Several different hydraulic fracturing treatment design methodologies have been adopted and used with varying success in East Texas and, specifically, in the Cotton Valley Sand Formation. Treatment designs have ranged from massive hydraulic fractures using crosslinked polymer fluids to low proppant concentration slickwater treatments (waterfracs) using only water plus a friction reducer. Operators have varying opinions regarding the benefits of the various design approaches, with the only common conclusion being that hydraulic fracturing must be employed to commercially produce hydrocarbons from these tight formations. The major design challenges include the need for long fractures, relatively limited height growth, good proppant coverage over the entire fracture surface, and low proppant pack damage. Neither conventional fracturing treatments nor slickwater fracturing treatments address all of these issues.
To meet the challenging design requirements, a new design methodology in which fibers are added to the fracturing fluid has resulted in added benefits for operators. The fibers assist in the transport of proppant based on a mechanical suspension mechanism and prevent proppant settling during fracture closure. As a result, the fluid viscosity is no longer the main factor in proppant transport and significantly lower polymer concentrations can be used without compromising proppant transport. For example, the polymer concentration used in several successful treatments at BHST in excess of 250°F has been reduced by about 50% when used in conjunction with the fibers. The lower fluid viscosity allows for the creation of the desired fracture geometry with controlled fracture height growth. In addition, reducing the polymer concentration has largely been accepted as a means to increase fracture conductivity. The use of fibers in conjunction with the polymer fluid is a new approach that has allowed for additional reduction in polymer loadings while still maintaining excellent proppant transport in over 90 jobs pumped to date.
The purpose of this paper is to share the fracture design methodology incorporated for several operators completing wells in East Texas. Typical job designs with fluid rheology and laboratory conductivity data are presented in conjunction with the placement success when using the fiber assisted transport design methodology. Initial production results are reviewed and compared to offset wells that have been stimulated using conventional methods.