64results about How to "Save on drilling costs" patented technology

The invention discloses a method for identifying natural gas hydrate (NGH) by using the incremental ratio between the wave impedance of longitudinal and traverse waves. The method comprises the following steps: (1) inverting the longitudinal wave impedance ZP=VP rho of strata and the transverse wave impedance ZS=VS rho of strata by using seismic data; (2) obtaining the longitudinal wave impedanceZP0 and the transverse wave impedance ZS0 of water-saturated strata; (3) obtaining the longitudinal wave impedance increments delta ZP=ZP-ZP0 and the transverse wave impedance increments delta ZS= ZS-ZS0; (4) obtaining the incremental ratio Ratio of the wave impedance of longitudinal and traverse waves; (5) inverting the porosity of strata; (6) determining the threshold value of the incremental ratio of the wave impedance of longitudinal and traverse waves according to the porosity; (7) judging whether the incremental ratio Ratio of the wave impedance of longitudinal and traverse waves is higher than the threshold value, if so, indicating that the strata contain the NGH; and (8) drawing the bisect where the incremental ratio of the wave impedance of longitudinal and traverse waves is higher than that of the threshold value, wherein the bisect can reflect the distribution range of underground NGH. The method of the invention improves the reliability of the identification results of NGH,greatly improves the exploration precision of NGH and reduces the dry-well rate.

The invention belongs to the field of mine water prevention and control and particularly relates to a reconstruction method for a seam which is threatened by double limestone water damage of a top plate and a bottom plate. Compared with original technologies of top and bottom plate reinforced grouting, downhole reinforced grouting and ground horizontal drilling treating coal seam bottom plate thin layer limestone by using ground vertical boreholes, according to the technology of the invention, advanced type high pressure grouting is conducted on a target layer by using a petroleum drilling machine to construct double-layer multiple branch consequent layer drilling, so that a coal seam top plate and bottom plate limestone water-bearing strata is reconstructed, and safe coal seam exploitation is realized. By means of the mode, the effects that the range of covering the target layer is wide, the hole drilling engineering amount is small, top plate and bottom plate holes share the same opening section, the cost of top plate water drainage is low, work of bottom plate reinforcement and reconstructing and water prevention and control conducts in advance are realized, and finally, the top plate is reconstructed into a weak water-bearing rock strata or a water-free rock strata and the bottom plate is reconstructed into a water-resisting strata. The technology can also be applied to mines, such as iron mines or nonmetal mines, which are threatened by double water damage of the top plate and the bottom plate, so that safe and economic resource exploitation is realized.

The invention discloses a gas reverse-circulation well-drilling method. According to the gas reverse-circulation well-drilling method, a well-drilling system comprising a well-drilling pump set, a topdrive, a top drive adapter, a rotary blowout-preventing flow guiding device, a blowout preventer group, a casing, a double-wall drill pipe, a flow channel conversion device, a conventional drilling rig and a drill bit is used; and the gas reverse-circulation well-drilling method comprises the steps that during gas injection and well-drilling, one path of injected gas passes through the top drive,the top drive adapter, the double-wall drill pipe, the flow channel conversion device, the conventional drilling rig and the drill bit to enter a well bottom annular space, the other path of the injected gas enters the well bottom annular space through the rotary blowout-preventing flow guiding device; and the two paths of injected gas converge in the well bottom annular space and then passes through the flow channel conversion device, the double-wall drill pipe and the top drive adapter to return to a grit chamber. The gas reverse-circulation well-drilling method has the advantages that thegas using amount is small, the drilling speed is high, and low-cost well drilling can be achieved; and the gas reverse-circulation well-drilling method meets the well-drilling well control and well-drilling safety requirements in the field of oil drilling.

