RU2465446C1 - Method of producing oil in porous fractured reservoirs reducing well product water content - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: proposed method comprises injecting displacement agent via injection wells and oil extraction via production well to water influx into well products making operation inefficient, injecting water-shutoff agent containing water-swellable particles with initial size smaller than flooded fracture follow section, conserving the well for composition structurisation period, developing and commissioning the wells. Grit from rubber-based elastomer resulted from crushing rubber 'AQUASTOP' channel or polymer grit resulted from crushing sealing gasket 'PLUG' are fed into fluid to be injected into production and injection wells, grit initial grain size being smaller than flooded fracture flow section but exceeding than of pores of oil-saturated block of bed. Said grit swells in water by, at least, 300% in 24 hours to concentration of 3-40 wt % in working fluid based on water thickened by polymer and bearing viscosity killer to release injection water. Said fluid is forced into bed by sweet water.

EFFECT: reduced water content, higher cementing properties of water-shutoff additive.

1 ex, 1 tbl

Description

The proposal relates to the oil industry, in particular, to methods for oil production in pore-fractured reservoirs, which reduce the water cut of well products, and can also be used to eliminate absorption during the construction and repair of wells.

A known method of oil displacement (patent RU No. 2267603, IPC ЕВВ 43/22, published on January 10, 2006), used in oil production and aimed at reducing water cut in well production. The method includes determining the pore diameter D of the _{pores of the} oil reservoir, injecting water through the injection well with the addition of rubber crumb, and selecting products through the producing well. After complete watering of the oil reservoir, water is pumped into it with the addition of crumbs from automobile tires with _crumb diameter D greater than or equal to 1.3 D _{then the} mass ratio of water: crumb is from 1: 0.3 to 1: 0.1, while more crumbs are served at the initial stage, and less - at the final stage of development of oil reservoir reserves.

The disadvantage of this method is that for injection into the formation of rubber crumb (RC) with a diameter greater than or equal to 1.3 D _then it is necessary to increase the injection pressure to a value that ensures fracturing or opening of cracks. And in conditions of flooding, damage from fracturing or opening of cracks can exceed the water-insulating effect from subsequent pumping of the RC, and the water cut of well production will increase even more. The method involves the use of RK obtained by processing automobile tires, which is not carried out from the formation only due to the excess of its diameter over the pore diameter of the formation. But in the process of field development, reservoir pressure differences can occur, which increase crack opening, which will lead to the removal of the RC into the well and termination of the effect of the application of the method. In addition, water does not have sufficient load-bearing capacity for pumping the rock, which can lead to uneven pumping, with the plugging of the near-well zone without the possibility of pumping crumbs into the depth of the reservoir.

The closest technical solution is a method of isolating water in pore-fractured oil reservoirs (patent RU No. 2187620, IPC ЕВВ 33/138, ЕВВ 43/32, published on 08/20/2002), used in oil production and aimed at reducing water cut in products wells. The method includes injecting a displacing agent through injection wells and oil production through production wells until the product is flooded, resulting in unprofitable operation, subsequent pumping of a water-insulating composition into the wells containing water-swelling particles with an initial particle size less than the flow cross section of water-filled cracks, leaving wells for the time of composition structuring, development and putting wells into operation. As water swellable particles, hydroxyethyl cellulose is used with a flow rate of 20-25 kg per linear meter of the insulated formation at a concentration of 1.5-2.0%.

The disadvantage of this method is that at the recommended concentration of water-swelling polymer of 2.0% and a flow rate of about 20 kg per meter of the insulated formation, each meter of the formation will block only 1.0 m ^{3 of} polymer suspension, which is not able to have a significant impact on the effectiveness of insulation work. In addition, the use of hydroxyethyl cellulose as a water-swellable polymer is not effective, since it swells unlimitedly in formation water (hereinafter, “unlimited swelling” means that the particles of plugging material injected into the formation swell in formation water over time, passing into a solution that does not have tamponing properties, but by “limited swelling” it should be understood that the particles of tamponing material injected into the formation swell in the formation water over time and without going into solution and preserving tamponing properties). These disadvantages lead to a reduction in the duration of the effect of the application of the method.

The technical objective of the proposal is to reduce the water cut of well products for a longer time by blocking waterlogged cracks with a water-insulating composition - crumbs from repeatedly and partially swelling elastomer in water pumped in a carrier fluid, increasing the plugging properties of the water-insulating composition.

