152results about How to "Good for flowback" patented technology

The invention relates to an acid fracturing method of a temperature-control and variable-viscosity acid in the exploitation of an oil-gas well, which comprises the steps that: a common chlorohydric acid pickling process is firstly used for removing the pollution of an embrasure; then, the temperature-control and variable-viscosity acid fracturing process, or an ahead-fluid temperature-control and variable-viscosity acid fracturing process, or a temperature-control and variable-viscosity acid fracturing enclosed acidizing process, or an ahead-fluid temperature-control and variable-viscosity acid fracturing enclosed acidizing process is adopted; the weight ratio of the components of the temperature-control and variable-viscosity acid are as follows: 100 portions of basic acid solution, 0.5 portion to 1.5 portions of the main agent of the temperature-control and variable-viscosity acid, 1 portion to 3 portions of a corrosion inhibitor of the temperature-control and variable-viscosity acid, 0.5 portion to 1 portion of an emulsion breaker, 0.5 portion to 1 portion of a ferric ion stabilizer and 0.5 portion to 1 portion of a high efficient discharge aiding agent; 2-percent KCL clear water is used for displacing the temperature-control and variable-viscosity acid into the stratum. The temperature-control and variable-viscosity acid is easily prepared on site, with low friction drag and strong pumpability, thereby being capable of being applied to high-discharge construction; under the high temperature condition of a storing layer, both the fresh acid and the residue acid have high viscosity, thus increasing the length of acid-etching cracks. After the construction is finished, the viscosity of the residue acid is reduced, which is beneficial to the back discharge of the residue acid.

The invention relates to a volume fracturing method for a crack net of a carbonate reservoir. The volume fracturing method comprises the following steps that (1) initial crack initiation is conducted,specifically, slickwater is injected into a pretreated formation for crack making, then gel acid is injected for conducting acid etching transformation on cracks, and the crack length is increased; (2) temporary blocking in the cracks is conducted, specifically, microcracks formed by acid etching formation are temporarily blocked through temporary blocking agents carried by the slickwater; (3) turning for acid fracturing is conducted, specifically, gel acid is injected into the temporarily-blocked formation, and after the temporary blocking agents are displaced in place by the gel acid, the gel acid turns to other parts for acid etching transformation; (4) crack making through slickwater is conducted, specifically, slickwater is injected into the formation subjected to acid etching transformation in the step (3) for crack making; and (5) crack-expansion supporting is conducted, specifically, sand-carrying fluid is injected into the formation subjected to crack making in the step (4) for supporting. According to the volume fracturing method for the crack net of the carbonate reservoir, liquid leak-off can be effectively reduced, the effect of 'near-control and far-expansion' is achieved, the abundant secondary cracks can be formed, connectivity with main cracks and natural cracks is improved, and thus the transformation effect of volume fracturing is improved.

The invention relates to an oil well cleanup additive which is applicable to residual liquid cleanup after fracture acidizing of an oil well in an oil field. The cleanup additive comprises the following ingredients according to weight percentage: 7.5-13.5% of dodecyldimethylbenzylammonium chloride, 2-3.5% of fatty alcohol-polyoxyethylene ether, 25-34% of polyoxyethylated alkyl alcohol-8, 3.5-5% of fatty alcohol-polyoxyethylene ether, 0.05-0.1% of fluorocarbon surfactant FN-3, and the allowance of water. A preparation method of the oil well cleanup additive comprises the steps as follows: fatty alcohol-polyoxyethylene ether, JFC-4, polyoxyethylated alkyl alcohol-8 and fatty alcohol-polyoxyethylene ether are added into an enamel reactor by proportion; the temperature is raised to 55-60 DEG C; 5% of water is firstly added while stirring; dodecyldimethylbenzylammonium chloride and fluorocarbon surfactant FN-3 are then added in proportion and stirred for 30 minutes; the water is then added and the mixture is cooled to normal temperature. The oil well cleanup additive reduces the adhesive force of residual construction liquid flowing in reservoir bed, thereby accelerating the flowback of residual liquid by 20-30 percentage points.

