Disclosed herein are compositions and methods for reducing fluid loss in a well bore, methods for wellbore strengthening and increasing the integrity of the borehole of an oil or gas well. Also disclosed are methods for artificially increasing the temperature of a subsurface formation in the wellbore to increase the apparent wellbore strength. The mechanism for accomplishing this revolves around increasing fracture propagation pressure by actively manipulating thermal wellbore stresses.

Disclosed herein are compositions and methods for reducing fluid loss in a well bore, methods for wellbore strengthening and increasing the integrity of the borehole of an oil or gas well. Also disclosed are methods for artificially increasing the temperature of a subsurface formation in the wellbore to increase the apparent wellbore strength. The mechanism for accomplishing this revolves around increasing fracture propagation pressure by actively manipulating thermal wellbore stresses.

The present invention relates to a carbonate reservoir filtration-loss self-reducing acid fracturing method. The carbonate reservoir filtration-loss self-reducing acid fracturing method comprises the steps: (1) calculating a fracture pressure and a fracture extension pressure of a reconstructed reservoir; (2) injecting an agent A into a stratum under a pressure higher than the stratum fracture pressure, so that fractures are generated on the stratum; (3) injecting an agent B into the stratum under a pressure higher than the stratum fracture pressure, such that the agent B extends the fractures and communicates with a natural fracture net; (4) pumping an acid liquor system agent C with a high etching power into the stratum under a pressure higher than the extension pressure but lower than the fracture pressure to improve the conductivity of the fractures; (5) injecting a displacing liquid agent D under a pressure lower than the stratum fracture pressure to jack acid liquor in a well casing into the stratum; and (6) shutting down a well and performing flow-back. The agent A is a gel acid or VES acid, the agent B is a filtration-loss self-reducing gel acid or filtration-loss self-reducing VES acid, the agent C is closed acid, and the agent D is a displacing liquid. According to the method of the present invention, precipitation type solid filter cakes are formed on wall surfaces of the fractures by utilizing a filtration-loss self-reducing system, so as to perform temporary blocking to reduce the filtration loss. The technology is simple with easy injection, and the filtration-reducing agent is easy to disperse and flow back, and the method is safe and environment-friendly.

The present invention relates to a carbonate reservoir filtration-loss self-reducing acid fracturing method. The carbonate reservoir filtration-loss self-reducing acid fracturing method comprises the steps: (1) calculating a fracture pressure and a fracture extension pressure of a reconstructed reservoir; (2) injecting an agent A into a stratum under a pressure higher than the stratum fracture pressure, so that fractures are generated on the stratum; (3) injecting an agent B into the stratum under a pressure higher than the stratum fracture pressure, such that the agent B extends the fractures and communicates with a natural fracture net; (4) pumping an acid liquor system agent C with a high etching power into the stratum under a pressure higher than the extension pressure but lower than the fracture pressure to improve the conductivity of the fractures; (5) injecting a displacing liquid agent D under a pressure lower than the stratum fracture pressure to jack acid liquor in a well casing into the stratum; and (6) shutting down a well and performing flow-back. The agent A is a gel acid or VES acid, the agent B is a filtration-loss self-reducing gel acid or filtration-loss self-reducing VES acid, the agent C is closed acid, and the agent D is a displacing liquid. According to the method of the present invention, precipitation type solid filter cakes are formed on wall surfaces of the fractures by utilizing a filtration-loss self-reducing system, so as to perform temporary blocking to reduce the filtration loss. The technology is simple with easy injection, and the filtration-reducing agent is easy to disperse and flow back, and the method is safe and environment-friendly.

A method of drilling may include mixing, at the surface, a base fluid, a polyvalent cation reactive polymer, and a delayed source of polyvalent cation so as to form a treatment fluid; placing the treatment fluid in a subterranean formation to form a solid plug including the polyvalent cation reactive polymer crosslinked with the polyvalent cation; contacting the solid plug with a breaker so as to transform the solid plug into a reclaimed treatment fluid; and removing the reclaimed treatment fluid. A system for drilling may include a treatment fluid, at the surface, including a polyvalent cation reactive polymer, and a delayed source of a polyvalent cation, where the treatment fluid is settable in the formation to form a solid plug including the polyvalent cation reactive polymer and the polyvalent cation; and a breaker, separate from the treatment fluid at the surface, capable of liquefying the solid plug.

A method of drilling may include mixing, at the surface, a base fluid, a polyvalent cation reactive polymer, and a delayed source of polyvalent cation so as to form a treatment fluid; placing the treatment fluid in a subterranean formation to form a solid plug including the polyvalent cation reactive polymer crosslinked with the polyvalent cation; contacting the solid plug with a breaker so as to transform the solid plug into a reclaimed treatment fluid; and removing the reclaimed treatment fluid. A system for drilling may include a treatment fluid, at the surface, including a polyvalent cation reactive polymer, and a delayed source of a polyvalent cation, where the treatment fluid is settable in the formation to form a solid plug including the polyvalent cation reactive polymer and the polyvalent cation; and a breaker, separate from the treatment fluid at the surface, capable of liquefying the solid plug.

An acid-generating fluid includes a thermally activated strong acid precursor. The thermally activated strong acid precursor can include a component selected from aldehydes, ketones, and combinations thereof, in combination with a precursor of a compound adapted to react to liberate sulfur dioxide; or it can include sulfur dioxide in combination with a precursor of a compound adapted to react to liberate a component selected from aldehydes, ketones, and combinations thereof.

Methods for intensification of oil production with the aim of increasing the oil recovery factor include the sequential treatment of BHZ with an emulsion, limiting water inflows by artificially reducing the permeability of highly permeable intervals of the reservoir, an oil pack, and preventing the interaction of the emulsion with an acid composition, which is injected after. The wettability of reservoir rock in the BHZ is preliminarily determined, and in the case of hydrophilicity of the reservoir rock a direct type of the emulsion with the following composition is used, % mass.: hydrocarbon phase—20-25, emulsifier—3-5, colloidal silicon dioxide nanoparticles—0.5-3, aqueous phase—rest. In the case of hydrophobicity of the reservoir rock in use the invert type of emulsion of the following composition, % mass.: hydrocarbon phase—40-45, emulsifier—3-5, colloidal silicon dioxide nanoparticles—1-3, aqueous phase—rest.

An acid-generating fluid includes a thermally activated strong acid precursor. The thermally activated strong acid precursor can include a component selected from aldehydes, ketones, and combinations thereof, in combination with a precursor of a compound adapted to react to liberate sulfur dioxide; or it can include sulfur dioxide in combination with a precursor of a compound adapted to react to liberate a component selected from aldehydes, ketones, and combinations thereof.

Treatment fluids for acid diversion during acid stimulation of a subterranean formation may include at least an acidizing fluid, a nanoparticle dispersion, and an activator. The treatment fluid may include from 40 weight percent to 70 weight percent acidizing fluid based on the total weight of the treatment fluid. The treatment fluid may include from 20 weight percent to 40 weight percent nanoparticle dispersion based on the total weight of the treatment fluid. The treatment fluid may include from 5 weight percent to 15 percent activator based on the total weight of the treatment fluid. Methods of treating a subterranean formation with the treatment fluids are also disclosed.