436 results about "Tube well" patented technology

Recovery of viscous hydrocarbon from subterranean formations is assisted by using a plurality of novel U-tube type wells, each with dual wellheads, a moveable wellbore packer, a lateral section with a concentric communication zone and with sequential injection production perforations in which heat is injected into the proximal perforations and hot oil and produced fluids are produced from the distal perforations, the whole process being controlled by modulating the production flow where the wellbore fluids are controlled to act as a hydraulic seal to limit bypass of injected fluids. The injection-production displacement process moves axially along the wellbore in a sequential manner as hydrocarbon volumes are depleted by injected fluid displacement of oil and oil and water production.

Methods for drilling a new well in a field having a plurality of existing cased wells using magnetic ranging while drilling are provided. In accordance with one embodiment, a method of drilling a new well in a field having an existing cased well includes drilling the new well using a bottom hole assembly (BHA) having a drill collar having by an insulated gap, generating a current on the BHA while drilling the new well, such that some of the current passes through a surrounding formation and travels along a casing of the existing cased well, measuring from the BHA a magnetic field caused by the current traveling along the casing of the existing cased well, and adjusting a trajectory of the BHA to avoid a collision between the new well and the existing cased well based on measurements of the magnetic field.

A coiled tubing completion system is provided with a plurality of completion apparatus, all of which is designed flush with the diameter of the coiled tubing outside diameter for avoiding upsets and are flexible, spoolable on a coiled tubing reel and having through bores large enough to pass wireline tools for performing other operations. The spoolable coiled tubing system may use standard coiled tubing well control equipment and can be used in live wells. The flush, flexible, spoolable and through bore completion equipment may include a tubing retrievable safety valve, an annular control valve, concentric gas lift valves, a zone packer, a landing nipple, a sliding sleeve, and may include at the end a non-flexible but flush and open bore production packer and pump out plug. The completion system may be retrieved through a retrieval system.

A method and apparatus for sensing conditions in a subsurface geologic formation heated for the extraction of hydrocarbons is disclosed. A time domain reflectometer in conjunction with an open wire transmission line is employed in real time to determine impedance discontinuities in the geologic formation. These impedance discontinuities correspond to physical conditions in the geologic formation. The open wire transmission line can include pipes running into the subsurface geologic formation or other conductors, including a split tube well casing. The method may operate in the low frequency window for subsurface electromagnetic propagation.

The invention discloses a vacuum tube well precipitation and disposal method for rapidly restoring in-situ water and soil in a polluted place. The method comprises the following steps: arranging a precipitation tube well in a polluted region, and arranging a vacuum pump air extracting system, a submerged pump water pumping system and a chemical filling pipe in the precipitation tube well; arranging a disposal well in the polluted region, and connecting the disposal well with the submerged pump water pumping system; starting the vacuum pump air extracting system so as to guide polluted water in soil to flow into the precipitation tube well; continuously adding a restoring chemical into the chemical filling pipe, and reacting with the polluted water entering the precipitation tube well; after reacting for certain time, starting the submerged pump water pumping system, delivering pumped water into the disposal well, infiltrating the water in the disposal well into the soil again, repeatedly operating in the way, and finishing restoring after detecting that water and oil specimens meet standards. The method has the advantages of low cost, high water collecting efficiency, large affecting radius and capability of promoting underground water hydraulic circulation, and realizes water and soil integrated restoration in the polluted place.

A tube well and technologies for drainage, pressure reduction and dewatering pertain to the technical field of construction; the technical problem, the process optimization of the well points of a deep well dewatering function, is required to be solved; the tube well comprises a well pipe, a top-to-down vacuum pump, a filtering pipe, a submerged pump lower than the bottom of a foundation pit in the tube well, a top-to-down water-resisting clay for hole sealing, filter materials and water-resisting clay and filer materials lower than the foundation pit bottom outside the tube well, the invention also comprises a tube well water stopper inside the well pipe and below the submerged pump which meets the depth requirements of the submerged pump, matches with the diameter of the tube well and has the functions of easy adjustment and setting of depth and flexible water interception effect response. At the stage of drainage and dewatering stage, the water interception function of the water stopper is activated to facilitate the drainage and dewatering; and at the pressure reduction and dewatering stage, the water interception function is removed to realize the pressure reduction and dewatering of a confined aquifer. The invention has the advantages of lowing project cost, saving resources, accelerating construction progress, facilitating inside foundation pit operation, safe construction and easy operation.

