TRANSIENT ANALYSIS OF ACOUSTICALLY DERIVED PRESSURE AND FLOW RATE DATA.
A pressure buildup test conducted on a sucker-rod pumping well is often distorted by long-duration wellbore storage. In fact, this distortion can be so severe that even a week's shut-in period may not allow a semilog analysis. A longer shut-in period becomes economically discouraging because of lost production. Low energy and low transmissivity in the reservoir, coupled with increased fluid compressibility, contribute to this long-duration storage phenomenon. One way of handling this problem clearly lies in the simultaneous treatment of downhole pressure and flow rate, estimated from rising annular liquid-level data by acoustic well sounding (AWS). Ascertaining the quality of the indirectly measured pressure and rate data constitutes one of the objectives of this study. Interpretation of several transient tests shows that automatic convolved-type-curve or history matching of field data is a powerful tool for reservoir parameter (total mobility, skin, fracture half-length, storage coefficient) estimation.