Backproduction of proppant from hydraulic fractures (proppant flowback) is a continuing operational problem in the oil and gas industry. Up to 20% of the proppant can be flowed back after the treatment. Curable resin-coated proppants are used to control proppant production, but are known to chemically interact with fracturing fluids and may be prone to several failure mechanisms. Curable resin-coated proppants also require either well shut-in or the use of activators at low temperatures. A new method to control proppant flowback relies on fibers mixed with the proppant to stabilize the proppant pack. The main advantage of this patented3 technology is that it is physical rather than chemical. Therefore, proppant flowback is controlled without specific shut-in time, temperature, or pressure constraints. This paper presents flowback results from fractures of dry gas wells (<1 millidarcy permeability) where fiber/proppant mixtures were used to control proppant flowback (11 cases). Fluid flowback rate, gas rate and proppant production were monitored during the cleanup period. These wells are compared to wells where either curable resin-coated proppants or no flowback control were used (15 cases). The fiber/proppant mixtures controlled flowback of proppant for both sand and ceramic proppants when used with all the proppant or in only the last part of proppant (tail-in). Flowback could begin right after the fracturing equipment was rigged down (15 to 30 minutes). Cleanup fluid flow rates were up to ten times higher than previously obtainable with curable resin-coated proppants and less proppant was flowed back. Faster flowback rates also resulted in earlier onset of gas production and reduced flowback time. Fibers allow greater latitude in flowback rate than curable resin- coated proppants without the need for shut-in time. Introduction Propped hydraulic fracturing is successfully used in many formations to enhance production. One associated problem is the backproduction of proppant during cleanup and throughout the life of the well (proppant flowback). Up to 20% of the proppant placed in the fracture can return during the cleanup period. The proppant that flows back has a detrimental wear effect on the production equipment. and requires the use of separators in the production line. Concern about proppant flowback can limit the flow rates during cleanup and production. Curable resin-coated proppants (RCP) are the predominant technology to control proppant flowback. They are used as all or the last part (tail-in) of the proppant in the fracture. The resin coating cures to form a strong proppant pack under conditions of sufficient closure stress, shut-in time, and temperature. Curable RCPs control proppant flowback in many cases but can have several disadvantages. They are known to interact with the fluid chemistry (pH, crosslinkers, breakers, etc.), can reduce fracture conductivity, and may be prone to failure under cyclic loading conditions. Further, RCPs need specific temperature, shut-in time and stress conditions to form a strong bond. Shut-in time can be as long as overnight, and at low temperatures (<150 F) additional chemical activators must be added to promote cure. P. 453

A study, directed at the improvement of hydraulic fracturing treatments performed in the Lobo Wilcox formation in south Texas, is presented. During the study, the performance of numerous gas wells fractured using a single-fluid (organometallic crosslinked) or a multiple-fluid (organometallic and borate crosslinked) technique was determined. During the multiple-fluid treatment (MFT) the organometallic-crosslinked fluid is pumped followed by a borate-crosslinked tail-in fluid. The field study indicates Lobo Wilcox wells fractured using conventional high-temperature fracturing fluids (organometallic-crosslinked fluids) exhibit poor production in comparison to wells fractured using multiple fluids. Improved fracturing fluid recovery and improved well performance were observed in wells fractured with multiple fluids. The improved well performance is attributed to less conductivity impairment by the borate tail-in fracturing fluid. This technique can be used in any high-temperature well to "economically" improve fracture conductivity.