碳酸盐矿物随埋深增加的溶蚀响应机制及其储层意义

以化学热力学为基础, 利用数值模拟方法, 研究不同埋深情况下碳酸盐矿物方解石(CaCO₃)和白云 石(CaMg(CO₃)₂)在含CO₂流体及含H₂S流体中的溶蚀响应机制。模拟结果表明, 在流体系统不发生改变的前提下, 随着埋深的增加, 相同条件下方解石的溶蚀量始终大于白云石。同时, 除温度、压力、酸性气体分压、流体成分之外, 封闭在溶蚀体系中的气体总量是影响碳酸盐矿物溶蚀的另一重要因素。当封闭气体总量相对较高时, 随着深度的增加, 这两种矿物的溶蚀量表现为先增大后减少, 此时白云石中溶蚀孔隙比方解石更为发育; 当气体总量较低时, 两种矿物的溶蚀量曲线单调性减少。

Dissolution Response Mechanism of the Carbonate Mineral with the Increase of Depth and Its Reservoir Significance

Based on the chemical thermodynamics, the dissolution response mechanism of the calcite and dolomite with the increase of depth in the CO₂-beared fluid and H₂S-beared fluid was studied by the method of numerical simulation. The result indicates that the dissolution of calcite is always more evident than dolomite in same conditions. The amount of gas confined in the dissolution system is another important factor which influences the dissolution of carbonate mineral except the temperature, pressure, partial pressure of the acid gas and the component of fluid. When the amount of confined gas is relative large, with the depth increases, the dissolution amount curve shows an increase followed by a decline. And the dissolution pore in the dolomite is more developed than that in the calcite. When the amount of confined gas is relative short, both minerals’ dissolution amount curves declines tonelessly.