This specification is formulated in order to standardize the management of trial production of coalbed methane wells and improve the level of engineering technology.
Trial production of coalbed methane includes trial production of exploratory wells and trial production of test well groups.
The trial production of coalbed methane should aim at obtaining true and complete data such as productivity, fluid properties, formation pressure, temperature and desorption pressure, and provide basis for further exploration or preparation of coalbed methane development plan.
2.TPO project planning and design
2. 1 The purpose of compiling the trial production engineering scheme of coalbed methane wells should be to obtain the real productivity, gas-liquid properties, pressure and temperature of coal seams. The principle of trial mining time is to meet the requirements of reserves declaration and real coal seam productivity.
2.2 According to drilling, logging, analysis and test data, determine the trial production horizon and interval, and define the purpose and goal of construction well.
2.3 According to coal seam physical parameters, gas content, critical analysis pressure, mechanical properties of coal seam roof and floor, etc. Using reservoir simulation software to predict the historical curve of gas-water production and the pressure distribution map of coal seam in different stages, comprehensively considering various factors such as nature, geography and production conditions, optimizing trial production equipment and determining production parameters.
2.4 Conduct stress sensitivity test of coal seam. According to the physical properties of the coal seam and the properties of the fluid contained in it, combined with the test results, the working system of different pumping and discharging stages is determined, which mainly includes the liquid level falling speed, casing pressure and throttling control.
2.5 Study and analyze the necessity of application of anti-corrosion, sand control, pulverized coal prevention, pump inspection, sand flushing and plugging removal, 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 trial mining is completed, sealing measures shall be taken at the height of 100 meters above the top boundary of coal seam. The principle is to ensure that the coal seam fluid does not leak and is easy to reuse. Considering the high leakage after coal seam drainage, cement plug is prohibited in principle.
2.8 can predict toxic gases such as hydrogen sulfide, and have complete disposal measures; Formulate reasonable and economical gas and water treatment measures.
3. Test production equipment
3. 1 ground equipment
3. 1. 1 workover rig has a lifting capacity of more than 25t, which can meet the operation requirements of coalbed methane wells within1000 m.
3. 1.2 generator is used as underground trial production equipment to meet the requirements of electric power and daily life.
3. 1.3 The sealing capacity of the well packer is 10MPa wellhead pressure.
3. 1.4 separator shall meet the gas-water separation capacity below 10× 104m3.
3. 1.5 The hoisting equipment adopts numerical control device to realize stepless speed regulation.
3. 1.6 Christmas tree has the sealing ability of 10MPa wellhead pressure.
3. 1.7 gas metering device meets the metering requirements of 50 ~ 50~ 100000m3/d/d, and has continuous metering capability, which can record both instantaneous flow and cumulative flow. The flowmeter should be calibrated regularly.
3. 1.8 communication equipment meets the communication requirements from the construction site to the base and project department, and realizes the electronic transmission of data and pictures.
3.2 downhole equipment
3.2. 1 The pipe has anticorrosion ability.
3.2.2 Pump: It is required to have certain sand control and pulverized coal prevention capabilities, and the comprehensive drainage capacity is 65,438+0.65,438+0 ~ 65,438+0.5 times of the actual daily water production. With the frequency conversion device, stepless speed regulation of displacement can be realized, which is suitable for the change of displacement in different stages.
3.2.3 Pump hanging: For fractured vertical wells, deviated wells, tubular pumps and sucker rod pumps, the suction port will be lowered to 20 ~ 100 m above the perforation section at the initial stage and to 100 m below the bottom boundary of the perforation section at the later stage. The bottom of submersible pump well and screw pump well is 25m away from the actual sand surface; For multi-branch horizontal wells and cave wells, the bottom of the pump drops to 5m above the perforation section or cave section.
