摘要
为研究裂缝岩心应力敏感性,通过改变围压的大小来实现岩石受到的有效应力变化,并分别计算不同有效应力下渗透率的变化来评价储层应力敏感性,同时分析了其对产能的影响。研究表明:含微裂缝岩心的应力敏感程度很弱,渗透率变化率低于30%,敏感曲线分为2个阶段:第Ⅰ阶段渗透率下降幅度超过20%,主要是以发生微裂缝受压闭合的拟塑性变形为主;第Ⅱ阶段渗透率下降幅度低于10%,该阶段主要以岩石骨架颗粒本体被压缩的弹性形变为主,实际储层的净应力多处于该阶段。因此,应用第Ⅱ阶段来评价含裂缝储层的应力敏感性更符合实际,含微裂缝岩心的应力敏感性均高于基质岩心。经计算可知含微裂缝岩心应力敏感对产能影响较小,由提高生产压差造成的应力敏感不会导致产能的大幅变化。
In order to the study the stress sensitivity of fractured cores,the in- lab experiments can change the effective stress on rocks through the change of enclosure pressure. The change of permeability with different effective stress is calculated to evaluate the stress sensitivity of reservoir. At the same time,its influence on productivity has been analyzed. The research indicates that,the stress sensitivity of micro- fractured cores is very weak and the change rate of permeability is lower than 30%; the sensitivity curve can be divided into 2 phases: in the 1st phase,the permeability decreases by 20%,mainly resulted from the pseudo- plastic deformation that the micro- fractures are closed under pressure; in the 2nd phase,the permeability decreases by 10% and the elastic deformation due to the compression of rock frames. The net stress of actual reservoir is generally in this phase. Therefore,2nd phase shall be applied to evaluate the sensitivity stress of the fractured reservoir,which is more consistent with the reality. The stress sensitivity of micro- fractured cores are higher than that in matrix cores. Through calculation,it can be known that the sensitivity stress of micro- fractured cores has little effect on productivity. The stress sensitivity resulted from the increase of production difference will not lead to the great change of productivity.
出处
《特种油气藏》
CAS
CSCD
北大核心
2015年第1期127-130,157,共4页
Special Oil & Gas Reservoirs
基金
国家重点基础研究发展计划("973"计划)"页岩气多场耦合非线性渗流理论研究"(2013CB228002)
关键词
微裂缝
应力敏感
有效应力
闭合
产能
micro-fractures,stress sensitivity,effective stress,closure,productivity
