TABLE OF CONTENTS Waterflooding is usually initiated in pressure depleted or nearly depleted reservoirs. Most commonly, solution gas drive reservoirs develop free gas saturation due to pressure depletion. Initially, the reservoir pressure is restored as the gas-filled pore volumes are refilled with the injected water, redissolving free gas back into the oil. The oil production response occurs after the fill-up of the gas space. The injected water eventually breaks through at the producing wells; generally, very little water is produced before the peak oil production rate is reached if the reservoir resembles a homogeneous formation. The timing of the oil response and water breakthrough, and the magnitude of the peak oil production rate depend upon the reservoir characteristics and the injection rate. After the peak production rate is reached, oil production rate declines with increase in water cut. Figure 8-1 illustrates the performance curve of a typical successful waterflood. [1]
A major waterflood asset management activity is to estimate reserves, recovery rates, and flood life for designing a project, and also to analyze past and future performance during the life of the flood for monitoring and evaluation purposes.
Commonly used techniques are:
Volumetric method
Empirical method
Classical method
Performance curve analyses
Simulation method
Even though reservoir engineers are mainly involved in this activity, geologists, petrophysicists and production engineers are also responsible for providing data, reviewing and verifying results of the reservoir performance analysis.
This chapter presents techniques used for...