The invention discloses a foaming cleanup additive for a gas well. The foaming cleanup additive is composed of a surfactant, a foam stabilizing agent, an auxiliary agent and water. The preparation method comprises a step of uniformly mixing the surfactant, the foam stabilizing agent, the auxiliary agent and water so as to obtain the finished foaming cleanup additive. The foaming cleanup additive has excellent foaming performance, can produce abundant and stable foam and has moderate salt resistance; the foaming cleanup additive has surface tension of 21.11 mN / m and good cleanup performance and is beneficial for flowback of an operation fluid; and the foaming cleanup additive makes full use of all the raw materials, combines a foaming agent and a cleanup additive, realizes two purposes, reduces cost and is convenient to use on site.

The invention provides a nanometer microemulsion cleanup additive. The invention provides a concentrate of the nanometer microemulsion cleanup additive. The concentrate comprises 20-45wt% of oil, 15-45wt% of a surfactant, 0.1-35wt% of a cosolvent, 0.1-5wt% of an organic acid, and the balance of water. The invention also provides the nanometer microemulsion cleanup additive prepared by using the concentrate. Amino silicone oil is used as the necessary component of the oil, so the nanometer microemulsion cleanup additive has high fluid flow-back efficiency; the nanometer microemulsion cleanup additive and a fracturing fluid are injected into an oil well to carry out fracturing reconstruction of an oil-gas reservoir, so the fracturing fluid has a good water lock damage clearing performance and promotes the flow-back of the fracturing fluid, thereby the fracturing reconstruction effect of the oil-gas reservoir is improved, and the output of natural gas is increased; and the nanometer microemulsion cleanup additive is simple to prepare, and is convenient to use.

The invention relates to microemulsion for improving core wettability. The microemulsion consists of a Gimini quaternary ammonium salt cationic surfactant, a nonionic surfactant and an aid of lower alkyl alcohol; a mass ratio of the Gimini quaternary ammonium salt cationic surfactant to the nonionic surfactant is 1:(1-60); and the aid accounts for 30 to 50 mass percent of the microemulsion. The microemulsion has a characteristics of oil-water miscibility, can improve the wetting condition of a stratum to a neutral weakly waterwet condition, and obviously reduce the surface tension of working fluid so as to reduce capillary pressure, remove water lock, reduce starting differential pressure and contribute to the flowback of the working fluid, so that the stratum is prevented from being damaged by the working fluid and the effect of stably increasing production of an oil gas well is achieved.

The invention relates to a novel modification system and process of a hot-dry-rock thermal reservoir, characterized by the combination of two stimulation measure processes, thermal stimulation and chemical stimulation. The process is characterized in that a naturally present fracture network is destructed by thermal stimulation to enhance permeability, partial minerals, scale and obstruction in shafts and fractures are dissolved by the chemical stimulation, and flow guiding capacity of the fractures is further improved. The repeating of the process enables a larger range of thermal reservoirs to be modified. By using the process, the problem of the prior art that after thermal stimulation, part of the fractures are closed along with the rise of the temperature of a cooling area and the problem that that a chemical stimulant disappears nearby an injection location during its excess speed of reacting with rock minerals at high temperature are solved, and the process enables greatly reduction in the risk of frequent microseism in a reservoir modification process when compared to traditional hydrofracturing. The process is widely applicable to the modification of hot-dry-rock thermal reservoirs.

