| Popis: |
Hall’s method is a simple tool used to evaluate performance of water injection wells. It is based on the assumption of steadystate radial flow. Besides historical injection pressures and rates, Hall’s method requires information about the mean ambient reservoir pressure, e p . In addition, it is assumed that the equivalent radius, e r , of the reservoir domain influenced by the well is constant during the observation period. Neither e p nor e r are available from direct measurement. Here we modify and extend Hall’s plot analysis, calling it slope analysis. Our modification relies on the analysis of the variations of slope of the cumulative injection pressure versus cumulative injection volume. In particular, our slope analysis produces an estimate of the mean ambient reservoir pressure, and requires only the injection pressures and rates. Such data are routinely collected in the course of a waterflood. Note that the slope analysis method requires no interruptions of regular field operations. The proposed slope analysis method has been verified with the numerically generated pressure and rate data, and tested in the field. In both cases it proved to be accurate, efficient, and simple. The obtained ambient reservoir pressure estimate can be used to correct the Hall plot analysis or to map the average reservoir pressure over several patterns or an entire waterflood project. Such maps can then be used to develop an efficient waterflood policy, which will help to arrest subsidence and improve oil recovery. |
