Extensive laboratory experiments on hydraulic fracturing have been performed with a convenient and proven apparatus, developed over the past ten years at MTT. Results of these experiments are presented, for instance:

  • Dimensions of created hydraulic fractures with various injected fluids and flow rates

  • Pressure measurements along the fracture length

  • Pressure responses to injection of various fluid sequences (e.g. viscosity and flow-rate variation)

These measurements generally confirm a variety of elastic models developed by Cleary in the early 1980s, which have since been widely adopted by the industry. However, we have had to greatly modify such models over the past five years, because the predictions of such purely elastic models do not seem to agree with most field measurements (e.g. with net pressure), suggesting that most existing industry models are inadequate for practical applications. The reason for such discrepancies between lab and field behavior is traced to nonlinear rock response in the near-tip region of the fracture, which we generally call the leading edge.

Other implications of these results for field applications are discussed, in particular with regard to the following primary issues:

  • The role of fracture propagation in shut-in analysis

  • The role of fluid rheology in fracture opening

  • The importance of near-wellbore tortuosity in interpretation of pressure responses measured in the field

  • The role of stress barriers in providing only partial containment of height growth

It is suggested that current industry concepts need major revision on these and other issues (see related paper, Ref. [1]).

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