Probing the influence of secondary fracture connectivity on fracturing fluid flowback efficiency  

作　　者：Yi-Ning Wu Li-Sha Tang Yuan Li Li-Yuan Zhang Xu Jin Ming-Wei Zhao Xiang Feng Cai-Li Dai 

机构地区：[1]School of Petroleum Engineering,China University of Petroleum(East China),Qingdao,266580,Shandong,China [2]Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China [3]College of Chemistry and Chemical Engineering,China University of Petroleum(East China),Qingdao,266580,Shandong,China

出　　处：《Petroleum Science》2023年第2期973-981,共9页石油科学（英文版）

基　　金：supported by the National Key Research and Development Program of China(Grant No.2019YFA0708700).

摘　　要：A deep understanding of the geometric impacts of fracture on fracturing fluid flowback efficiency is essential for unconventional oil development. Using nuclear magnetic resonance and 2.5-dimensional matrix-fracture visualization microfluidic models, qualitative and quantitative descriptions of the influences of connectivity between primary fracture and secondary fracture on flowback were given from core scale to pore network scale. The flow patterns of oil-gel breaking fluid two-phase flow during flowback under different fracture connectivity were analyzed. We found some counterintuitive results that non-connected secondary fracture (NCSF, not connect with artificial primary fracture and embedded in the matrix) is detrimental to flowbackefficiency. The NCSF accelerates the formation of oil channeling during flowback, resulting in a large amount of fracturing fluid trapped in the matrix, which is not beneficial for flowback. Whereas the connected secondary fracture (CSF, connected with the artificial primary fracture) is conducive to flowback. The walls of CSF become part of primary fracture, which expands the drainage area with low resistance, and delays the formation of the oil flow channel. Thus, CSF increases the high-speed flowback stage duration, thereby enhancing the flowback efficiency. The fracturing fluid flowback efficiency investigated here follows the sequence of the connected secondary fracture model (72%) > the matrix model (66%) > the non-connected secondary fracture model (38%). Our results contribute to hydraulic fracturing design and the prediction of flowback efficiency.

关 键 词：Fracturing fluid Secondary fracture connectivity Flowback efficiency Dual media Microfluidic model 

分 类 号：P618.13[天文地球—矿床学]