Research On The Reusing Technology Of Fracturing Fluid

Fracturing technology is one of the main measures to improve the low-permeability oiland gas production, the fracturing fluid as an important part of fracturing technology isessential. At present, fracturing fluid used in the oilfield is disposable flowback. The fracturingflowback fluid contains a lot of chemicals. As a result, the fracturing flowback fluid is apollution sources that can not be ignored in oilfield. This paper presents a reusing technologyof fracturing fluid, which recycling the flowback fluid as a new fracturing fluid to continue touse. It will not only save a lot of chemical materials and water resources, reduce emissions, butit also can shorten the construction cycle and the production schedule. Thus, this technology isan effective method to deal with the problem of flowback fluid.According to requirements of the fracturing fluid currently in Nanniwan oil productionplant in Yanchang oilfiled, a new reusing technology of hydroxy-propylguar fracturing fluidwas developed. At the beginning, the optimal formulation of the fracturing fluid system isdetermined by laboratory experiments:0.30%hydroxy-propylguar+0.04%crosslinkingaccelerant II+0.15%the demulsifier II+0.35%cleanup agent Ⅰ+0.35%fungicide; thecross-linker is borax, the mass concentrations are0.5%, the ratio of hydroxy-propylguar andborax is100:8; slowly-releasing gel breaker is SCH-01, the ratio of hydroxy-propylguar andgel breaker is100:0.05. And then the mixing ratio and the amount of cross-linker, gel breakerand other additives were optimized35℃, and get reusing fracturing fluid formulas withdifferent mixing ratio. The performance evaluation results of the fracturing fluid system showthat, the fracturing fluid system has good performance of shearing resistance, and it alsopossesses the advantage of perfect gel-breaking capacity, low filter loss and little residue,realizing the reuse of fracturing fluid. This kind of reusing fracturing fluid formula has beenapplied for Liu287-6well and Liu287-7well of Nanniwan oil production plant in Yanchangoilfiled, in Naniwan oilfield, and successful rate was100%. From tracking of10days of oilproduction, the cumulative yield are the higher than the other five similar well contrast. Byeconomic accounting, reusing fracturing fluid system reduces the production costs andreactant ratio, and creates a certain social and economic benefits.Acid fracturing fluid system has the property of effectively inhibiting clay swelling,which can greatly reduce the damage to the reservoir, thus a new technology of the reutilization of the organic borate-zirconate cross-linking weak acidic fracturing fluid wasdeveloped in this study,. At the beginning, the organic borate-zirconate crosslinker YM-A1was prepared for carboxymethyl-hydroxypropyl guar gum (CMHPG) fracturing fluid systemunder weak acidic condition. This type of system was breaking by a slowly-releasing gelbreaker SCH-04, and the broken fluid could be used for recovery and utilization. The optimumcondition for the secondary crosslinking of the broken fluid is determined: the volume ratio ofthe broken fluid and the base fluid is1:3, the optima pH is4~6, the optima temperature is60℃~70℃,the mass concentrations of the organic borate-zirconate crosslinker YM-A1andthe slowly-releasing gel breaker SCH-04are0.35%and0.04%~0.05%respectively. Theperformance evaluation results show that, the organic borate-zirconate cross-linking weakacidic fracturing fluid system from the secondary crosslinking of the broken fluid has goodperformance of rheological property and shearing resistance, and it also possesses theadvantage of perfect gel-breaking capacity, low filter loss and little residue, realizing thereutilization of the weak acidic fracturing fluid system.Besides, the feasibility of reusing technology of others fractures fluid system were alsoinvestigated, including polyhydroxy alcohol fracturing fluid system and free-polymerfracturing fluids. On the research of alcohol fracturing fluid reusing, we get the optimumformulation of the reusing: the volume ratio of the broken fluid and the base fluid is1:2,accelerant is0.18%, the mass concentrations of the organic borate-zirconate crosslinker FOBand the slowly-releasing gel breaker SCH-04are0.8%~1.0%and1.0%respectively. Theperformance evaluation results show that, the polyhydroxy alcohol fracturing fluid systemfrom the secondary crosslinking of the broken fluid has good performance of rheologicalproperty and shearing resistance, and it also possesses the advantage of perfect gel-breakingcapacity, low filter loss and little residue, so it has good prospects of practical application. Atlast the reusing possibility of free-polymer fracturing fluid was also put forward. However, itneeds further studies for the actual reusing in the future.