1. General Provisions
This specification is formulated to standardize the management of trial mining of coal bed methane wells and improve the engineering technology level.
Trial mining of coalbed methane includes trial mining of exploratory wells and trial mining of test well groups.
Trial mining of coalbed methane shall be aimed at obtaining true and complete information on production capacity, fluid properties, formation pressure, temperature and desorption pressure, etc., so as to provide a basis for further exploration or preparation of coalbed methane development programs.
2. Trial mining engineering program and design
2.1 The preparation of the trial mining engineering program for CBM wells shall be aimed at obtaining the real production capacity, gas and fluid properties, pressure and temperature of the coal seam. The trial mining time shall be based on the principle of being able to meet the requirements of reserve declaration and obtaining the real production capacity of coal beds.
2.2 Based on the drilling, logging, analysis and assay data, determine the test mining layer, well section, and clarify the purpose and target of the construction well.
2.3 Based on the physical properties of the coal seam, gas content, critical resolution pressure, mechanical properties of the top and bottom plates of the coal seam, and other parameters, use the reservoir simulation software to predict the historical curve of gas and water production, and the distribution map of the pressure of the coal seam at different stages, and take into account the factors of nature, geography, and production conditions to optimize the test mining equipment and determine the parameters of production.
2.4 Carry out coal seam stress sensitivity test, according to the physical properties of the coal seam and the nature of the fluid it contains, combine the test results to determine the working system of different pumping stages, mainly including the rate of liquid level decline and the control of sleeve pressure and nozzle.
2.5 Research and analyze the necessity of applying technologies such as anti-corrosion, anti-sand, anti-coal dust, pump checking, sand flushing, and unblocking, and screen the main supporting technologies and corresponding process parameters.
2.6 Analyze the potential factors of reservoir damage, screen well fluids compatible with the reservoir, and put forward reservoir protection measures.
2.7 After the completion of test mining, it is required to take blocking measures 100m above the top boundary of the coal seam, and the principle is to ensure that no leakage of the coal seam fluid occurs, and also to facilitate the reuse. Considering the high leakage loss after drainage of the coal seam, cement plug is prohibited in principle.
2.8 Predict toxic gases containing hydrogen sulfide and other toxic gases, and have complete disposal measures; prepare reasonable and economically feasible gas and water treatment measures.
3. Trial mining equipment
3.1 Surface equipment
3.1.1 The well dressing machine has a lifting capacity of more than 25t, and it can meet the requirements for the operation of coalbed methane wells within 1000m.
3.1.2 The generator can meet the requirements of power and daily life for downhole test mining equipment.
3.1.3 The well sealer has a sealing capacity of 10MPa wellhead pressure.
3.1.4 The separator meets the gas-water separation capacity of less than 10×104m3.
3.1.5 The lifting equipment adopts numerical control device to realize stepless variable speed adjustment.
3.1.6 The oil extraction tree has a sealing capacity of 10MPa wellhead pressure.
3.1.7 The gas measurement device meets the measurement requirements of 50-100000m3/d, and has the continuous measurement capability, which can record the instantaneous flow rate and cumulative flow rate, and the flowmeter should be calibrated at regular intervals.
3.1.8 Communication equipment to meet the communication needs from the construction site to the base and the project department of the three places, to achieve electronic transmission of data and pictures.
3.2 Downhole equipment
3.2.1 The oil pipe has anti-corrosion ability.
3.2.2 Pump: It is required to have certain anti-sand and anti-coal dust ability, and the combined drainage capacity is 1.1 to 1.5 times of the actual daily water production, and by cooperating with the frequency conversion device, it can realize stepless variable speed adjustment of the drainage capacity, which is suitable for the change of the drainage capacity at different stages.
3.2.3 Pump hookup: for fracturing straight wells and inclined wells, the suction port of tubular pumps and rod pumps is 20-100m above the shot hole section at the initial stage, and 10m below the bottom boundary of the shot hole section at the later stage; for submerged oil electric pump wells and screw pump wells, the lowest end of the pump hookup is 25m away from the sand surface of the actual exploration; for multi-branched horizontal wells and cavernous wells, the lowest end of the pump hookup is 5m above the shot hole section or the cavernous well section. p>
3.2.4 Drainage equipment standard selection: daily water production <100m3, give priority to the selection of pumping equipment as lifting equipment; daily water production of 100 to 200m3, and the coal seam out of the sand, coal dust situation is not serious, select the screw pump; daily water production of 100 to 200m3, and the coal seam out of the sand, coal dust, serious, or the daily water production of >200m3 selection of the submerged oil electric pump.
