裂缝性致密砂岩储集层酸压增产机理

Stimulation Mechanism of Acid Fracturing in Fractured Tight Sandstone Reservoirs

水力压裂和基质酸化对裂缝性致密砂岩储集层的增产改造都有很大的局限性。酸化压裂应用于该类储集层,增产效果非常显著。针对具体储集层计算了天然裂缝产生剪切滑移的条件,同时模拟了酸液对钙质充填裂缝以及剪切滑移裂缝的作用效果。研究表明,与常规增产作业相比,酸压主要依靠2种作用获得较高的导流能力:天然裂缝在水力作用下发生剪切滑移,裂缝能依靠其表面的凹凸不平形成自支撑;酸液溶蚀裂缝中充填物、伤害物以及部分岩石基质使得残余裂缝未闭合空间增大,从而增加了裂缝的导流能力。在机理研究的基础上给出了工艺实施建议。

Hydraulic fracturing and matrix acidizing as the stimulation measures for fractured tight sandstone reservoir have their limita- tions. Acid fracturing technology applied to the target reservoir has obtained the remarkable effect to increase production. For specific reser- voir, this paper calculated the shear-slip conditions occurred in natural fractures and simulated the effect of acid fracturing liquid on calcite -infilling fracture and shear-slip fracture by experiment. The study shows that compared with the conventional stimulation operations, acid fracturing mainly relies on the following two effects to obtain high flow conductivity： shear-slip occurs in natural fracture under the action of hydraulic stress, and the surface roughnessof fractures can form the self-supporting; acid liquid corrodes the fillings, harmful substances and part of rock matrix to increase residual unclosed fracture space, hence improving the fracture conductivity. On the basis of mechanism study, this paper puts forward implementation suggestion of the process.