The invention discloses high temperature-resisting cleaning CO2 foam fracturing liquid suitable for unconventional oil and gas reservoir development. The high temperature-resisting cleaning CO2 foam fracturing liquid in gas phase is CO2; the high temperature-resisting cleaning CO2 foam fracturing liquid in liquid phase is high temperature-resisting cleaning fracturing liquid; the foam mass is 52 percent to 75 percent. The high temperature-resisting cleaning CO2 foam fracturing liquid is prepared from the following raw materials in percentage by weight: 0.3 to 0.65 percent of thickening agent, 0.2 to 0.5 percent of viscosity synergist, 0.2 to 0.3 percent of pH (Potential of Hydrogen) value modifier, 0 to 0.2 percent of high-temperature stabilizing agent, 0.01 to 0.1 percent of gel breaker and water, wherein the thickening agent is prepared from acrylamide, vinylpyrrolidone, maleic acid, anionic functional monomers, an initiating agent, inorganic salt and the like; the viscosity synergist is mainly prepared from an anionic surfactant; the pH value modifier is mainly prepared from an organic acid. According to the high temperature-resisting cleaning CO2 foam fracturing liquid disclosed by the invention, the temperature-resisting ability is up to 140 DEG C, the sand carrying performance is excellent, the frictional resistance is low, the foam stability is strong, the content of residual slag is extremely low, the stratum compatibility is good, back flowing is easy, the construction effect is quickly obtained, and important significances to effective development of an unconventional oil and gas reservoir and protection of a reservoir stratum are obtained.

The invention discloses a fracturing prepad fluid, comprising the following ingredients: 1-10 wt% of biological enzyme, 0.1-1 wt% of clay stabilizing agent, 0.01-0.1 wt% of fluorocarbon surfactant, 0.01-0.5 wt% of wettability reversal agent, 0.01-1 wt% of composite activator, and the balance of water. The fracturing prepad fluid disclosed herein not only overcomes the disadvantages of routine prepad fluids and has the advantage of fracture forming of routine prepad fluids, but also has the effects of peeling off residual oil on the surface of a rock core, cleaning and unblocking oil gas seepage channels, reducing the viscosity of crude oil, changing the wetability of the rock core, reducing the surface and interfacial tension to benefit for flowback, and preventing the clay from expansionand migration, and the like. The more the fracturing prepad fluid enters a reservoir, the larger the spread range is, and the larger the action scopes of the fracturing prepad fluid on cleaning and unblocking of the oil gas seepage channels are. The fracturing prepad fluid is beneficial for increasing the oil gas yield.

The invention provides a gel composition and a nitrogen-foamed gel composite temporary plugging agent containing the same. The gel composition comprises the following components in percentage by mass: 1.0% of partially hydrolyzed polyacrylamide, 1.5% of formaldehyde, 0.5% of hydroquinone and the balance of water. The nitrogen-foamed gel composite temporary plugging agent comprises nitrogen and foamed gel, wherein the foamed gel is a mixture of the gel composition and a high-temperature-resistant foaming agent; and the volume ratio of the nitrogen to the foamed gel is (40-60):1. The invention also provides a coupled internal / external swirl foam generator which can be used as a facility for preparing the nitrogen-foamed gel composite temporary plugging agent. The invention also provides a method for inhibiting high-throughput-frequency well steam channeling interference of thick oil, which has the characteristics of small formation damage, strong selectivity for measures and the like and has the effect of gas energization.

The invention provides high-temperature resistant CO2 foam cleaning and associated fracturing fluid and a preparation method and application thereof. The high-temperature resistant CO2 foam cleaning and associated fracturing fluid comprises a fracturing fluid base solution, a cross-linking agent, a gel breaker and liquid CO2, wherein the cross-linking agent and the gel breaker account for 0.3%-0.8% and 0-0.05% of the fracturing fluid base solution in parts by weight separately; and the liquid CO2 accounts for 30%-70% of total volume of the CO2 foam cleaning and associated fracturing fluid. The high-temperature resistant CO2 foam cleaning and associated fracturing fluid provided by the invention has the characteristics of being few in additive types, simple in preparation, controllable in crosslinking, low in residue, low in damage, low in friction, high in foaming efficiency, high in flowback rate and resistant to high temperature.

