Abstract: The invention discloses a method for predicting the optimal shut-in duration by coupling fluid flow and geological stress, comprising the following steps: determine basic parameters; obtain the fracture length, fracture width and reservoir stress distribution based on the basic parameters; calculate the oil saturation, pore pressure, and permeability and porosity after coupling change in different shut-in durations on the basis of the principle of fluid-solid coupling; take the oil saturation, pore pressure, and permeability and porosity obtained in Step 3 as initial parameters and calculate the production corresponding to different shut-in time on the basis of the productivity model; finally select the optimal shut-in time based on the principle of fastest cost recovery. The present invention can accurately predict the optimal shut-in duration after fracturing to improve the oil and gas recovery ratio in tight oil and gas reservoirs with difficulty in development and low recovery.

Abstract: The invention discloses a testing device and method for simulating the flowback in the shut-in period of fractured wells, comprising a fracturing fluid tank, a flowback fracturing fluid tank, a hydraulic fracturing pump, a flowback fluid collection beaker, and a shut-in flowback testing system; the shut-in flowback testing system is composed of a box body and an acoustic wave testing device, a temperature control device, a fracturing string and a square rock block arranged in the box body; a stress loading plate and a hydraulic block are successively arranged between the four surfaces of the square rock block and the inner walls of the box body; the acoustic wave testing device consists of an acoustic wave transmitting probe and an acoustic wave receiving probe; the four outer surfaces of the box body are provided with hydraulic tanks.

Abstract: The present disclosure discloses an experimental apparatus and method for simulating transport of a sand-carrying fluid in a fracturing fracture. The apparatus may include a spiral proppant transport device, a stirred tank, a screw pump, a liquid transport pump, a pressure gauge, a proppant transport and distribution system, a cyclone desander, a waste liquid recycle container, a proppant recycle container, and a fracturing fluid tank. The spiral proppant transport device may be communicated with the stirred tank. The waste liquid recycle container and the fracturing fluid tank may be communicated with the stirred tank via the liquid transport pump. A bottom end of the stirred tank may be communicated with the proppant transport and distribution system through the screw pump. It is possible to simulate the sand-carrying fluid paved under a closure pressure by setting a computer to precisely control a transparent cuboid fracture member including hydraulic tanks.

Abstract: A natural gas hydrate solid-state fluidization mining method and system under an underbalanced positive circulation condition, used for performing solid-state fluidization mining on a non-rock-forming weak-cementation natural gas hydrate layer in the ocean. Equipment includes a ground equipment system and an underwater equipment system. The construction procedure has an earlier-stage construction process, underbalanced hydrate solid-state fluidization mining construction process and silt backfilling process. Natural gas hydrates in the seafloor are mined through an underbalanced positive circulation method, and problems such as shaft safety, production control and environmental risks faced by conventional natural gas hydrate mining methods such as depressurization, heat injection, agent injection and replacement are effectively solved.

Abstract: A hydrate solid-state fluidization mining method and system under an underbalanced reverse circulation condition are used for solid-state fluidization mining on a non-rock-forming weak-cementation natural gas hydrate layer in the ocean. Equipment includes a ground equipment system and an underwater equipment system. The construction procedure includes an earlier-stage construction process, pilot hole drilling construction process, reverse circulation jet fragmentation process, underbalanced reverse circulation fragment recovery process and silt backfilling process. Natural gas hydrates in the seafloor are mined through an underbalanced reverse circulation method. Problems such as shaft safety, production control and environmental risks faced by conventional natural gas hydrate mining methods such as depressurization, heat injection, agent injection and replacement are effectively solved.

Abstract: A crushing system for large-size natural gas hydrate rock samples, which mainly includes a crushing and stirring control subsystem, crushing and stirring execution subsystem and hydrate preparation subsystem. Full automatic control to parameter acquisition and experimental process is achieved by utilizing modern automation technology, including the function of automatically crushing the large-size natural gas hydrate rock samples and also monitoring, collecting and storing the drilling pressure, the torque and the internal furnace pressure and temperature parameters during the crushing process in real time, to provide reliable guarantee for the follow-up researches on crushing mechanism, crushing efficiency, drilling parameter optimization, rock crushing ability evaluation of a crushing tool and the like of the large-size natural gas hydrate rock samples and necessary experimental verification means for optimization of on-site exploiting construction conditions of natural gas hydrate.

Abstract: The present invention discloses a tri-cationic viscoelastic surfactant, a preparation method and an application thereof, and clean fracturing fluid. According to the present invention, N,N?-dimethyl-1,3-propanediamine and epichlorohydrin are used to prepare an intermediate A, and then the intermediate A and a fatty acid amidopropyl dimethylamine is used to prepare the tri-cationic viscoelastic surfactant. The preparation process is simple. And the clean fracturing fluid including the surfactant have excellent temperature and shear resistance, good suspended sand performance, simple on-site preparation, automatic gel breaking, low damage to formation, low cost and simple preparation process. The clean fracturing fluid including the surfactant also has strong temperature resistance, and the viscosity of the product can be maintained at 42 mPa·s after 80 minutes at 180° C. and 170 s?1, which is higher than the viscosity requirement (>25 mPa·s) of the clean fracturing fluid in on-site construction.