The problem is solved by the method of oil production in pore-fractured reservoirs, which reduces water cut in well production, including pumping a displacing agent through injection wells and oil production through production wells until water cut in well production, resulting in unprofitable operation, subsequent pumping of a water-insulating composition containing water swellable particles into the wells smaller than the flow cross section of flooded cracks, abandonment of wells for the time of structuring the composition, development and introduction of a well Jin in operation.

New is that crumb from an elastomer based on rubber from crushing the profile of a swelling rubber “AQUASTOP” or polyurethane from crushing of a sealing pad “Plow” with an initial particle size smaller than the flow area of flooded cracks is pumped into the production and injection wells as a water-insulating composition in a carrier fluid , but with a large cross section of the pores of the oil-saturated blocks of the formation, swelling boundedly in water by at least 300% in 24 hours, with a concentration in the carrier fluid of 3-40 wt.%, carrier fluid They are used on an aqueous basis, thickened with a polymer and containing a viscosity destructor, which ensures the destruction and release of water after injection into the formation; after injection, they are pressed into the formation with fresh water.

The essence of the proposed technical solution lies in the fact that during oil production in the reservoir area with pore-fractured productive reservoirs after flooding of production wells, which leads to unprofitable operation, tamponing of flooded cracks is carried out. For this purpose, the water-swellable crumb from an elastomer based on rubber or polyurethane with an initial particle size smaller than the cross-sectional area of cracks is pumped into production and injection wells. The crumb is pumped in a water-based carrier fluid, losing the ability to hold the crumb in suspension after injection into the formation. After pumping into the formation, the carrier fluid loses its ability to hold the crumb in suspension with the simultaneous release of water. The crumb from an elastomer based on rubber or polyurethane, absorbing water, swells by at least 300% in 24 hours. Due to the multiple increase in crumb in volume, the passage section of the cracks is blocked by it. In contrast to hydroxyethyl cellulose, which, after swelling in water, is similar in properties to a gel and, over time, passes into a solution that does not have tamping properties, crumb from an elastomer has elasticity. After swelling in water with a simultaneous increase in volume, the crumb from the elastomer due to the presence of elasticity is less susceptible to leaching from cracks. Thereby, an increase in the tamponing properties of the water-insulating composition and a decrease in the water cut of the well production over a longer time are achieved.

The method is implemented as follows. On the site of the reservoir with pore-fractured productive reservoirs, the displacing agent is injected through injection and oil production through production wells until the wells are irrigated, resulting in unprofitable operation.

The increase in watering of well production leads to unprofitable operation, since when watering there is a decrease in oil production rate and the cost of raising a mixture of oil with increasing water volume increases. The costs of oil preparation and subsequent disposal of water extracted with oil also increase. The point in time when the operation becomes unprofitable is determined in the oil producing organization conducting the development of the field.

During oil production in carbonate pore-fractured reservoirs, watering of production wells most often occurs due to breakthrough of water through a system of fractures. Breakthrough water blocks oil filtration from porous reservoir blocks, and water cut progresses. In order to block the influx of water, waterlogged cracks are plugged by injection of a water-insulating composition. For this purpose, crumbs from an elastomer based on rubber or polyurethane, which is repeatedly and limitedly swelled in water, are pumped into the carrier fluid of the same name, watered in production wells and receiving the largest volume of displacing agent in injection wells. A crumb is used with an initial particle size smaller than the cross section of the cracks, but larger than the cross section of the pores of the oil-saturated blocks of the formation. Due to its initial size, such crumbs obviously cannot get into the pores of oil-saturated blocks of the reservoir and reduce the flow of oil. Since the particles of crumb from the elastomer are smaller than the cross-sectional area of the cracks, there is no need to increase the pressure when pumping to a value that ensures an increase in crack opening. This reduces the risk of increased water cut due to increased water flow through open cracks and the formation of new cracks.