An alcohol-based fracturing liquid for oil or gal well is prepared from low-carbon alcohol and its thickening agent, water, cross-linking agent, degelating agent, pH regulator and surfactant. It can remove the water locking in stratum, so benefiting the return of liquid from stratum.

The present invention discloses a retardance and low damage acid solution system for high temperature condensate oil gas reservoir acidification. The acid solution system is suitable for acidification modification of high temperature deep well, particularly condensate gas reservoir, and comprises the following components, by weight, 0.5-3 parts of hydrofluoric acid or 6-12 parts of fluoroboric acid, 8-10 parts of an organic ester, 0.01-0.05 part of a catalyst, 0.1-1 part of a corrosion inhibitor, 0.1-1 part of an iron ion stabilizer, 0.1-1 part of a clay stabilizer, 1-2 parts of a cleanup additive, and 80-100 parts of water. According to the present invention, effects of retardance and corrosion inhibition of the acid solution system can be well achieved at a high temperature, and water blocking can be released and acid solution backflow can be easily achieved with the finally produced methanol and the carbon dioxide.

The invention relates to a high-strength temporary blocking agent for oil and gas wells and a preparation method and application thereof. The temporary blocking agent for oil and gas wells is prepared from the following ingredients through crosslinking reaction: thickening agent, dispersing agent, adhesive and a temperature resistant material with mass ratio of (2.5-3):(1.3-2):(2.8-3):(1.7-2), preferentially, 3:2:3:2. The temporary blocking agent for oil and gas wells has the advantages of high strength, filter cake formation, good solubility and controllable time, flowback is facilitated and the method is simple to operate.

The invention discloses a gas self-production agent, a use of the gas self-production agent, and a self-produced gas foam acidizing method for oil wells and water wells. The gas self-production agent can produce gas in an acid environment or at an oil well bottom temperature. An active ingredient of the gas self-production agent is ammonium carbamate. The gas self-production agent has the advantages of low requirement on gas production conditions, large gas yield, simplification of foam acidizing processes for oil wells and water wells, reduction of a foam acidizing cost, and improvement of acidizing effects.

The invention relates to a flow guiding and fracturing method. The flow guiding and fracturing method is characterized in that the adding of propping agent and the designing of fracturing fluid are carried out through unevenly perforating in a short pulse mode, the propping agent can be unevenly placed in a fracturing seam in a pier column mode, i.e. the expansion of the fracturing seam is kept by forming a propping agent pier column in a fractured fracturing seam, oil gas flows through a channel formed by the propping agent pier column without passing through a propping agent filling body any more, unlimited flow guiding capacity can be generated due to a pier column structure, the flow back of liquid and polymer can be more facilitated, and the damage to the surface of the fracturing seam is smaller. The flow guiding capacity of the fracturing seam formed by the fracturing of the propping agent pier column does not depend on the performance of the propping agent, and thus the propping agent in high quality does not need to be chosen.

The invention relates to a low concentration guanidine gum fracturing fluid for gas well. The fracturing fluid is composed of hydroxypropyl guar gum, an anti-swelling stabilizer, a bactericide, a foaming cleanup additive, a conditioning agent, a temperature stabilizing agent, a chelating agent, a crosslinking agent, a gel breaker, and water. The provided fracturing fluid overcomes the shortages of a conventional fracturing fluid for gas well such as a large using amount of thickening agent, a large amount of residues after gel breaking, and the like. The preparation cost is low. The performance on resisting temperature and shearing is good. The using concentration of guanidine gum is greatly reduced. The damage on stratum is obviously reduced. Prominent economic benefit is created, and the application prospect is wide.

