Water lock prevention/removal technology used in the “three-high” tight sandstone gas reservoirs of the Tarim Oilfield

The development of the tight sandstone gas reservoirs of high temperature, high salinity and high pressure in the Tarim Oilfield is impacted by the water lock effect. In order to deal with this situation, the efficient water lock prevention/removal agent suitable for these gas reservoirs was screened and compounded on the basis of existing technologies. And its formula is 0.1% modified alkyl indicant +0.02% fluorocarbon surfactant +4% methanol. Then, imbibition experiment, displacement experiment and liquid retention experiment were carried out on the natural cores taken from tight sandstone gas reservoirs, so as to evaluate the efficient water lock prevention/removal agent. The experimental results show that the compounded system has better adsorptivity and surface activity. After the cores are treated, their imbibition capacity is reduced greatly and their water saturation is decreased by over 15%. With the increase of the displacement pressure, the core permeability increases. When the displacement pressure is as high as 3.445 MPa, the average improvement rate of the gas log permeability of the treated cores is over 50%. Under the same displacement pressure, the seepage capacity of the core is increased, the water saturation is decreased and the water lock effect is alleviated significantly after it is treated. The studies on this compounded system provide a certain technical guidance for the productivity recovery and improvement of tight sandstone gas reservoirs.