Abstract: A method for intelligently determining hydrate drilling and production risks based on fuzzy judgment.

Abstract: The present disclosure discloses an experimental apparatus and method for simulating transport of a sand-carrying fluid in a fracturing fracture. The apparatus may include a spiral proppant transport device, a stirred tank, a screw pump, a liquid transport pump, a pressure gauge, a proppant transport and distribution system, a cyclone desander, a waste liquid recycle container, a proppant recycle container, and a fracturing fluid tank. The spiral proppant transport device may be communicated with the stirred tank. The waste liquid recycle container and the fracturing fluid tank may be communicated with the stirred tank via the liquid transport pump. A bottom end of the stirred tank may be communicated with the proppant transport and distribution system through the screw pump. It is possible to simulate the sand-carrying fluid paved under a closure pressure by setting a computer to precisely control a transparent cuboid fracture member including hydraulic tanks.

Abstract: Dynamic segmentation model to divide bottom hole net pressure curve into different stages based on slope of curve includes: step S1, establish calculation model of bottom hole net pressure: according to wellhead pressure during hydraulic fracturing in shale gas reservoir, calculate bottom hole net pressure based on fluid dynamics theory; step S2, establishing dynamic segmentation model to divide bottom hole net pressure curve into different stages based on slope of curve by numerical analysis theory; step S3, establish recognition model to recognize extension behavior of underground fracture network based on rock mechanics and fracture mechanics; and step S4, combine step S1, S2, and S3 to realize automatic diagnosis for wellhead pressure curve of hydraulic fracturing in shale gas horizontal well. A diagnosis and analysis method of the wellhead pressure curve of hydraulic fracturing in shale gas horizontal well is described.

Abstract: A method for optimizing perforation parameters to maintain uniform fracture growth in multi-stage hydraulic fracturing of horizontal well and device therefor are provided. The method includes steps of: S1: collecting the geological and engineering parameters of the targeted pay zone, and estimating the net inlet pressure of fractures within the targeted fracturing stage of horizontal well; S2: calculating the perforation friction coefficient required for maintaining the uniform fracture growth in multi-stage hydraulic fracturing of horizontal well; S3: calculating the perforation characteristic parameter; and S4: determining the optimized perforation parameters. The method considers the stress heterogeneity, the stress shadowing and the perforation erosion in the process of dynamic hydraulic fracturing propagation, and also the influence of perforation erosion.

Abstract: An ultra-high temperature fracturing fluid, including the following components in mass percentages: 0.4 wt %-0.8 wt % of a polymer thickener, 0.015 wt %-0.02 wt % of a non-metallic crosslinking agent, 0.04 wt %-0.06 wt % of a gel breaker and the rest is water. The polymer thickener is obtained by a polymerization of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, rigid monomer and cationic hydrophobic monomer in a weight ratio of 55-70:15-20:15-20:0.5-3:0.1-1.0, the polymerization temperature is 30-40° C. and the polymerization time is 8-10 hours. The fracturing fluid of the present invention can effectively solve the technical problems that traditional fracturing fluids are easily decomposed at high temperatures and affect performance.

Abstract: The invention provides a method for predicting a reservoir reform volume after vertical well volume fracturing of a low-permeability oil/gas reservoir. The method sequentially includes the following steps: (1) calculating an induced stress produced by a hydraulic fracture in a three-dimensional space; (2) calculating a stratum pore pressure obtained after leak-off of fracturing fluid; (3) calculating a stratum pore elastic stress obtained after the leak-off of the fracturing fluid; (4) overlapping the stress fields obtained in the step (1), (2) and (3) with an original crustal stress field to obtain a new crustal stress field, and calculating the magnitude and direction of the overlapped three-direction effective principal stress in the reservoir space; (5) calculating an open fracturing determination coefficient M of a natural fracture in the reservoir space and a shear fracturing area determination coefficient S of the natural fracture.

Abstract: The present invention provides a surface-active two-tailed hydrophobic associated polymer and a preparation method thereof. The surface-active two-tailed hydrophobic associated polymer is prepared using a micellar free radical copolymerization method including: adding a surfactant sodium lauryl sulfate and a hydrophobic monomer N-phenethyl-N-alkyl (methyl) acrylamide or N-benzyl-N-alkyl (methyl) acrylamide into an aqueous solution containing acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and surface-active macromonomer polyoxyethylene lauryl ether (methyl) acrylate, wherein the surfactant is used to solubilize the hydrophobic monomer in the formed micelle; adjusting pH to 6-8 with sodium hydroxide, and copolymerizing the hydrophobic monomer and a water-soluble monomer by means of photoinitiation. The properties, such as viscosifying property, temperature resistance, salt resistance and hydrolysis resistance, of the hydrophobic associated polymer can be effectively improved.