3.2.5 Selection of pumping machine: using API calculation method and chart selection method for pumping machine selection, using lifting optimization design technology to optimize the lifting system, the main content includes: pump depth, pump diameter, pumping rod size and ratio, oil pipe size, ground equipment models, working parameters; in the economic and technical conditions allow and meet the premise of water production, the smaller the pump diameter, the smaller the rod load, which is conducive to the utilization of equipment, and at the same time, the pump diameter can be used as a pumping rod, and the pump diameter can be used as a pumping rod. The smaller the pump diameter, the smaller the light rod load, is conducive to the utilization of equipment, and at the same time, in order to improve the stroke efficiency and pumping efficiency, try to utilize the long stroke, small stroke; hanging point load should be compared to the oil wells with a certain additional safety coefficient, 10% additional for the wells with slope less than 4 °; greater than 4 ° of the inclined wells with additional 10% to 50%; high water production wells (>200 m3/d), the inner diameter of the gas casing shall not be less than 150mm.
4 Discharge and extraction works
4.1 Pumping and discharge system
4.1.1 Pumping and discharge is started with the minimum working system, and the discharge is gradually increased to ensure that the flow pressure at the bottom of the well drops evenly and slowly. For straight (inclined) wells, the daily drop of liquid surface is less than 20m in the early stage of extraction, and the daily drop of liquid surface should be less than 5m when approaching the depth of desorption; for special wells such as cavernous wells and multi-branch horizontal wells, the rate of drop of liquid surface should be controlled, and it should be less than 5m/d in general. the pumping process should be continuous, and there should be no intermission without any special circumstances.
4.1.2 Control the annulus pressure with nozzle or needle valve, casing pressure control to 0.5MPa is appropriate, in principle, not more than 1.0MPa.
4.1.3 When there is coalbed methane output, but can not be measured continuously, should be ignited at the exit once every 8 hours, to describe the situation of gas production, and if the gas production is continuous, casing and tubing output gas should be drawn out to enter the surface process together. Measurement.
4.2 Working system of pumping wells
4.2.1 The pumping wells should be regularly tested and analyzed with diagnostics, and measures such as adjusting reference and changing pumps should be taken in time.
4.2.2 Regularly carry out system efficiency tests, adopt advanced optimization design technology to improve the efficiency of the pumping unit well system, and improve the efficiency of the system by adjusting the working parameters and selecting energy-saving and consumption-reducing equipment.
4.2.3 Adjust the balance of pumping unit wells in time, and keep the balance ratio between 85% and 100%.
4.2.4 According to the relevant standards and regulations to do routine maintenance of ground equipment.
4.2.5 Gas anchors and other anti-gas measures should be taken, and anti-skewing measures should be taken for inclined wells and wells where rod and pipe skewing occurs, such as righting.
4.3 Working system of electric submersible pumps
4.3.1 According to the characteristics of coal seams, underground fluid characteristics, pressure, temperature and other information, reasonably select electric submersible pumps and pump hanging depth, so that the electric submersible pumps are kept in the optimal working range, to ensure high efficiency, economy, reasonable and safe operation.
4.3.2 electric submersible pump normal operation according to the motor rated current 1.2 times the transfer of overload protection, according to the motor of the actual current of 0.8 times the transfer of underload protection, underload delay start time shall not be less than 30min. motor current imbalance can not be greater than 5%, the voltage imbalance shall not be greater than 3%.
4.3.3 Strengthen the transformer, control cabinets and other equipment maintenance, if there is an overload shutdown or underload shutdown, should be checked in accordance with the regulations, identify the causes and take effective measures before restarting the electric submersible pump. Electric submersible pump start and stop should be operated by professional management personnel.
4.3.4 The wellhead frequency conversion device should be used to adjust the motor speed at the right time to ensure the coordination of supply and discharge.
4.3.5 Strengthen the analysis of the current card, combined with other dynamic information on the working conditions of the electric submersible oil pump to carry out a comprehensive diagnosis, and take timely adjustment measures to ensure that it operates under reasonable ground driving conditions.
4.4 Working system of screw pump wells
4.4.1 According to the characteristics of gas wells, carry out systematic optimization design of surface driving equipment, rod and pipe column, downhole pump, working parameters and so on.
4.4.2 Screw pumps should be tested for hydraulic performance before use, and it is strictly prohibited to use them without meeting the index requirements.
4.4.3 Screw pumps should adopt anti-reversal devices, and downhole pipe columns must be anchored.
4.4.4 The degree of submergence of the screw pump well during normal production should be more than 100m, the temperature of the output liquid at the pump hanging should be lower than the rated temperature resistance index of the stator of the screw pump, and the hydrogen sulfide content of the output liquid should be less than 2.5 percent.