A variable-viscosity acid liquid is composed of the following compositions in percent by weight: 19.9-25.0% of hydrochloric acid, 1.0-7.5% of hydrofluoric acid, 5-7% of a viscosity-changing agent, 1-2% of an acidifying corrosion inhibitor, 0.1-0.5% of an ferric-ion stabilizing agent, 0.3-0.4% of a demulsification cleanup additive, 1-1.5% of a clay stabilizing agent, 1-2% of an acidifying mutual solvent, and the balance water. The invention provides the variable-viscosity acid liquid, and the variable-viscosity acid liquid has self-diverting flow-dividing effect and is capable of realizing general acidifying and uniform acid distribution.

The invention discloses a clean steering acid liquid system for acidification and a preparation method thereof. The clean steering acid liquid system comprises a solution A and a solution B, wherein the solution A comprises the following raw materials in parts by weight: 32-71 parts of 31% hydrochloric acid solution, 0.5-2.0 parts of ferric ion stabilizer, 0.5-2.0 parts of corrosion inhibitor, 1.0-2.0 parts of surfactant, 3.0-4.0 parts of clay stabilizer, and 19-63 parts of water; the solution B comprises the following raw materials in parts by weight: 8-15 parts of mutual solvent and 85-92 parts of water. The preparation method comprises the following steps: adding the surfactant to a container containing water; evenly agitating, and then adding the clay stabilizer, the corrosion inhibitor and the ferric ion stabilizer; finally adding the hydrochloric acid solution, so as to prepare the solution A; and adding the mutual solvent to the container containing water, so as to prepare the solution B for gel breaking of the clean steering acid liquid system. By adopting the acid liquid system disclosed by the invention, the formula is simple in component, good in steering effect, and free of damage to a reservoir, and controls the self-steering function.

Belonging to the technical field of oilfield chemistry, the invention relates to a modified acrylamide polymer fracturing fluid. The modified acrylamide polymer fracturing fluid is composed of the following components by mass: 0.4-0.6% of a modified acrylamide polymer thickening agent; 0.2-0.5% of a cross-linking agent; 0.1-0.5% of a surfactant; 0.3-1.0% of a clay stabilizer; and the balance water. According to the invention, on the basis of existing fracturing fluid, a vinyl monomer able to inhibit amide group hydrolysis and a salt tolerant and hydrophilic sulfonate group are introduced to the polymer thickening agent, thus greatly enhancing the heat resistance and salt tolerance of the fracturing fluid. A preferable matching crosslinking agent series is selected to reduce the sensitivity of the pH value to crosslinking, and the formed polymer fracturing fluid system has good hot shearing performance and salt resistance. The pH value range of fracturing fluid crosslinking can be widened, and the crosslinking time is moderate. The modified acrylamide polymer fracturing fluid can be widely applicable to fracturing transformation measures of hypotonic reservoirs.

Provided is a slickwater fracturing fluid suitable for being used at a hypersalinity condition. The slickwater fracturing fluid is prepared from, by mass, 0.15-0.45% of polymer viscosifier, 0.05%-0.15% of chelating agent, 0.05%-0.15% of dispersing agent, 0.02%-0.05% of clay stabilizer, 0.30%-0.50% of structure stabilizer, 0.02%-0.06% of gel breaker and the balance water. The slickwater fracturingfluid has the advantages of being low in viscosity, friction and cost and easy to recycle, easily flowing back and the like; the problems are mainly solved that at the hypersalinity condition, polymers are poor in salt resistance and sand-carrying stability and does not easily disperse; the problem can also be solved that vegetable glue fracturing fluid easily rots; after being filtered, flow-backliquid can be further directly recycled, and requirements of large-scale fracturing construction of compact oil-gas reservoirs can be effectively met.

The invention belongs to a superhigh temperature weighted fracturing fluid and preparation thereof. The liquid is prepared from the following raw materials in parts by weight: 500 parts of water, 12-15 parts of a temperature-resistant thickener, 15-30 parts of a high-temperature crosslinking agent, 125-195 parts of an inorganic weighting agent, 20-30 parts of a discharge aiding agent, 8-15 parts of a bactericide, 5-10 parts of a temperature stabilizer and 0.1-0.3 part of a gel breaker, wherein the temperature-resistant thickener is carboxymethyl and hydroxypropyl guanidine glue, the high-temperature crosslinking agent is an organic zirconium crosslinking agent, and the inorganic weighing agent is any one of sodium chloride or sodium bromide. The superhigh temperature weighted fracturing fluid has the advantages of low content of residues and good temperature resistance and shear resistance.