3.2.4 Standard selection of drainage equipment: sunrise water quantity; Submersible pump is 200m3.
3.2.5 Selection of pumping unit: the pumping unit is selected by API calculation method and chart selection method, and the lifting system is optimized by lifting optimization design technology. The main contents include: pump depth, pump diameter, sucker rod size and proportion, tubing size, surface equipment model, working parameters, etc. On the premise that the economic and technical conditions allow and meet the water production, the smaller the pump diameter, the smaller the polished rod load, which is beneficial to the utilization of equipment. At the same time, in order to improve stroke efficiency and pump efficiency, long stroke and small stroke times should be used as much as possible; The hanging point load should add a certain safety factor to the oil well, and the well with deviation less than 4 should add10%; Additional10% ~ 50% for inclined shafts greater than 4; For high-yield water wells (> 200m3/d), the inner diameter of gas casing shall not be less than 150mm.
4. Drainage and mining engineering
4. 1 pumping system
4. 1.65438+ For vertical (deviated) wells, the daily liquid drop is less than 20m at the initial stage of drainage, and the desorption depth should be less than 5m when it approaches. For special wells such as cave wells and multi-branch horizontal wells, the drop speed of liquid level should be controlled, which should generally be less than 5 m/d, and the pumping process should be continuous, and it is not allowed to be interrupted halfway without special circumstances.
4. 1.2 Annular pressure is controlled by choke or needle valve, and casing pressure is controlled at 0.5MPa, which shall not exceed 1.0MPa in principle.
4. 1.3 When coalbed methane is produced, but continuous gas measurement is impossible, it should be ignited at the exit every 8 hours to describe the gas production. If gas production is continuous, the gas generated by casing and tubing should be exported to the surface flow for measurement.
4.2 Working system of pumping wells
4.2. 1 For pumping wells, the indicator diagram and dynamic liquid level should be tested and diagnosed regularly, and measures such as adjusting parameters and replacing pumps should be taken in time.
4.2.2 Regularly test the system efficiency, adopt advanced optimization design technology to improve the system efficiency of pumping wells, and improve the system efficiency by adjusting working parameters and selecting energy-saving and consumption-reducing equipment.
4.2.3 Adjust the balance of pumping wells in time to keep the balance ratio between 85 %~ 100%.
4.2.4 According to relevant standards and regulations, do a good job in daily maintenance of ground equipment.
4.2.5 Gas prevention measures such as gas anchor should be taken, and eccentric wear prevention measures such as righting should be taken for inclined wells and rod-tube eccentric wear wells.
4.3 ESP working system
4.3. 1 According to the characteristics of coal seam, downhole fluid, pressure, temperature and other data, reasonably select the electric submersible pump and its suspension depth, so that the electric submersible pump is always in the best working range and ensures efficient, economical, reasonable and safe operation.
4.3.2 During the normal operation of the ESP, the overload protection is adjusted according to 1.2 times the rated current of the motor, and the underload protection is adjusted according to 0.8 times the actual current of the motor. Under-load delayed start-up time shall not be less than 30 minutes. The unbalance of working current and voltage of the motor is not more than 5% and 3% respectively.
4.3.3 Strengthen the maintenance of transformers, control cabinets and other equipment. When there is overload shutdown or underload shutdown, it should be checked according to regulations, find out the reasons and take effective measures before restarting the ESP. The start and stop of ESP should be operated by professional management personnel.
4.3.4 Wellhead frequency conversion device should be adopted to adjust the motor speed in time to ensure the coordination of supply and discharge.
4.3.5 Strengthen the analysis of current card, comprehensively diagnose the working condition of submersible pump in combination with other dynamic data, and take timely adjustment measures to ensure the operation under reasonable ground driving conditions.
4.4 Working system of screw pump well
4.4. 1 According to the characteristics of gas wells, the surface drive equipment, sucker rod string, downhole pump and working parameters are systematically optimized.
4.4.2 The hydraulic performance of the screw pump should be tested before use, and it is forbidden to use it if it fails to meet the index requirements.
4.4.3 Screw pump should be equipped with anti-rotation device, and downhole string must be anchored.
4.4.4 During normal production of screw pump wells, the submergence degree should be above 100 m, the temperature of the produced fluid at the pump hanger should be lower than the rated temperature resistance index of the screw pump stator, and the hydrogen sulfide content of the produced fluid should be less than 2.5%.
4.4.5 Strengthen the daily maintenance of ground drive device of screw pump, do a good job in daily management and working condition analysis, and handle problems in time when found.
