Method of well construction in unstable reservoirs

Abstract

FIELD: oil and gas industry.SUBSTANCE: method of constructing a well in unstable reservoirs includes the initial opening of a weakly cemented formation that is heterogeneous in permeability and the nature of the extracted product with the intersection of a contact dividing the formation by saturation, lowering a production string containing a perforated section at the formation level with holes plugged with magnesium plugs, performing direct single-stage cementing of the well with a cement slurry with the injection of the last portion of the cement slurry, initiating the formation of a cement wellbore filter, the creation, upon completion of cementing the well, at the formation level of a cement wellbore filter due to the action of hydrochloric acid on the magnesium plugs and the last portion of the cement slurry, and controlled extraction of well products. A fractured deep filter is created along the cement wellbore filter and the product passing through it in the depth of the formation. At the level of the contact dividing the layer by saturation, an impermeable screen is formed. A fractured deep filter and impermeable screen are created around the well through rows of proppant-reinforced horizontal hydraulic fractures and drilled radial channels. After creating a cement wellbore filter, a hydraulic fracturing assembly and a diverter are lowered into the production casing at the formation interval, and a coiled tubing pipe with a cable-controlled drilling head is lowered into them. When lowering the hydraulic fracturing assembly, the diverter is successively installed and fixed with a pressure sealing shoe at the level of interlayers with different permeability, as well as the contact separating the formation according to saturation. The formation along the bedding of rocks is drilled with parallel radial channels, through which directional hydraulic fracturing is carried out with the formation of horizontal hydraulic fractures, reinforced with proppant. An insulating composition is pumped into the horizontal hydraulic fracture at the level of the contact dividing the formation by saturation, forming an impermeable screen, and through the horizontal hydraulic fracture at the level of interlayers with different permeability, a fractured deep filter is pumped parallel to the cement wellbore filter, and well products are withdrawn from the depth of the formation.EFFECT: reduction in filtration resistance in the near-wellbore zone, a reduction in rock destruction, sand removal and coning from various contacts dividing by saturation with an increase in the uniformity and rate of product extraction, an increase in formation coverage, and an increase in oil recovery and gas recovery from the reservoir.1 cl, 4 dwg

Description

[0001] The invention relates to the oil and gas production industry, in particular to methods for constructing a well in an unstable section and can find application in the development of a poorly cemented heterogeneous formation with zones of varying permeability and saturation, when production is associated with the destruction of rock, the removal of sand, and the risk of unwanted fluids breaking through into the well.

[0002] A method for constructing wells in unstable reservoirs is known, including hydraulic fracturing (HF) using a HF assembly with a packer and the creation of a sand filter based on vertical HF fractures secured with proppant. A positive feature of this method is the additional formation stimulation by vertical HF fractures in both oil and gas wells, increasing the drainage surface of the near-wellbore zone and reducing its filtration resistance [Patent for Invention RU No. 2464410].

[0003] The disadvantage of this method is that it cannot be used in a thin-layered environment due to the unpredictability of the propagation of vertical hydraulic fractures.

[0004] A method for constructing a well in unstable reservoirs is known, which includes the initial opening of a weakly cemented formation, lowering a production string containing a section perforated with holes with plugged magnesium plugs at the formation level, performing direct single-stage cementing of the well with a cement slurry with the pumping of the last portion of the slurry initiating the formation of a cement filter near the wellbore, the creation of a cement filter near the wellbore at the formation level upon completion of cementing the well due to the action of hydrochloric acid on the magnesium plugs and the last portion of the cement slurry, the collection of well production while limiting the removal of sand and the breakthrough of unwanted fluid into the well. The method has no restrictions on the thickness of the formation, but its cement filter near the wellbore is designed for use only in gas wells [Aksenova N.A., Ovchinnikov V.P., Anashkina A.E.Technology and technical means for completing wells with unstable reservoirs: monograph / - Tyumen: TIU, 2018. - P. 122-124, prototype].

[0005] A disadvantage of this method is the reduction in well productivity due to increased filtration resistance in the cement filter, its clogging, and rapid failure during intense sand production, such as from a superreservoir. This method is difficult to use in formations with heterogeneous permeability and production characteristics, when penetrating a contact that differentiates saturation (gas-water, gas-oil, or water-oil). The cement filter is designed to pass gas only and does not provide for the recovery of the liquid component of the product, which limits the method's capabilities, formation coverage, and oil recovery, increasing process risks and well production costs.

