Method suitable for improving and increasing yield of gas lift drainage composite reservoir of cluster gas well group

Abstract

The invention discloses a method suitable for improving and increasing yield of a gas lift drainage composite reservoir of a cluster gas well group, which comprises the following steps of: through a gas field wellhead connection process, effectively reducing the wellhead pressure of a gas supply well by utilizing two main functions of suction and pressurization drainage of a compressor, and continuously discharging and mining to assist exhaust and lifting the well; and finally, the platform forms a unified and unique output channel to be output to a trunk pipe network. Secondly, designing a water lock removing agent injection end and a dry gas injection end on a pipeline and a wellhead, conveying to a reservoir through high pressure, and retaining a well testing end, so as to effectively reform the reservoir and monitor the effect; and finally, separation liquid generated by the field separation device is returned to the main pipeline through the auxiliary pipeline and the pump body, so that the field environmental protection requirement is ensured, and the transfer cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and in particular to a method for enhancing production by compound reservoir transformation of gas lift liquid drainage applicable to cluster gas well groups. Background Art

[0002] In the middle and late stages of the development of low-permeability tight sandstone gas reservoirs in the western region of China, as the formation pressure gradually decreases, on the one hand, most single wells have no natural production capacity or the production capacity is lower than the lower limit of industrial gas flow, and it is necessary to carry out reservoir stimulation to obtain commercial natural gas production. Moreover, the conventional process of improving the process by chemicals cannot ensure the application depth and time of the chemicals in the reservoir. On the other hand, the liquid-carrying capacity of gas wells decreases, and the wellbore and formation are severely liquid-accumulated. The Southwest Gas Field is located in a hilly area, mostly platform cluster well groups. The surface gathering and transportation uses a radial gas gathering pipeline network. The single well group is mixed-transported to the gas gathering station, and the external transportation pressure is high. The liquid accumulation mainly comes from the formation and condensate water. The water production of gas wells gradually increases. The foam drainage measures are restricted by condensate oil, and the drainage effect is poor. The production capacity of high and low pressure wells on the same platform interferes with each other, and the gas well water lock phenomenon is serious.

[0003] Taking the Xujiahe Formation gas reservoir as an example, the following problems generally exist in the well groups of this gas reservoir: ① Most of the gas reservoirs are inefficient reservoirs, with poor physical properties of the reservoir matrix, low porosity, dense, small throat characteristics, and generally underdeveloped fractures. The productivity of single and gas wells is low, and acid fracturing stimulation is a necessary means; ② The gas reservoir has a large amount of water production, and gas wells generally produce water, which has a great impact on the production of gas wells. During testing, about 50% of the gas wells produce water; after production, more than 90% of the production wells produce water, and some wells have a large amount of water production. Affected by water production, the gas well production decreases rapidly. In the middle and late stages of production, as the pressure decreases, it is difficult to flow by itself, and in severe cases, it is directly flooded and shut down; ③ Some production wells are completed with downhole throttling technology. In the later stage, as the formation pressure decreases, some throttles fail.

[0004] At present, in-depth research and application have been carried out on current conventional acid fracturing stimulation measures and various gas drainage and production processes. The process of gas lifting and restarting each well in the compressor platform well group has gradually become the main aggressive liquid drainage measure for liquid drainage in gas reservoirs in the middle and late stages. However, for the restrictive problems such as the mutual interference of high and low pressure entering the station caused by the unified and unique external transmission pipeline of the cluster well platform, the ineffective cycle of gas lifting caused by reservoir water blocking and water locking, and the monitoring of the transformation effect in the near-wellbore area of the reservoir, the traditional construction process cannot meet the needs of gas field engineers. Summary of the Invention

[0005] In order to solve problems such as the mutual interference between high and low pressures after single-well gas lift one by one in a conventional platform well group, the inability to establish an effective cycle for single-well reservoir water-sealing and water-lock gas lift, and the existence of surface liquids on site, the present invention provides a method for enhancing production through gas lift liquid drainage and composite reservoir transformation applicable to cluster gas well groups, realizing the main functions of pressure reduction and suction and gas lift liquid drainage within the well group; forming a unified and unique inlet gathering and transportation function; through the addition of process transformation and utilization of the characteristics of compressors, realizing auxiliary functions such as water-lock release agent injection, dry gas injection, testing and monitoring, etc.; and through the reuse of functions, realizing the on-site online transfer function of separated liquids.

[0006] To solve the above technical problems, the technical solution of the present invention is: a method for enhancing production through gas lift liquid drainage and composite reservoir transformation applicable to cluster gas well groups, comprising the following steps:

[0007] a. Modify the wellhead connection of the cluster gas well group; all well gas supply pipelines in the well field are connected in series through high-pressure pipelines to the sand remover for pretreatment to the inlet of the three-phase separator to form a gas supply process; all assisted drainage casing pipelines are respectively equipped with high-pressure valves and then connected in series to the outlet of the natural gas compressor to form an assisted gas lift casing process;

[0008] b. Modify the connection of on-site equipment of the cluster gas well group;

[0009] Gas supply process: wellhead → sand remover → three-phase separator → natural gas compressor; when there is no gas volume provided within the well group, natural gas from the main pipeline network can be reversely extracted through any single well as the starting gas source;

[0010] Gas lift and dry gas injection soaking well process: natural gas compressor → single well casing valve or tubing-casing cross-connection process;

[0011] Agent accompanying injection process: agent tank → venturi tube → high-pressure injection process;

