Field Development Optimization in a Giant Oil Field in Azerbaijan and a Mature Oil Field in the North Sea
Authors: Litvak Michael , Gane Brian , McMurray Lesley , Skinner Roger 
Published: October 2008

The recently developed field development optimization technology based around BP's Top Down Reservoir Modeling (TDRM) methodology 1 has been applied to optimizing the location and drilling schedule of both primary and sidetrack wells while simultaneously optimizing the water injection strategy (location of water injectors, their drilling schedule, and water injection rates) in a giant oil field in Azerbaijan. The optimal development plan was selected by maximizing the Net Present Value (NPV) of the project subject to some predefined field development rules. The field development optimization technology is based on a comprehensive integrated reservoir model representing both the reservoir geology and surface facilities.

More than 8000 field development cases were automatically generated and evaluated by the Top Down Depletion Planning (TDDP) optimization procedure. The optimum field development plan was compared to the base case field development plan. Significant improvements in oil recovery, sweep efficiency, and net present value were demonstrated in the optimal case compared with the base case. The optimal case suggests that early drilling of water injection wells will be beneficial to the project and it also defines the optimal well spacing.

In a second study, the TDDP field development optimization technology was applied to optimize the location and drilling schedule of sidetrack wells in a mature oil field in the North Sea. In this case, ten history matched reservoir models were simultaneously used in the optimization procedure to evaluate the uncertainties in the predictions. In this study the averaged incremental oil recovery across all ten models was maximized and the uncertainties in incremental oil recovery with the optimal well sidetracking strategy evaluated.

The two field applications described in the paper clearly demonstrate that this field development optimization technology is a powerful and sufficiently general tool to aid field development planning.

Introduction

This paper addresses the problems of optimizing field development in a giant oil field in Azerbaijan and a mature oil field in the North Sea. A powerful field development optimization technology presented in papers 2 is applied. It relies on the TDRM workflow, an optimizer (based on a Genetic Algorithm), job management in a computer network and specialized results handling tools.

The major strength of the developed technology is its capability to handle and optimize a large range of field development issues. For example, new well locations, well sidetracking strategy, drilling schedule, water/gas injection program and well trajectories have been optimized in two studies presented in the paper. The optimization procedure is based on integrated models of reservoir and surface facilities that permit optimization of both the subsurface and facility components of the field development at the same time. For example, locations of new/sidetrack wells, their drilling schedule, facility capacities, and structure of the surface pipeline network system can be optimized simultaneously.

In the first study, a part of a giant structure in the Caspian Sea (Azerbaijan) is considered. Development drilling (pre-drill wells) in the field has already started with first oil expected in several years. Only a single realization of the reservoir model has been utilized in this study.