A Study On The Complex Phase Behavior And Driving Mechanics Of Recovering Deliverability In Condensate Gas Well By Methanol Injection

The study on how to decrease the condensate mass and water blocking of inverse water imbibitions near the wellbore and improve the gas well productivity is always the key subjects in condensate gas reservoir exploitation, especially the condensate gas reservoir at high-temperature & high-pressure and with abundant gaseous water. The study has great significance in improving low-permeability, high-temperature & high-pressure and with abundant gaseous water condensate gas reservoir exploitation.This paper systematically carries out the experimental study on the formation fluid PVT phase behavior test of high-temperature & high-pressure and with injected methanol and abundant gaseous water condensate gas system, and builds up the gas/liquid/liquid three-phase equilibrium calculation model and how to use the low permeability condensate gas reservoir single well injected methanol add nitrogen puff & huff to decrease the condensate mass and water blocking of inverse water imbibitions near the wellbore to improve the gas productivity. The outcome of the study can be applied in the condensate gas reservoir exploitation. The following are the contents of this paper:1. This paper designed a suit of phase test method for the high-temperature & high-pressure and with injected methanol and abundant gaseous water condensate oil/gas system. Employed PVT equipments (RUSKA-PVT & DBR-PVT) in the Key State Lab of the Oil & Gas Reservoir Geology and Exploration in SWPI, the injected methanol and gaseous water condensate gas dew point pressure, constant composition expansion, constant volume depletion experiment was carried out and tested. It will provide dependable formation fluid PVT phase parameters for improving the productivity in the injected methanol condensate gas well exploitation.2. By using the condensate gas reservoir formation oil & gas/water/ methanol system PVT phase behavior test method, this paper investigated and tested oil & gas system of Q69 condensate. The test results indicate that with the injected methanol increasing, the dew pint pressure of condensate oil/gas will fall; injecting methanol can effectively decrease the condensate volume. However, the volume will not continue to decrease. There should be a optimum volume of injected methanol.3. A new set of exploration method of improving gas well productivity has been designed for deep low-permeability condensate gas reservoir using injected methanol add nitrogen when there are the condensate mass and water blocking of inverse water imbibitions near the wellbore .This method has been tested and experimented using the RUSKA high pressure PVT equipment and the long core flooding equipment from Canada Hycal corp.4. The methanol and formation match experiment and vapor pressure test show that, methanoland formation can dissolve each other in any proportion without deposition, and there is no salt damage in formation condition; injecting methanol will results in the increase of formation fluid vapor pressure.5. The long core experiment of injecting methanol add nitrogen huff & puff shows that the injected methanol can effectively eliminate water blocking. In the early stage of exploitation, the drive pressure is low. The gas injection can decrease condensate mass successfully, and increase gas phase permeability, and then can enhance the gas well productivity. The experiment results indicate that it is feasible to inject methanol slog before gas injection to remove water block and gas puff & huff can decrease the condensate liquid.6. The thermodynamics model was established for hydrocarbon mixture containing polarity (methanol, water etc.), which combining cubic EOS (PR, LHSS) with GE activity coefficient model.7. Using the gas/liquid/liquid three-phase equilibrium calculation model to calculate the P-T phase diagram, dew point, constant composition expansion and constant volume depletion of Q69 well's fluid with injected methanol and abundant gaseous water.8. The Q69 single well gas injection puff &huff numerical simulation results shows that gas injection puff & huff can efficiently decrease the condensate volume and enhance the gas phase relative permeability. The gas injected volume is larger, the result of the gas puff & huff is better.