高灰质白云岩酸蚀改造机理研究

Research of acid etching stimulation in high-lime dolomite

长庆油田高灰质白云岩储层具有储层薄且致密、应力遮挡差、非均质性强、裂缝发育较差等改造难点,储层改造效果较差。本文通过薄片鉴定、电镜扫描以及X衍射全岩检测技术对高灰质白云岩进行了不同条件下的酸蚀微观机理研究,包括矿物类型及储集空间酸蚀机理、矿物产状及孔隙结构酸蚀机理、岩石矿物化学成分酸蚀机理三个方面。定性分析了方解石含量升高,可能会导致施工过程中工作压力和停泵压力降低,微观分析认为是由酸液过度溶蚀及滤失导致。过度溶蚀还可导致泥质增加、颗粒分散运移,对储层造成伤害。

The high-lime dolomite reservoir in Changqing oilfield has many difficulties such as thin and tight reservoir, poor stress shielding, high anisotropy and poor fracture development, thus the effect of reservoir stimulation is very bad. In this paper, the acid etching micro-mechanism of high-lime dolomite under different conditions has been studied by thin section identification, scanning electron microscopy and X-ray diffraction whole-rock detection technology, including mineral type and reservoir space etching mechanism, mineral occurrence and pore structure etching mechanism and mineral chemical composition etching mechanism.Qualitative analysis shows that the increase of calcite may lead to the decrease of work pressure and pump shutdown pressure, and microscopic analysis shows that excessive acid dissolution and filtration leads to the increase of calcite. Excessive acid dissolution may also leads to clay increament and particle dispersion and transportation which resulting in damage to the reservoir.