压敏效应对文东异常高压低渗油田开发的影响

Influence of pressure-sensitive effects upon development of Wendong low-permeability oilfield with abnormal high pressure

文东油田原始地层压力系数1.71～1.88,储层处于欠压实状态.投入开发后,地层压力下降,储层在有效围压的作用下,孔喉变小,部分孔隙变成无效孔隙,渗透率不断降低;有效围压的作用越强,渗透率降低幅度越大;渗透率越低,这种关系越明显,并且这种过程是不可逆的.渗透率的下降导致注水压力升高,采油指数大幅下降.因此开发此类油藏,必须注意注水时机及地层压力界限的保持,并根据地层压力的下降状况采取相应的开发对策.

The original formation pressure coefficient of Wendong oilfield is between 1.71 and 1.88 and the reservoirs keep in under-compaction condition. Formation pressure drops after being put into production.Under the action of effective peripheral pressure,the pore and throat become smaller,and furthermore partial pores turn inefficient,so the permeability reduces a great deal;the more serious effective peripheral pressure is,the bigger permeability reduces;when the less permeability is, the more obvious the above relation,and this process is irreversible. Permeability reduction results in higher water injection pressure and a larger decline degree of oil production index. Therefore when this kind of oil reservoirs being bring into development,water injection time and maintenance of formation pressure limit must be considered seriously. In addition,corresponding development measurement must be adapted according to pressure decline situation.