The Impact of Fracturing Fluids on Conductivity and Performance in Low-Temperature Wells

Abstract

Abstract A study investigating the performance of low temperature wells following hydraulic fracturing is presented. Emphasis is placed on proper fracturing fluid and breaker selection to minimize proppant proper fracturing fluid and breaker selection to minimize proppant damage and maximize fracture conductivity. The study indicates borate crosslinked fluids yield minimal damage whereas organometallic crosslinked fluids consistently yield severe damage. A detailed discussion of the impact of fluid-induced proppant damage on well performance is given. Although previously reported laboratory work has addressed the topic of in-situ fracture conductivity, the results of conductivity damage in wells with low bottomhole static temperatures have not been reported. A detailed discussion of extensive laboratory conductivity testing at 100 degrees F is presented to address the issue of conductivity impairment (damage) in low temperature wells. The conductivity and permeability of Jordan sand placed with several fluid incorporating various crosslinkers and breaker systems is reported. The data indicate crosslinked fracturing fluids can be used in low temperature wells to yield high fracture conductivity. However, the amount of damage observed is a function of both the cross-linker and breaker system. Subsequent to laboratory testing, the impact of the fluid/ breaker system on the performance of oil and gas wells was evaluated. Numerous fracture design and production simulations were performed to evaluate the effect of fluid systems on well performance. performed to evaluate the effect of fluid systems on well performance. These data indicate production can increase 50% or more simply by incorporating a "cleaner" fracturing fluid system. In conclusion, fracturing fluid and breaker selection are variables that must be considered when designing a fracture treatment in a low temperature well. This study indicates proppant placed with a borate crosslinked fracturing fluid containing a persulfate/amine breaker exhibits minimal conductivity impairment persulfate/amine breaker exhibits minimal conductivity impairment resulting in improved well performance. Introduction During the past decade research directed at improving hydraulic fracturing of low temperature wells has not been emphasized. However, emphasis has been placed on high temperature wells including the development of high temperature fracturing fluids and high strength proppants. Recently, workovers and shallow drilling activity have stimulated interest in methods to improve the performance of low temperature wells. Improved fracturing technique can play an important role in this effort. A key to success is improved fracture conductivity. The contribution of proppant permeability/fracture conductivity to well performance has long been recognized. Normally, an improvement in conductivity yields improved well performance. However, quantification of the increase in production performance. However, quantification of the increase in production is difficult since the in-situ permeability of various proppants placed with fracturing fluid systems has not been quantified. placed with fracturing fluid systems has not been quantified. Although the permeability of proppants at various closure stresses and temperatures has been determined in the laboratory, the actual in-situ proppant permeability of the fracture may be an order of magnitude less. Thus, design engineers have incorporated correction factors to compensate for conductivity impairment. The source and extent of conductivity impairment has previously been reported. The work has evolved from simple short-term conductivity tests performed at room temperature to long term tests performed at elevated temperature and pressure. Additionally, performed at elevated temperature and pressure. Additionally, investigators have incorporated various fracturing fluids and additives in order to determine their effect on in-situ conductivity. The data indicate significant conductivity damage (50 to 75 %) can occur as a result of filter cake deposition and embedment. Normally, the amount of impairment is predominantly a function of the fracturing fluid/breaker system in a low closure stress environment. Penny reported the results of conductivity testing as a function of the fracturing fluid systems, shear history, rock hardness, and time/temperature on conductivity. The goal of his work was to quantify the various factors that effect in-situ conductivity. The data indicated titanate crosslinked hydroxypropyl guar (HPG) fracturing fluids yielded 43 to 69 % conductivity damage at 175 to 300 degrees. Subsequently, data published at 150 degrees indicated titanate crosslinked guar was significantly more damaging than a borate crosslinked guar fluid. P. 347