碎屑岩储层中长石溶蚀动力学及定量预测研究

Feldspar-rich clastic reservoirs serve as significant targets for petroleum exploration and carbon sequestration. Extensive feldspar alteration buffers the pH value of fluid-rock systems in these reservoirs, and in addition, affect the development of secondary pores and the geological storage of CO2. With arkose rocks in the Dongying Sag, the characteristics of feldspar dissolution at different depths will be studied by analyzing micro-features of the leached feldspars and secondary minerals, and then the key diagenetic environments will be investigated by testing geochemical parameters of minerals and fluids. Feldspar dissolution experiments with fluid-mineral systems close to equilibrium and in dynamic equilibrium will be conducted, with constraints of the geological environments. The features of minerals and fluids prior to and after the experiments will be tested. With combination of crystal structures, chemical bonds and subsurface reservoirs, dissolution mechanisms and alteration paths of feldspar minerals in different geological settings will be deciphered. Feldspar dissolution rates will be quantitated by testing of the changes of minerals, elements and isotopic composition prior to and after experiments. Kinetic equations will be fitted with combination of the feldspar dissolution rates and the condition parameters of the experiments. Using reservoir thermal history and fluid evolution history as framework, numerical simulations of feldspar dissolution will be conducted with the constraints of chemical reactions and mass transfer. The research achievements can enrich the theories of quantitative fluid-rock interactions and provide guidance for prediction of secondary pores and capacity evaluation of carbon sequestration in subsurface reservoirs.

富长石碎屑岩储层是油气勘探的重要目标，也是CO2地质封存的重要潜在场所。储层中普遍发育的长石溶蚀对水-岩体系酸碱度具有重要缓冲作用，进而影响着次生孔隙的发育和成岩固碳作用。本项目以东营凹陷富长石碎屑岩储层为对象，通过微观特征和地化参数分析，解剖不同深度储层中长石溶蚀特征，厘定关键成岩环境；开展地质环境约束的近平衡-动态平衡状态下长石溶蚀实验，分析实验前后固-液变化，结合晶体结构、化学键特征及储层案例，阐明不同埋藏地质环境中长石溶蚀机理；检测动态平衡实验前后矿物、元素和同位素变化，结合有效比表面积和溶蚀时间，定量长石溶蚀速率，并结合实验条件拟合其动力学方程；以储层热史-流体演化史为框架，以溶蚀速率和动力学方程为约束，开展耦合化学反应和物质传输的长石溶蚀数值模拟研究，建立储层中长石溶蚀的定量预测方法。研究成果可以丰富定量水-岩作用理论，对储层中次生孔隙预测和碳封存潜力评价等具有科学参考意义。

富长石碎屑岩储层是油气勘探的重要目标，也是CO2地质封存的重要潜在场所。本项目系统统开展了浅层地表和实验室不同温压条件下长石溶蚀热模拟实验、渤海湾盆地东营凹陷和珠江口盆地白云凹陷等典型富长石碎屑岩储层中长石溶蚀环境、机理和路径、近平衡-动态平衡条件下长石溶蚀速率模拟实验以及基于长期数值模拟的长石溶蚀和CO2地质封存定量预测等相关工作。.研究结果表明：完整的长石溶蚀作用包括长石晶体化学键断裂、淋滤埃米层中元素扩散传输、孔隙流体场中物质传输和次生矿物再沉淀的四个过程，沉积盆地浅层开放体系→深层封闭体系中，长石溶蚀机理从优先溶解-扩散控制机制逐渐转变为界面溶解-再沉淀机制。浅层→深层-超深层埋藏过程中大气淡水、烃源岩热演化生酸和原油水热氧化生酸依次溶解长石，具有接力成孔意义，且伴随不同成岩体系中长石溶蚀机理和路径的变化，长石溶蚀从浅层净增孔效应逐渐转变为深层近封闭-封闭体系下的调孔-保孔效应，从而保障了深层-超深层碎屑岩储层中长石溶孔和优质储层的发育。埋藏条件近平衡条件下，次生矿物的沉淀反馈、物质传输速率、温度、有效比较面积等主控了储层中长石的溶蚀速率，次生矿物沉淀过程中Al和SiO2（aq）的慢速消耗以及K+的剩余和积累造成长石溶蚀速率的降低呈现幂函数趋势，非线性过渡态方程可以用来计算和约束近平衡-平衡条件下长石溶蚀的速率。形成了地质条件-化学动力学-成岩物质传输综合约束的、跨尺度的流体-岩石作用短期物理-长期模拟研究技术，可以用来预测不同地质条件下，长期地质时间内富长石碎屑岩储层中长石溶蚀成孔量和CO2地质封存量。.研究成果为沉积盆地浅层-深层长石溶蚀成孔作用和CO2地质封存的研究提供了新思路，为深层富长石砂岩储层的油气勘探和CO2地质封存研究提供了科学参考。发表论文12篇，其中SCI收录论文8篇（一区3篇、二区5篇），授权国家发明专利4项，国际学术论坛AAPG Europe Workshop in CCS特邀报告1次，获省部级科技进步一等奖1项。