The invention relates to a new welling drilling method for efficient rock breaking by means of heating power jet flow, and a complete set of construction scheme. According to the system composition, a continuous coil tubing unit, an electric measuring instrument truck, a cable, an air injection pipeline, a fuel injection pipeline, a fuel reaction cavity, a heating power jet flow nozzle, a ground pump set and the like are included. According to the technology, on the basis of the principle that the continuous heated surfaces of rocks crack until the rocks are decomposed in a splitting mode, the heating power jet flow acts on the rocks on the deep well hard formation, the non-contact efficient rock breaking is achieved under heat transfer and impact force of high-temperature and high-pressure fluid media, and the energy utilization rate of the well bottom is improved; the technological process is simple, the continuous oil tube well drilling technology is combined, a drill bit does not need to be replaced, the time of the tripping operation is shortened, abrasion to a tubular column is reduced, and the cost of the drilling operation is reduced. According to the new welling drilling method for efficient rock breaking by means of heating power jet flow, the heating power jet flow technology is creatively guided into the continuous oil tube well drilling, popularization and application of the continuous tube technology are facilitated, and oil and gas resources are efficiently exploited.

The invention relates to underground engineering construction, in particular to a construction method of a foundation pit confined water inrushing emergency water-lowering well. The method comprises: drilling the emergency water-lowering well near the position wherein the inrushing of confined water happens by first drilling a steel protective casing in an overburden layer above a confined water bearing stratum and then drilling the water-lowering well in the steel protective casting, and after the well is drilled, operating the water-lowering well to reduce the water head of confined water; and after a cushion layer is constructed completely, preparing for well sealing by first pumping the water and silt residue between the steel protective casting and the well pipe, then welding a water retaining steel plate, cutting off the steel protective casting and the pipe well from top down according to preset steel protective casting and pipe well cutting off positions and finally sealing the pipe well after the initial setting of poured concrete, wherein the well pipe mouth and the protective casing mouth are sealed by welding iron plates.

The invention provides an overpressure vacuum dewatering combined dynamic consolidation foundation treatment method, which comprises the following steps that: a pressurizing system is arranged, namely a certain number of micropore pressurizing tubes with a certain depth are arranged among longitudinal drainage well points, rubber sealing films are sleeved outside the pressurizing tubes, and high-pressure air is transmitted to the pressurizing tubes directly by an air compressor through a guide pipe; a vacuum dewatering system is arranged, namely a set of dewatering and drainage system provided with a vacuum pump for improving efficiency is arranged in a light-weight well point and tube well dewatering system additionally, wherein the air displacement of the vacuum pump is more than or equal to 100L / s, and the vacuum degree of the system is between 65 and 90kPa; and in a dynamic consolidation system, dynamic consolidation is performed by selecting pounders with different energy according to the dewatering conditions of strata, the moisture content of soil and permeability. Soft soil is pressurized laterally by the pressurizing system while the vacuum dewatering is performed, so that water molecules in soil bodies flow directionally to accelerate the consolidation of the soil bodies. By the method, the pressurization effect of vacuum combined loading of between 80 and 120kPa can be achieved, dewatering can be accelerated, the consolidation effect can be improved, and the construction process is quick, high-efficiency, energy-saving and environment-friendly.

