The minifrac procedure used in the oilfield services industry is a one-step procedure. The most important information one tries to obtain from minifrac testing is an effective fluid loss coefficient, CEFF, which is the average of the early time fluid loss coefficient, Cvc, and the late time fluid loss coefficient, Cw. Since Cvc could be much larger than Cw, this procedure works reasonably well only if the early fluid loss period, commonly referred to as spurt time, Ts, is short compared to the overall job time. However, since the spurt time is sometimes on the order of several minutes, which is in the same order as the minifrac pumping time, this method tends to overestimate the magnitude of CEFF, resulting in the overdesign of a job treatment when spurt time is large.

A mathematical algorithm has been developed in this paper to determine both the Cvc and Cw, TS and spurt volume, VSP from the conventional minifrac treatment such that they can be adequately used to design the full-scale treatment.

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