深埋、封闭-半开放-开放体系原位碳酸盐岩溶蚀模拟实验及其对深部碳酸盐岩储层成因的启示

A large number of basic geology researches and simulation experiments have been done to study the pore dissolution mechanism; although fruitful results have gained, unified understanding still can not achieve. By Diamond Anvil Cell (DAC), we not only simulated the carbonate dissolution/precipitation process under different acid fluids, temperatures and pressures environment in a closed condition, but also realized the in-situ observation of experimental process and the in-situ detection of experimental result. But in the real geological environment, the fluids in carbonate strata may change with the redox reaction, or the entrance of external fluid (such as hydrothermal fluid) can break the closed system. On the basis of former experiment research, this program tries to upgrade the existing experimental equipment and redesign a multi-chamber HDAC dissolution simulation experimental equipment, and configure relevant T-P control system, in-situ observation system and in-situ Raman detection system. This can realize the in-situ simulation of carbonate rock dissolution/precipitation in a whole “closed system→(semi)open system→closed system” conversion process, reacting with different acid fluids under various T-P environments. Together with the study of reef-shoal facies carbonate reservoir in Sichuan Basin and the dolostone and hydrothermal fluid reservoir in Tarim Basin, the development and evolution mechanism of deep carbonate reservoir pore can be synthetically interpreted.

针对深部碳酸盐岩储层中的孔隙溶蚀机理已开展了大量基础地质和模拟实验研究，取得了丰硕但并不统一的认识。课题组前期利用金刚石压腔（DAC）实现了封闭体系中碳酸盐岩在不同酸性流体、温度、压力条件下的溶蚀/沉淀行为，并实现了对实验过程的原位观测和对实验结果的原位检测。但在实际地质情况中，碳酸盐岩储层中的流体可能因氧化-还原作用而发生变化，或因外来流体（如深部热液）的加入，导致体系封闭性发生改变。本研究力图在前期实验研究的基础上，通过对现今溶蚀实验设备的升级改造，设计全新的多体腔水热金刚石压腔溶蚀模拟实验装置，并配套相关的温压控制系统、原位观测系统和原位拉曼检测系统，实现原位模拟“封闭→（半）开放→封闭体系”转换过程中不同酸性流体在不同温度压力条件下与碳酸盐岩相互作用过程中的溶蚀/沉淀行为，结合四川盆地礁滩储层和塔里木盆地白云岩及热液储层的实例研究，综合解释典型深部碳酸盐岩储层孔隙的形成与演化机理。

深层碳酸盐岩储层溶蚀孔隙形成机理与实验模拟已经成为储层研究的热点和难点。利用改进后的水热金刚石压腔对封闭-半开放-封闭体系中不同温压条件下碳酸盐岩与不同酸性流体的溶蚀/沉淀行进行模拟，实现了对实验过程的原位观察和实验结果的原位检测，结合埋藏条件下水-岩平衡体系热力学模拟计算，分析溶蚀孔隙形成机理。对于埋藏阶段短期开放很快又进入平衡封闭的过程，实验结果显示新的酸性流体的加入导致碳酸盐岩出现短期加速溶蚀，溶蚀量与流体通量有关，酸性流体充足的情况下，会发生大规模溶蚀。深部阶段性开放体系下的碳酸盐岩沉淀或溶蚀程度（规模）决定于流体通量和流体性质的改变。结合两轮自然科学基金项目，阐明了深层、超深层条件下碳酸盐岩储层发育的两大主因。一是优越的沉积盖层和稳定的构造条件形成的封闭埋藏体系有利于早期孔隙体系的保存，形成以粒间孔、模孔和表生岩溶孔为特点的碳酸盐岩储层；二是张性构造破裂和酸性流体注入形成的开放体系有利于在深部新增储集空间，形成以溶孔、裂缝、角砾和胶结为特点的深层热液溶蚀-胶结型碳酸盐岩储层。