Abstract

This paper concerns a gas condensate reservoir located in the South of Oman. The field is characterized by compositional grading resulting in a CGR range of 500-1700 m3/MMm3. The field is sour containing approximately 3% H2S and 15% CO2. The reservoir is a dolomite stringer floating and encased in the Ara Salt at an average depth of 4000m. Gross thickness is approximately 100m and the average porosity is 11pu, average permeability is 25mD. The initial reservoir pressure is 470 bara and the dew point pressure (depth related) is 20-30 bara below the initial reservoir pressure. The aquifer is anticipated to be weak with high salt content of 280,000 ppm, which is a flow assurance concern for production. First production started in 2013.

The gas-condensate field is part of an integrated gas-oil project with 8 oil and 2 gas fields where some of the oil fields are planned to be developed by miscible gas injection using non-associated gas. Integrated modelling enabled the selection of a development concept that optimizes the UR of the oil and gas Fields, ensures the gas sales commitments, while making maximum use of the existing facilities and thereby maximizing the value of the project.

The subsurface complexity required a full field compositional modelling approach to address:

  • Quantification of uncertainties on field performance

  • Optimization of the field development plan

  • Support the appraisal/development drilling campaign

The Integrated dynamic model results show that the condensate recovery factor is increased from 18% (depletion) to 24% by partial recycling with first injection expected in 2020. The Field will be the first PDO gas field developed under partial gas recycling.

This paper presents a methodology to evaluate/optimize the rich gas condensate reservoir including gas recycling and will also cover modelling challenges of compositional gradient and condensate banking.

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