Chapter 2 - Water Influx

Abstract

This chapter provides the various water influx calculation models and a detailed description of the computational steps involved in applying these models. Active water drive reservoirs are typically characterized by a gradual and slow reservoir pressure decline. It is suggested that if during any long period the production rate and reservoir pressure remain reasonably constant, the reservoir voidage rate must be equal to the water influx rate. The simplest model that can be used to estimate the water influx into a gas or oil reservoir is based on the basic definition of compressibility. When an oil well is brought on production at a constant flow rate after a shut-in period, the pressure behavior is essentially controlled by the transient flowing condition. It is found that the Carter and Tracy water influx model does not require superposition and allows direct calculation of water influx. The primary difference between the Carter and Tracy technique and the van Everdingen and Hurst technique is that Carter and Tracy technique assumes constant water influx rates over each finite time interval.