The invention specifically relates to a temporarily plugging / shielding protection agent and a preparation method thereof, belonging to the field of temporary plugging agents for energy exploitation. The temporarily plugging / shielding protection agent is prepared by successively coating organic acid solid particles with ethyl cellulose, which is mixed with a pore-foaming agent, at first and then with a protective agent next. The temporarily plugging / shielding protection agent provided by the invention is applied to the development of oil and natural gas in tight clastic rock reservoirs, and ismainly used for reservoir protection during fracturing completion. The temporarily plugging / shielding protection agent is used in the process of fracturing to form a temporarily plugging / shielding zone under the action of pressure difference so as to reduce fracturing fluid loss and prevent fracturing fluids from entering strata; in a later phase, a coated material is slowly dissolved and releasedthrough micropores, which is beneficial for gel breaking and flowing back of fracturing fluids; after the coated material, i.e., a gel breaker, is dissolved and released, a flexible coating becomes ahollow flexible shell, so the flexible coating is not supportive and is thus peeled off from a temporarily plugged surface and discharged back together with the gel-broken fracturing fluid; and aftercompletion of construction, no residue is left in the strata, so reservoir damage is reduced.

The invention discloses a micro-emulsion completion fluid. The micro-emulsion completion fluid comprises the following components: an oil phase, a water phase, a surfactant, an auxiliary surfactant, a salt and a cleaning agent, wherein the cleaning agent is selected from an oxidant and a biological enzyme. The completion fluid provided by the invention has good comprehensive performance and facilitates cleaning of the formation damages caused by the drilling fluids, especially by the water-base drilling fluids; and the micro-emulsion completion fluid is capable of increasing crude oil yield when the well is put into operation. The completion fluid provided by the invention has wide application prospect.

The invention relates to a hydrophobic and oleophobic fluorine-containing group-modified drag reducer for hydraulic fracturing of an inverse emulsion, and belongs to the technical field of application of chemical agents in oil-gas field engineering. The hydrophobic and oleophobic fluorine-containing group-modified drag reducer is prepared by initializing inverse emulsion polymerization with a water-soluble monomer A1, a fluorine-containing monomer A2, a mutual solvent A3, water A4, an oil phase B and a free radical initiator C. According to the drag reducer, a water-phase mixture is dispersed into an oil phase represented by mineral oil or paroline to form a 'W / O' inverse emulsion; a small fluorine-containing segment with low surface energy and friction coefficient and the minimal surface tension in a solid material is introduced; the drag-reducing property of an original drag reducer is reserved; the drag reduction efficiency can reach 70% when the drag reducer is applied to hydraulic fracturing; meanwhile, the affinity between drag reducer molecules and the affinity between the drag reducer molecules and a reservoir rock are reduced by introduction of the fluorine-containing group; the drainage assisting performance and the reservoir protection performance after the hydraulic fracturing process are improved; and the problems that the drag reducer for shale oil and gas development at present is poor in flowback performance, serious in reservoir damages and high in biotoxicity are solved.

The invention relates to a medium-high temperature oil reservoir phenolic gel self-degradation temporary plugging agent and a preparation method thereof. The temporary plugging agent is prepared fromthe following components in percentage by mass: 2 to 2.5 percent of low molecular weight polymer, 0.2 to 0.25 percent of phenolic cross-linking agent, 0.2 to 0.6 percent of aldehyde cross-linking agent, 0.05 percent of stabilizer, 0.1 percent of catalyst, 0.5 to 2 percent of gel breaker and the balance of water, wherein the sum of the mass percent of all the components is 100 percent. The gel temporary plugging agent provided by the invention can meet the requirements that the oil reservoir temperature is 60-100 DEG C, the plugging time is adjustable within 120-168h, and the gel breaking timeis adjustable within 168-240h; the plugging rate of a rock core reaches 98% or above, the permeability damage rate after gel breaking is 10% or below, a high-permeability layer of a target stratum canbe effectively plugged, flowback is easy after automatic gel breaking, damage to the stratum is extremely small, and the plugging agent can be suitable for most conventional oil reservoirs and has good field application value.

