Similarity-based laboratory study of CO_(2) huff-n-puff in tight conglomerate cores  

作　　者：Yu-Long Yang Yu Hu Ya-Ting Zhu Ji-Gang Zhang Ping Song Ming Qin Hai-Rong Wu Zhao-Jie Song Ji-Rui Hou 

机构地区：[1]State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum-Beijing,Beijing 102249,China [2]College of Carbon Neutral Energy,China University of Petroleum-Beijing,Beijing 102249,China [3]Unconventional Petroleum Research Institute,China University of Petroleum-Beijing,Beijing 102249,China [4]Research Institute of Petroleum Exploration and Development,Xinjiang Oilfield,Karamay 834000,China

出　　处：《Petroleum Science》2023年第1期362-369,共8页石油科学（英文版）

基　　金：This study is financially supported by CNPC Innovation Foundation(2020D-5007-0214);Major Strategic Project of CNPC(ZLZX2020-01-04);Beijing Municipal Excellent Talent Training Funds Youth Advanced Individual Project(2018000020124G163)。

摘　　要：Tight conglomerate reservoirs are featured with extremely low permeability,strong heterogeneity and poor water injectivity.CO_(2) huff-n-puff has been considered a promising candidate to enhance oil recovery in tight reservoirs,owing to its advantages in reducing oil viscosity,improving mobility ratio,quickly replenishing formation pressure,and potentially achieving a miscible state.However,reliable inhouse laboratory evaluation of CO_(2) huff-n-puff in natural conglomerate cores is challenging due to the inherent high formation pressure.In this study,we put forward an equivalent method based on the similarity of the miscibility index and Grashof number to acquire a lab-controllable pressure that features the flow characteristics of CO_(2) injection in a tight conglomerate reservoir.The impacts of depletion degree,pore volume injection of CO_(2) and soaking time on ultimate oil recovery in tight cores from the Mahu conglomerate reservoir were successfully tested at an equivalent pressure.Our results showed that oil recovery decreased with increased depletion degree while exhibiting a non-monotonic tendency(first increased and then decreased)with increased CO_(2) injection volume and soaking time.The lower oil recoveries under excess CO_(2) injection and soaking time were attributed to limited CO_(2) dissolution and asphaltene precipitation.This work guides secure and reliable laboratory design of CO_(2) huff-n-puff in tight reservoirs with high formation pressure.

关 键 词：Tight conglomerate reservoir CO_(2)huff-n-puff Similarity-based equivalent pressure Enhanced oil recovery 

分 类 号：TE357.7[石油与天然气工程—油气田开发工程]