Temporal variations in geochemistry of hydraulic fracturing fluid and flowback water in a tight oil reservoir  

作　　者：Jie Tian Liang Wang Li-Pin Ni Li-Wei Mou Shu-Te Su Mehdi Ostadhassan 

机构地区：[1]College of Energy,Chengdu University of Technology,Chengdu,610059,Sichuan,China [2]Geological Research Institute,CNPC Logging,Xi'an,710000,Shaanxi,China [3]Exploration and Development Research Institute,Xinjiang Oilfield Branch,PetroChina,Karamay,834000,Xinjiang,China [4]Institute of Geosciences,Marine and Land Geomechanics and Geotectonics,Christian-Albrechts Universit€at,Kiel,24118,Germany

出　　处：《Petroleum Science》2023年第5期3013-3021,共9页石油科学（英文版）

基　　金：supported by the National Natural Science Foundation of China(No.U2003102).

摘　　要：Hydraulic fracturing facilitates the development and exploitation of unconventional reservoirs.In this study,the injected hydraulic fracturing fluid(HFF)and flowback and produced water(FPW)in tight oil reservoirs of the Lucaogou Formation in the Junggar Basin are temporally sampled from day 1 to day 64.Freshwater is used for fracturing,and HFF is obtained.The chemical and isotopic parameters(including the water type,total salinity,total dissolved solids(TDS),pH,concentrations of Na^(+),Cl^(-),Ba^(+),K^(+),Fe^(2+)+Fe^(3+),and CO_(3)^(2-),dD,and δ^(18)O)are experimentally obtained,and their variations with time are systematically analyzed based on the flowback water.The results show that the water type,Na/Cl ratio,total salinity,and TDS of the FPW change periodically primarily due to the HFF mixing with formation water,thus causing δD and δ^(18)O to deviate from the meteoric water line of Xinjiang.Because of watererock interaction(WRI),the concentrations of Fe^(2+)+Fe^(3+)and CO_(3)^(2-)of the FPW increase over time,with the solution pH becoming more alkaline.Furthermore,based on the significant changes observed in the geochemistry of the FPW,three separate time intervals of flowback time are identified:Stage Ⅰ(<10 days),where the FPW is dominated by the HFF and the changes in ions and isotopes are mainly caused by the WRI;Stage Ⅱ(10-37 days),where the FPW is dominated by the addition of formation water to the HFF and the WRI is weakened;and finally,Stage Ⅲ(>37 days),where the FPW is dominated by the chemistry of the formation water.The methodology implemented in this study can provide critical support for the source identification of formation water.

关 键 词：Tight oil reservoirs ISOTOPE Flowback and produced water(FPW) Inorganic ions Hydraulic fracturing fluid(HFF) 

分 类 号：TE357.1[石油与天然气工程—油气田开发工程]