The invention discloses a light well point drainage construction technology. In the technology, a hole is drilled on a slurry protective wall by a conventional geological drilling rig, a filter pipe is arranged in the wall to form a tube well; high pressure water is adopted to inject and flush the inside of the filter pipe to destroy the slurry structure layer of the protective wall and ensure a filter layer is automatically formed on the periphery of the filter pipe; a water outlet pipe the front end of which is provided with a submersible pump is arranged in the filter pipe; and finally, the submersible pump is started to realize well point drainage, wherein the diameter of the tube well is less than or equal to 200mm, the distance among the tube wells is between 3 and 10m; and a return water pipe is arranged on the water outlet pipe. The light well point drainage construction technology provided by the invention is improved on the basis of the traditional light well point drainage; by adjusting the drilling machinery, the diameter and distance of the tube wells and combining the tube well forming technology with the flow rate adjustment controlled water pumping technology, great drainage effect can be obtained, the movement is convenient, the construction speed is fast, the influence range is small, energy sources are saved, and the assembly and disassembly are convenient; and light well point drainage construction technology provided by the invention is suitable for foundation pit excavation of medium and small depth natural sloping in weak to strong water permeable soil layers.

The invention discloses a construction method of large tube well fixed point precipitation, sealing bottom free concrete and a steel sheet pile cofferdam deepwater bearing platform and relates to the construction method of a deepwater bearing platform of a bridge. The construction method aims to solve problems that a double wall steel cofferdam and sealing bottom concrete construction method is large in sealing bottom concrete thickness, large in steel plate pile length and large in construction difficulty. The construction method comprises the following steps of: inserting steel plate piles into a sand layer under water, connecting adjacent steel plate piles in a clamping manner so as to form a cofferdam which is higher than a water level and sealed; uniformly setting a plurality of large tube wells along an inner circle of the cofferdam; pumping out the water from a cofferdam area by using a submersible electric pump; at the same time, connecting the steel tubes or shape steels with steel plate piles which are exposed outside the water level in the horizontal direction so as to form horizontal cofferdam support beam groups, wherein the plurality of horizontal cofferdam support beam groups are arranged in the height direction; after the water in the cofferdam is completely pumped out, an underlayer is paved; and a reinforcement cage for manufacturing the deepwater bearing platform is arranged on the underlayer and concrete is cast so as to form the deepwater bearing platform.

A method for on-site measuring permeability coefficient of landfill gas adopts a measurement system comprising a lower opened tube well, a gas pressure sensor, a gas pressure display recording instrument, an extraction pipeline valve, a leachate emptying valve, a leachate emptying pipe, a gas measuring apparatus and a centrifugal fan. The method adopting extraction mode comprises the following step tube well internal pressure and extraction flow rate are recorded after the gas is stable; and the permeability coefficient of landfill gas is obtained after the substitution to a stationary model. In the method, not only are the conventional extraction pipeline and equipment in a landfill utilized, but also the defects of easy explosion and high hazards which are caused after air and methane are mixed when gas injection mode is adopted are overcome, further the characteristics of landfill covering permeability and permeability coefficient difference in horizontal direction and vertical direction of the landfill caused by layered landfilling and compaction are fully considered. Therefore, the method provided by the invention has the advantages of high measurement accuracy, simple system, and convenience in operation; in addition, key parameters are provided for the pollution control and the recycling of the landfill gas, so that the method has a promised application prospect.

The invention discloses a method for extracting coal bed gas in a stable mining region by ground well drilling, comprising the following steps of: hole distribution, well drilling, well cementation and well completion, wherein the hole distribution step can effectively reduce the destroy rate of a drilling well and improve the utilization rate of the drilling well by adopting a reasonable distribution principle so as to achieve the optimal extraction effect by using the least number of drilling wells; and simultaneously, the well drilling step adopts a third-opening well drilling way and selects reasonable well parameters, and two well completion processes of uncased hole well completion or liner tube well completion are adopted so that the well drilling structure and the construction process are reasonable, the extraction efficiency is also effectively improved, the possibility of destroying the drilling wells is reduced, and the well drilling accidents are reduced.