4.5 Midway Operating System
4.5. 1 The operation should be designed reasonably based on the principles of safety, reliability and rationality on the basis of analyzing the underground technical conditions at that time.
4.5.2 Compatibility test should be conducted between the killing fluid and the coal seam, and parameters such as density and viscosity of the killing fluid should be optimized to prevent and reduce the damage to the coal seam, and the produced fluid from the coal seam should be used as much as possible (filtered and sterilized).
4.5.3 If drilling, milling and grinding processes are adopted in the operation, reasonable WOB, ROP and tools shall be determined to ensure that the casing is not damaged.
4.5.4 All tools (tubing, sucker rod) and instruments shall be clean, and inspected and measured on the ground before running in the well.
4.5.5 Adopt reliable wellhead blowout preventer and formulate feasible well control measures to ensure construction safety.
4.5.6 Strictly measure the fluid volume of pressure loss wells and evaluate possible coal seam damage.
5. Reservoir simulation
5. 1 CBM well has a long production time, and its gas production mechanism is different from that of conventional oil and gas. In order to obtain the complete production characteristics of coalbed methane wells in a short time, reservoir simulation must be carried out. The simulation should adopt international common software such as COALGAS and COMMET, and advocate independent development of software.
5.2 The forecast items include: daily production of gas and water, cumulative production of gas and water, changes of formation pressure, etc.
5.3 Reservoir simulation should include the following aspects: pre-production simulation is mainly used to predict the water and gas production in the initial stage, and guide the design according to the prediction; Combining simulation with actual production during trial production, the simulation parameters are revised, and the production characteristics of the next stage are predicted by using the revised parameters; If the coincidence rate between the fitting curve of production history and the actual production curve for two consecutive months is above 90%, it is considered that the trial mining is over.
6. Data access
Data acquisition includes daily data acquisition during normal pumping, stimulation measures, midway operation data acquisition and test data acquisition.
6. 1 Daily data entry
6. 1. 1 The admission items include: well start-up time, working system, choke, casing pressure, oil pressure, annular dynamic liquid level or bottom hole flowing pressure, gas-water production, cumulative production, sampling time, sampling position, gas composition, produced water quality analysis, solid particle production description and ignition description.
6. 1.2 Suitable pressure gauges shall be selected for oil casings, separators and pipelines, and the measuring pressure shall be within the range of 1/3 ~ 2/3.
6. 1.3 Gas and water shall be continuously metered with instantaneous flow and cumulative flow, and the flowmeter shall be calibrated regularly.
6. 1.4 When gas is measured by gas meter, it is measured every 4 hours 1 time, and the daily output is the average.
6. 1.5 sampling requirements: sample at wellhead or gas-water separator; At the initial stage of the site, water samples are taken every day for simple analysis, and chlorine, pH value, sand content and pulverized coal content are required. Viscosity analysis is needed for wells fractured with gel before fracturing fluid is discharged; Sample every 30 days for gas-water total analysis 1 time, with 3 samples each time, with a sample size of not less than 500ml, the water types of water samples should be consistent, the chlorine radical difference is less than 10%, the oxygen content of natural gas samples is less than 2%, and the sample density difference is less than 0.02; Special sampling requirements should be carried out under the guidance of professionals.
6. 1.6 Encourage the use of remote automatic metering for CBM production test wells.
6.2 Increase production measures and midway operation data admission.
6.2. 1 Drilling through includes time, tubing specification, number of threads, penetration, pressure stop in case of blockage, bottom hole depth, caliper diagram, pipe string structure diagram and caliper trajectory description.
6.2.2 The inspection of the pump includes the model and name of the pump, the model and depth of each accessory, the schematic diagram of the pipe (rod) column structure and the scouring distance.
6.3 Test operation access (mainly including injection/pressure drop well test, flowing pressure/static pressure point test, indicator diagram test of pumping well, annular dynamic liquid level test, etc.). )
6.3. 1 The trial operation shall implement total quality management, strictly abide by industry standards and relevant regulations, ensure the validity of access data, and meet the needs of trial production management and dynamic analysis.