The water-swellable crumb from an elastomer based on polyurethane is made by mechanical crushing of an elastomer used for the manufacture of the Plow sealant according to TU 5775-003-96657532-2008 (NPK STREAM LLC, Moscow). As part of the elastomer used for the manufacture of the Plow sealing gasket, in addition to the polyurethane base, there are acrylic resin and amorphous silica, which ensures swelling upon contact with water. The water-swellable crumb from an elastomer based on rubber is made by mechanical crushing of an elastomer used for the manufacture of an AQUASTOP swelling rubber profile in accordance with TU 5775-002-46603100-03 (LLC Akvabaryer, Moscow). The swelling profile “AQUASTOP” contains rubber based on ethylpropylene rubber as the main component.

The crumb from an elastomer based on rubber or polyurethane is used under the same conditions, the method of using these two types of crumbs is completely identical and their cost and application efficiency are approximately the same. Absorbing water from an elastomer based on rubber or polyurethane swells by at least 300% in 24 hours. The optimal mass concentration of swelling crumb from an elastomer in a carrier fluid and the mass of swelling crumb from an elastomer for work in one well vary depending on the injectivity wells. The optimal mass concentration of swelling crumb from elastomer in the carrier fluid, established experimentally, is 3.0-40 wt.%. Mass concentration of crumb from an elastomer of less than 3 wt.% Does not provide plugging of cracks. When the mass concentration of crumbs from the elastomer is more than 40 wt.%, The carrier fluid does not hold all the crumbs from the elastomer in suspension, and difficulties arise when pumping. The optimal mass of swelling crumb from elastomer for carrying out work in one well, established experimentally, is from 0.1 t to 8 t of crumb. When using less than 0.1 tons of crumbs, the effect of its use will be insignificant. The maximum crumb mass is limited by the injection pressure, which should not exceed the permissible pressure on the formation (burst pressure, leading to the formation of new cracks). The volume of the carrier fluid is from 3 m ³ to 240 m ³ .

The elastomer crumbs are pumped in a water-based carrier fluid, which holds the crumbs in suspension before injection into the formation due to the presence of sufficient viscosity. Sufficient viscosity is ensured by the presence of thickening components in the composition of the carrier fluid, for example, synthetic polymers, polysaccharides of plant origin, or others. After injection into the formation, the carrier fluid loses its ability to hold the crumb in suspension, which is ensured by the presence of a destructor in the composition of the carrier fluid. Changing the content of the destructor allows you to ensure the loss of the carrier fluid viscosity and the ability to hold the crumb in suspension after a certain period of time. As the carrier fluid can be used known compositions, for example a viscoelastic composition, including (in wt.%) A reagent based on polysaccharides - 1-3; alkali metal hydroxide - 0.05-0.45; aluminum sulfate or copper sulfate - 0.15-0.3; urea monoperoxyhydrate - 0.1-0.2 and water (patent RU No. 2116433, IPC ЕВВ 33/138, publ. 07.27.1998) or a polysaccharide liquid consisting of (in wt.%) liquid gelling agent 0.8 -1.2; Surfactant - degradation regulator 0.05-0.25; borate stapler BS-1 0.2-0.4; destructor XB; 0.0025-0.1 and water (patent RU No. 2381252, IPC С09К 8/68, publ. 02/10/2010). The specified viscoelastic composition and polysaccharide liquid have the necessary bearing capacity, ensure that the crumb from the elastomer is kept in suspension when it is pumped.

The need to pump crumbs from an elastomer in a water-based carrier fluid that loses its ability to hold the crumb in suspension after injection into the formation is caused by the following reasons. Until the moment of injection into the formation, the carrier fluid must hold the crumb in suspension, otherwise the crumb from the elastomer will precipitate at the time of pumping through the pipes, which will lead to the overlapping of the pipe cross section from the elastomer and the inability to pump into the formation. The carrier fluid keeps the crumb in suspension due to the presence of sufficient viscosity. After injection into the formation, the destruction of the carrier fluid should occur, since for the maximum swelling of the crumbs from the elastomer water is needed that is “not bound” in the carrier fluid. At the initial moment after injection into the formation, a viscous carrier fluid blocks the flow of water into the well and keeps the crumb from the elastomer in the cracks, preventing it from leaving the formation. Then there is a destruction of the carrier fluid with the release of "free" water. The crumb from the elastomer absorbs water released from the carrier fluid and contained in the formation, while simultaneously increasing in size (by at least 300% in 24 hours). Increasing in size, the crumb from the elastomer overlaps the cross-section of the cracks and blocks the flow of water through the cracks in the producing wells. Due to the multiple increase in size and the presence of elasticity, the crumb from the elastomer can no longer exit the formation. The crumb from the elastomer, pumped into the injection well, blocks cracks along which the bulk of the injected water moves. In this case, the redistribution of the pathways of the injected water with the coverage of previously undrained zones of the formation occurs, which leads to an increase in oil recovery and a decrease in water cut. Due to the physicochemical properties possessed by an elastomer based on rubber or polyurethane, the elastomer crumb swells to a limited extent and does not dissolve in water over time, therefore, the duration of the effect of the application of the method increases. The water-swollen crumb from an elastomer based on rubber or polyurethane has greater elasticity and better plugging properties, in comparison with polymer particles that turn into gel upon contact with water. Due to this, it is able to withstand large pressure drops that occur during field development. This allows to reduce the water cut of production wells to a greater extent and for a longer time than in the closest technical solution.

