ABSTRACT
The influence of high-velocity flow of a liquid of constant compresibility on the transient pressure behavior of a naturally fractured well is studied in this paper. The study is based on a numerical solution to the radial liquid flow problem as described by Warren and Root but considering high-velocity flow through Forchheimer equation. An expression for the rate-dependent pseudo-skin term is derived. It is demonstrated through an integration of the Forchhaimer equation and the simulation of drawdown tests that consider no skin damage that this pseudo-skin in essentially equal to the product Dqw, where D is the turbulent term coefficient defined as βρk/2πrwhμ. It was also found that the correlation of Ramey et al. for the end of the wellbore storage period in homogeneous systems, can be extended for conditions of high-velocity flow in naturally fractured reservoirs provided that the apparent skin s’ is used instead of the skin factor s. This study also considers the influence of high-velocity flow on pressure buildup tests. The effects of a finite formation skin and wellbore storage are also included in this work. One main conclusion of this work is that after the high-velocity flow region is stabilized, the slope of the semilog straight line for matrix dominated flow is equal to the conventional value of liquid flow of 1.151. Results of this study show that pressure derivative analysis with Bourdet et al.'s type curves are to be taken with caution when high-velocity flow affects the test.