The invention relates to the technical field of geothermal energy development, in particular to a geothermal well novel technology. The technology improves the ability of leading geothermal energy inrock strata into geothermal wells through a heat conduction well cementing technology and a enhanced conductivity fracturing technology, and achieves high efficiency heat taking and heat transferringusing through spiral plate type condensing section gravity heat pipe heat exchanger. The technology comprises the following concrete process that after completing drilling a geothermal well and casinga sleeve pipe, the heat conduction well cementing is carried out, that is, thermal insulation cement slurry is injected in the low temperature section of the formation, and heat conduction cement slurry is injected into a stratum high temperature section to complete well cementing; after solidification of the heat insulation cement slurry and the heat conduction cement slurry of the well cementing, subsection perforation fracturing is carried out in the sleeve pipe of the stratum high temperature section, cracks are produced in high temperature strata, and heat conduction material is filled into the cracks to form a heat guiding belt extending from the sleeve pipe to the stratum; and finally, the condensing section of gravity heat pipe heat exchanger connected with the sleeve pipe is installed on the ground to form a high-yield geothermal well system in which rapid heat transfer in the stratum and high efficiency heat transfer in a well cylinder finally.

The invention discloses a liquid lubricant for a drilling fluid and a preparation method of the liquid lubricant. The liquid lubricant is prepared from the following raw materials by weight: 500 to 600 parts of methyl oleate, 170 to 230 parts of silicone oil, 170 to 230 parts of white oil, 30 to 80 parts of backlogged oil, 40 to 80 parts of an emulsifier, 40 to 80 parts of a surfactant, and 15 to 20 parts of a covering agent. The liquid lubricant can be used for a water-based drilling fluid, is approximately not changed in lubricity at 200 DEG C high temperature, can be used for reducing the pulling up force and the torque of a drill stem greatly, and is relatively high in resistance reducing lubricity.

The invention of city waste water central heating(refrigeration) apparatus belongs to a new energy saving and environmental protection air conditioning apparatus in engineering field, comprising rotating type continuous filtration dirt separator, waste water lift pump, waste water source heat pump special evaporator, condenser, semiisolated helical lobe compressor and refrigeration accessory, has solved the technical problems of wasting underground water source, regional limitation, low heat exchanging rate of soil, hard to be extended to large area, heat exchanger blocked by waste water which has corrodibility, using the technical program: install rotating type continuous filtration dirt separator, and evaporator and condenser designed to do desilting automatically and continuously so that there is no block and ensure the system cam work normally. The invention has the properties : low investment and operating cost, no regional limitation, can realize resource cyclic utilization, notable environmental benefit, and can be adopted widely in central heating(refrigeration) engineering of central heating(refrigeration).

The invention relates to the field of geothermal exploitation and provides a well completion method for reinforcing a hydrothermal type geothermal system. According to the method, a geothermal reservoir stratum is drilled through firstly, a microseism technology is utilized to conduct stratum microresistivity scanning imaging and dip angle combination logging, the stratum crack growing direction is recognized, then a branch hole is dilled in the perpendicular direction of crack growing, a hydraulic fracturing technology is adopted for fracturing a branch well section, thus a high-permeability geothermal reservoir stratum is constructed so as to enable a stratum fluid to enter a well drum along a fractured crack, the fluid is exploited to the ground through the well drum, and then power generation is conducted. According to the method, a branch well, microseism detection, a treatment system and the hydraulic fracturing technology are sufficiently utilized, the geothermal reservoir stratum crack is effectively recognized, the reservoir stratum is opened at a largest limitation, geothermal energy of the geothermal reservoir stratum is sufficiently utilized, and hydrothermal type geothermal energy exploitation efficiency is greatly improved.

The invention discloses an automatic treatment method for a two-single-oil-pipe one-upright pillar drilling rig string. A power drill pipe box and a power catwalk are arranged on the ground in front of a drilling rig side by side; a buffering manipulator is installed on a table top of the drilling rig; an iron roughneck, a mud blowout preventing box and a power lifting sub are also installed on the table top of the drilling rig; the iron roughneck is installed in an area between a mouse hole and a well mouth; a power slip is installed in a turntable of the drilling rig; the power lifting sub is suspended on a lifting ring of a travelling and lifting system of the drilling rig; a two-single-oil-pipe one-upright pillar which has been constructed is stored in the power drill pipe box; and thecatwalk is used for conveying the two-single-oil-pipe one-upright pillar. According to the automatic treatment method for the two-single-oil-pipe one-upright pillar drilling rig string disclosed by the invention, the problems of time consumption in the processes of constructing the upright pillar and detaching the upright pillar into single oil pipes in the prior art are solved.

