渤中油田疏松砂岩注水扩容解堵机理研究

Mechanism of Water Injection for Capacity Expansion and Plug Removal of Unconsolidated Sandstone in Bozhong Oilfield

针对渤中油田疏松砂岩多孔介质力学的特性,提出注水扩容增加疏松砂岩孔隙度,提高渗透性,从而解堵近井地带提高生产率的增产思路。通过室内实验测量渤中油田扩容注水条件下的疏松砂岩扩容变形参数,结合CT岩心成像技术,对疏松砂岩扩容机理及变化规律进行研究。实验结果表明:疏松砂岩在低围压条件下具有较强的剪胀效应,剪胀扩容量随轴向形变的增加而增大;高排量下疏松砂岩形成单缝,慢排量下疏松砂岩形成多裂缝,有利于形成复杂张剪扩容区。在实验基础上,结合数值模拟理论,现场试验证明采用扩容解堵技术使地层产生高渗扩容带穿透污染区域,解堵后可以恢复较高的注水量。

According to the characteristics of porous media mechanics of loose sandstone in Bozhong oilfield,this paper puts forward the idea of increasing production by waterflooding to increase porosity and permeability of loose sandstone,so as to unblock the area near the well and improve productivity.Based on the laboratory experiment,the deformation parameters of unconsolidated sandstone under the condition of expanding water injection in Bozhong oilfield are measured,and the expanding mechanism and changing rule of unconsolidated sandstone are studied by combining with CT core imaging technology.The experimental results show that:(1)under the condition of low confining pressure,loose sandstone has a strong dilatancy effect,and the dilatancy capacity increases with the increase of axial deformation;(2)under the condition of high displacement,loose sandstone forms a single fracture;while under the condition of slow displacement,loose sandstone forms multiple fractures,which is conducive to the formation of complex dilatancy area.On the basis of experiments,combined with numerical simulation theory,the field test shows that the technology of expanding capacity and removing plugging can make the formation produce high permeability and expanding belt penetrate the polluted area,and the high water injection can be recovered after removing plugging.