[0012] Separation and liquid drainage process: separator → liquid drainage tank;

[0013] Transfer and liquid drainage process: liquid drainage tank → screw booster pump → pressure gauge seat of the export pipeline → purification station;

[0014] c. Determine the construction displacement of the equipment according to the single well depth, liquid accumulation depth, etc. If necessary, for deep liquid accumulation gas wells, foam drainage agents can be used for pre-treatment to reduce the liquid column density in the wellbore and reduce the initial gas lift starting pressure;

[0015] d. Select the well with severe liquid accumulation as the gas lift assisted drainage well for construction, and other gas wells in the well group as the gas supply source for gas supply and suction. After the casing pressure of the gas lift well gradually rises and the liquid returns after being lifted through, reduce the displacement to avoid gas channeling affecting the gathering and transportation system; if the initial gas lift pressure exceeds the rated pressure of the equipment, through the tubing-casing cross-connection process, inject gas positively to suppress the liquid accumulation in the tubing, artificially lower the liquid level height in the tubing, and reduce the gas lift starting pressure;

[0016] e. Continuous gas lift assisted drainage measures are used to drain wells. The return fluid is monitored through the wellhead sampling valve. In the early stage, the source of the wellbore fluid accumulation can be determined by color and temperature. In the later stage, the direction of the formation fluid accumulation can be determined by the mineralization degree, and it can be verified whether the return fluid is connected to the edge and bottom water;

[0017] f. For continuous measures, after the gas lift well returns the accumulated liquid, the gas is ineffective in flushing the wellbore, and the casing pressure still cannot return to the normal level. It is judged whether it is affected by water seal and water lock, and the high-temperature dry gas injection + water lock agent + dry gas injection pressure-holding segment plugging and well-spitting measures are formulated to eliminate the blockage of the near-well area and the influence of water seal;

[0018] g. When the gas lift measure well effectively reaches the normal level, it will be converted into a gas supply well. The gas wells in the well site will be drained one by one by gas lift, so as to achieve effective drainage of the whole well group and record the production cycle and liquid volume of each well, and schedule the construction replacement rounds;

[0019] h. The gas supply wells in the well site form a stable gas supply, and the gas lift wells are put into the station at a stable pressure. The accumulated liquid separated by the pressure reduction of the gas supply wells enters the separator and is transported to the trunk pipeline network through the screw pump; the accumulated liquid discharged by the gas lift wells enters the production trunk line to ensure that no waste liquid is generated on site;

[0020] i. When the measure well achieves stable operation through gas lift measures and meets the normal production level, conduct unstable well test analysis after the measures, compare the changes of various parameters before and after, and judge the next measures.

[0021] Furthermore, in step b, all processes are connected using high-pressure pipelines and high-pressure accessories.

[0022] Furthermore, the gas wells in the well group are analyzed through geological static data and gas testing, well testing, production data, and liquid level dynamic data. Unstable well testing analysis is carried out before gas lift measures are taken. Before implementing measures, the permeability, liquid level, gas-water boundary, skin and other parameters of the gas wells are determined, the remaining reserves are determined, a gas lift implementation plan is formulated, and the gas lift construction procedures are scheduled.

[0023] Furthermore, in step b, all pipeline processes are anchored to the ground, and after the pipeline is connected, the nitrogen pressure test is carried out to 25MPa, and there is no puncture or leakage for 15 minutes.

[0024] Furthermore, the number of single wells in each well group is ≥3.

[0025] Furthermore, the distance from the well group external transmission trunk pipeline to the gas gathering station is ≤ 2 kilometers.

[0026] Furthermore, the downhole oil casing of the gas lift drainage well in the well group is connected or there is a connecting channel at the upper end of the fracturing packer or the packer is unsealed, and there is no casing change.

[0027] Furthermore, during gas lift operations, when some gas wells cannot form a gas lift circulation due to downhole tools, a circulation channel can be established by mechanically drilling holes in the tubing without moving the production string and without killing the well and polluting the reservoir.

[0028] The present invention solves problems such as high-low pressure interference after single-well gas lift in a conventional platform well group, inability to establish an effective circulation in single-well reservoir water blockage and water lock gas lift, and the presence of surface liquids on site. It realizes the main functions of pressure reduction and suction and gas lift liquid drainage within the well group; forms a unified and unique inlet gathering and transportation function; realizes auxiliary functions such as injection of water lock removal agent, injection of dry gas, and testing and monitoring through process transformation and addition, taking advantage of the characteristics of the compressor; and realizes the online transfer function of separated liquid within the well site. Substantially, for gas field workers, the main role is to use the gas lift liquid drainage of the measure gas lift well and the pressure reduction and suction of the gas supply well to fundamentally improve the gas recovery rate of the gas well and realize the increase in the production of the platform well group.

[0029] (1) The invention uses pressurized and heated natural gas to the annulus of the casing of the assisted exhaust gas lift well to supplement the production energy of the gas well. The natural gas mixes with the wellbore fluid, reducing the flowing pressure gradient (density of the gas-liquid mixture) in the lift pipe and the backpressure on the bottom hole, and increasing the flow velocity of natural gas from the bottom hole to the wellhead.

[0030] (2) The invention continuously drains the accumulated liquid at the bottom and around the wellbore. The potential energy of the pressure drop funnel near the wellbore increases, and the pressure difference at both ends of the original "water-in-gas" infiltration zone increases, forcing the accumulated liquid to precipitate from the reservoir, restoring the seepage capacity of the high and low permeability zones and dredging the gas flow channel at the distal end.

