How "Fracture Conductivity is King" and "Waterfracs Work" Can Both be Valid Statements in the Same Reservoir

Abstract

Abstract Having worked in the field of Hydraulic Fracturing for forty years has allowed the author an opportunity for close observation of several cycles of conceptual applications of hydraulic fracturing. In 1970, the oilfield was using quite a plethora of varying frac fluids from Slick Water to heated asphalt, gelled diesel, emulsion frac fluids, linear gels, and a few crosslinked fluids, although there was some separation between applicable fluids for gas reservoirs and oil producers. By the mid-1970’s we had witnessed the death of heated asphalt as a frac fluid while emulsion fluids and Slick Water fracs were mostly put out to pasture. The age of the crosslinked gels had begun to dominate most of the fracture stimulation technology landscape, mostly because it was judged that this fluid type was able to suspend and place high concentrations of proppant. The emphasis on achieving high Fracture Conductivity with more effectively propped fractures became dominant. The 1980’s saw the industry fracturing technology and laboratory testing migrate toward more realistic test conditions for evaluation of packed proppant bed conductivity, especially with longer testing times, using elevated test temperatures, and by the latter part of the decade to incorporate the presence of frac fluids and their residue. However, in the late 1980’s, a few operators in tight sandstone applications in East Texas started re-inventing Slick Water fracs. Even though pumping rates and treatment volumes were 2x- to 4x larger than previous crosslinked gel fracturing treatments, they typically were placing only 15–25% of the proppant volume, yet claiming improved well economics. To add further consternation, in the next decade, George Mitchell found a unique application in the Barnett Shale for Slick Water fracs and eventually showed the world that some of these hydrocarbon-source shales can actually be commercial producers themselves. This paper will discuss much of the "frac fluid history" mentioned above, review historical highlights of laboratory fracture conductivity testing and field applications trying to illustrate the need for high conductivity as investigators began finding much lower predicted conductivity as they began seeking to emulate insitu reservoir conditions. Back then and still today, we continue to ask: Are we abandoning one of our most significant beliefs, Fracture Conductivity is King, every time we use Waterfracs?