No abstract

Block B is located in northwest of Oman basin and its target formation is thin Early Cretaceous Shuaiba limestone reservoir with high porosity and low permeability. The reservoir is confined by faults towards northeast and southwest and trapped by lithology towards northwest and southeast. It was brought on stream in 1990 with vertical producers and the development situation was deteriorated heavily for years of natural depletion.Based on the detail geological and reservoir engineering study, the line driving horizontal producer/injector patterns along the striking of the faults were optimized and implemented in the full block. During the early stage of water injection, the ratio of injection/production was about 3 to restore the formation pressure as soon as possible and made the free gas dissolve back into the oil. When the formation pressure was resumed to about bubble point pressure, the ratio of injection/production was reduced for balance. Close monitoring of production performance and streamline study were carried out to guide the magnitude of production and injection and keep the waterflooding front advancing evenly to increase the sweep efficiency. As of Dec., 2010, great success was achieved as the oil rate was increased from less than 2,000b/d at the depletion stage to 10,000b/d and the recovery factor was about 30%.

Reservoir characterization is the most important in building robust geological and simulation models. The improvement in reservoir characterization enhances the understanding of the reservoir heterogeneity and reduces the uncertainties on field development. This can be achieved with better descriptions of reservoir frameworks and properties. D oilfield is located in northwest of Oman and it has been rejuvenated by water injection since 2001 using horizontal well line driving pattern. In this paper, comprehensive reservoir characterizations of thin Early Cretaceous Upper Shuaiba limestone reservoir of this oilfield were carried out based on the current data for guiding the further adjustment plan and achieving better development results. Horizontal well correlation modes were defined based on the reservoir boundary encountered by the horizontal trajectory to construct the reservoir framework. The interpretation and identification of small faults and fractures were identified based on seismic data, FMI logging, core data and production data. Under the guidance of depositional model, data from horizontal wells has been fully used in combination of pseudo-wells to build the 3D geological model to accurately delineate small faults, reservoir boundaries and property distributions. Based on fracture parameters derived from static and dynamic data, fracture network model and equivalent permeability model have been built constrained by fracture density. The intelligent reservoir characterization provides a reliable geological guidance to ensure the reasonable placements of infill horizontal well trajectories through the reservoir. The real horizontal drilling indicates that the oil reservoir accounts for 90% of the total horizontal section for D oilfield.

No abstract