[0031] (3) For gas supply wells with a certain production capacity (production capacity limited by the external transmission pressure), the invention reduces the wellhead pressure through wellhead compression equipment, enabling the gas supply well to reach the critical liquid-carrying flow velocity, thereby increasing the flow velocity of natural gas from the bottom hole to the wellhead, increasing the production, and achieving the purpose of pressure reduction, suction, and production increase.

[0032] (4) The injected gas is high-temperature dry gas after separation, purification, and pressurization, continuously injected through a compressor, forming a continuous phase with the formation gas phase. At the same time, due to the good compressibility and expansibility of natural gas, the energy release helps to overcome the restraint of capillary force, thereby reducing the water lock effect and condensate oil blockage phenomenon. The water lock removal agent can also be used to reduce the water saturation, prevent clay swelling, reduce the surface tension of the rock, achieve rock wetting reversal, promote oil and gas aggregation, and at the same time assist the high-temperature hot dry gas to increase the gas phase saturation in the near-wellbore zone, increase the pressure difference at both ends of the pore throat, displace the pore water, and improve the gas phase seepage effect.

[0033] (5) After the invention realizes stable voltage output, avoids interference between wells, and the process flow operates, the original gas supply wells in the platform provide gas sources through gas well test valves, stop the production into the station, and the original external transmission channel of the platform is only the production process of the gas lift well into the station. After the continuous drainage stage, the gas and liquid production of the platform tends to be stable, avoiding interference between high-pressure and low-pressure wells in traditional platform wells and ensuring the stability of the production system pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the present invention or related technologies, the following will briefly introduce the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a schematic diagram of gas lift-assisted drainage of wellbore liquid;

[0036] Figure 2 It is the process of chemical agent injection into the Venturi tube;

[0037] Figure 3 It is a 70-type double-wing high-pressure gas production tree;

[0038] Figure 4 It is a schematic diagram of the process flow of gas lift drainage and reservoir stimulation for enhanced production in a cluster well group;

[0039] Figure 5 It is the double logarithmic pressure build-up graph of Well HC15 in HC Gas Reservoir before and after measures. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The following will Figures 1-5 clearly and completely describe the technical solutions of the present invention in conjunction with the appended

[0041] drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0042] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0043] To make the purpose, technical solutions and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail in conjunction with the drawings.

[0044] In the well group of the present invention, the tubing valves and casing valves at the wellheads of each individual well are connected in series, and the individual wells are connected by pipelines to form a network connection. By installing high-pressure gate valves to control the process switching, a series-connected compressor gas supply pipeline and a compressor gas lift liquid drainage pipeline are formed. These two main functional pipelines are connected to auxiliary equipment such as natural gas compressors, separators, desanders, and liquid drainage tanks. Secondly, a chemical injection port is added to the gas lift pipeline, and an injection dry gas pipeline is formed through the original pipeline. A main pipeline pressure gauge seat is connected behind the liquid drainage tank to form an auxiliary transfer liquid accumulation pipeline. The test valve at the wellhead is left as a monitoring port, and a monitoring liquid level port is reserved for the single-well casing. Applying this process can achieve the arbitrary switching (gas supply / gas lift) measures for each individual well in the well group, realize the functions of suction pressure reduction and gas lift liquid drainage; realize the reservoir stimulation process for dry gas and chemical treatment; realize the monitoring of gas lift measures and the effect of the gas well recovery ability; realize the function of no liquid accumulation on site and the function of unifying the pressure of high- and low-pressure gas wells into the station. It effectively improves the economic benefits and usage effects of single sets of equipment.

[0045] Main functions and principles:

[0046] 1. Gas lift liquid drainage function and principle: In low-production cluster well groups, the self-production capacity is relatively low, high-production high-pressure wells inhibit the production capacity of other low-pressure wells in the well group, low-production wells do not have the ability to carry water during production, the liquid level in the tubing rises rapidly during production, serious liquid accumulation leads to a rapid decline in production and wellhead pressure, and intermittent production has to be adopted. At the site, the maximum displacement of the injection end of the natural gas compressor is 1500 m 3 / h, and the maximum injection pressure is 25 MPa. Using the gas sources provided by itself and other wells in the well group, the natural gas purified by the separator is continuously injected into the annulus of the measure well through the compressor boost, mixed with the fluid in the wellbore, and then through the expansion potential energy of the high-pressure gas and the formation-produced gas, the flowing pressure gradient, the density of the gas-liquid mixture, and the backpressure on the bottom of the gas well in the lifting wellbore are reduced, the vertical lifting capacity and the liquid-carrying flow velocity are increased, and the liquid accumulation is discharged, thereby overall increasing the production of the platform.

[0047] The gas lift assistance drainage process of the natural gas compressor is analogous to the principle of an open "U" tube. When the formation pressure drops and the gas volume in the two-phase fluid in the wellbore of a low-production liquid-producing and gas-producing well cannot reach the critical liquid-carrying flow velocity, the liquid will fall back and easily form liquid accumulation in the wellbore. On the ground, the compressor is used to inject high-pressure compressed gas into the annulus or tubing of the wellbore, mixed with the fluid in the wellbore, and then through the expansion potential energy of the high-pressure gas and the formation-produced gas, the flowing pressure gradient, the density of the gas-liquid mixture, and the backpressure on the bottom of the gas well in the lifting wellbore are reduced, the vertical lifting capacity and the liquid-carrying flow velocity are increased, so as to achieve the purpose of draining and producing the liquid accumulation, thereby increasing the production of low-production gas wells and restoring the production capacity level before the influence of liquid accumulation.