[0006] The objective of the invention is to expand the scope of use of the method and its functional capabilities in the development of a weakly cemented formation that is heterogeneous in permeability and the nature of the extracted product, including a supercollector.

[0007] The technical result of the invention is a reduction in filtration resistance in the near-wellbore zone, a reduction in rock destruction, sand removal and coning from the side of various contacts dividing by saturation (gas-water, gas-oil, water-oil) with an increase in the uniformity and rate of product selection, an increase in formation coverage, an increase in oil recovery and gas recovery of the deposit, a reduction in technological risks and costs for the production of well products.

[0008] The technical result is achieved by constructing a well in unstable reservoirs, including the initial penetration of a poorly cemented formation with heterogeneous permeability and production characteristics, intersecting the contact dividing it by saturation (gas-water, gas-oil, or water-oil). Running a production string containing a perforated section at formation level with holes plugged with magnesium plugs. Direct single-stage cementing of the well with a cement slurry is performed, with the final portion of the slurry injected to initiate the formation of a cement filter. Upon completion of well cementing, a cement filter is created at formation level by the action of hydrochloric acid on the magnesium plugs and the final portion of the cement slurry. Controlled production of well products is achieved, limiting sand production and the breakthrough of unwanted fluids into the well.

[0009] According to the invention, a fractured depth screen is created along the cement wellbore filter and the fluid passing through it, taking into account the formation's structure. This screen is created separately for interlayers with different permeabilities. At the level of the formation's saturation contact, an impermeable screen is formed to limit the breakthrough of unwanted fluid into the wellbore. The fractured depth screen and impermeable screen are created around the wellbore through rows of proppant-supported horizontal hydraulic fractures and drilled radial channels, the ends of which, on the production casing side, are cased with a liner with a swellable packer. The number of rows of proppant-supported horizontal hydraulic fractures is equal to the sum of the interlayers with different permeabilities and the formation's saturation contacts.After creating a cement wellbore filter, a hydraulic fracturing assembly and a diverter are lowered into the production casing over the formation interval, followed by a coiled tubing pipe with a cable-controlled drilling head. During the hydraulic fracturing assembly's descent, the diverter is sequentially installed and secured with a pressure sealing shoe at the level of interlayers with different permeabilities, as well as the saturation contact. The formation is drilled along the bedding plane with parallel radial channels, through which directional hydraulic fracturing is performed, creating horizontal hydraulic fractures reinforced with proppant. In this case, an insulating composition is pumped into the horizontal hydraulic fracture at the level of the contact dividing the formation by saturation and an impermeable screen is formed, and through the horizontal hydraulic fractures at the level of interlayers with different permeability - a fractured deep filter parallel to the cement wellbore filter, well products are withdrawn from the depth of the formation.In this case, the sampling of products through a cracked deep filter from a layer with greater permeability is carried out through a nozzle installed in the corresponding tail pipe, and the sampling of products is carried out regardless of its composition.

[0010] The proposed method for constructing a well in unstable reservoirs is explained using the example of a horizontal gas condensate layer with bottom water in the drawings shown in Figs. 1-4.

[0011] Fig. 1 shows a diagram of the implementation of the proposed method, the stage of the primary opening of a heterogeneous weakly cemented formation, completion of well cementing and creation of a cement near-wellbore filter; Fig. 2 - the same, the stage of developing a heterogeneous weakly cemented formation with limiting the removal of sand and water by an additional fractured deep filter and an impermeable screen; Fig. 3 - the same, the stage of lowering the hydraulic fracturing assembly, the diverter, the coiled tubing pipe, the drill head into the well with subsequent drilling of the formation with radial channels, the formation of horizontal hydraulic fracturing fractures and an impermeable screen; Fig. 4 - shows view a-a in Fig. 3 (reduced scale).

[0012] The following designations are used in the drawings above. Well 1; poorly cemented heterogeneous formation 2 with low-permeability interlayer 2a, high-permeability interlayer 2b, tight rock interlayer 2ab and gas-water contact 2c; production casing 3 with perforated section 3a and holes 3b; last portion 4 of cement slurry initiating formation of cement wellbore filter 5; fractured depth filter 6 separate for low-permeability interlayer (6a) and high-permeability interlayer (6b); impermeable screen 7 at the level of gas-water contact; part (sector) of impermeable screen 7a; rows 8 of horizontal fractures 9 of hydraulic fracturing secured with proppant; parallel radial channels 10 cased with liners 11 on the side of production casing; GRP assembly 12; deflector 13 with spring 13a and pressure sealing shoe 13b; coiled tubing pipe 14 with cable-controlled 14a drilling head 14b; nozzle 15.

