低渗砂岩气藏中压敏效应对产能的影响

INFLUENCE OF PRESSURE-SENSITIVE EFFECT ON PRODUCTIVITY OF LOW PERMEABLE SAND GAS RESERVOIRS

应力敏感性是指骨架应力和孔隙流体压力共同作用产生的压差对微观孔隙结构的影响。低渗透储层的孔隙结构比高渗透储层的更加复杂 ,这种复杂性增加了岩心受压行为的复杂性。随着生产的进行 ,储集层压力下降 ,有效压力也不断变化 ,而有效压力的大小决定了应力敏感性的严重程度。在压力敏感性实验过程中 ,文章采用改变围压的方法来近似地模拟储层所承受压力的变化 ,主要研究了压力变化对储集层渗透率的影响。根据实验结果 ,建立了有效压力与储集层渗透率之间的经验关系式 ,并以此为基础 ,推导出考虑压力敏感性时的低渗透砂岩气藏的产能公式与压力分布公式 。

Stress sensitivity means the influence of pressure difference produced by joint working of the matrix stress and the porous fluid pressure on the porous microstructure. The porous structure of low permeable reservoirs is more complicated than that of high permeable reservoirs, which enhances the complexity of the behaviors while the core is compressed. The effective pressure changes continuously as the reservoir pressure decreases due to exploitation. The effective pressure decides the degree of stress sensitivity. In pressure sensitivity experiments, the confining pressure is altered to simulate the variation of the pressure borne by the reservoir. The influence of pressure variation on the permeability of the reservoir is investigated. Based on the experimental results, the experiencing relation between the effective pressure and the permeability is established. Then the productivity formula and the pressure distribution formula are derived considering the pressure sensitivity for low permeable sand gas reservoirs. Also, the influence of pressure sensitivity on the productivity of low permeable sand gas reservoirs is analyzed.