The invention provides a ground area stripe coal mine gas outburst elimination technique. The ground area stripe coal mine gas outburst elimination technique comprises the following steps that a branch arrangement mode is optimized; a well location of a vertical well is optimized; a deflection point is optimized; a branch parameter is optimized; a reservoir modification technology is optimized; well drilling and deflecting are carried out; drilling of a main branch section is completed, and a coal rock core is observed; drilling of branches is completed; main branch hydraulic jetting fracturing is completed; and drainage and mining is started according to a drainage and mining design. The ground area stripe coal mine gas outburst elimination technique has the beneficial effects that the development cost of ground coal bed gas can be reduced, a gas extraction period can be shortened, the aim that coal seam gas-bearing capacity is quickly reduced is realized, and a great promoting function of improving coal mine production and accelerating rapid development of the coal industry is achieved.

The invention provides a single-hole observation device and method for double layers of underground water levels of a karst mountainous area, and belongs to the technical field of water conservancy and hydropower engineering. The above device comprises an inner pipe, a casing pipe and a sealing component, wherein the casing pipe is clung to the hole inner wall of the broken rock mass section of aborehole hole; the inner wall of the casing pipe and the outer wall of the inner pipe are arranged at intervals; the inner pipe comprises an upper end and a lower end, wherein the lower end of the inner pipe extends out of the casing pipe and enters to be below the lowest water level of the lower layer; and the sealing component is sheathed to the inner pipe. The above method is combined with theabove device, and before the above device is installed, a stepped hole is drilled in advance. When the above device and the above method detect double layers of underground water levels, the amount ofboreholes is reduced, a purpose of accurately testing double layers of stable underground water levels of the karst mountainous area is achieved, drilling cost is saved, meanwhile, time for investigation work is saved, and the device and the method have good economic benefits.

The invention discloses a nail-shaped bored pile compound foundation structure for reinforcing embankment soft foundation. The nail-shaped bored pile compound foundation structure comprises an embankment, a hard shell layer, a soft clay layer and a hard clay layer from top to bottom, wherein the embankment is provided with a plurality of pile holes; each pile hole penetrates through the hard shell layer, the soft clay layer and the hard clay layer from the embankment; a diameter of each pile hole at a certain depth under the embankment is larger than that of the upper part and the lower part of the pile hole. A ground level is taken as a boundary; the pile holes are equipped with medium coarse sand above the boundary and cured cement paste or cement mortar below the boundary. The invention also discloses a construction method of the nail-shaped bored pile compound foundation structure for reinforcing the embankment soft foundation. By arranging the nail-shaped bored piles in soft embankment of roads with damages and forming the compound foundation with clay among the piles, stability of subgrade is enhanced and subgrade settlement is reduced.

The invention relates to a drill bit for particle percussion drilling in the field of drill bits for drilling. The drill bit for particle percussion drilling comprises a drill bit joint, a drill bit body and a cutting head, wherein a thread and a striking clamp are arranged on the drill bit joint, and the drill bit body is inlaid with gauge protection teeth and lateral incision teeth. The middle of the lower part of the cutting head is a conical and convex, and the outer edge of the lower part of the cutting head is provided with two sections of centrosymmetric annular lateral wings; the conical bulge at the middle of the lower part of the cutting head is provided with percussion teeth in an inlaying manner, and the two sections of annular lateral wings on the outer edge of the lower part of the cutting head are provided with cutting teeth in an inlaying manner; and nozzles are installed on the conical bulge at the middle of the lower part of the cutting head and the two sections of annular lateral wings on the outer edge of the lower part of the cutting head respectively. The drill bit for particle percussion drilling is suitable for the field of particle drilling, and capable of rapidly drilling in extra-hard stratums and soft-hard interacted stratums which are hard to drill by conventional drill bits, so that the drilling operation is more rapid and efficient.

