Friction-reduced water, i.e. “slickwater”, fracturing was first introduced in the late 1950's. It fell out of favor with the advent of gelled fluids systems; however, slickwater fracturing has seen a large resurgence with the increasing development of unconventional reservoirs. Slickwater fracturing has once again become popular for stimulating these tight gas sand and shale gas systems.
The main advantages of slickwater fracturing treatments are the economics and the adequate conductivity they can place in low permeability reservoirs. Additionally, it is possible for slickwater treatments to create long, complex fractures which enhance the well's “stimulated reservoir volume” (Mayerhofer et al. 2008). Most treatments use large quantities of water pumped at very high rates. However, the relationship between complexity and rate is not well understood.
This paper presents an experimental study on slickwater fracturing performed by using a unique testing system, which was developed to study slickwater fracturing treatments at a laboratory scale. The intent was to study the effects of rate on the complexity of growth in the reservoir. Laboratory results were scaled to field conditions by applying scaling law analysis. The scaled results suggest that for field water fracturing treatment design in shale reservoirs, large injection volumes result in large SRA (“stimulated reservoir area”, a comparison term to “stimulated reservoir volume”) which should result in increased production. The optimal injection rate can vary for different reservoir conditions. At low injection rates, reservoir complexity does not seem to affect fracture network growth. At the same time, different rock types will also affect the fracture network growth in water fracturing processes. Quantitatively, the laboratory results agree well with the conclusions drawn from actual field applications.