Experimental Study On Water Injection And Gas Injection Before And After Fracture In JA Tight Sandstone Reservoirs

JA tight sandstone reservoir with the characteristic of small pores, large surface area to volume ratio, low abundance of reserve, low oil recovery and poor water drive development economic benefit, so it is necessary to carry out fracturing to generate artificial fracture, providing high speed flow channel for underground fluid and improving the water absorption capacity and the oil production ability of the reservoir.It improves the oil recovery ultimately. After the reservoir is fractured, the oil well production is high fistly, but the effect is very poor later. Therefore, on the basis of water flooding, it is necessary to study the gas injection enhanced oil recovery of the oil reservoir.In this paper,7 natural cores of JA tight sandstone reservoir are selected, and the axial fracturing method is used to carry out the artificial fracture. Before fracturing,8 groups of displacement experiments were carried out, including water drive experiment, nitrogen drive experiment, surfactant flooding experiment, natural gas water alternative injection displacement experiment and CO2 huff and puff experiment. Among them, the water drive recovery is generally 40%, the nitrogen gas drive, surfactant drive,0.056mol+0.1376mol natural gas water alternative injection displacement on the basis of water drive respectively to improve the recovery rate of 5.1%,11.8% and 44.4%.0.023mol, 0.035mol,0.039mol and 0.053mol CO2 injection of huff and puff experiment, on the basis of water drive respectively to improve the recovery rate of 19.6%,26.3%,27.8% and 37.5%. Considering the increase of amount of oil and the oil exchange ratio, the most suitable flooding way selected in the tight sandstone for reservoir exploitation is CO2 huff and puff, the best injection volume is 0.035mol, the oil exchange ratio is as high as 0.3841g/g.After fracturing,3 groups of displacement experiments are carried out, including water drive experiment, natural gas water alternative injection displacement experiment and CO2 huff and puff experiment. The effect of crack on the oil displacement is studied. The results show that after fracturing, water drive recovery is only 30%.0.0291mol+0.0741mol natural gas water alternative injection displacement and 0.0275mol CO2 injection of huff and puff experiment respectively to improve the recovery rate of 22.23% and 27.78%. Increasing oil effect of CO2 huff and puff after fracturing becomes worse than before fracturing, but it is still one of the effective measures to improve the oil recovery. Oil and water relative permeability experiments show that JA tight sandstone reservoir is hydrophilic, the irreducible water saturation and residual oil saturation are high, the two phase flow range is narrow, and the water displacement efficiency is about 40%, which is consistent with the experimental results. Oil expansion test and chromatography analysis show that the main factor of CO2 which can increase amount of oil is increasing the volume of crude oil,secondly,it can extract the light component of crude oil and lower the viscosity of crude oil.The reservoir sensitivity parameters and the best injection quantity are analyzed when the reservoir is carried out CO2 huff and puff. However, because of each flooding experiment of the tight sandstone core takes a long time, so we use the numerical simulation method, respectively studing porosity, permeability and oil saturation and CO2 injection effect of four parameters on exploitation.Results show that the porosity in the 9.27%?24% range, numerical value is bigger and is conducive to the implementation of CO2 huff and puff; permeability within the scope of 0.3443mD?1000mD, numerical value is bigger and is conducive to the implementation of CO2 huff and puff; oil saturation in 45%?70% range, numerical bigger is conducive to the implementation of CO2 huff and puff; CO2 optimum injection volume is 0.4 PV.The experimental results are compared with the numerical simulation results, this paper believes that the screening of CO2 as the driving medium is reasonable. CO2 huff and puff method is feasible. The derivation of CO2 huff and puff Similarity criterion. By using the similarity criterion, the experimental injection quantity of CO2 is transformed into the field injection quantity. It provides technical reference for the rational development of JA tight sandstone reservoir.