The proposed method can also be used in the elimination of absorption in the process of construction and repair of wells. With lesser efficiency, water-swellable crumb from an elastomer based on rubber or polyurethane with an initial particle size larger than the cross-sectional area of cracks can be used, and clay solution, hydrocarbon fluids and emulsions, including the addition of various fillers, can also be used as a carrier fluid. Before, after, and also simultaneously with crumb from the elastomer, waterproofing compositions based on polymers, sodium silicate, organosilicon compounds, resins, and others can be pumped into the carrier fluid.

An example of a practical application using crumbs from an elastomer based on polyurethane. An oil deposit in a carbonate pore-fractured reservoir is developed using injection and six production wells. Wells at a depth of 780 m opened a carbonate formation with a thickness of 12 m. The cross-sectional section of cracks in the developed formation, determined by the results of core studies, is less than 1 mm. The site is developed by pumping wastewater into an injection well. After a year of operation, a progressive flooding of four production wells with pumped water began; when the water cut reached 97%, the operation of the wells became unprofitable. In order to reduce water cut, we conducted the treatment of the injection and four intensely watered production wells with a water-insulating composition. 8 tons (corresponding to 25 wt.%) Of water-swellable crumbs from an elastomer based on polyurethane in 32 m ^{3 of} carrier fluid were pumped into the injection well. 4 tons (corresponding to 25 wt.%) Of water-swellable crumbs from an elastomer based on polyurethane in 16 m ^{3 of} carrier fluid were pumped into each production well. We used a water-swellable crumb based on polyurethane with an initial particle size of 0.1-0.5 mm, obtained by mechanical crushing of an elastomer used to make the Plow sealing gasket according to TU 5775-003-96657532-2008 (NPK STREAM LLC, Moscow). As the carrier fluid used polysaccharide gel (according to patent RU No. 2381252, IPC С09К 8/68, publ. 02/10/2010). To prepare a polysaccharide gel, a liquid gelling agent was initially prepared by mixing 50.0% by weight of guar gum; 3.0 wt.% Neftenol VKS-N and 47.0 wt.% Diesel fuel. Then a polysaccharide gel was prepared by mixing 1.0 wt.% Of a liquid gelling agent; 0.1 wt.% Surfactant - degradation regulator; 0.3 wt.% Borate crosslinker BS-1; 0.1 wt.% Destructor XB and 98.5 wt.% Fresh water. To prepare the polysaccharide gel, we used a mobile unit for the preparation and injection into the well of solutions from bulk and liquid chemicals (KUDR - 10). A description of the reagents used is given in the table.

Table Name Characteristic GOST, TU Diesel fuel - GOST 305-82. 4.2.2. Guar gum fine hygroscopic white powder, is a chemically unmodified natural polymer Import production Neftenol VKS-N a mixture of anionic and nonionic surfactants based on ethoxylated nonylphenols and an aqueous solution of potassium chloride, a light to dark brown mobile liquid TU 2483-025-54651030-2008 Surfactant degradation regulator nitrogen-containing compound, translucent yellow to brown liquid TU 2499-070-17197708-03 Borate stapler BS-1 boron-containing compound, translucent yellow to brown liquid TU 2499-069-17197708-03 Destructor XB alkali metal persulfate (Na or K) or ammonium, inorganic compound, white powder TU 2499-074-17197708-03

When pumping, the water-swellable crumb was injected into the polysaccharide gel using the APS-8M mixture preparation unit manufactured by PKB AUTOMATIKA CJSC. The pumping was carried out through tubing pipes deflated to the perforation interval. The polysaccharide gel with swellable crumb after pumping into The tubing was pumped into the reservoir with fresh water. The well was left for 48 hours while waiting for the crumb to swell. During this time (according to the results of laboratory studies conducted under conditions close to the reservoir) , the crumb from elastomer used was swollen by 400% .Then the treated wells were mastered and put into operation.

