Analysis of the behavior of the Ding well model for off-centered wells and its impact on gradient-based well location optimization

Analysis of the behavior of the Ding well model for off-centered wells and its impact on gradient-based well location optimization

De Zeeuw, J.Q.

Jansen, J.D. (mentor)
Ashoori, E. (mentor)
Joosten, G. (mentor)

Civil Engineering and Geosciences

Geoscience & Engineering

Petroleum Engineering

2015-08-26

The computer assisted optimization of well locations in reservoirs can result in a better planning of the reservoir development and non-trivial optimal locations can be found. Currently most optimizers use gradient-free methods which require significant computing capacity. Especially when considering decision making under uncertainty there is a need for faster, but still accurate optimizers to handle a variety of reservoir realizations. Some gradient based well location optimization methods have been proposed in literature that make use of the adjoint method to calculate all gradients in the field at the cost of only one forward and one backward simulation. The proposed methods are however using some approximation of the gradient of the objective function with respect to the exact well locations. This study shows a new method to derive the direct gradient of the objective function with respect to exact well locations via a well model for off-centered wells. However, the study shows multiple issues arising from this well model for off-centered wells and what their impact is on this new gradient-based well location optimization method. First, the off-centered well model is found not to be able to model wells located on exact grid block edges. Second, when moving wells from grid block to grid block the well model does not behave smoothly, which jeopardizes its suitability for well location optimization. A mitigation strategy is developed and tested, but this does not solve this issue. Third, the well model is not fully correct in modelling off-centered wells for both single-phase flow and multiphase flow, and again this jeopardizes its suitability for the new gradient-based well location optimization method. The use of an off-centered equivalent wellblock radius instead of the Peaceman wellblock radius is found to solve most of the suspect behavior for single-phase flow for off-centered wells. The issues related to multiphase flow are not solved in this study, but some potential solutions are proposed.

Ding well model
optimization
gradient-based
well location
off-centered well

http://resolver.tudelft.nl/uuid:e9e5bab5-09e0-4bf9-b1c1-9508d381c0c6

51.9983106, 4.3764585

Student theses

master thesis

(c) 2015 De Zeeuw, J.Q.