Abstract: An ultra-high temperature fracturing fluid, including the following components in mass percentages: 0.4 wt %-0.8 wt % of a polymer thickener, 0.015 wt %-0.02 wt % of a non-metallic crosslinking agent, 0.04 wt %-0.06 wt % of a gel breaker and the rest is water. The polymer thickener is obtained by a polymerization of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, rigid monomer and cationic hydrophobic monomer in a weight ratio of 55-70:15-20:15-20:0.5-3:0.1-1.0, the polymerization temperature is 30-40° C. and the polymerization time is 8-10 hours. The fracturing fluid of the present invention can effectively solve the technical problems that traditional fracturing fluids are easily decomposed at high temperatures and affect performance.

Abstract: The present invention provides a surface-active two-tailed hydrophobic associated polymer and a preparation method thereof. The surface-active two-tailed hydrophobic associated polymer is prepared using a micellar free radical copolymerization method including: adding a surfactant sodium lauryl sulfate and a hydrophobic monomer N-phenethyl-N-alkyl (methyl) acrylamide or N-benzyl-N-alkyl (methyl) acrylamide into an aqueous solution containing acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and surface-active macromonomer polyoxyethylene lauryl ether (methyl) acrylate, wherein the surfactant is used to solubilize the hydrophobic monomer in the formed micelle; adjusting pH to 6-8 with sodium hydroxide, and copolymerizing the hydrophobic monomer and a water-soluble monomer by means of photoinitiation. The properties, such as viscosifying property, temperature resistance, salt resistance and hydrolysis resistance, of the hydrophobic associated polymer can be effectively improved.

Abstract: The invention provides a method for predicting a reservoir reform volume after vertical well volume fracturing of a low-permeability oil/gas reservoir. The method sequentially includes the following steps: (1) calculating an induced stress produced by a hydraulic fracture in a three-dimensional space; (2) calculating a stratum pore pressure obtained after leak-off of fracturing fluid; (3) calculating a stratum pore elastic stress obtained after the leak-off of the fracturing fluid; (4) overlapping the stress fields obtained in the step (1), (2) and (3) with an original crustal stress field to obtain a new crustal stress field, and calculating the magnitude and direction of the overlapped three-direction effective principal stress in the reservoir space; (5) calculating an open fracturing determination coefficient M of a natural fracture in the reservoir space and a shear fracturing area determination coefficient S of the natural fracture.

Abstract: The present invention discloses a sulfonate lycine type hydrophobic associated polymer and a preparation method thereof. A preparation process of the sulfonate lycine type hydrophobic associated polymer comprises the following steps: firstly, mixing acrylamide and acrylic acid in an aqueous solution; adjusting pH of the system to be around 6 to 8; adding 3-(dimethylamino propyl methacrylamide) propanesulfonate, N-aryl-N-alkyl (methyl) acrylamide and lauryl sodium sulfate and stirring till the solution is clear; and after nitrogen is introduced for deoxidization, adding a photoinitiator azobis (isobutylamidine hydrochloride) for performing polymerization under photoinitiation conditions.

Abstract: The present invention discloses a sulfonate lycine type hydrophobic associated polymer and a preparation method thereof. A preparation process of the sulfonate lycine type hydrophobic associated polymer comprises the following steps: firstly, mixing acrylamide and acrylic acid in an aqueous solution; adjusting pH of the system to be around 6 to 8; adding 3-(dimethylamino propyl methacrylamide) propanesulfonate, N-aryl-N-alkyl (methyl) acrylamide and lauryl sodium sulfate and stirring till the solution is clear; and after nitrogen is introduced for deoxidization, adding a photoinitiator azobis (isobutylamidine hydrochloride) for performing polymerization under photoinitiation conditions.

Abstract: The present disclosure provides an experimental loop system for fluidization exploitation of solid-state marine gas hydrate, comprising: four modules, namely a gas hydrate sample large-amount and rapid preparation module, a gas hydrate multi-scale smashing and slurry fidelity transfer module, a gas hydrate slurry pipeline conveying characteristic experiment module, and a data collection and monitoring and safety control module. The gas hydrate experimental loop device provided by the present disclosure may be used for researching the synthesis, decomposition, gas storage rate and phase equilibrium of gas hydrate, and researching the pipeline conveying flow resistance and heat transfer characteristics, and is significant for solving the blockage problem in the gas pipeline conveying process, storage and conveying of the gas hydrate, solid-state fluidization exploitation of the marine gas hydrate and pipeline conveying experimental simulation thereof.