[0048] 2. Suction pressure reduction function and principle:

[0049] Any well within the well group can be used as the initial gas supply source. The gas supply time and volume can be adjusted at any time according to the production capacity and water flooding degree of each well. When the initial gas lift gas source starting volume cannot be provided within the entire well group, the trunk line gas source can be introduced from a single well as the initial gas source through the reverse transportation mode of the process.

[0050] Using the gas supply well as the gas supply source, the produced natural gas is heated, pressure-regulated, purified and dehydrated through a multi-functional separator and then transported to the natural gas compressor. The inlet pressure of the compressor in this process is 0.4 - 1.7 MPa, and the external transmission pressure of the well group in the conventional block is about 3.2 - 5.4 MPa (medium-pressure pipe network). The compressor can effectively reduce the pressure at the gas supply wellhead, increase the liquid-carrying flow rate of the gas well, reduce the abandonment pressure of a single well, and achieve the purpose of increasing production.

[0051] Table 1 Critical flow rate calculation table of Φ73mm tubing in the Gray model of the HC Xujiahe gas reservoir

[0052]

[0053]

[0054] The process uses other low-production liquid-accumulating gas wells in the well group as the gas supply source. After purification and dehydration through the separator, the natural gas compressor is used to assist in exhausting the gas lift wells. On the one hand, this can reduce the pressure at the gas supply wellhead and achieve the purpose of increasing production by reducing pressure and suction; on the other hand, for the gas lift liquid drainage wells, the liquid in the production wellbore and formation is drained, reducing the bottom-hole back pressure of the well, thereby overall increasing the production of the well group.

[0055] 3. Injection agent's water seal and water lock release functions and principles:

[0056] A Venturi branch is added to the pipeline at the rear end of the compressor to form a negative pressure ejector suction port. Natural gas enters through the inlet of the Venturi tube using this port and is discharged through a nozzle with a very small cross-section. As the cross-section decreases, the pressure of the compressed air decreases and the flow rate increases. At this time, a vacuum is generated at the inlet of the adsorption chamber, causing the agent to be sucked into the Venturi tube and enter the diffusion chamber together with the natural gas to reduce the gas flow rate.

[0057] During daily maintenance, foam drainage agents, corrosion inhibitors, and desulfurization agents are injected concomitantly. The reservoir can also be transformed through water lock release agents. The principles of water lock release and water seal release are as follows:

[0058] Definition of water lock: It is generally considered that in low-permeability gas reservoir reservoirs, due to the fine throat, poor permeability, and reservoir heterogeneity, after external water invasion, a water film is formed on the rock surface under the action of surface tension, resulting in an increase in the starting pressure at both ends of the throat, an increase in the water saturation of the reservoir near the wellbore, a decrease in gas-phase permeability, and a decrease in production capacity. After shutting in and opening the well, the liquid in the wellbore undergoes reverse dialysis in the low-permeability layer under the action of back pressure, rock wettability, and capillary pressure, forming water lock damage.

[0059] Usually, methanol-based mixed formation water is used to gasify and reduce the water saturation, while preventing clay swelling. Surfactants, wettability reversal agents, oxalic acid, etc. are used to reduce the surface tension of the rock, achieve rock wettability reversal, promote oil and gas accumulation. At the same time, high-temperature hot dry gas is assisted to increase the gas phase saturation in the near-wellbore zone, increase the pressure difference at both ends of the pore throat, displace the pore water, and improve the gas phase seepage capacity.

[0060] 4. Dry gas injection for plugging removal, drainage assistance, displacement function and principle:

[0061] Primary gas-liquid separation is carried out at the front end of the compressor, and molecular sieve and high-temperature three-phase secondary separation are carried out inside the compressor skid. The purified dry gas has a gas injection end. The dry gas has the functions of plugging removal, drainage assistance, and displacement, which helps to overcome the restraint of capillary force, reduce the water lock effect and relieve the asphaltene deposition plugging.

[0062] 5. Function and principle of online transferring water to the main pipeline:

[0063] The screw pump is used to pump the accumulated liquid at the site such as compressors and separators from the back end of the drainage tank to the main pipeline network. Since the gas wells in the well field are continuously produced by assisted gas lift, a positive pressure forward drive is formed in the pipeline. The accumulated liquid can be transported to the gas gathering station for unified treatment along with the production dry gas. Generally, the outlet end can be connected to the seat of the main pipeline pressure gauge. By transferring, it is ensured that there is no accumulated liquid at remote sites, avoiding safety and environmental protection issues, and at the same time preventing the roads in winter and rainy seasons from affecting production.

[0064] 6. Function and principle of stable pressure external transmission and avoiding interference between wells:

[0065] After the process flow runs, the original gas supply wells in the platform provide gas sources through the gas well test valves and stop the production into the station. The original external transmission channel of the platform is only the production process of the gas lift wells entering the station. After the continuous drainage stage, the gas and liquid production volume of the platform tends to be stable, avoiding the interference between high-pressure and low-pressure wells in the traditional platform wells, and ensuring the stability of the production system pressure.