The invention relates to the technical field of tunnels and underground projects, in particular to an excavation method of a tunnel shaft. By drilling a plurality of holes of smaller diameters at themoment, the underground water condition, the adverse geology condition and the like can be pre-judged, the matching degree of geological exploration data can be verified conveniently, so that guidancecan be provided for follow-up construction, and the construction risk and difficulty are lowered; and meanwhile, excavation is conducted from the upper side to the lower side, the limitation of forming a main tunnel at the bottom of the shaft is not needed, the non-explosion type construction manner can be adopted, and therefore the safety is high; rock and soil can be drilled loose in advance,the construction efficiency of excavation is improved, the work period is shortened, especially the operation time of an artificial deep foundation pit is shortened, the safety risk is effectively lowered, and construction cost is saved; and the excavation method of the tunnel shaft has broad popularization significance.

The invention discloses a drilling parameter optimization method based on a plastic energy dissipation ratio. The method comprises the following steps that: S1: according to the mechanical models of plastic fracture and brittle fracture in a well drilling rock cutting process, independently establishing a mechanical specific work calculation model under the situations of the plastic fracture and the brittle fracture of rock; S2: utilizing the mechanical specific work calculation model under the situations of the plastic fracture and the brittle fracture of the rock, carrying out combination toobtain a mechanical specific work final calculation model; S3: on the basis of the mechanical specific work final calculation model, establishing a plastic energy dissipation ratio calculation model;S4: through a cutting test, obtaining parameters in the plastic energy dissipation ratio calculation model; S5: solving the plastic energy dissipation ratios under different cutting depths by the plastic energy dissipation ratio calculation model; and S6: comparing the plastic energy dissipation ratios under different cutting parameters, optimizing the optimal cutting parameter. By use of the method, the optimal cutting parameter can be optimized, and therefore, purposes that drilling efficiency is improved and well drilling cost is lowered are finally achieved.

The invention discloses a device for overcoming a blasting foundation, and particularly relates to the technical field of engineering blasting. The device comprises an explosive column fixing part anda round steel plate, wherein the explosive column fixing part and the round steel plate are integrally formed, the explosive column fixing part is provided with a funnel shape arc-shaped inner surface and comprises a explosive column fixing cavity at the upper part and an energy gathering cavity at the lower part, a funnel-shaped small head faces towards one side of the round steel plate, the round steel plate can reflect the shock wave generated during blasting, the energy gathering cavity has the energy gathering function, the explosion energy density can be improved, the inner surface of the energy gathering cavity is covered with a layer of red copper sheet, the shock wave generated by explosion is converted into high-energy metal jet flow, the transverse action range is further expanded, an opening of the funnel-shaped big head of the explosive column fixing part is provided with a large circle, the diameter of the large circle is 0.8-0.9 time of the diameter of blast hole, and the diameter of the large circle is 1.05 times of the diameter of the explosive; the opening of the funnel-shaped small head of the explosive column fixing part is provided with a small circular shape,the small circle is a guide hole, the diameter of the small circle is smaller than the diameter of the large circle, the diameter of the small circle is 0.4-0.5 time of the diameter of blast hole.

The invention firstly aims to provide a protective device used for a karst cave. The protective device comprises a sleeve, a sleeve connector and a sleeve blade leg. A first external thread and a first internal thread are arranged on the sleeve, a second internal thread is arranged on the inner wall of the lower end of the sleeve connector, and the outer wall of the lower end of the sleeve connector is of a first cone-frustum-shaped structure wide in upper portion and narrow in lower portion. A second external thread is arranged on the outer wall of the upper end of the sleeve blade leg, and the outer wall of the lower end of the sleeve blade leg is of a second cone-frustum-shaped structure wide in upper portion and narrow in lower portion. The overall structure is simple, the sleeve, the sleeve connector and the sleeve blade leg are in threaded connection, and installing is convenient. The cone-frustum-shaped structure on the sleeve connector facilitates broaching. The cone-frustum-shaped structure on the sleeve blade leg facilitates perforation of non-karst-cave filling, and therefore the protective device used for the whole karst cave is stably buried and is high in practicability. The invention secondly aims to provide a water-based channel drilling method. Operation is convenient, the drilling cost is lowered, and time consumed for sleeve burying and cutoff is shortened.

