Hydraulic fracturing is a well-established completion technique, most notably in the tight and unconventional gas reservoirs of North America. Although still not nearly as prevalent, fracturing is the completion method of choice throughout the world, providing unparalleled contact between the reservoir and the wellbore. Placing a fracture means that it takes less energy to move the oil or gas from the reservoir to the wellbore. Flow rates are increased dramatically and reservoirs can be depleted to significantly lower pressures prior to abandonment. The process is accomplished by physically breaking the formation apart with extreme pressure and then placing a highly conductive and crush-resistant material ("proppant") inside the fracture. Subsequently, oil and gas will flow through the "propped" fracture and into the wellbore. Because the propping material has a permeability that is orders of magnitude greater than the formation, virtually all flow passes from the reservoir into the fracture and then along the fracture into the well. The hydraulic fracture length can reach significant distances into the formation, providing the inflow area that is essential to the production of gas from tight and unconventional formations, although remarkable results can also be achieved from medium- and high-permeability reservoirs.

Although fracturing is often perceived as a technique for low-permeability reservoirs or remediation of mature fields, the best results are achieved from the best wells. One 100-md oil reservoir, effectively fractured, will produce the equivalent of 20 to 30 massive fracture treatments in 1-md reservoirs - and this factor increases to 50 to 70 for gas wells, due to the mitigation of turbulence within the reservoir.

This paper is concerned with the processes of candidate selection, treatment design and treatment evaluation, and in particular with the best practices that help optimise these procedures, including measurements that make fracturing more successful, wellbore design, treatment design techniques and materials selection. Finally, the paper will consider how these processes may subsequently evolve.

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