[0066] 7. Function and principle of shut-in huff and puff and micro-fracturing:

[0067] Through process switching, it can be ensured that the chemicals and dry gas are assisted by the compressor to be discharged to the tubing and annulus space of any single well. The injection pressure can be increased to the designed pressure of 25 MPa through the equipment. For low-production and low-pressure shallow gas wells, it can ensure the action depth and action radius of the injection medium, ensure pressure balance during the shut-in huff and puff measures, and at the same time form a micro-fracturing effect on the shallow reservoir, improve the permeability and skin factor in the near-wellbore zone, effectively displace the wettability of the low-permeability reservoir rock, and improve the gas phase permeability.

[0068] 8. Function and principle of monitoring the measure effect and analyzing and comparing the single-well unstable well test:

[0069] After the traditional gas lift measure in the gas well, the liquid is produced and drained, and the oil casing recovery ability and gas production are implemented to judge the measure effect. However, the change of the reservoir after transformation and the improvement of the edge and bottom water distribution cannot be monitored. Through the unstable well test analysis and comparison before and after the measure at the test port reserved in the process, the skin of the reservoir, the permeability of the near-well zone, the length of the micro-fracture created by fracturing, and the reaction of the edge and bottom water boundary after continuous gas lift are mastered. Through the casing port reserved in the process, the liquid level change is monitored at all times, and the reservoir effect and liquid accumulation condition in the wellbore are mastered.

[0070] Construction process transformation:

[0071] (1) Before the transformation of all wells in the well field, they are closed. Close the single-well production main valve and valves 2-9 and conduct airtightness inspection to ensure that there is no leakage in the valves.

[0072] (2) Prepare connection components such as high-pressure N80 steel pipes, nipples, valves, screw threads, slips, tees, screw plugs, and surface compensating cores, and prepare screw thread sealant for the connection parts.

[0073] (3) Wellhead process: Take single well a in the well group as an example ( Figure 3 )

[0074] Test and monitoring end: Connect a tee above the No. 7 test valve, horizontally install a surface compensating core, and connect a screw plug above to reserve a test port, which can be used for putting foam rods and later well test monitoring;

[0075] Oil pipe gas supply end: Horizontally connect a nipple, tee, and screw plug at the No. 9 oil pipe production valve. All wells in the well field are connected in series horizontally to form a gas supply pipeline; Provide gas source for on-site compressed gas lift;

[0076] Auxiliary drainage casing end: Horizontally connect a nipple, tee, and screw plug (surface compensating core) at the No. 6 casing valve. All wells in the well field are connected in series horizontally to form an auxiliary gas lift casing pipeline, and a monitoring casing liquid level port is reserved at the surface compensating core; Form a reverse lift annular space pipeline;

[0077] Oil-casing cross-connection process: Short-circuit connect the No. 8 oil pipe production valve and the No. 5 casing valve. This process is used to balance pressure, can be used for normal lifting of the oil pipe, and purging the pipeline in winter when it is frozen.

[0078] Inter-well process: The gas supply pipelines of all wells in the well field are connected in series through high-pressure pipelines to the desander for pretreatment and then to the inlet of the three-phase separator to form a gas supply process; After installing high-pressure valves respectively, all the auxiliary drainage casing pipelines are connected in series to the outlet of the natural gas compressor to form an auxiliary gas lift casing process; ( Figure 4 )

[0079] (4) Equipment process pipeline: All processes are connected with high-pressure pipelines and high-pressure accessories.

[0080] Gas supply process: wellhead → desander → three-phase separator → natural gas compressor; when there is no gas supply in the well group, reverse extraction of natural gas from the main pipeline network can be used as the starting gas source through any single well;

[0081] Gas lift and dry gas injection well soaking process: natural gas compressor → single well casing valve (reverse lift) or oil casing connection process (positive lift, well soaking);

[0082] Pharmacy injection process: Pharmacy tank → Venturi tube → high-pressure injection process;

[0083] Separation and drainage process: separator → drainage tank;

[0084] Transfer and drainage process: drainage tank → screw booster pump → external transmission pipeline pressure gauge seat → purification station.

[0085] (6) All pipeline processes are anchored to the ground. After the pipeline is connected, the nitrogen pressure test is 25MPa, and there is no puncture or leakage for 15 minutes.

[0086] Solution operation process:

[0087] (1) The gas wells in the well group are analyzed through geological static data and gas test, well test, production data, and liquid level dynamic data. Unstable well test analysis is carried out before gas lift measures are taken. The gas well permeability, liquid level, gas-water boundary, skin and other parameters are determined before the measures are implemented. The remaining reserves are determined, the gas lift implementation plan is formulated, and the gas lift construction procedures are arranged;

[0088] (2) The equipment construction displacement is determined according to the single well depth, liquid accumulation depth, etc. If necessary, foaming agents can be used for pre-treatment of deep liquid accumulation gas wells to reduce the density of the liquid column in the wellbore and reduce the initial gas lift start-up pressure;

[0089] (3) Wells with serious liquid accumulation are selected as gas lift auxiliary drainage wells for construction, and other gas wells in the well group are used as gas supply sources for gas suction. When the casing pressure of the gas lift well gradually rises and the liquid is lifted and returned, the displacement is reduced to avoid gas channeling affecting the gathering and transportation system. If the initial gas lift pressure exceeds the rated pressure of the equipment, the oil casing channeling process can be used to positively inject gas to suppress the liquid accumulation in the tubing, artificially lower the liquid level in the tubing, and reduce the gas lift starting pressure.

[0090] (4) Continuous gas lift assisted drainage measures are used to drain wells. The return fluid is monitored through the wellhead sampling valve. In the early stage, the source of the wellbore fluid accumulation can be determined by color and temperature. In the later stage, the direction of the formation fluid accumulation can be determined by the mineralization degree, and it can be verified whether the return fluid is connected to the bottom water.

