水锁效应对低渗透储层的损害及抑制和解除方法

DAMAGE TO LOW-PERMEABILITY RESERVOIR BY WATER LOCKING EFFECT AND ITS INHIBITING AND REMOVING METHODS

低渗透特低渗透油藏普遍存在着水锁损害 ,而且渗透率越低 ,水锁伤害越严重 ;造成水锁效应有内在和外在两方面的因素。储层致密、孔隙喉道小 ,油藏压力低、存在绿泥石薄膜状的孔隙衬边结构是造成储层产生水锁效应的内在因素 ;驱动压差小、外来流体与岩石的润湿角小、粘度大及油水界面张力大是造成储层产生水锁效应的外在因素。渗透率越低 ,孔喉半径越小 ,油层压力越低 ,越容易产生水锁损害 ,且越难以解除其损害。通过室内实验研究认为 :提高排液速度可以提高渗透率的保留率 ,抑制水锁效应 ;向油层中挤注一定的表面活性剂体系工作液 ,可以有效地提高油相渗透率的保留率 ,减弱和部分消除水锁效应 ;在注入水中加入优化后的表面活性体系 ,可以改变低渗透油藏流体的渗流特性 ,可以有效地增大油水两相同流区 ,改善其水驱开发效果。

The water-locking damage is commonly found in specially low-to-low permeability oil reservoirs and the lower the permeability, the more serious the damage by water locking. There are two aspects of factors. i. e. internal factors and external factors, in forming water locking effect. The internal factors include compact reservoir, small pore throats, low reservoir pressure and existent thin-film chlorite pore lining structure; and the external factors are composed of poor driving pressure difference, a small wetting angle of rock with extraneous fluid, high viscosity, and large oil-water interface tension. The lower the permeability and the smaller the pore throat radius as well as the lower the reservoir pressure, the easier the formation of water locking damage, and it is difficult to be removed. Through experimental study in laboratory, it was considered that the reservation rate of permeability may be raised by speeding up fluid discharge, thus inhibitting the water locking effect; through injecting a certain of surfactant system treatment fluids into oil reservoir, the reservation rate of oil-phase permeability can be effectively raised, thus weakening and partially removing the water locking effect; by means of adding optimized surfactant system into the injected water, the percolation characteristics of the fluids in low permeability oil reservoir can be changed and the oil-water concurrent flowing area may be effectively enlarged, thus improving the development effectiveness of water drive oil reservoir.