Field presented here is giant heterogeneous carbonate field consist of multi-stacked reservoirs, located in offshore Abu Dhabi. It consists of a very large rich gas cap with oil rim. Current development plan is oil production from oil rim with peripheral water injection & crestal gas injection. Long Term Development Plan "LTDP" of field consists of co-development of oil rim (through water injection at GOC) and gas cap (through partial gas recycling) to maximize oil, condensate & gas value. Details of LTDP are in Ref. 7. To further maximize condensate value, mid-term plan is complete gas recycling by production of rich gas through gas cap producer located downdip of structure and injection of dry gas through gas injector located in the crest.
To de-risk midterm plan, a gas cap producer pilot has been drilled in one of prolific reservoir. Main objectives of gas producer pilot were to reduce uncertainty of CGR, assess gas well capacity & assess gas offtake impact on oil rim. This paper presents optimization of gas cap development in terms of number of wells, trajectory, location & completion based on learning of gas cap pilot.
Literature data indicate that below dew point pressure, gas condensate reservoirs exhibit growth of a condensate bank around the wellbore, which effectively reduce the relative permeability to gas flow & well capacity. Flow in near wellbore region is also impacted by saturation dependent inertial forces (non-Darcy flow). On the other hand at high capillary number improvement in gas relative permeability counteracts the PI reduction. All this effects have been considered in gas cap development.
In this study using a fit for purpose sector model extracted from full field model, all the three phenomenon's non-Darcy effect, condensate blockage and relative permeability improvement at higher capillary number has been studied for different well trajectories such as vertical well, deviated well and horizontal well. Based on simulation results horizontal well was chosen for piloting to minimize impact of condensate blockage, gas turbulent effect and produce the condensate reservoir more efficiently. Sector model was fine-tuned based on pilot results which were further upscaled in the full field simulation. Based on pilot learning well trajectory, location & completion has been optimized for different flow units which leads to significant cost saving.