The formulation, development, implementation and application of a complete three-dimensional hydraulic fracturing simulator, 3DHFRAC, is described. The simulator consists of two principal components: the first represents the solid deformation, crack opening and propagation, using a surface integral scheme, hybridised with finite-elements as needed, and a condition of critical stress-intensity-factor or energy-release-rate to track the motion of the fracture perimeter; the second captures the fluid flow along the open fracture, and into the reservoir. The simulator has been tested extensively by comparison to analytical results, other simpler models cad laboratory experiments: the latter are most vindictive because they have provided a comprehensive self-consistent data-set showing repeatibility and verifying the basic concept of the model, namely a characteristic time deriving from pressures, material moduli and fluid viscosity. Thus uniquely vindicated, the 3DHFRAC model may be applied to study a variety of field conditions: fracture containment by stress-contrast between reservoir and adjacent strata; the role of earth-stress and hydrostatic head gradients in controlling vertical growth of the fractures; fracture propagation after shut-in and its effect on deductions about fluid leak-off coefficients from minifrac tests; and the evolution of interfaces between different fluids, including the transportation of proppant, in typical complex job schedules. An even more exciting application of the model is proposed, namely that of fracture diagnostics in real-time during the job, or at least as a post-mortem determination of fracture geometry: this employs a concept called "surge analysis", namely the matching of measured transient pressure response to the calculations of pressures caused by changes in flow or rheology. Such a capability would finally bring the effort of modelling to full fruition.

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