Waterflooding is currently the most commonly used method to improve oil recovery
after primary depletion. The reservoir heterogeneity such as permeability distribution
could negatively affect the performance of waterflooding. The presence of high
permeability streaks could lead to an early water breakthrough at the producers and thus
reduce the sweep efficiency in the field. One approach to counteract the impact of
heterogeneity and to improve waterflood sweep efficiency is through optimal rate
allocation to the injectors and producers. Through optimal rate control, we can manage
the propagation of the flood front, delay water breakthrough at the producers and also
increase the sweep and hence, the recovery efficiency. The arrival time optimization
method uses a streamline-based method to calculate water arrival time sensitivities with
respect to production and injection rates. It can also optimize sweep efficiency on
multiple realizations to account for geological uncertainty. To extend the scope of this
optimization method for more general conditions, this work utilized a finite difference
simulator and streamline tracing software to conduct the optimization.
Apart from sweep efficiency, another most widely used optimization method is
to maximize the net present value (NPV) within a given time period. Previous efforts on
optimization of waterflooding used optimal control theorem to allocate
injection/production rates for fixed well configurations. The streamline-based approach
gives the optimization result in a much more computationally efficient manner.
In the present study, we compare the arrival time optimization and NPV
optimization results to show their strengths and limitations. The NPV optimization uses
a perturbation method to calculate the gradients. The comparison is conducted on a 4-
spot synthetic case. Then we introduce the accelerated arrival time optimization which
has an acceleration term in the objective function to speed up the oil production in the
field. The proposed new approach has the advantage of considering both the sweep
efficiency and net present value in the field.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-12-7238 |
| Date | 2009 December 1900 |
| Creators | Tao, Qing |
| Contributors | Datta-Gupta, Akhil |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | application/pdf |
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