克拉2气田的储层应力敏感性

STRESS SENSITIVITY OF THE RESERVOIRS IN THE KELA-2 GAS FIELD

克拉2气田是一个异常高压气田,在其开发过程中,储层岩石所承受的有效上覆压力变化大,容易产生变形,引起孔隙度和渗透率变小,这对气田开发产生较大的影响。利用克拉2气田实际岩心,实验分析了其应力敏感性特征,研究预测了气田开发过程中储层物性的变化规律及其影响因素。结果表明:克拉2气田储层孔隙度和渗透率与有效上覆压力均呈幂函数关系,孔隙度变化规律较一致,比孔隙度变化区间小;渗透率的变化较为复杂,岩石初始渗透率越低,随有效压力增大其下降速率越快,相同有效压力下下降的幅度越大。克拉2气田衰竭开采至废弃压力,储层综合物性变化不大,孔隙度绝对值降低0.5%～1.5%,综合渗透率降低18.2%。这些变化对气藏产能的影响不大。

In its development process of the Kela-2 gas field under abnormally high pressure,as the effective overburden pressure is changed dramatically,the reservoir rock deforms easily to cause the porosity and permeability to become smaller,which will have a relatively great impact on the gas field development.Using the actual core in the Kela-2 gas field,the characteristics of stress sensitivity have been studied in laboratory experiments and the research predicted the change laws and affecting factors in the gas field development.Results indicate that in the Kela-2 gas field,the reservoir permeability and porosity are related to the power function with the effective overburden pressure,porosity change laws are relatively consistent and the porosity change intervals are comparatively small;the change of penetration rate is relatively complex:the lower the initial penetration rate of the rock is,with the effective pressure increasing,the sooner the decline rate and the greater the decline rate under the same effective pressure are.As the Kela-2 gas field has been developed with depletion-drive to the abandonment pressure,the reservoir comprehensive physical properties changed insignificantly,the absolute value of porosity reduced from 0.5% to 1.5% and the integrated penetration rate decreased by 18.2%;these changes have little effect on the production capacity of gas reservoir.