Models for Monitoring PWRI Fracturing
Reinjection of produced water has become a viable method for disposal, for support and for drive. Characteristic elements of these injection operations include long-term injection with consequent stress changes due to poro- and thermoelastic effects. Dilute concentrations of entrained particles in the produced water add another level of complexity. These micron-sized particles can plug the formation during matrix injection. During injection above fracturing pressure, these fines and carried-over oil will alter the near-fracture permeability, will afford development of external filter cake on the fracture faces and can plug the fracture tips or reduce the fracture conductivity itself. Successful produced water injection operations usually entail the intentional or unintentional development of hydraulic fractures. Success is measured on an economic basis and, as such, economic planning and performance evaluation require reliable predictions of fracture geometries and the capacity of fractures to accommodate fluid. The basic mechanisms for fracture growth during produced water injection, available in the public domain, are summarized. Hydraulic fracturing for, or as a result of, produced water reinjection is compared with hydraulic fracturing for stimulation. Finally, various public domain models for designing and evaluating produced water hydraulic fracturing are briefly summarized.
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