[0091] (5) For continuous measures, after the gas lift well returns the accumulated liquid, the gas is ineffective in flushing the wellbore, and the casing pressure still cannot return to the normal level. It is judged whether it is affected by water seal or water lock. High-temperature dry gas injection + water lock-releasing agent + dry gas injection pressure-holding section plugging and well-spitting measures are formulated to eliminate the blockage of the near-well area and the influence of water seal;

[0092] (6) When the gas lift well reaches the normal level, it is converted into a gas supply well. The gas wells in the well site are drained one by one by gas lift, and the whole well group is drained effectively. The production cycle and liquid volume of each well are recorded, and the construction replacement rounds are scheduled;

[0093] (7) The gas supply wells in the well site form a stable gas supply, and the gas lift wells are put into the station at a stable pressure. The accumulated liquid separated by the pressure reduction of the gas supply wells enters the separator and is transported to the trunk pipeline network through the screw pump; the accumulated liquid discharged by the gas lift wells enters the production trunk line to ensure that no waste liquid is generated on site;

[0094] (8) When the well reaches stable operation and meets the normal production level through gas lift measures, an unstable well test analysis is carried out after the measures are taken to compare the changes in various parameters before and after and determine the next measures.

[0095] (9) When some gas wells cannot form a gas lift construction cycle due to the influence of downhole tools (failed packers, throttles), a circulation channel can be established by mechanically perforating the tubing without moving the production string or polluting the reservoir.

[0096] Well selection principles and drainage and production implementation boundaries

[0097] The present invention is applicable to low-yield and low-efficiency cluster well groups in China. In the later stages of development, such well groups often face problems such as low-pressure mining and bottom hole accumulation. After the recovery rate is increased by densifying the well network, some new wells are deployed in old well fields. The simultaneous production of new and old wells causes high and low pressure interference, resulting in large-scale shutdown of old wells. Effective drainage measures and pressurized mining technology are urgently needed. The reservoir in the Central Sichuan Basin is buried at a depth of 2200m. The existing equipment is designed to have a pressure of 25MPa, which meets the drainage needs. In view of the problems faced, the required conditions are achieved in combination with the existing equipment parameters. The principles for using well groups are as follows:

[0098] 1. The remaining reserves of the well group are abundant, with the potential for economic utilization, and the number of platform wells is ≥ 3;

[0099] 2. The daily production of a single well was low before the measures were taken, and the historical production test results were good, but the low production was affected by liquid accumulation;

[0100] 3. The downhole oil casing of the gas lift drainage well in the well group is connected or there is a connecting channel at the upper end of the fracturing packer or the packer is unsealed, and there is no casing change.

[0101] 4. The distance from the well group external transmission trunk pipeline to the gas gathering station is ≤ 2 kilometers.

[0102] On the one hand, the main purpose of parameter gas lift is to take the depth of liquid accumulation in the drainage well, daily drainage volume and casing injection pressure as the main purpose of parameter gas lift. On the other hand, the auxiliary reservoir transformation effect is formulated to formulate the implementation steps of the invention and distinguish the implementation boundaries, as shown in the following table:

[0103] Table 2 Gas well boundaries for this process

[0104]

[0105] From 2019 to 2023, a total of 9 experimental well groups were tested in the Xujiahe Formation gas reservoir in Hechuan, central Sichuan. On average, each well group had 4 wells. Before the measures, the average production of each well group was 1.2×10 4 m 3 / d. After the measures, the average daily production was 3.6×10 4 m 3 / d. By effectively deploying the experimental well groups and strongly discharging liquid at the lower part of the structure of the entire gas reservoir, the daily liquid discharge of 36 gas wells in 9 groups was 1440 m 3 . The low-yield and low-efficiency gas wells were effectively restored to production, the gas reservoir recovery rate was increased, and the natural decline rate of the gas reservoir reached 0 from 2020 to 2023. New wells were effectively reduced. At the same time, by effectively discharging liquid at the edge, the water breakthrough time of the gas wells in the high part of the structure and the advancing speed of the edge water were slowed down.

[0106] Taking the HC-15 well group as an example below, this well group has four wells (X1, X2, X3, H5). The primary gas lift measure was implemented on Well X2 in 2010. The gas test without restriction was 9.6×10 4 m 3 / d. After production, water was produced, with a daily water production of 6 m 3 / d and an oil production of 0.5 t.

[0107] In 2011, the casing pressure dropped from the initial 18 to 12 MPa, and the gas volume dropped to 2×10 4 m 3 / d, with a water production of 3.0 m 3 / d. In 2013, it was converted to intermittent production. Before the measures in 2019, the tubing pressure was 4.5 MPa (equal to the export pressure), and the casing pressure was about 10.2 MPa. The estimated daily gas production was 0.3 - 0.4×10 4 m 3 , and the estimated daily water production was 0 m 3 . The tubing-casing pressure difference gradually increased. A flowing pressure gradient test was conducted that year. From the pressure gradient test curve, the liquid level depth was 20 m, and the pressure gradient was 1.13 MPa / 100 m.

[0108] Before the measures, the average daily gas production of the 4 wells in the entire Well 15 group was about 13000 m 3 or so, and the average daily liquid production was 7 m 3 or so. Among them, Well H5, a newly put into production well, had a daily gas production of 10000 m 3 . The tubing pressure of this well reached 12 MPa, inhibiting the production of other gas wells in the well group.

