Abstract
Abstract
This paper describes the development and application of a new field development technology to optimize the locations of new and sidetracked wells within an oil or gas field, the drilling schedule, water and gas injection strategies, production/injection rates, and surface facilities. The field development plan optimization is informed using BP's Top-Down Reservoir Modeling (TDRM) methodology. An economic indicator (e.g. net present value, incremental rate of return, capital efficiency, discounted payback, etc.) or oil/gas recovery is maximized subject to field development constraints. Only drilling targets in geologically defined areas are considered. Sidetrack wells are additionally limited by distance from their parent well. Drilling rig constraints (rig availability, drilling time, drilling costs, etc.) are incorporated. Economic constraints on project costs are also taken into account.
Multiple integrated reservoir models, representing different combinations of sub-surface description and surface facilities, can be handled within this new field development optimization system. The system generates the optimum field development option by maximizing a percentile of either the selected economic indicator or the oil/gas recovery. Associated risks can be considered as constraints. Probability distribution functions of the maximized objective function and associated constraints are determined with a powerful optimization procedure developed using a combination of public and proprietary techniques. A large range of field development issues from well locations, drilling schedule, injection strategy and facilities modifications can be addressed.
Applications of the developed technology for field development optimization in a giant new offshore oil field, and a mature oil field are presented. These applications clearly demonstrate that the new development optimization technology is a sufficiently general tool for analysis to inform field development planning. Significant improvements in oil recovery, sweep efficiency, and net present value are demonstrated in the comparison with the reference field development cases.
Introduction
The very challenging problem of the field development optimization is addressed in this paper. A powerful field development optimization technology is presented which is applicable in existing or new oil/gas fields.
We concentrated on two major issues: how the optimum field development plan can be determined and how uncertainties in the reservoir description can be taken into account in the optimization process. The real power of the presented technology is the large scope of field development problems that can be addressed. We describe tools to optimize timing for development of different reservoir zones, locations of new and/or sidetrack wells, their drilling schedule, well trajectories, water/gas injection strategy (e.g. how many injectors are needed, in what locations, when and in what order they should be drilled, what perforations should be open for injection), well production/injection rates, facility capacities, surface pipeline network structure, facility modification program, etc.
The innovative methodology developed is the primary reason for the success in applying the technology in large oil fields. It is based on integrated models of reservoir and surface facilities, and allows optimizing subsurface and facility parts 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.
Long term field development optimization is considered, using an economic indicator (e.g. net present value, incremental rate of return, capital efficiency, discounted payback, etc.) or oil/gas recovery as the objective function for ranking evaluated field development options. The dependency of drilling cost on new/sidetrack well locations and their trajectories are taken into account.