Investigation of influence factors on CO_(2) flowback characteristics and optimization of flowback parameters during CO_(2) dry fracturing in tight gas reservoirs  

作　　者：Xiao-Mei Zhou Lei Li Yong-Quan Sun Ran Liu Ying-Chun Guo Yong-Mao Hao Yu-Liang Su 

机构地区：[1]National Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao,266580,Shandong,China [2]School of Petroleum Engineering,China University of Petroleum(East China),Qingdao,266580,Shandong,China [3]Shengli Oil Field Dongsheng Jinggong Petroleum Development(GROUP)Stock Co.,Ltd.,Dongying,257000,Shandong,China [4]Exploration and Development Research Institute of Shengli Oilfield Company,Sinopec,Dongying,257000,Shandong,China

出　　处：《Petroleum Science》2023年第6期3553-3566,共14页石油科学（英文版）

基　　金：support from the National Natural Science Foundation of China(No.51904324,No.51974348);the Prospective Basic Major Science and Technology Projects for the 14th Five Year Plan(No.2021DJ2202).

摘　　要：CO_(2) dry fracturing is a promising alternative method to water fracturing in tight gas reservoirs,especially in water-scarce areas such as the Loess Plateau.The CO_(2) flowback efficiency is a critical factor that affects the final gas production effect.However,there have been few studies focusing on the flowback characteristics after CO_(2) dry fracturing.In this study,an extensive core-to-field scale study was conducted to investigate CO_(2) flowback characteristics and CH_(4) production behavior.Firstly,to investigate the impact of core properties and production conditions on CO_(2) flowback,a series of laboratory experiments at the core scale were conducted.Then,the key factors affecting the flowback were analyzed using the grey correlation method based on field data.Finally,taking the construction parameters of Well S60 as an example,a dual-permeability model was used to characterize the different seepage fields in the matrix and fracture for tight gas reservoirs.The production parameters after CO_(2) dry fracturing were then optimized.Experimental results demonstrate that CO_(2) dry fracturing is more effective than slickwater fracturing,with a 9.2%increase in CH_(4) recovery.The increase in core permeability plays a positive role in improving CH_(4) production and CO_(2) flowback.The soaking process is mainly affected by CO_(2) diffusion,and the soaking time should be controlled within 12 h.Increasing the flowback pressure gradient results in a significant increase in both CH_(4) recovery and CO_(2) flowback efficiency.While,an increase in CO_(2) injection is not conducive to CH_(4) production and CO_(2) flowback.Based on the experimental and field data,the important factors affecting flowback and production were comprehensively and effectively discussed.The results show that permeability is the most important factor,followed by porosity and effective thickness.Considering flowback efficiency and the influence of proppant reflux,the injection volume should be the minimum volume that meets the requirement

关 键 词：CO_(2)fracturing Tight gas reservoir Fracturing fluid flowback Parameter optimization 

分 类 号：TE35[石油与天然气工程—油气田开发工程]