[0109] Judging from the production data, the current productivity of Well X2 is low, and it can no longer carry water for production. The tubing liquid level is high, and serious liquid accumulation has led to a rapid decline in pressure and production, forcing intermittent production to be adopted. The production valve on site was closed, and the tubing head pressure increased by 0.02 MPa in 72 hours, indicating that there is serious liquid accumulation in the wellbore and the near-well area of this well, and there is basically no production.

[0110] In June 2019, this well was put into production by gas lift measures. Initially, Well H5 in the well group was used as the gas source, and the design process of the present invention was adopted. The initial daily backflow and liquid production of this well reached 120 m 3 , and the highest daily gas production per single well reached 6.8×10 4 m 3 , and continuous single-well gas lift was carried out for 19 days, with a stage production increase of 95×10 4 m 3 , and the stage liquid drainage volume was 1600 m 3 .

[0111] After the gas lift measures of this well were successful, the assisted gas lift construction of other gas wells in this well group was carried out in sequence. The single-well backflow was carried out one by one through 23, 14, and 16 days. When the single-well gas volume and liquid drainage volume were stable, it was converted into a gas supply well. Finally, Wells X1, X2, and X3 in the well group were used as gas supply wells, and Well H5 was used as the gas lift assisted drainage well and the only production channel into the station in the well group. The production of the well group reached 65,000 m³ / day under stable control from 13,000 m³ / day before the measures.

[0112] Through the comparison of the unstable well test analysis of Well X2 in this well group in 2016 and 2019, it can be seen that the near-well permeability of this well has increased, the skin factor has decreased, the productivity coefficient has increased, and the basic physical properties of the reservoir have been effectively improved through drainage.

[0113] Table 3 Comparison table of single-well unstable well test interpretation of Well HC-15 in HC gas reservoir (before and after measures)

[0114]

[0115] Among them, for Well X1, a single well in Well Group HX-7, after 36 m³ of liquid was backflowed after the measures, gas and liquid did not flow out. Later, through a high-temperature dry gas pre-slug, the main slug of the water lock release agent, and a dry gas pressure buildup post-slug, the well was shut in for 48 hours and then flowed back by huff and puff. After 3 m³ of black-brown liquid was produced, the casing and tubing pressure recovered to 8 MPa, and the daily gas production recovered to 5,000 m³ / day.

[0116] In view of the characteristics of different pressures of multiple wells in a cluster well group, the present invention, through the wellhead connection process of the gas field, first utilizes the two main functions of compressor suction and pressurized liquid drainage to effectively reduce the wellhead pressure of the gas supply well and continuously drain and assist the gas lift well, and finally forms a unified and unique external transmission channel on the platform to output to the main pipeline network; secondly, the pipeline and wellhead are designed with a water lock release agent injection end and a dry gas injection end, which are transported to the reservoir under high pressure and left at the well test end to effectively carry out reservoir transformation and monitor the effect; finally, the separated liquid generated by the on-site separation device is returned to the main pipeline through the auxiliary pipeline by means of a pump, ensuring the on-site environmental protection requirements and saving the transfer cost.

[0117] Through the transformation of the pipeline of the platform well group, each single well and compressor equipment are connected in an unconventional way. Through the suction and pressurization of the compressor, two main functional pipelines of suction pressure reduction and gas lift liquid drainage are formed in the well group, achieving the reduction of the wellhead pressure of the gas supply well in the platform well group, achieving pressure reduction and suction for increased production, and at the same time, the gas lift liquid drainage measure well, so as to overall improve the main function of the well group output.

[0118] A single and unique inlet channel is formed, and all wells in the well group avoid the gathering and transportation function of high and low pressure interference.

[0119] By setting a water lock release agent injection end on the pipeline, through the pumping capacity of the compressor, and entering the reservoir through pressurization, the functional mechanism of releasing the water lock is effectively exerted, ensuring the auxiliary function of the action depth and time of the agent.

[0120] By setting a dry gas injection end on the pipeline, the dry gas has the functions of plugging removal, drainage assistance, and displacement, which helps to overcome the bondage of capillary force, reduce the water lock effect and relieve the anti-condensation blockage of condensate oil.

[0121] Through the continuous drainage of each single well, the pressure drop funnel near the wellbore increases, the seepage capacity of the low-permeability zone is restored, and the gas flow channel at the far end is dredged. Through transformation measures such as agents and dry gas injection, the monitoring function of the permeability and skin change of the single well reservoir is monitored through unstable well testing.

[0122] The wellbore liquid separated and discharged by the on-site separation device is simultaneously pressurized and pumped back to the main pipeline network through the on-site auxiliary pipeline, avoiding the liquid storage in the single well group and effectively reducing the environmental protection risk and transfer cost.

