Abstract
Abstract
A new optimization technology has been demonstrated for giant oil and gas-condensate fields. Because of the very large number of wells involved, optimization is carried out on well patterns, well spacing in patterns, order of drilling different zones, etc. Earlier developed technology for the optimization of well placement, drilling schedule, well trajectories, and injection strategy has been extended for the optimization of field development schemes involving a very large numbers of wells.
The powerful optimization procedure is based on a global optimization technique such as the Genetic Algorithm and other mixed integer optimizers. Potential field development schemes that match field development constraints are identified. A global optimizer is then applied to determine the optimum field development scheme relative to pre-defined economic criteria and analysis. A statistical proxy procedure is utilized to reduce the number of optimization iterations and computing time required to solve this difficult optimization problem.
Economic indicators (e.g. net present value, incremental rate of return, capital efficiency, discounted payback, etc.) or oil/gas recovery are maximized subject to field development constraints. The multiple reservoir models representing uncertainties in reservoir geology are handled within the workflow and are represented in predicted results.
The applications of this optimization technology is clearly demonstrated to be a powerful and sufficiently general tool for analysis of most real world field development planning issues. Significant improvements (3–13 %) in oil/gas recovery and net present value are demonstrated in the optimum cases when compared with the best manually achieved reference field development case.
Introduction
One of the critical issues facing an owner, investor or operator of an oil or gas accumulation is the definition of the "optimal" development plan to maximize the expected recovery of hydrocarbons or financial profits from production of their hydrocarbon accumulation.
The choices associated with development are great, including items such as: the well type, horizontal or vertical, wellbore length within any given interval, wellbore trajectory, completion technology, e.g., (cased and perforated, slotted linear, gravel packed), well placement, well spacing, producer to injector ratio, drilling order, production and injection rate limits, pattern type, oil, water and gas production and facility limits, type and amount of artificial lift, etc.
These choices when coupled with the uncertainty in the subsurface characterization such as: structural depth of pay, compartmentalization via faults or stratigraphic discontinuity, variability in the distribution of porosity, permeability, rock type and saturation, etc very quickly lead to a daunting number of potential development designs that require evaluation in order to determining an optimum development plan.
Even with advances in today's reservoir and facility simulation technologies and computer hardware, most investigators when faced with such a large number of complex possibilities adopt a manual or semi-manual method of analysis and selection of the design which they then assert is optimum. Typically tens, rather than hundreds of designs are actually fully simulated and investigated. From these results a final design is selected.