Step-rate injection tests are frequently performed in water injection wells for waterflooding reservoirs and in mini-fracture tests for stimulation treatments designs. In both applications, the data are usually analyzed to determine the fracture propagation gradient. To enhance the usefulness of step-rate test data, the current paper describes a new method of analysis that also determines the injectivity index of the well and fracture, the fracture length, width and effective leak-off rate. Injectivity analysis provides additional formation data which is useful for fracture designs, formation evaluation and optimizing water injection rates. Injection at gradients above the fracture gradient will greatly increase the injectivity of wells as determined by a fracture sensitivity parameter which is determined from step-rate data.

This analysis procedure has been successfully applied to multiple well tests conducted in Alaska and West Texas for waterfloods. In both waterfloods, multiple fracture gradients are indicated by the standard analysis. Injectivity analysis has determined the fracture gradient in both field cases using data from multiple wells. The analysis has also been successfully applied to low-permeability stimulation designs in the Rocky Mountains.

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