The evolution of fracturing technology has provided the industry with numerous advances, ranging from sophisticated fluid systems to tip-screenout designs to propagation modeling. Interestingly, these advances typically have focused on conventional designs that use a crosslinked-fluid system. However, as the development of unconventional (e.g., tight gas, shales, coalbed methane) or underpressured reservoirs has increased, so has the demand for innovative hydraulic-fracture designs. The most recent of these design changes has been the popular method of placing proppant with slickwater, linear gel, or hybrid treatments.
Although our industry has significant expertise in fracture design, most of our experience has been in conventional crosslinked-fluid systems. However, there are many aspects of crosslinked-fluid design that either do not apply to slickwater treatments or, in some cases, are contrary to the requirements of slickwater treatments.
This paper will begin by reviewing the motivation, benefits, and concerns with slickwater fracturing and discuss why this seemingly old method has regained popularity over conventional crosslinked designs in many reservoirs. In addition, the authors will detail some of the important theories related to slickwater fracturing, including fracture width and complexity, proppant transport and settling, and conductivity requirements. In each scenario, emphasis will be placed on the different strategy employed compared to crosslinked-fluid designs, and the mistakes or misunderstandings that are frequently made will be highlighted.
Where appropriate, laboratory testing, field measurements, reference material, and other resources are presented to support the observations made by the authors. This paper will serve as a resource to any engineer or technician who is designing/pumping slickwater fracs, or who is considering this technology for potential application. By applying the concepts presented in this paper, engineers will be able to appropriately evaluate the potential benefits of using this technique in their completions, as well as draw on the experiences of others to take full advantage of this technology.