The invention discloses a construction method for hoisting an engineering tube well stand pipe of a high-rise building. The construction method includes: (1) construction is prepared; (2) a main lifting hoist and an auxiliary hoist are set; (3) a pipeline is conveyed to a tube well portion horizontally; (4) the section of the pipeline at the topmost end of the stand pipe is hoisted through the main lifting hoist; (5) the reciprocal second section of the pipeline of the stand pipe is hoisted through the auxiliary hoist; (6) the two pipelines are aligned and connected through bolts; (7) the main lifting hoist hoists the two connected pipelines to a certain height, the auxiliary hoist hoists the reciprocal third section of the pipeline of the stand pipe to the height the same as that of the two connected pipelines, and the third section pipeline is connected with the two sections of pipelines; (8) the whole stand pipe is hoisted to an installation position for support fixing; (9) after one stand pipe is constructed, the other stand pipes are sequentially hoisted; and (10) the steps are performed until the whole stand pipe is connected. The construction method for hoisting the engineering tube well stand pipe of the high-rise building is easy and convenient to operate, fast and efficient and convenient to use, reduces the cost, and improves the efficiency.

The invention discloses a deep thick muddy soft soil layer vacuum pipe well precipitation construction structure in the field of engineering construction and a construction method thereof. The structure comprises a precipitation well, the upper end of the inner side of the precipitation well is sleeved with a solid steel pipe, the outer side of the solid steel pipe is filled with cohesive soil, the lower end of the precipitation well is sleeved with a steel pipe filter pipe, the outer side of the steel pipe filter pipe is filled with a medium-coarse sand filter material, the top end of the precipitation well is sealed, the bottom end of the precipitation well is filled with aggregate to form a filter layer, a sinking pump is arranged in the precipitation well and is connected with a vacuum pump, and a draining pipe is arranged at the tail end of the vacuum pump. The method comprises the steps of lofting before construction, drilling construction, well pipe machining and putting, precipitation construction, precipitation pipe well closing and the like. The muddy layer water containing rate is effectively reduced, through vacuum precipitation, the muddy water containing rate is reduced to about 20%.

The invention relates to a prefabricated downcast pipe pile in a building foundation pit and a use method thereof. The prefabricated downcast pipe pile is a hollow cylinder and comprises a pipe wall and a conical tip. A plurality of water permeable holes are formed in the upper portion of the pipe wall at intervals. A filter barrel is arranged inside the prefabricated downcast pipe pile, the upper end of the filter barrel is open, and the lower end of the filter barrel is closed. The use method of prefabricated downcast pipe piles sequentially includes the first step of prefabricating the prefabricated downcast pipe piles, the second step of determining the total quantity and arrangement intervals of the prefabricated downcast pipe piles, the third step of installing the prefabricated downcast pipe piles and injecting water to clean the piles one by one, the fourth step of placing immersible pumps and water outlet pipes into the prefabricated downcast pipe piles, and the fifth step of stopping the immersible pumps from pumping water, cleaning holes, injecting cement mortar, and making part of the cement mortar permeate outwards via the water permeable holes and solidify to the outside soil of the prefabricate downcast pipe piles. By means of the prefabricated downcast pipe pile, the construction period of pipe wells is shortened. Meanwhile, the anti-floating performance of the prefabricated downcast pipe pile is improved by changing the pile to be an uplift pile.

An apparatus having a modular support frame with a top deck. The top deck has a passage therein. A tower is mounted on the top deck. A moveable plate and a track are positioned within the passage. The movable plate is slidingly attached to the track. A support rotary table is disposed within the modular support frame and suspends jointed tubulars. A coiled tubing injector head interface plate is operatively attached to the movable plate, and positioned over the first aperture of the movable plate. The first aperture is positioned over the well in a first position. A rotary table is positioned over the well in a second position. The apparatus is mounted on a transport vehicle in a transport position and moved to a well site. A lifting mechanism lifts the apparatus into an upright position. Well intervention work is conducted with coiled tubing and jointed tubulars.

The present invention is water source heat pump pipe well formed through reforming used engineering precipitating well. The engineering precipitating well after completing normal precipitating task is reformed through flushing, water pumping test, water refilling test, measuring water temperature, laying submerged water pump to form water source heat pump pipe well. By means of pumping out water and refilling water and the heat exchange of underground water and the stratum, an opened low temperature water source geothermal circulating system is formed.