4.4.5 Strengthen the daily maintenance of screw pump ground drive device, improve the daily management and analysis of working conditions, and find problems in a timely manner.
4.5 Midway operation work system
4.5.1 The operation should firstly be based on the analysis of the downhole technical condition at that time, and make a reasonable design according to the principle of safety, reliability and reasonableness.
4.5.2 Pressure fluid should be tested for compatibility with the coal seam, optimize the density, viscosity and other parameters of the pressure fluid to prevent and reduce the injury of the coal seam, and adopt the output fluid of the coal seam as far as possible if possible (filtering and sterilization are required).
4.5.3 If drilling, milling and grinding processes are used during the operation, reasonable drilling pressure, drilling speed and tools should be determined to ensure that the casing is not damaged.
4.5.4 All tools (including tubing and pumping rods) and instruments should be clean, inspected and measured on the surface, and confirmed to be reliable before being lowered into the well.
4.5.5 Adopt reliable wellhead blowout preventive devices and formulate feasible well control measures to ensure construction safety.
4.5.6 Strictly measure the amount of leaking pressure well fluid, and evaluate the possible coal seam injury.
5. Reservoir simulation
5.1 Coalbed methane wells have a long production time, and the mechanism of gas production is different from that of conventional oil and gas, so the complete production characteristics of coalbed methane wells should be obtained in a short time with the help of reservoir simulation. The simulation should adopt the internationally recognized software such as COALGAS and COMMET, and advocate the independent development of software.
5.2 Predicted items include: daily production of gas and water, cumulative production of gas and water, and change of formation pressure.
5.3 Reservoir simulation should include the following aspects: simulation before trial mining is mainly used to predict the initial stage of water and gas production, and guide the design according to the prediction; simulation during trial mining is combined with the actual production for the purpose of correcting the simulation parameters, and using the corrected parameters to predict the characteristics of the next stage of production; if the production history fitting curve and the actual production curve have a consecutive 2-month conformity rate of 90% or more, the trial mining is considered to be over.
6. Data acceptance
Data acceptance includes daily data acceptance during normal pumping, data acceptance of production increase measures and midway operation, and data acceptance of test data.
6.1 Daily Data Recording
6.1.1 The items to be recorded include: well start-up time, working system, nozzle, casing pressure, oil pressure, annular fluid level or bottoming out flow pressure, gas and water production, cumulative production, sampling time, sampling site, gas components, water analysis, description of solid particulate matter production, description of ignition, etc.
6.1.2 The data recording work includes the following items
6.1.2 Oil casing, separator, tubing are selected appropriate pressure gauge, the measured pressure requirements in the pressure gauge 1/3 ~ 2/3 range range.
6.1.3 Gas and water should be measured continuously, both instantaneous flow and cumulative flow, the flow meter should be calibrated regularly.
6.1.4 If the gasket flowmeter measurement of gas, every 4 hours to measure the gas 1 time, the daily output using the average value.
6.1.5 Sampling requirements: take samples at the wellhead or gas-water separator; take a water sample daily at the beginning of the site, and carry out a simple analysis, which is required to make the amount of chlorine root, pH, sand and coal dust. For wells with freeze gel fracturing, viscosity analysis is required to be done before discharging the fracturing fluid; take samples for gas and water analysis once every 30 days, with 3 samples each time and a sample volume of not less than 500 ml; water samples should be consistent with the water type, the difference of chlorine root is less than 10%, the oxygen content of natural gas samples is less than 2%, and the difference of density of the samples is less than 0.02; special sampling is required to be carried out under the guidance of professional staffs.
6.1.6 Encourage the use of remote automated metering for coalbed methane test mining well groups.
6.2 Production enhancement measures and midway operation data admission
6.2.1 Passing wells include time, tubing specification, number of roots, square in, encountered obstruction to pressurize the tonnage, bottoming depth of the well, through the well gauge sketches, tubing structure schematic diagrams, and description of through the well gauge traces.
6.2.2 Inspection of the pump includes the pump model, the name of each accessory, model, depth, tube (rod) column structure schematic, anti-punching distance.
6.3 Testing operations (mainly including injection/pressure drop test, flow pressure/static pressure point test, pumping well schematic test and annulus dynamic liquid level test and other projects) admission
6.3.1 Testing operations should implement comprehensive quality control, strictly comply with industry standards and related regulations, to ensure that the validity of the recorded information, to meet the needs of the test mining management and dynamic analysis.
