多轮次注CO_(2)对储层矿物溶蚀规律实验研究

Experimental Study on Mineral Dissolution Behavior in Reservoirs Under Multi-stage CO_(2) Injection

为了明晰CO_(2)封存过程中多相体系CO_(2)-地层水与岩石相互作用以及油藏CO_(2)注入过程中滞留CO_(2)的动态变化规律,采用了CO_(2)饱和地层水静态溶蚀实验、大PV注入CO_(2)/饱和CO_(2)地层水动态交替驱溶蚀实验以及核磁共振分析,研究了低渗和中高渗储层的矿物、产出流体及渗透率孔隙度的变化情况,根据多轮CO_(2)驱数据以及Boltzmann方程建立适用于目标区块的注入PV数与渗透率和孔隙度的数学模型。研究结果表明:CO_(2)注入能显著提高储层的渗透率。其中,通过XRD和ICP-OES分析发现,CO_(2)能溶蚀储层矿物中的奥长石、钾长石和白云石,产出液中钙离子浓度显著上升,与中高渗岩心相比,低渗透岩心在化学反应后受到的CO_(2)溶蚀作用更为剧烈。

In order to elucidate the interactions between CO_(2) in multiphase systems and rocks,the interactions between formation water and rocks during CO_(2) sequestration,as well as the dynamic changes in retained CO_(2) during the injection process in reservoirs,a series of experiments were designed and conducted.These experiments included static dissolution experiments with CO_(2)-saturated formation water,dynamic alternating injection and dissolution experiments of CO_(2) and CO_(2)-saturated formation water with significant pressure-volume(PV)variations,and nuclear magnetic resonance(NMR)analysis.Changes in minerals,produced fluids,permeability,and porosity in both low-permeability and medium-high-permeability reservoirs were investigated.Based on the results of multiple rounds of CO_(2) injection experiments and the Boltzmann equation,mathematical models were established to predict injection PV,permeability,and porosity for target reservoir blocks.The results of the study indicated that CO_(2) injection could significantly enhance reservoir permeability.Through X-ray diffraction(XRD)and inductively coupled plasma optical emission spectroscopy(ICP-OES)analysis,it was discovered that CO_(2) could dissolve minerals such as orthoclase,microcline,and calcite within the reservoir.This dissolution led to a significant increase in calcium ion mass concentration in the produced fluids.Furthermore,compared to medium-high-permeability cores,low-permeability cores exhibited more pronounced CO_(2) dissolution effects after chemical reactions.