Abstract
The development of high rich gas condensate carbonate reservoirs remains very challenging for the industry especially when the fluid is near critical conditions Ref (5). In some cases, the presence of high pressure, high H2S and CO2 in these reservoirs adds further to the complexity. In these circumstances, it is very important that detailed field development screening and planning are conducted to identify effective and cost competitive development solutions early in a fields life, preferably before starting commercial production.
A compositional simulation model of the richest gas condensate carbonate reservoir in the south of the Sultanate of Oman has been built to identify and select an optimum development scheme for the field. A representative fluid model based on Equation of State (EOS) is used for predicting the complex and dynamic phase behavior of the reservoir hydrocarbons. The performed simulations confirm that achieving maximum ultimate recovery for both gas and condensate is very challenging in this type of reservoir. The most effective recognized technique for maximizing the condensate recovery is gas recycling for pressure maintenance. A feasibility comparison was performed between no gas injection (depletion production), partial pressure maintenance (10 and 20 years of gas re-injection) and full pressure maintenance (long term gas re-injection). In addition, different sensitivities were considered to come up with an optimum development based on key economic indicators: Net Present Value (NPV); Value Investment Ratio (VIR) and Unit Technical Cost (UTC).
On the basis of the study results, it clearly appears that a gas recycling development is the best option to significantly increase condensate recovery (up to doubling it). However, economical evaluations show that a gas depletion development leads to higher NPV and VIR, mainly due to the early production of gas and the expected high surface facilities Capital Expenditure (CAPEX) associated with gas recycling in this type of high pressure, high souring, and very rich gas condensate carbonate reservoir.
This paper highlights and summarizes the challenges faced during the identification of a cost competitive development in high-pressure, highly sour, very rich gas condensate carbonate reservoirs.