A circulation sieve tube well completion method is applied in the sieve tube completion of an oil-gas well. The method is characterized as follows: A. a sieve tube well completion string is put down into a well; B. drilling fluid is injected; C. balls are thrown to build the pressure, and an expansion sieve tube suspender is set; D. balls are thrown to build the pressure, and a passage between a drill strings and a sieve tube cluster is got through; E. drilling fluid is injected to wash the interior wall of the sieve tube cluster; F. the sieve tube completion string is got out and the circulation sieve tube well completion work is completed. The effect of the method is that the circulation sieve tube well completion method can realize the well completion by suspending the sieve tube, and break through the traditional practice of sieve tube suspending construction. In the construction course, the drilling fluid can be circulated at any time to reduce the damage to an oil layer to the minimum and promote the oil layer penetration rate recovery value and the recovery rate to the maximum extent when the well is drilled. Compared with a conventional sieve tube well completion method, the well completion by suspending circulation sieve tube can be finished just by putting down the construction string once, which promotes the well completion efficiency and saves the construction cost.

The present invention relates to a water pocket capable of preventing the reverse flow of rainwater from a drain by reducing the rate of water outflow, by percolating a portion of the rainwater, which concentrates at a sump of the drain during flooding when the water level suddenly swells, deep underground through the water pocket. In order to achieve the above aim, a water pocket for preventing the reverse flow of rainwater from a drain according to the present invention comprises: a rainwater inlet tank connected to a side of a drain sump via a connecting pipe, into which rainwater collected at the sump is admitted through the connecting pipe; a percolation well formed in-ground below the floor of the rainwater inlet tank; a first perforated pipe having a cylindrical shape and a plurality of through-holes defined in the periphery thereof, and which is inserted within the percolation well to define a space between the walls of the percolation well; a second perforated pipe having a cylindrical shape and a plurality of through-holes defined in the periphery thereof, which is inserted within the first perforated pipe and has a non-woven fabric coupled tightly to an outer portion thereof to filter impurities; a filter layer filled with aggregate in a space between the percolation well and the first perforated pipe; and a filter mesh fastened so as to block the top of the first perforated pipe, wherein rainwater is discharged through only the outlet of the sump during normal flow conditions, and during abnormal flow conditions, rainwater that flows into the rainwater inlet tank through the connecting pipe is percolated and stored in the ground through the first and second perforated pipes and the filter layer.

The invention relates to a water conservancy project foundation pit tube well combined light well point dewatering and drainage method. The method comprises four steps of foundation pit geological data collection, tube well layout scheme design and check, tube well water yield check and tube well construction operation. Compared with a traditional drainage construction technology, on one hand, theconstruction amount of drainage construction operation is effectively simplified, the construction operation efficiency is improved, the operation cost of drainage construction and drainage operationis effectively reduced, on the other hand, the efficiency of foundation pit drainage operation is effectively improved, the influence of construction drainage on engineering construction is reduced,and the efficiency and quality of foundation pit construction operation are improved.

The invention is applied to the field of drain of tubular wells and provides a well point positioned pumping tubular well and a well point positioned pumping method. The pumping tubular well comprises a sand-free tube well section and a water storage tube well section, wherein the sand-free tube well section is positioned above a certain position of a first water-resisting layer below the precipitation depth of a foundation pit and is used for collecting a water source in a water-containing layer within the precipitation depth of the foundation pit; and the water storage tube well section is positioned below the certain position of the first water-resisting layer below the precipitation depth of the foundation pit, is connected with the sand-free tube well section and is used for storing the water source in the water-containing layer within the precipitation depth of the foundation pit. According to the well point positioned pumping tubular well and the well point positioned pumping method disclosed by the invention, by adopting a precipitation tubular well consisting of the sand-free tube well section and the water storage tube well section, the water source in the water-containing layer within the precipitation depth of the foundation pit is effectively collected, the effect that more water and the precipitated water are pumped without polluting an underground water source in an independent water-containing source below the precipitation depth of the foundation pit is realized, and the difficult problem that the water cannot be dredged under the condition that water cannot be dredged is solved. In addition, by adopting an automatic pumping method with a positioned water level, the total pumping time is greatly shortened and the cost of foundation pit engineering is greatly reduced.

