FULL-FIELD RESERVOIR MODELING OF CENTRAL OMAN GAS-CONDENSATE FIELDS

Gas reserves sufficient for a major export scheme have been found in C entral Oman. To support appraisal and development planning of the gas and condensate fields, a dedicated, multidisciplinary study team compr ising both surface and subsurface engineers was assembled. The team fo stered a high level of awareness of cross-disciplinary needs and chall enges, resulting in timely data acquisition and a good fit between the various work activities. A field-development plan was completed in Ma rch 1994. The foundation of the subsurface contributions was a suite o f advanced full-field reservoir models that were used to do the follow ing. 1. Provide production and well requirement forecasts. 2. Quantify the impact of uncertainties on field performance and project costs. 3 . Support the appraisal campaign. 4. Optimize the field-development pl an. 5. Derive recovery actor ranges for reserves estimates. The models were constructed early during the study, initially with general data with large uncertainty ranges and gradually refined with new appraisal data. This ultimately resulted in more than 20 full scenarios, quanti fying and ranking the remaining uncertainty ranges. Geological/petroph ysical uncertainties were quantified by use of newly developed, 3D pro babilistic modeling tools. An efficient computing environment allowed a large number of sensitivities to be run in a timely, cost-effective manner. The models also investigated a key concern in gas-condensate f ields, well impairment caused by near-well condensate precipitation. I ts impact was assessed by use of measured, capillary-number-dependent, relative permeability curves. Well-performance ranges were establishe d on the basis of equation-of-state (EOS) single-well simulations and translated into the volatile-oil full-field models with peudorelative permeability curves for the wells. The models used the sparse availabl e data in an optimal way and, as part of the field-development plan, s ustained confidence in the reserves estimates and the project, which i s currently in the project specification phase.