[0013] The method is carried out as follows.

[0014] During the construction of well 1 in unstable reservoirs, the primary opening of a weakly cemented, heterogeneous in permeability layer 2 is carried out, for example, a low-permeability interlayer 2a and a high-permeability interlayer 2b (superreservoir) separated by an interlayer 2ab of dense rocks (Figs. 1, 2). In this case, the heterogeneous in the nature of the product withdrawn from interlayers 2a, 2b (e.g., gas, condensate) layer 2 with water in the bottom part and a gas-water contact 2c is a single development object. A production casing 3 containing a perforated section 3a at the level of layer 2 with holes 3b plugged with magnesium plugs (not shown) is lowered into the drilled well 1. Then, direct single-stage cementing of well 1 is carried out with cement slurry with the injection of the last portion 4 of the solution initiating the formation of a cement wellbore filter 5 at the level of formation 2.After cementing is completed, hydrochloric acid (not shown) is pumped into well 1, and its action on the magnesium plugs and the last portion 4 of the cement slurry creates a gas-permeable (but not condensate-permeable) cement filter 5 at the level of formation 2 that limits sand removal. Next, along the created cement filter 5 and the product passing through it, a fractured depth filter 6 is created in the depth of formation 2, taking into account its structure, separately for interlayer 2a (filter 6a) of low permeability and interlayer 2b (filter 6b) of high permeability. Simultaneously, an impermeable screen 7 is formed at the level of gas-water contact 2c, limiting the breakthrough of undesirable fluid, namely, bottom water, into well 1.The fractured depth filter 6 (6a, 6b) and the impermeable screen 7 are formed around the well 1 through rows 8 of horizontal fractures 9 reinforced with proppant and drilled radial channels 10, the ends of which on the side of the production string 3 are cased with a liner 11 with a swellable packer. In this case, the number of rows 8 of horizontal fractures 9 reinforced with proppant is equal to three - the sum of interlayers with different permeability (two interlayers) and contacts dividing the formation by the nature of saturation (one contact). After cementing the well 1 and creating a cement wellbore filter 5, the hydraulic fracturing assembly 12 and the diverter 13 are lowered into the production string 3 to the interval of the formation 2, and a coiled tubing pipe 14 with a drilling head 14b controlled by a cable 14a is lowered into them (Fig. 3).When lowering the hydraulic fracturing assembly 12, the diverter 13 is successively installed and secured via the spring 13a and the pressure sealing shoe 13b at the level of the interlayers 2a, 2b with different permeabilities, as well as the gas-water contact 2c, which separates them by the saturation nature. At each specified level, the formation 2 is drilled along the rock stratification by parallel radial channels 10, through which directional hydraulic fracturing is carried out, forming horizontal fractures 9 of the hydraulic fracturing system, reinforced with proppant (Figs. 3, 4). Drilling of the formation 2 begins, for example, from the lower level corresponding to the gas-water contact 2c. After activating the pressure sealing shoe 13b at the level of the gas-water contact 2v, the coiled tubing pipe 14 and the drilling head (for example, a hydraulic monitor) 14b are put into operation, first with a sand-liquid mixture, then with clean liquid.In this case, formation 2 at the level of gas-water contact 2c is drilled along the rock bedding with parallel radial channels 10, possibly with processing (not shown) to further weaken the strength of the rocks around these channels. Then, coiled tubing pipe 14 and drill head 14b are raised into the hydraulic fracturing assembly 12 (not shown), directional hydraulic fracturing of formation 2 is carried out, a horizontal hydraulic fracture 9 is created, reinforced with proppant, into which an insulating, for example, gelling composition is pumped and a part (sector) of the impermeable screen 7a is formed. Next, by manipulating the pressure sealing shoe 13b, the deflector is turned, for example, by 180° and in a similar order the missing part of the impermeable screen is created, obtaining an impermeable screen 7 (Fig. 2) around the wellbore 1 blocking gas-water contact 2c.The near-wellbore, most dangerous zone of well 1 is additionally reinforced with liner 11 with possible installation (not shown) of a downhole cement bridge, using separate tripping operations of coiled tubing pipe 14. Upon completion of work at the lower level with the formation of an impermeable screen 7 along the gas-water contact 2c, the hydraulic fracturing assembly 12, the diverter 13, the coiled tubing pipe 14 and the drill head 14b are moved to the next level and in a similar sequence the remaining rows 8 of horizontal fractures 9 of the hydraulic fracturing are created in the middle part of the interlayers 2a, 2b. In this case, the ends of the radial channels 10 on the side of the production string 3 are also cased with a liner 11 with a swelling packer to strengthen the near-wellbore zone of the well 1. The development of a heterogeneous formation 2 (Fig. 2) is carried out with the limitation of the removal of sand and water by an additional fractured deep filter 6 and an impermeable screen 7, regardless of the nature of the well product being extracted (gas, condensate).The product is withdrawn from the depth of formation 2 through two rows 8 of horizontal fractures 9 of the hydraulic fracturing system, secured with proppant, located in the middle portion of interlayers 2a and 2b—a fracture depth filter 6 parallel to the cemented wellbore filter 5. (This allows for the extraction of well product also in the liquid phase, including high-viscosity oil.) To ensure uniform product extraction from interlayers 2a and 2b, as well as to reduce the destruction of the most poorly cemented superreservoir (interlayer 2b), its liner 11, connected to the fracture depth filter 6b, is equipped with additional hydraulic resistance, namely, a choke 15.

