A New Diagnostic Analysis Method For Waterflood Performance

摘要

Despite the widespread application of reservoir simulation to study waterflood reservoirs, petroleum engineers still need simple predictive tools to forecast production decline, estimate ultimate oil recovery, and diagnose the production performance from the historical field data.rnOn the basis of the Buckley-Leverett (BL) equation and the assumption of a semilog relationship between the oil/water relative permeability ratio and water saturation, a consistent analytical solution can be derived asrnf_o(1-f_o)=(E_v/B)1/t_Drnwhere fo is the oil fractional flow, t_D is the fraction of cumulative liquid production to related formation volume, B is the relative permeability ratio parameter, and E_V is the volumetric sweep efficiency. Two equivalent linear plots can be developed: a log-log plot and a reciprocal-of-time plot. The log-log plot has a slope of -1 and intercept of E_V/B. The reciprocal time plot has a slope of E_V/B and an intercept value of 0. Both plots can be applied for the diagnostic analysis of waterflood reservoirs.rnModel and field case studies show the benefits of this technique as a production-decline-analysis tool in forecasting the waterflood production decline and the ultimate oil recovery. This method also can be applied as a diagnostic tool to evaluate various aspects of waterflood performance. Examples include assessing waterflood maturity, calculating volumetric sweep efficiency, distinguishing the normal waterflood breakthrough from the premature water breakthrough through hydraulic fractures, and examining the consequences of operational changes. The appropriate use of this analytical method will help to optimize the field waterflood operation.