Zhao Jinsheng, Zhang Ziyi, Xiao Yuanxiang, Hou Shan, Li Pan, Zhang Sipeng
School of Petroleum Engineering, Xi'an Shiyou University 18 Dianzi Road, Yanta Xi'an Shaanxi 710065 China
Research Institute of Carbon Neutrality Future Technology, Xi'an Shiyou University Xi'an Shaanxi 710065 China.
RSC Adv. 2025 Jul 2;15(28):22556-22564. doi: 10.1039/d5ra02362a. eCollection 2025 Jun 30.
The injection of CO into low-pressure tight gas reservoirs can achieve the purposes of enhancing reservoir energy, increasing gas reservoir recovery and reducing carbon emissions. For the CO energized fracturing process, it can also improve the fracturing fluid flowback efficiency and reduce water blocking effects. In the context of "dual carbon" strategy, studying the CO storage behavior during CO injection in tight carbonate gas reservoirs is of great significance. In this paper, the CO storage effect and influencing factors of CO injection in tight carbonate core samples are experimentally investigated. The main factors affecting the bound CO storage are analyzed by means of nuclear magnetic resonance (NMR), threshold pressure gradient testing, and X-ray diffraction. Additionally, the influence of dissolved-solidified CO storage on mineral composition and pore size distribution is also investigated. The results show that the CO injection pressure has a significant impact on the bound CO storage. When the pressure is higher than the supercritical pressure, the bound CO storage rate can reach over 60%. And the dissolved-solidified CO storage rate is at its peak of 10-15% when the pressure is between 5 MPa and 7 MPa. With the decreasing core permeability and the increasing threshold pressure gradient, the bound CO storage rate increases. For tight carbonate gas reservoirs, the dissolution and solidification storage of CO mainly occurs in small pores, medium pores and large pores. The dissolved-solidified CO storage rate is affected by the mineral composition. Dolomite and calcite are the main dissolution minerals of CO in water, thereby changing the pore throat distribution of the reservoir. This study can provide theoretical guidance for optimizing CO injection technology, predicting storage effects, and optimizing gas well production in tight carbonate gas reservoirs.
向低压致密气藏注入二氧化碳可实现增强储层能量、提高气藏采收率和减少碳排放的目的。对于二氧化碳增能压裂过程，还可提高压裂液返排效率并降低水锁效应。在“双碳”战略背景下，研究致密碳酸盐岩气藏注二氧化碳过程中的二氧化碳储存行为具有重要意义。本文通过实验研究了致密碳酸盐岩岩心样品注二氧化碳的储存效果及影响因素。借助核磁共振（NMR）、启动压力梯度测试和X射线衍射分析了影响束缚二氧化碳储存的主要因素。此外，还研究了溶解-固化二氧化碳储存对矿物组成和孔径分布的影响。结果表明，注二氧化碳压力对束缚二氧化碳储存有显著影响。当压力高于超临界压力时，束缚二氧化碳储存率可达60%以上。当压力在5MPa至7MPa之间时，溶解-固化二氧化碳储存率达到峰值10%-15%。随着岩心渗透率降低和启动压力梯度增大，束缚二氧化碳储存率增加。对于致密碳酸盐岩气藏，二氧化碳的溶解和固化储存主要发生在小孔、中孔和大孔中。溶解-固化二氧化碳储存率受矿物组成影响。白云石和方解石是二氧化碳在水中的主要溶解矿物，从而改变储层的孔喉分布。该研究可为优化致密碳酸盐岩气藏注二氧化碳技术、预测储存效果和优化气井生产提供理论指导。
