Wang Zhixing, Hou Jirui
Research Institute of Enhanced Oil Recovery, Unconventional Petroleum Research Institute, China University of Petroleum (Beijing) Beijing 102249 China
Key Laboratory for Greenhouse Gas Sequestration and Oil Exploitation in Beijing, Unconventional Petroleum Research Institute Beijing 102249 China
RSC Adv. 2021 Jun 1;11(32):19712-19722. doi: 10.1039/d1ra02549j. eCollection 2021 May 27.
Diffusion coefficients are necessary to describe the mass transfer and adsorption rate of CO in formation fluids. However, data is scarcely reported for actual reservoir conditions of high pressure and temperature, which are normal in most scenarios of the CO-enhanced oil recovery process in China's fractured-vuggy reservoirs and carbon storage process. Accordingly, this work employed the pressure decay method (PD) and relevant mathematical models to determine the CO diffusion coefficient in both liquids and cavern filling porous media at 50 MPa and 393 K. The effects of the type of reservoir fluids, the properties of carven filling porous media, and water saturation on CO diffusion coefficients were investigated. Results in bulk reservoir liquids showed that the CO diffusion coefficient in the oil sample was 4.1243 × 10 m s, much higher than those in the pure alkane phase, pure water and brine sample from reservoirs. Results of CO diffusion in carven filling porous media saturated with oil demonstrated a significant dependence on properties such as porosity and permeability, and a correlation in the CO diffusion coefficients between the bulk oil phase and cavern filling porous media in the form of touristy was documented. CO diffusion in the fractured cavern porous media was much higher than that without fracture. An increase in water saturation reduced CO diffusion coefficients in the carven filling porous medium studied, herein. Thus, the CO diffusion coefficient is essentially related to the type of liquid and properties of the filling media.
扩散系数对于描述地层流体中CO的传质和吸附速率是必要的。然而，在高压和高温的实际储层条件下，相关数据鲜有报道，而在中国缝洞型油藏的CO2强化采油过程和碳储存过程的大多数情况下，高压和高温是常态。因此，本研究采用压力衰减法（PD）和相关数学模型来测定50MPa和393K条件下液体和洞穴填充多孔介质中CO2的扩散系数。研究了储层流体类型、洞穴填充多孔介质性质和含水饱和度对CO2扩散系数的影响。在储层液体主体中的结果表明，油样中CO2的扩散系数为4.1243×10⁻⁹m²/s，远高于纯烷烃相、纯水和储层盐水样品中的扩散系数。CO2在油饱和洞穴填充多孔介质中的扩散结果表明，其对孔隙度和渗透率等性质有显著依赖性，并且记录了主体油相和洞穴填充多孔介质中CO2扩散系数之间呈线性相关。CO2在裂缝洞穴多孔介质中的扩散远高于无裂缝情况。本文中，含水饱和度的增加降低了所研究洞穴填充多孔介质中CO2的扩散系数。因此，CO2扩散系数本质上与液体类型和填充介质性质有关。
