All information gathered through drilling and completion of the wildcat and appraisal wells and analysis of data obtained, is used to prepare a Reservoir Development Plan. This plan includes not only spacing of development wells, as affected by surface and subsurface conditions, but also the control procedures determined for manipulating the reservoir fluid pressure changes and flow characteristics over the productive life of the reservoir.
For flowing wells, this involves choke sizes and variations, in order to manipulate the flowing bottomhole pressure of the wells within technical and economic limits. It also involves fluid injection into the reservoir, to manipulate that pressure and therefore control the production of hydrocarbons from the reservoir and encroachment of external fluids such as water and gas into the reservoir.
The onshore development plan will be quite different than the offshore development plan. One of the major decisions in preparing the offshore development plan is selection of offshore platform locations and number of platforms, to optimize production within economic limits from the reservoir in a reasonable lifetime. If an offshore platform is placed in the wrong location, as determined by later drilling, this will result in a major economic loss compared to drilling a single well in the wrong onshore location. The decision, therefore, for offshore development may be far more critical than decisions foe development of an onshore reservoir.
Economics, both at the time of development, and that anticipated over the productive life of the reservoir, place limits on the extent to which the best technology can be applied. For example, an offshore reservoir might be best developed on a 40-acre spacing (16 wells per square mile).
However, the cost of the platforms as related to hydrocarbon prices may justify the drilling of only three wells per mile on an average basis, by directional drilling from centralized platforms. It cannot be anticipated, therefore, that as high a percentage of the original hydrocarbon in place will be recovered during the life of production of the reservoir with three wells per mile as would have been recovered has the best available technology been applied, requiring 16 wells per mile.