The invention discloses a mounting device for a combined type vertical tube in a high-rise tube well and a mounting method thereof, belonging to the technical field of mechanical and electrical installation, and aiming to solve various problems of the modularizing mounting of the present mounting device for the combined type vertical tube. The mounting device comprises a tube wall lug and a tube well pothook which are arranged in a matching manner; single pipelines are fixed on a sharing bracket through a bracket fixing plate; the bracket fixing plate is fixed on the tube well wall. The mounting method comprises the following steps: firstly, welding a lug on the outer wall of the single vertical tube; fixing the vertical tube in the sharing bracket by a hoop so as to form a vertical tube set; arranging a pothook on the corresponding position on the tube well wall; wholly hanging the vertical tube set to a floor; suspending the lug on the preset pothook; vertically splicing the verticaltube set in turn; and finally closing the opening of the pothook through a safety pin. According to the invention, the tube wall lug and the tube well pothook are utilized to realize the temporary fixing of the vertical tube set, the flexible time is supplied for the re-testing of the tube set position, and the mounting precision and quality are further improved.

The invention discloses a super pressure suction joint pumping system and an operating method thereof. The pumping system comprises a rainfall tube well, a vacuum pump and an air compressor, wherein the vacuum pump and the air compressor are located outside the rainfall tube well; pumping pipes of the vacuum pump are connected to the inside of the bottom of the rainfall tube well; air compressor pipes of the air compressor are connected to the inside of the rainfall tube well and communicated with the pumping pipes; an exhaust tube is fixed to a well lid of the rainfall tube well; one port of the exhaust tube is formed in the upper portion of the rainfall tube well, the other end of the exhaust tube is located outside the rainfall tube well and split to two branch tubes, one branch tube is provided with a valve A and communicated with the pumping pipes, and the other branch tube is provided with a valve B and communicated with the air compressor pipes. The super pressure suction joint pumping system and the operating method thereof have the advantages that the structure is simple; all mechanical devices are disposed outside the well; installation is convenient and fast; the cost is low; one set of pumping system can drive six to twelve rainfall tube wells at the same time, and the water collecting efficiency and the pumping efficiency of the rainfall tube well can be effectively improved.

The invention discloses a foundation pit dynamic rainfall indoor model testing method and device under the condition of multiple water-bearing layers. Through the arrangement of layered water supply interlayers and connection with a water tank capable of ascending and descending and pressure adjustable pressurizing pumps, stable, uniform and differential water power supply is provided for the water-bearing layers in the rainfall model test, accordingly, layering simulation for different pressure bearing water layer and phreatic layer hydrologic conditions on the site is achieved, the water tank position, the pressurizing pump pressure and the water suction pump rotation speed are dynamically adjusted in the rainfall process, a stable boundary water head of each water-bearing layer is maintained, and the model pit interior water level is controlled. A water level observation system is composed of a PVC observation pipe well, a water level indicator inductor and a water level digital display instrument, a water suction system is composed of a PVC water suction pipe well, water suction pumps and a flow meter, the water suction flow is dynamically controlled, and the water level and water suction flow changes inside and outside a test foundation pit in the rainfall process are monitored in real time. The parameter influence rule in foundation pit rainfall is explored through adjustment on the waterproof curtain obstruction ratio, the water suction pipe filter pipe length, position and other parameters.

