Denbury Resources

Abstract: This paper (SPE 110451) was accepted for presentation at the SPE Annual Technical Conference and Exhibition, Anaheim, California, 11–14 November 2007, and revised for publication. Original manuscript received for review 30 July 2007. Revised manuscript received for review 22 December 2008. Paper peer approved 27 March 2009. Summary As the development of tight/unconventional and partially depleted gas reservoirs has increased, so has the demand for more-innovative hydraulic-fracture designs. Operators are increasingly placing proppant with slickwater, linear gel, or hybrid fracture designs. While the benefits of these designs typically are attributed to a reduction in gel damage of the proppant pack, many operators mistakenly believe that the resulting fractures are not conductivity-limited. Because few (if any) models on the market can adequately model the propagation of a slickwater fracture along with the associated proppant transport and deposition, it becomes difficult to optimize these fracture designs. This has led many operators to assume incorrectly that only small-diameter sand or resin-coated sand may be placed in these types of designs, and that these products supply ample flow capacity. However, one east Texas operator has combined insight into proppant transport with an appropriate understanding of realistic proppant-pack conductivity to develop a novel, hybrid slickwaterfracture design. This design has allowed the placement of largerdiameter, higher-conductivity proppant in fractures that many believed could not be placed in fractures either operationally or economically. Additionally, this operator has developed a unique pumping strategy to place the highest-conductivity proppant in portions of the fracture where it provides the most value. This paper will present a case history of these new hybrid slickwater-fracture designs in this operator’s east Texas Cotton Valley Taylor (CV-T) completions. The design theory and sequential improvements will be documented, including larger-diameter, higher-strength proppants, and a novel placement design. Field results from the first six wells fractured will be presented, showing substantial increases in gas production compared with similar offset completions. Economics will also be shown to illustrate the tremendous value added to completions using this hybrid fracture design.