In this work we develop, validate, and apply the "reciprocal rate method" to estimate oil reserves using only rate-time production data. This approach requires the development of boundary-dominated flow, and can be used to validate reserve extrapolations from numerical/analytical reservoir models. The methodology does presume that flowing well bottomhole pressures are approximately constant but we will demonstrate that the method is tolerant of substantial changes in the flowing bottomhole pressure.
This approach requires a plot of the reciprocal of flowrate (1/q) and the so-called "material balance time" (cumulative production/flowrate or Np/q). The "secret" to this approach is the use of material balance time this function accounts for most variation in rate/pressure, and permits the extrapolation of the 1/q function.
This methodology has been applied for oil wells (including oil wells with high water production) and in all cases, the reciprocal rate method has proven to be robust and consistent.
The primary technical contributions of this work are: Direct method to estimate reserves using only rate-time data (time, rate, and cumulative production).The reciprocal rate method is based on variable-rate theory, and is more rigorous than Arps approach (exponential or hyperbolic rate relations).