6.3.2 Before the construction of the test should be clear test well conditions, wellbore conditions should be able to ensure that the test instrument is free to get up and down; the construction should be strictly implement the design, to take all the accurate information.
6.3.3 Test instruments, meters and their calibration devices should be in accordance with the relevant provisions of the state, industry measurement of calibration, and regular adjustment and calibration, more than the calibration validity is not allowed to use.
6.3.4 Test data interpretation should be compared and verified by various methods, and detailed analytical curves, data and results of analysis and interpretation of test wells are required to be provided, and at the same time, comprehensive analysis should be made with reference to geological, logging and core data, so that the selected interpretation model and calculation parameters are accurate and reliable.
6.3.5 The success rate of test construction is more than 90%, the passing rate of test data is more than 99%, and the rate of regular calibration of instruments and their calibration devices is 100%.
6.3.6 Requirements for injection/pressure drop test well: it should be carried out before the first discharge of coal bed; special coal bed methane test well equipment should be selected, which can realize multiple switching of wells downhole; high-performance downhole electronic manometers, with accuracy of not less than 0.05%FS and resolution of not less than 0.001MPa, sampling interval of not more than 3s, and not less than 20,000 sampling points at one time; ground surface direct reading equipment should be used; before injection, the instrumentation and its calibration device should be calibrated and checked regularly. Direct-reading equipment should be used; before injection, step injection rupture test should be carried out; the injection rate should be moderate, which does not lead to the rupture of the coal seam, but also can cause enough pressure excitement in the coal seam. The fluctuation value of the rate of the injection process is not more than 10%; the injection time is 8~10h, and it should be ensured that the radius of influence of the injection process is not less than 10m, and the shut-in well is not less than 3 times of the injection time; in the process of injection/pressure drop, it is required to record the value of the pressure at the wellhead and the amount of the injection continuously; the liquid used for the test is anti-expansion activated water with filtration treatment, so as to minimize the harm of the injected liquid to the coal seam. The volume of liquid dispensing is two times of the predicted injection volume.
6.3.7 The liquid level is measured once a day on site, and the liquid level is restored for 24h after the test mining stops.
7. Dynamic analysis of coalbed methane test mining
7.1 Analysis of the output state of coalbed methane gas wells: According to the theoretical simulation and indoor calculations of the desorption pressure, the time of desorption of the gas discharge, the dynamic liquid level is projected, and the fluid level changes before and after the gas discharge from the wells are analyzed, as well as the nature of the fluids.
7.2 Analysis of changes in production capacity of coalbed methane wells: analyze the factors of changes in gas production, extend the stable production time, and continuously improve the recovery rate of coalbed methane reservoirs based on the geological characteristics of the coalbed methane reservoirs in the block, the controlled reserves of a single well, and the permeability of the coal beds, and other information.
7.3 According to the characteristics of coal rank, analyze the reasonable working system and the amplitude of lowering liquid surface of CBM wells, and control the technical methods of coal dust output and sand prevention.
7.4 Coal bed methane wells developed in large well groups and blocks should analyze the degree of interrelationship between well interference and the speed of pressure drop in coal bed methane reservoirs, etc., and put forward effective methods for rapid and reasonable overall pressure drop.
7.5 According to the energy condition of the coal seam, analyze the matching condition between the capacity of water and gas production of coalbed methane wells and the pumping equipment, put forward the potential of the pumping equipment and the problems, improve the efficiency of the equipment, and maximize the potential of the gas reservoir.
7.6 Dynamic analysis of coalbed methane well test and extraction shall include monthly and annual production operation data and curve; comprehensive development data table and drainage and gas extraction curve; contour map of pressure distribution in coalbed methane reservoir; cumulative water output and gas output curve of a single well in coalbed methane reservoir; data table of gas and water components and properties of coalbed methane wells; data table of drainage and extraction process of coalbed methane wells and data of pumping efficiency analysis; and analysis of pumping efficiency of coalbed methane wells. Data table. The above analysis is mainly for straight wells, for the dynamic analysis of horizontal wells, multi-branch wells and other special wells, the relevant information should be supplemented and improved in practice.
7.7 Coalbed methane well test mining technology analysis should include: analysis of wellbore management; analysis of pumping machine ground accessories and downhole accessories; analysis of the effect of output water treatment and environmental protection requirements; analysis of the production logging technology and effect; analysis of gas, water measurement equipment, instruments, meters, analysis of the effect of the use of the gas, water metering equipment, instruments, analysis of the quality of downhole work; analysis of the effect of the promotion of new processes, new technologies.