneous extraction of oil from the producing wells. The exposure time depends on the volume of injected reagents and can range from several hours to several days.

The use of this method of producing high-viscosity oil from carbonate reservoirs provides the following advantages:

- ensuring stable mobility of oil in a dense carbonate reservoir due to complex thermogasdynamic effects;

- reduction of corrosion wear of tubing.

Claims (1)

A method for producing highly viscous oil from carbonate reservoirs, including drilling injection and production wells from a surface on a specific grid, installing tubing in them, pumping a displacing agent and taking oil from production wells, characterized in that they are pumped into a carbonate reservoir before pumping the displacing agent a saturated aqueous solution of ammonia in a volume of 0.08 pore volume, then a buffer liquid - a 5% solution of sodium chloride in a volume equal to 2-3 m in height of the tubing, Then a 35-40% aqueous formalin solution is supplied in a volume of 0.07 pore volume, after which a catalyst solution is injected - sodium hydroxide or potassium hydroxide in the amount of 7% of the volume of the previously supplied liquid, which is forced into the collector using acetate buffer in a volume equal to 2-3 m in height of the tubing, then 30% hydrogen peroxide is fed in a volume of 0.1 pore volume, acetate buffer in a volume of 2-3 m in height of the tubing, then 5% solution of manganese as a catalyst for hydrogen peroxide The ode injected into the reservoir by a displacing agent supplied in an amount equal to one volume of the tubing, withstand and resume the displacement of the displacing agent with the simultaneous extraction of oil from the producing wells.