Challenges in adjoint-based optimization of a foam EOR process

Challenges in adjoint-based optimization of a foam EOR process

Namdar Zanganeh, M.
Kraaijevanger, J.F.B.M.
Buurman, H.W.
Jansen, J.D.
Rossen, W.R.

Civil Engineering and Geosciences

Geoscience & Engineering

2014-08-01

We apply adjoint-based optimization to a Surfactant-Alternating-Gas foam process using a linear foam model introducing gradual changes in gas mobility and a nonlinear foam model giving abrupt changes in gas mobility as function of oil and water saturations and surfactant concentration. For the linear foam model, the objective function is a relatively smooth function of the switching time. For the nonlinear foam model, the objective function exhibits many small-scale fluctuations. As a result, a gradient-based optimization routine could have difficulty finding the optimal switching time. For the nonlinear foam model, extremely small time steps were required in the forward integration to converge to an accurate solution to the semi-discrete (discretized in space, continuous in time) problem. The semi-discrete solution still had strong oscillations in gridblock properties associated with the steep front moving through the reservoir. In addition, an extraordinarily tight tolerance was required in the backward integration to obtain accurate adjoints. We believe the small-scale oscillations in the objective function result from the large oscillations in gridblock properties associated with the front moving through the reservoir. Other EOR processes, including surfactant EOR and near-miscible flooding, have similar sharp changes, and may present similar challenges to gradient-based optimization.

adjoint-based optimization
simulation
enhanced oil recovery
foam

http://resolver.tudelft.nl/uuid:8bbdae14-70fa-4721-a188-5b0bd55f7484

Springer

2015-08-01

1420-0597

Computational Geosciences, 18 (3-4), 2014; Revised manuscript

https://doi.org/10.1007/s10596-014-9412-4

Institutional Repository

journal article

(c) 2014 Springer
The Author(s)