The invention discloses a method for dewatering a foundation pit by using a bored cast-in-place pile. The method comprises the following steps of: excavating a pile hole, hoisting a reinforcement cage in the pile hole, and fixing the reinforcement cage at an orifice by using a steel pipe or groove steel; hoisting water filtering pipes of which the bottoms are welded and sealed by steel plates to the orifice of the pipe hole, winding filter screens on the walls of the water filtering pipes, clamping upper openings of the water filtering pipes by using clamp plates, and arranging the clamp plates on the orifice of the pile hole; inserting all the water filtering pipes and well pipes into the pile hole sequentially section by section until a hole bottom is reached, wherein the length of each water filtering pipe is the same as an over-excavation depth; uniformly and continuously filling pisolith and fine sand to the periphery of outer walls of the well pipes in turn; putting the reinforcement cage down, and pouring concrete; and binding a cable on a water suction pipe by using a rope, lowering a water pump to a position which is 1 to 1.5m away from the hole bottom, hoisting the water pump by using a steel wire rope, and placing the water pump at a well mouth. By the method, a drill hole has two functions, the hole drilling construction of the well pipes is prevented, construction processes are reduced, and construction cost is reduced; and the method is particularly suitable for projects with pile formation difficulties or without dewatering conditions in the field.

The invention discloses a protective construction method of excavating a large area deep foundation pit in a running sand confined water soil layer. The method comprises the steps of: firstly, controlling the precipitation depth of the deep foundation pit in a range of 500mm to 1000mm below the excavation surface; disposing a circle of sandless tubular wells around the outer periphery of the deep foundation pit, wherein each sandless tubular well is 2 meters far from the deep foundation pit edge, 6 to 10 meters deeper than the bottom of the deep foundation pit, and 15 to 20 meters far from the neighboring sandless tubular well; laying reinforcing steel mesh sheets and disposing a circle of light-duty wellpoints on an inward side slope of the deep foundation pit; after starting the excavation, arranging a soil nail wall provided with weep holes for anchoring on a side slope of silty sand layer and silty clay layer with silt seam. By the method in the invention, the excavation of the large area deep foundation pit in the running sand confined water soil layer is ensured to be smooth, with no need to enlarge the excavation area. The difficulty of construction and the construction cost are lowered and the construction period is shortened.

The invention discloses a gas pumping-injecting interactive type foundation pit precipitation system and a precipitation method thereof, relates to the technical field of civil engineering construction, and aims to improving dewatering efficiency of a low-permeability soil layer. The system comprises at least two pumping-injecting interactive precipitation units, wherein each pumping-injecting interactive precipitation unit comprises a well tube, a filter tube, a precipitation tube, a gas pumping gate valve, a gas injecting gate valve and a vacuum pump which are sequentially connected in series from top to bottom, wherein a submersible pump and a liquid level meter are arranged in the filter tube; the upper-end tube opening of the well tube is sealed by a well lid; the vacuum pump is connected to a gas hole in the well lid by virtue of the gas pumping gate valve; a high-pressure gas source is connected to the gas hole in the well lid by virtue of the gas injecting gate valve; each pumping-injecting interactive precipitation unit is used as a strong vacuum tube well for precipitating a foundation pit soil body; and when water yield of each pumping-injecting interactive precipitation unit is obviously reduced, each pumping-injecting interactive precipitation unit is converted into a gas injecting well for use. The system and the method provided by the invention are especially suitable for precipitation of the low-permeability soil layer.

The invention relates to a well completion method through a sieve tube under the underbalanced condition, which is applied to the field of oil drilling well cementation technology. The well completion method is characterized in that a sleeve column with a temporary plugging type sieve tube descends to a well; the sleeve column has a structure that the sleeve column is connected with a guide shoe, the temporary plugging type sieve tube and a sleeve from bottom to top; a drilling and milling tool descends to the sleeve column through a drill rod; and finally, the part of the plugging blind end face of the temporary plugging type sieve tube protruding the inner wall of a base tube is milled or cut and cleaned through the drilling and milling tool. The method has the advantages that with the adoption of the sleeve column with the temporary plugging type sieve tube, when the sleeve is lowered, annular air of the inside and the outside of a sieve tube column are not communicated so as to protect a production layer and avoid pollution on the production layer. After the lowering of the sleeve is completed, the part of the plugging blind end face protruding the inner wall of the base tube is removed through the drilling and milling tool to unblock the plugging so that oil gas can enter the sleeve column. The method solves the difficult technical problem of using the sieve tube to realize the underbalanced well completion after the underbalanced well drilling.