The Systematic Closing of the Performance Gap in Hydraulic Fracturing

Abstract

Hydraulic fracturing is the overwhelming completion method in the international petroleum industry. It is estimated, that today it has become a $20 billion industry. It is also one of the most challenging enterprises, incorporating scientific information from geology, reservoir and production engineering, rock mechanics, complex fluid rheology and field economics. More than a decade ago we introduced the concept of Unified Fracture Design (UFD) as a means towards physical optimization. Since then UFD has been adopted by a great number of practitioners and hundreds of papers have been published. Not all approaches have been successful, nor have they been done appropriately. In this work we relook at the whole issue in a systematic way. We have identified and describe here a 9-step sequence to mitigate the gaps and help in the optimized field application of modern hydraulic fracturing. These include:Required minimum reservoir characterization: Typical log description.Estimate of k, h, interlayer stress contrast, distance from water.Optimization of fracture size using UFD. Maximum dimensionless PI at optimum conductivity. Optimization of drainage shape and stimulated reservoir volume (SRV).Unique monitoring execution, other than the traditional net pressure or injection variables. New benchmark indicators are used, cross-plotting descriptive variables such as: level of pressure vs. volume of fluid injected vs. operational characteristics, such as tip screen-out.4. Fracture injection tests, designed for fluid efficiency, closure pressure, leak-off coefficient and the newly developed capability for after-closure analysis for well and reservoir variables.For multifrac applications such as shale gas, horizontal wells in very low-permeability formations, zonal isolation and perforation strategies are essential issues.Design of injection schedule to accomplish the desired fracture geometry is the next concern. What happens if things go wrong? The strategy of contingencies must be in place before the execution starts.On-the-fly redesign responding to contingencies, such as net pressure constraints and formation barriers. Ability for alternative plans quickly.Once the job is completed the next step is whatever is necessary to close the fracture and flow the well back. What needs to be done in different geologic settings?Finally, to close the circle, performance evaluation is indicated, which involves comparison between actual performance and expectations and the definitive reconciliation of any discrepancies.

Natural Fractures and Their Effects on Reservoir Reconstruction in Lower Cambrian Shale, Southeast Chongqing, China

“…Therefore, the characteristics of natural fractures are important for reservoir evaluation, as they can inform engineering designs and reservoir evaluation, and help to predict the effects of hydraulic fracturing (Cipolla et al, 2008;Sondergeld et al, 2010;Guo et al, 2013;Li et al, 2013). Some literatures are found on shale fractures currently in internal, (Nelson, 1985;Zeng et al, 1998;Adams, 2013;Bychina, 2014;Gomaa, 2014). And method for fracture characterization on shale is the same as sand reservoirs.…”