The invention discloses a docking connected solution mining method for mirabilite salt mine, which comprises following procedures. (1) Two connected horizontal wells are drilled on main reaction seam as the mining channel; after each horizontal well is built in three-segment deflecting it achieves the cave of main reaction seam and is connected with the cave; the upper soft sedimentary stratum and the flow sand seam are enveloped respectively; the mining open-hole channel is only maintained in the main reaction seam. (2) Brine is mined in said mining channel. The merit is that not only the mining cost is low and the brine concentration is high but also the mining speed is astonished; two wells are the mining well group and the ore-controlling area is big; the method avoids the phenomena of single-well convection frequent plugging well; the production flow is simple and easy; and the mirabilite mining efficiency is improved greatly, the mining cost is decreased.

The invention relates to the technical field of hot dry rock heat energy utilization, in particular to a high-efficiency dry hot rock technology and heat pump coupling heating system. The problems that the heating efficiency of a dry hot rock heating system is low and the efficiency of a ground source heat pump is reduced due to long-term operation are solved. The system comprises a dry hot rock heating system arranged under the ground and a heat pump system arranged on the ground surface; the dry hot rock heating system is connected with a plate heat exchanger set which is connected with theheat pump system; and the heat pump system is connected with a terminal heating system. In the long run, the heating system can operate throughout the year, the heat exchange efficiency of the whole system is higher than that of the traditional ground source heat pump, the cost performance is high, and operation is stable and durable.

The invention discloses a pore-forming construction method for an old bridge pile site in-situ percussion drill matched with a rotary drilling rig. The construction method comprises the following steps: step 1, leveling a site; step 2, setting out a pile position; step 3, burying a pile casing; Step 4, percussion drilling in place; step 5, centering inspection; step 6, slurry preparation and circulation; and step 7, percussion drilling; Step 8, lifting the percussion drill; and step 9, secondarily re-measuring the pile casing. The percussion drill is matched with the rotary drilling rig for drilling construction, the advantages of combination of the two devices are exerted, when a newly-built bridge pile foundation coincides with or conflicts with an old bridge pile foundation, the percussion drill is used for constructing the old pile foundation part, the rotary drilling rig is used for rapidly forming holes below the old pile foundation, the construction sequence is clear, and construction is safe and reliable; The unit price cost of percussion drill construction is much higher than that of rotary drilling rig construction, part of drilling construction cost is saved on the premise that the rotary drilling rig is adopted for hole forming of the part below the old pile foundation, the equipment cost is obviously saved, and the construction efficiency is high.

The invention discloses a cast-in-situ facing concrete structure based on a WISA formwork system and a construction method thereof. The method comprises the steps that a deepening drawing is drawn considering water, electricity, building and structure, and the deepening drawing is confirmed; formworks, small transverse ridges and fixing strips are processed; the formworks, the small transverse ridges and the fixing strips are installed; a fire box box body reservation box, a fire riser reservation box and a horizontal pipe reservation box are processed; the single-side formworks are installed;steel bars are bound, and water and electricity pipelines are pre-embedded after binding of the steel bars is completed; the formworks are sealed; and the curved surface structure formworks are processed and reinforced, and detail nodes are processed. The concrete structure comprises an inner mold structure and an outer mold structure which are abutted to two sides of the concrete and pulled together by counter pulling screw rods. According to the cast-in-situ facing concrete structure, a formwork discharging effect is ensured and the later port opening cost is reduced through synchronous planning of pre-embedded ports for water and electricity installation and the formworks; the formwork reinforcing system is stable, and the structure has a good formwork discharging effect; the curved surface structure protective layer is good in control and the binding of the steel bars is simple; the operation is simple, and the construction period is short; and the repeated utilization rate of thecurved surface formworks is high.

