Zhang Yulong, Teng Xiaolan, Zhai Wenya, Shi Wei, Liu Yaobo, Liu Yuan, Wang Xiao
Engineering and Technology Research Institute, Sinopec Southwest Oil and Gas Branch, Deyang, Sichuan 618000, China.
Exploration and Development Research Institute, PetroChina Xinjiang Oilfield Branch, Karamay 834000, China.
ACS Omega. 2025 Jun 3;10(23):24097-24104. doi: 10.1021/acsomega.4c09892. eCollection 2025 Jun 17.
To study the mechanism of CO injection in tight sandstone gas reservoirs for enhanced recovery and geological storage, we conducted experimental studies based on the reservoir conditions in West Sichuan. These studies focused on the properties of CO and CH, their adsorption and diffusion under high temperature and high pressure, the interactions of CO with tight sandstone and formation water, and the displacement efficiency of the CO injection in long core samples. The results show that under reservoir conditions, the adsorption capacity of CO in tight sandstone is nearly four times higher than that of CH, and its diffusion capacity is also four times higher. This enables CO to replace adsorbed CH through competitive adsorption. Due to the greater density of CO compared to CH, gravitational differentiation causes CO to sink below CH, pushing CH upward in the reservoir. This process facilitates the sequestration of CO and enhances the recovery of natural gas. Additionally, CO injection dissolves feldspar and calcite in dense sandstone minerals, generating kaolinite, iron dolomite, and chlorite. The dissolution effect exceeds precipitation, leading to an increase in permeability by 73.25 to 91.15% and an increase in porosity by 0.65 to 0.72%. This improves the reservoir's seepage characteristics, reduces the minimum flow pressure of liquids in the pores, decreases water-phase trapping damage, and ultimately increases gas recovery. This study provides technical guidance for the efficient development of tight sandstone gas reservoirs and geological storage of CO.
为研究致密砂岩气藏注CO₂提高采收率及地质封存的机理，我们基于川西储层条件开展了实验研究。这些研究聚焦于CO₂和CH₄的性质、高温高压下的吸附与扩散、CO₂与致密砂岩及地层水的相互作用，以及长岩心样品中注CO₂的驱替效率。结果表明，在储层条件下，致密砂岩中CO₂的吸附能力比CH₄高近四倍，其扩散能力也是CH₄的四倍。这使得CO₂能够通过竞争吸附取代吸附的CH₄。由于CO₂的密度比CH₄大，重力分异导致CO₂下沉至CH₄下方，在储层中将CH₄向上推。此过程有利于CO₂的封存并提高天然气采收率。此外，注CO₂使致密砂岩矿物中的长石和方解石溶解，生成高岭石、铁白云石和绿泥石。溶解作用超过沉淀作用，导致渗透率提高73.25%至91.15%，孔隙度增加0.65%至0.72%。这改善了储层的渗流特性，降低了孔隙中液体的最小流动压力，减少了水相圈闭损害，最终提高了气藏采收率。该研究为致密砂岩气藏的高效开发及CO₂地质封存提供了技术指导。