The invention relates to the technical field of fracturing and production increasing of an oil well or natural gas well, and in particular relates to a low damage carboxymethyl hydroxypropyl guanidine gum foam fracturing fluid of a low permeability gas reservoir and a preparation method of the low damage carboxymethyl hydroxypropyl guanidine gum foam fracturing fluid. The low damage carboxymethyl hydroxypropyl guanidine gum foam fracturing fluid of the low permeability gas reservoir contains the following components in parts by weight: 100 parts of base solution, 0.2-0.5 part of cross-linking agent, 0.03-0.04 part of gel breaker, and liquid nitrogen, wherein the liquid nitrogen accounts for 5-7 percent of total volume of the base solution and the cross-linking agent. The base solution, the cross-linking agent and a gel breaker are pumped into an underground fracturing stratum, and the liquid nitrogen is pumped, the base solution, the cross-linking agent, the gel breaker and the liquid nitrogen are mixed uniformly on the underground fracturing stratum, thus the low damage carboxymethyl hydroxypropyl guanidine gum foam fracturing fluid reaches the purpose of fracturing operation, and has the advantages of low content of residue after fracturing, good gel breaking property, rapid flowback, little damage to reservoir stratum water, and good fracturing effect. According to the low damage carboxymethyl hydroxypropyl guanidine gum foam fracturing fluid, the production cost is lowered, and the working efficiency is increased.

The invention discloses a method for improving the permeability of a broken and soft oil and gas reservoir and belongs to the field of oil and gas field development. The method comprises the following steps that a vertical well is vertically-downwards dug from the ground to the position of 1-2 meters below the oil and gas reservoir, and a horizontal well is dug in the horizontal direction. Oriented perforating is conducted from an oil and gas reservoir base plate to the overlying oil and gas reservoir through an oriented perforating gun of the horizontal well, and afterwards fracturing fluid is pumped by a high pressure pump for fracturing the oil and gas reservoir. After fracturing, a seepage passage is formed under the supporting effect of a supporting agent on fracturing fractures, and thus the permeability of the oil and gas reservoir is improved. According to the method for improving the permeability of the broken and soft oil and gas reservoir, on the one hand, fracturing of the oil and gas reservoir and expanding of cracks are facilitated, the permeability of the reservoir is improved; and on the other hand, through the fracturing technology of perforating upwards, fractured rock debris is prone to being discharged from fracturing holes under the gravity effect of the rock debris, and thus the problem that direct fracturing and slag returning are difficult in a coal layer is solved. Meanwhile, through the fracturing technology of perforating upwards, the stress from a bottom rock layer to the upper portion oil and gas reservoir is in a progressively- decreasing state, and thus fracturing of the upper portion oil and gas reservoir is facilitated.

The invention discloses a recyclable fracturing fluid used for fracturing construction of a sandstone gas reservoir. A primary fracturing fluid comprises the following components in weight percent: 1% to 5% of chloridization stearic acid dimethylamino alcohol ester methyl ammonium, 1% to 5% of potassium chloride and the balance of water. The recyclable fracturing fluid has the advantages of leak-off of the fracturing fluid can be lowered, the pollution to the stratum can be reduced, and flowback liquid is reclaimed on the ground directly, so that earth surface pollution can be avoided; the flowback liquid is reclaimed, so that the water consumption can be lowered; the flowback liquid can be reused after being subjected to ground treatment.