The invention provides a steam assisted gravity drainage method. The steam assisted gravity drainage method includes the following steps: a first step, arranging a first well and a second well, wherein the first well is a horizontal well, and the second well is a vertical well; a second step, performing steam injection and oil extraction, wherein steam injection is performed on the first well, and oil extraction is performed on the second well; a third step, performing supplementary reversed steam injection and oil extraction, perforating an upper part of an oil layer of the second well, putting a dual-pipe well structure in the second well, setting a supplementary steam injection point on the upper part of the oil layer, and setting an oil extraction point on a lower part of the oil layer, wherein the supplementary steam injection point and the oil extraction point are separated from each other by an isolator, continuous steam injection is performed on the second well, and oil extraction is performed on the second well and the first well. The steam assisted gravity drainage method can improve the efficiency and the quality.

The invention discloses a method for building a bushing inner-sieve-tube artificial natural gas migration passage between gas reservoirs, and the method is characterized by comprising the following steps of selecting a gas reservoir to be developed which is appropriate to develop inside or surrounding a developed gas field; building a construction well; forming an uncased hole between the gas reservoir to be developed and a production gas reservoir of the developed gas field; loading a bushing inside the uncased hole on the two gas reservoir well sections; conducting well cementing for an annular well section between the uncased hole and the loaded bushing; forming a perforation hole on the two gas reservoir well sections in the bushing well section after the well cementing by utilizing a perforation gun; and loading a sieve tube into the bushing well section, and setting a bridge plug above or in front of the two gas reservoir well sections after the sieve tube is loaded to seal, so that the bushing inner-sieve-tube migration passage is formed. The bushing inner-sieve-tube artificial natural gas migration passage is conveniently built between the reservoir sand of the production gas reservoir of the developed gas field and the selected gas reservoir to be developed, and the economy and efficiency in development of the selected gas reservoir to be developed inside or surrounding the offshore developed gas field can be realized.

The invention relates to the technical field of petroleum drilling equipment, in particular to an automatic pipe column processing device suitable for a petroleum drilling and a working method of the automatic pipe column processing device. The automatic pipe column processing device comprises a ground pipe column automatic conveying unit, a pipe column automatic conveying unit from the ground to a drill floor, a drill floor stand column automatic processing unit and a stand column storage unit. The units are matched to achieve automatic drilling operation of the drilling pipe column. According to the automatic pipe column processing device and the working method, the problem that time and labor are consumed in the aspects of building and storing of the stand columns by means of an existing automatic pipe column processing method is well solved.

The invention provides an electrochemical adsorption treatment device and process for water-based waste drilling fluid. The electrochemical adsorption treatment device for the water-based waste drilling fluid comprises a mud tank, a mud pump, a flow meter, an electrolytic bath, an electrode and an automatic control system, wherein the mud tank is circularly communicated with the mud pump; the mud pump is communicated with the flow meter; the mud tank is communicated with the flow meter; the flow meter is communicated with the electrolytic bath; the electrode comprise an anode and a cathode; the electrode is arranged in the electrolytic bath; the automatic control system is electrically connected with the electrode; the automatic control system is electrically connected with the flow meter. According to the electrochemical adsorption treatment device and process for the water-based waste drilling fluid, which are provided by the invention, a chemical treating agent is not added; an effective component in drilling fluid is not destroyed; inferior solid phases of a superfine micro-particle and the like in waste drilling fluid can be effectively removed; thus, main performance indexes of the density, the silt content, the solid content and the like of the waste drilling fluid are decreased; the rheological characteristic of the waste drilling fluid is improved, and the recycling performance index requirement of waste-based drilling fluid is met.

