Robust Workflow to Assess and Optimize Condensates Recovery from Rich Gas Reservoirs: A Case Study from Abu Dhabi, UAE

ABSTRACT Optimal recovery from a rich gas condensate reservoir is always a big question for an E&P operator, wherein the correct choice between prioritizing condensate recovery or gas exports must be made at the right time. This paper discusses a detailed technical evaluation workflow which highlights all the steps required to be executed to make an informed decision towards implementing an optimized reservoir management scheme, through a case study from onshore Abu Dhabi, UAE. The workflow starts with an in-depth evaluation of available data followed by an exhaustive well screening and candidate selection for extracting sectors from an existing subsurface model. The sector selection process honors the variation of rock properties, wells' performance, expected condensates dropout volumes etc. The next task is to enhance the existing sector models to accurately model condensate drop out and blockage phenomena. The impact of Non-Darcy flow and velocity dependent relative permeability on wells' performance is captured and modeled appropriately. Assessment of the impact of CO2/N2/Chemical injection along with injection volumes & rates on sectoral performance, is made. The detailed workflow has been used to identify and investigate several reservoir management strategies viz. drilling infill producers, MRC peripheral injector wells, non-HC gas injection, chemical injection etc. Furthermore, the optimized time for blowdown has been identified, precisely balancing the prioritization of condensates recovery along with gas sales. It has been identified that after ~50 years of production under partial lean gas recycle mode, ~ 27% of the initial condensate in place has already dropped out as liquid in the reservoir, which would increase to ~34% in the next 60 years if the planned reservoir management scheme is not modified. Appropriate non-HC gas (CO2 /N2) injection schemes along with carefully planned peripheral MRC gas injectors and infill wells, could potentially mitigate the risk of losing precious condensate in the reservoir and increase recovery to 75-80%. A carefully planned chemical injection scheme could also reduce the risk of near wellbore condensate blockage. The proposed development schemes need to go through further evaluation of risk assessment, project economics and piloting phases to substantiate the recovery numbers.