[0015] The use of the proposed method provides increased protection of a heterogeneous, poorly cemented formation from destruction and coning, reduces filtration resistance in the near-wellbore zone due to the parallel connection of a fractured deep filter to a cement filter with the possibility of increasing the uniformity and rate of formation fluid extraction, regardless of the nature of the product being extracted.

Claims

A method for constructing a well in unstable reservoirs, which includes the initial opening of a weakly cemented formation that is heterogeneous in permeability and the nature of the extracted product with the intersection of a contact dividing the formation by saturation - gas-water, gas-oil, water-oil, lowering a production string containing a perforated section at the level of the formation with holes plugged with magnesium plugs, performing direct single-stage cementing of the well with a cement slurry with the pumping of the last portion of the cement slurry, initiating the formation of a cement near-wellbore filter, the creation upon completion of cementing of the well at the level of the formation of a cement near-wellbore filter due to the action of hydrochloric acid on magnesium plugs and the last portion of the cement slurry, controlled extraction of well products with limitation of sand removal and breakthrough of unwanted fluid into the well, characterized in that,that along the cement wellbore filter and the product passing through it, in the depth of the formation, taking into account its structure, a fractured depth filter is created, separately for interlayers with different permeability, and at the level of the contact dividing the formation by saturation, an impermeable screen is formed, limiting the breakthrough of undesirable fluid into the well, and the fractured depth filter and impermeable screen are created around the well through rows of horizontal hydraulic fractures reinforced with proppant and drilled radial channels, the ends of which on the side of the production casing are cased with a liner with a swelling packer, and the number of rows of horizontal hydraulic fractures reinforced with proppant is equal to the sum of interlayers with different permeability and contacts dividing the formation by saturation, and after the creation of the cement wellbore filter, a hydraulic fracturing assembly and a diverter are lowered into the production casing onto the interval of the formation,and a coiled tubing pipe with a drill head controlled by a cable is lowered into them, when lowering the hydraulic fracturing assembly, the diverter is successively installed and fixed with a pressure sealing shoe at the level of interlayers with different permeability, as well as the contact separating the formation by saturation and the formation along the bedding of rocks is drilled with parallel radial channels, through which directional hydraulic fracturing is carried out with the formation of horizontal hydraulic fracturing cracks, fixed with proppant, while an insulating composition is pumped into the horizontal hydraulic fracturing crack at the level of the contact separating the formation by saturation and an impermeable screen is formed, and through the horizontal hydraulic fracturing cracks at the level of interlayers with different permeability - a fractured deep filter parallel to the cement near-wellbore filter, wellbore production is withdrawn from the depth of the formation, while the selection of products through the fractured deep filter from the interlayer with greater permeability is carried out through the choke,installed in the corresponding tailpiece, and the selection of products is carried out regardless of its composition.

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