The invention discloses a simulation method and system for the rotating speed of a drill pipe in the tripping-in process of a deepwater guide pipe. The simulation method comprises the steps that layered soil bodies for experimental use are configured in a soil box according to soil body distribution of a target sea-bed area, a predetermined experimental condition is maintained, and the rotating speed of a motor in an injection and tripping-in device is adjusted for many times, so that the rotating speed of the drill pipe is adjusted; reference signals are collected through a multichannel data collector which electrically communicates with a pressure sensor, a tension sensor, a displacement sensor and a jet pump, and the reference signals comprise a pressure signal, a tension signal and a displacement signal; and according to the collected reference signals, a target drill pipe rotating speed in the tripping-in process of the deepwater guide pipe under the predetermined experimental condition is selected. According to the simulation method and system for the rotating speed of the drill pipe in the tripping-in process of the deepwater guide pipe, indoor experimental simulation and evaluation can be conducted on the rotating speed of the drill pipe in the tripping-in process of the deepwater guide pipe.

The invention discloses a method for building a bushing perforation fracturing-type artificial natural gas migration passage between gas reservoirs, and the method is characterized by comprising the following steps of selecting a gas reservoir to be developed; building a construction well; forming an uncased hole between the selected gas reservoir to be developed and a production gas reservoir of a developed gas field; loading a bushing into the uncased hole on two gas reservoir well sections; utilizing cement for well cementing of an annular well section between the uncased hole and the loaded bushing; forming a perforation hole on the reservoir well section of the bushing well section by utilizing a perforation gun; fracturing a reservoir section in the two gas reservoir storage layer well sections after the perforation of the bushing well section to form a fracturing crack; and setting a bridge plug above or in front of the two gas reservoir well sections to seal, so that the migration passage is formed. By adopting the development method, the migration passage is conveniently built between the reservoir sands of the production gas reservoir of the developed gas field and the selected gas reservoir to be developed, and economy and efficiency in development of the selected gas reservoir to be developed inside or surrounding the developed offshore gas field can be realized.

The invention discloses a method for identifying porous natural gas hydrates by using AVO attribute analysis. The method comprises the following steps of: (1) inverting actual longitudinal wave velocity or transverse wave velocity of a stratum by using seismic data; (2) determining the position of a high-speed abnormal region on a seismic section according to existing velocity information data, and selecting the position of a reflection interface; (3) extracting a reflection amplitude value on a CRP gather adjacent to the selected reflection interface position from the pre-stack seismic data, calculating a reflection coefficient, and drawing a change relation of the reflection coefficient along with an incident angle; (4) using a Shuey approximation equation to obtain a fitting curve of the reflection coefficient of the adjacent CRP gather changing along with the incident angle; and (5) determining the response characteristic type of reflection interface AVO according to the fitted curve so as to judge whether the porous natural gas hydrate is contained in the stratum or not. According to the method, the reliability of identifying the porous natural gas hydrate is contained in the stratum is improved.

The invention belongs to the technical field of ocean energy exploration, and relates to a method for identifying natural gas hydrate by using a longitudinal and transverse wave velocity increment cross plot. The method comprises the following steps: S1, obtaining actual longitudinal wave velocity Vp and transverse wave velocity Vs; S2, calculating the longitudinal wave velocity Vp0 and the transverse wave velocity Vs0 of the water-saturated stratum; S3, calculating a longitudinal wave velocity increment delta Vp and a transverse wave velocity increment delta Vs; S4, determining a threshold curve; S5, drawing a longitudinal and transverse wave velocity increment cross plot; S6, judging whether a natural gas hydrate stratum is contained or not; S7, determining a porosity theoretical line of the natural gas hydrate; and S8, estimating the saturation range of the natural gas hydrate to be measured according to the porosity theoretical line of the natural gas hydrate. According to the method, the reliability of natural gas hydrate identification is improved, the position of the natural gas hydrate is accurately explored and identified, the dry well rate is reduced, and the drilling cost is saved; and the offshore drilling safety is ensured.