Hydraulic fracturing or fracking as it is commonly known is a technique in which high pressure fluid with sand is used to crack open hydrocarbon bearing formations that have very low permeability and cannot flow on its own. The Shale reservoirs, like Barnett Shale, Eagle Ford Shale & Montney Formation are best examples of formation that require hydraulic fracturing to flow.
Hydraulic fracturing is a complex treatment, that requires significant pre-job planning, candidate selection, screening, designing, fluid & proppant selection, simulation and procurement. With the popularity of fracking and current shale gas boom in the United States, fracturing services are available at relatively low costs.
To ensure successful hydraulic fracking, designing the right treatment with appropriate fluid & proppant selection is key to successful treatment. The foremost question that needs resolution when designing fractures is what should be the size of job (in terms of proppant & fluid volume). This is important, as more material means larger job which ultimate means a costlier job.
Micheal J. Economides & Peter Valko developed a workflow called Unified Fracture Design or UFD to design (in essence size) a fracture treatment to ensure maximum production and economic value. The idea is based on identifying most optimum productivity index of the reservoir based on its reservoir properties and given proppant volume. This optimum production index or Jd as its called is compared with most optimum dimensionless fracture conductivity (see plot below). Once a match is found, corresponding frac length, width is calculated that will be created if said proppant volume is pumped in that reservoir.
The approach of answering the "how much proppant volume?" question undertaken by Economides & Valko is commendable, as the real prize is post frac production. Therefore we should not devise a proppant volume and calculate its post frac rate, but identify the maximum achievable production from a specific shale reservoir and calculate required proppant volume to realize that maximum production.
We have a detailed blog on Unified Fracture Design which explains the workflow and teaches how one can use this novel workflow to design their treatments. Find it here.