6.3.2 Before the test construction, the downhole conditions should be clearly tested, and the borehole conditions should ensure the smooth tripping of test instruments; During construction, the design should be strictly implemented and all data should be accurate.
6.3.3 Testing instruments, meters and their calibration devices shall be verified in accordance with the relevant provisions of national and industrial metrology, and adjusted and calibrated regularly. Those that exceed the validity period of calibration verification are not allowed to be used.
6.3.4 The interpretation of test data should be compared and verified by various methods, which requires detailed well test analysis curves, data and analysis interpretation results, and comprehensive analysis with reference to geological, logging and core data, so as to make the selected interpretation model and calculation parameters accurate and reliable.
6.3.5 The first success rate of test construction is over 90%, the qualified rate of test data is over 99%, and the calibration rate of instruments and their calibration devices is 100%.
6.3.6 Water injection/pressure drop well test requirements: it shall be conducted before the first coal seam drainage; Special well test equipment for coalbed methane should be selected, which can realize multiple well opening and closing underground; High-performance downhole electronic manometer, with an accuracy of not less than 0.05%FS, a resolution of not less than 0.00 1MPa, a sampling interval of not more than 3s and a sampling point of not less than 20,000 points; Ground direct reading equipment should be used; Before injection, a step-by-step injection fracturing test shall be conducted; The injection speed should be moderate, which will not cause coal seam cracking, but also cause enough pressure excitation in coal seam. The fluctuation value of injection rate does not exceed 65438 00%; The water injection time is 8 ~ 10h, and the influence radius of the water injection process should be ensured to be not less than 10m, and the shut-in time should be not less than 3 times of the water injection time; In the process of injection/pressure drop, it is required to continuously record the wellhead pressure value and injection quantity; The test liquid is filtered anti-swelling active water to reduce the damage of injection liquid to coal seam. The liquid preparation is twice as much as expected.
6.3.7 Measure the liquid level once a day at the site, and restore the liquid level 24 hours after the trial production stops.
7. Dynamic analysis of coalbed methane trial production
7. 1 production state analysis of coalbed methane well: according to theoretical simulation and indoor desorption pressure calculation, calculate the discharge time and dynamic liquid level of desorption gas, and analyze the liquid level change and fluid properties of coalbed methane well before and after exhaust.
7.2 Analysis of coalbed methane well productivity change: According to the geological characteristics of coalbed methane reservoir in the block, the controlled reserves of single well, coal seam permeability and other data, analyze the factors of gas production change, prolong the stable production time, and continuously improve the recovery ratio of coalbed methane reservoir.
7.3 According to the characteristics of coal rank, analyze the reasonable working system and liquid level drop range of coalbed methane well, control the coal powder output and sand control technology.
7.4 For coalbed methane wells developed in large well groups and blocks, the degree of inter-well interference and the pressure drop speed of coalbed methane reservoir should be analyzed, and an effective method for rapid and reasonable overall pressure reduction should be put forward.
7.5 According to the energy situation of coal seam, the matching between the gas productivity of coalbed methane well and swabbing equipment is analyzed, and the potential and existing problems of swabbing equipment are put forward, so as to improve the efficiency of equipment and maximize the potential of gas reservoir.
7.6 Dynamic analysis of CBM well trial production should include monthly and annual production operation data and curves; Comprehensive development data sheet and drainage gas production curve; Isogram of pressure distribution in coalbed methane reservoir; Relationship curve between cumulative water production of coalbed methane reservoir and gas production of single well: data table of gas-water composition and properties of coalbed methane well; Data sheet of drainage and production technology of coalbed methane well and pump efficiency analysis data; Analysis data sheet of swabbing efficiency of coalbed methane wells. The above analysis is mainly aimed at vertical wells. For the dynamic analysis of special wells such as horizontal wells and multilateral wells, relevant data should be supplemented and improved in practice.
7.7 Technical analysis of trial production of coalbed methane wells should include: analysis of wellbore management; Application effect analysis of ground fittings and underground fittings of pumping unit: analysis of produced water treatment effect and environmental protection requirements; Production logging technology and effect analysis; Analysis of the use effect of gas and water metering equipment, instruments and meters; Quality analysis of underground operation; Analysis of popularization effect of new technology and new technology.