延长油田CO₂-岩石-地层水相互作用规律

InteractionLawbetweenCO₂，RockandFormationWaterinYanchangOilfield

汤瑞佳 黄春霞 余华贵 江绍静 王维波

TANG Ruijia，HUANG Chunxia，YU Huagui，JIANG Shaojing ，WANG Weibo

为明确实施CO2 驱油和地质封存可能引起的物理化学变化，利用扫描电镜、X 射线衍射仪、电感耦合等离子体发射光谱仪和离子色谱仪分析了延长油田储层的矿物组成，研究了CO2- 岩石- 地层水之间相互作用的规律。结果表明，延长油田储层岩石主要组成为：18.7% 石英、18.2% 钾长石、30.1% 斜长石、0.5% 方解石、4.4% 浊沸石和28.1% 黏土矿物。地层水平均矿化度为71.34g/L，pH值为5.5，水型为CaCl2 型。岩石-CO2- 地层水发生作用后，随着CO2 分压的增大，岩石表面的溶蚀现象愈来愈明显。在油藏温度44℃下，反应压力由0 增至20MPa 时，岩石表面C 元素含量呈波动上升，Na、K 元素含量逐渐降低，地层水矿化度由95210 增至107063mg/L，地层水中Na+、K+、Ca2+、HCO3-质量浓度呈增加趋势。反应压力由5 增至20MPa 时，岩石片溶蚀率先增加后降低，压力为10MPa时的溶蚀率最大（0.72%）。 压力越大，CO2 在水中的溶解度越大，溶蚀率越高；温度和矿化度越高，CO2 溶解度越低。随着反应压力的升高，CO2 对砂岩中的钾长石和斜长石的溶蚀作用逐渐增强。图8 表3 参14

To make clear the physical and chemical changes caused by CO2 flooding and geological storage ，the mineral composition of reservoir and the law of interaction between CO2，rock and formation water in Yanchang oilfield was studied by using SEM，XRD，EDS ，ICP-AES and IG. The results showed that the reservoir rock of Yanchang oilfield was composed of 18.7% quartz，18.2% potassium feldspar，30.1% plagioclase，0.5% calcite ，4.4% laumontite and 28.1% clay minerals. The average salinity of formation water was 71.34g/L with CaCl2 type ，and the pH value was 5.5. After the reaction of CO2，rock and formation water，the corrosion of rock surface became worse with increasing partial pressure of CO2. At reservoir temperature of 44℃，when the reaction pressure increased from 0 to 20MPa，the content of C element in rock surface fluctuating rose，while that of Na，K elements gradually decreased，the salinity of formation water increased from 95210 mg/L to 107063 mg/L，and the mass concentration of Na+、K+、Ca2+、HCO3-showed an increasing trend. When the reaction pressure increased from 5 to 20MPa，the corrosion rate of piece rock increased first and then decreased. When the pressure was 10MPa，the maximum corrosion rate was 0.72%. The higher pressure，the higher solubility of CO2 in water and corrosion rate was. The higher temperature and salinity ，the lower solubility of CO2 in water was. With increasing reaction pressure ，the dissolution of potassium feldspar and plagioclase in sandstone by CO2 gradually increased.