An example of a practical application using crumb from an elastomer based on rubber. An oil deposit in a carbonate pore-fractured reservoir is developed using injection and six production wells. Wells at a depth of 1144 m opened a carbonate formation with a thickness of 18 m. The cross-sectional section of cracks in the developed formation, determined by the results of a core study, is less than 1 mm. The site is developed by pumping fresh water into an injection well. After a year of operation, a progressive flooding of three production wells with pumped water began; when the water cut rate of 98% was reached, the operation of the wells became unprofitable. In order to reduce water cut, we conducted the treatment of the injection and three intensely watered production wells with a water-insulating composition. 7 tons (corresponding to 25 wt.%) Of water-swellable crumbs from an elastomer based on polyurethane in 28 m ^{3 of} carrier fluid were pumped into the injection well. 3 tons (corresponding to 19 wt%) of water-swellable crumbs from an elastomer based on polyurethane in 16 m ^{3 of} carrier fluid were pumped into each production well. We used a water-swellable crumb based on polyurethane with an initial particle size of 0.1-0.5 mm, obtained by mechanical crushing of an elastomer used to make the profile of the swelling rubber "AQUASTOP" according to TU 5775-002-46603100-03 (LLC "Aquabarrier", Moscow).

As the carrier fluid used polysaccharide gel (according to patent RU No. 2381252, IPC С09К 8/68, publ. 02/10/2010). To prepare a polysaccharide gel, a liquid gelling agent was initially prepared by mixing 50.0% by weight of guar gum; 3.0 wt.% Neftenol VKS-N and 47.0 wt.% Diesel fuel. Then a polysaccharide gel was prepared by mixing 1.0 wt.% Of a liquid gelling agent; 0.1 wt.% Surfactant - degradation regulator; 0.3 wt.% Borate crosslinker BS-1; 0.1 wt.% Destructor XB and 98.5 wt.% Fresh water. To prepare the polysaccharide gel, we used a mobile unit for the preparation and injection into the well of solutions from bulk and liquid chemicals (KUDR - 10). A description of the reagents used is given in the table. When pumping, the water-swellable crumb was injected into the polysaccharide gel using the APS-8M mixture preparation unit manufactured by PKB AUTOMATIKA CJSC. The pumping was carried out through tubing pipes deflated to the perforation interval. The polysaccharide gel with swellable crumb after pumping into The tubing was pumped into the reservoir with fresh water. The well was left for 48 hours while waiting for the crumb to swell. During this time (according to the results of laboratory studies conducted under conditions close to the reservoir) the crumb from elastomer used was swollen by 440% .Then the treated wells were mastered and put into operation.

The application of the proposed technical solution allows 1.2-1.4 times to extend the effect of the application of the method by blocking flooded cracks with a water insulating composition with increased water insulating properties - crumbs from repeatedly and limited to swell elastomer in water pumped in a carrier fluid.

Claims (1)

A method of oil production in pore-fractured reservoirs, which reduces water cut in well production, including pumping a displacing agent through injection wells and oil production through production wells to water the production wells, resulting in unprofitable operation, subsequent pumping a water-insulating composition containing water swelling particles with an initial size into the wells smaller flow cross section of flooded cracks, abandonment of wells for the time of structuring the composition, development and commissioning of wells characterized in that crumb from an elastomer based on rubber from crushing of the profile of a swelling rubber "AQUASTOP" or polyurethane from crushing of a sealing pad "Plow", with an initial particle size less than the cross-section, is pumped into production and injection wells as a water-insulating composition in a carrier fluid flooded cracks, but with a large cross section of the pores of oil-saturated blocks of the formation, which swell limitedly in water by at least 300% in 24 hours, with a concentration in the carrier fluid of 3-40 wt.%, carrier fluid They are water-based, thickened with polymer and containing a viscosity destructor, which ensures the destruction and release of injection water into the formation; after injection, they are pressed into the formation with fresh water.