[0123] The above-described embodiments are only the preferred embodiments of the present invention and not all the feasible embodiments of the present invention. For those of ordinary skill in the art, any obvious changes made without departing from the principles and spirit of the present invention should be considered to be included within the scope of the claims of the present invention. Although the present invention has been described above with reference to the embodiments, various improvements can be made to it and components therein can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no technical conflict, the various features in the disclosed embodiments of the present invention can be combined with each other in any way, and the exhaustive description of these combinations is not given in this specification only for the sake of saving space and resources. Therefore, the present invention is not limited to the specific embodiments disclosed in the text but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for increasing production by gas lift and liquid drainage composite reservoir transformation applicable to cluster gas well groups, It is characterized in that The following steps are involved: a. Reconstruction of the wellhead connection of the cluster gas well group; the gas supply pipelines of all wells in the well site are connected in series through high-pressure pipelines to the desander pretreatment to the inlet of the three-phase separator to form a gas supply process; all the auxiliary exhaust casing pipelines are respectively equipped with high-pressure valves and connected in series to the outlet of the natural gas compressor to form an auxiliary exhaust casing lifting process; b. On-site equipment connection for cluster gas well transformation; Gas supply process: wellhead → desander → three-phase separator → natural gas compressor; When there is no gas supply in the well group, reverse extraction of natural gas from the main pipeline network can be used as the starting gas source through any single well; Gas lift and dry gas injection well soaking process: natural gas compressor → single well casing valve or oil casing connection process; Pharmacy injection process: Pharmacy tank → Venturi tube → high-pressure injection process; Separation and drainage process: separator → drainage tank; Transfer and drainage process: drainage tank → screw booster pump → external transmission pipeline pressure gauge seat → purification station; c. Develop equipment construction displacement according to the single well depth, liquid accumulation depth, etc. If necessary, use foaming agents for pre-treatment of deep liquid accumulation gas wells to reduce the density of the liquid column in the wellbore and the initial gas lift start-up pressure; d. Select wells with serious liquid accumulation as wells for gas lift and drainage construction, and use other gas wells in the well group as gas supply sources for gas suction. When the casing pressure of the gas lift well gradually rises and the liquid is returned after lifting, reduce the displacement to avoid gas channeling affecting the gathering and transportation system. If the initial gas lift pressure exceeds the rated pressure of the equipment, the oil-casing channeling process can be used to inject gas forward to suppress the liquid accumulation in the tubing, artificially lower the liquid level in the tubing, and reduce the gas lift start-up pressure; e. Continuous gas lift assisted drainage measures are used to drain wells. The return fluid is monitored through the wellhead sampling valve. In the early stage, the source of the wellbore fluid accumulation can be determined by color and temperature. In the later stage, the direction of the formation fluid accumulation can be determined by the mineralization degree, and it can be verified whether the return fluid is connected to the edge and bottom water; f. For continuous measures, after the gas lift well returns the accumulated liquid, the gas is ineffective in flushing the wellbore, and the casing pressure still cannot return to the normal level. It is judged whether it is affected by water seal and water lock, and the high-temperature dry gas injection + water lock agent + dry gas injection pressure-holding segment plugging and well-spitting measures are formulated to eliminate the blockage of the near-well area and the influence of water seal; g. When the gas lift measure well effectively reaches the normal level, it will be converted into a gas supply well. The gas wells in the well site will be drained one by one by gas lift, so as to achieve effective drainage of the whole well group and record the production cycle and liquid volume of each well, and schedule the construction replacement rounds; h. The gas supply wells in the well site form a stable gas supply, and the gas lift wells are put into the station at a stable pressure. The accumulated liquid separated by the pressure reduction of the gas supply wells enters the separator and is transported to the trunk pipeline network through the screw pump; the accumulated liquid discharged by the gas lift wells enters the production trunk line to ensure that no waste liquid is generated on site; i. When the measure well achieves stable operation through gas lift measures and meets the normal production level, conduct unstable well test analysis after the measures, compare the changes of various parameters before and after, and judge the next measures.

2. The method for increasing production by gas lift and liquid drainage composite reservoir transformation applicable to cluster gas well groups according to claim 1, It is characterized in that In the above step b, all processes are connected by high-pressure pipelines and high-pressure accessories.

3. The method for enhancing production by means of gas lift liquid drainage and composite reservoir stimulation applicable to cluster gas wells according to claim 1, characterized in that, the gas wells in the well group are analyzed through geological static data, well testing, production data, and liquid level dynamic data. Unstable well testing analysis is carried out before the gas lift measure to determine parameters such as the permeability, liquid level, gas-water boundary, and skin of the gas well before the measure, determine the remaining reserves, formulate a gas lift implementation plan, and schedule the gas lift construction process.

4. The method for enhancing production by means of gas lift liquid drainage and composite reservoir stimulation applicable to cluster gas wells according to claim 1, characterized in that, in step b, all pipeline processes are anchored with ground anchors, and after the pipelines are connected, nitrogen is used for pressure testing at 25 MPa without leakage for 15 minutes.

5. The method for enhancing production by means of gas lift liquid drainage and composite reservoir stimulation applicable to cluster gas wells according to claim 1, characterized in that, the number of individual wells in each well group ≥ 3.

6. The method for enhancing production by means of gas lift liquid drainage and composite reservoir stimulation applicable to cluster gas wells according to claim 1, characterized in that, the distance from the well group's external transmission main pipeline network to the gas gathering station ≤ 2 km.

7. The method for enhancing production by means of gas lift liquid drainage and composite reservoir stimulation applicable to cluster gas wells according to claim 1, characterized in that, in the gas wells with gas lift liquid drainage in the well group, the oil casing is connected underground, or there is a communication channel above the fracturing packer, or the packer is released, and there is no casing deformation.

8. The method for enhancing production by means of gas lift liquid drainage and composite reservoir stimulation applicable to cluster gas wells according to claim 1, characterized in that, when a part of the gas wells cannot form a gas lift construction cycle due to downhole tools during gas lift construction, a circulation channel can be established by means of mechanical punching of the tubing without moving the production string and without well killing and polluting the reservoir.

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