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From seismic to simulator through geostatistical modelling and inversion: Makarem gas accumulation, Sultanate of Oman
- Source: First Break, Volume 20, Issue 2, Feb 2002,
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- 01 Feb 2002
Abstract
G. Shanor, M. Rawanchaikul & M. Sams from Jason Geosystems Middle East and R. Muggli, G. Tiley & J. Ghulam from Petroleum Development Oman discuss how reservoir characterization results achieved with an integrated team effort led to a significant increase in reserves of the Makarem Field, Sultanate of Oman. This paper presents an applied workflow and the results of an integrated team effort to define the commercially recoverable reserves associated with the Buah fractured carbonate reservoir of the Makarem sour-gas accumulation in the Sultanate of Oman. The status at the start of the study was that three wells had been drilled into the field, a discovery well Makarem-1 and two exploratory-appraisal wells Makarem-2/-3. Tests of Makarem-1/-3 showed good flow rates, but the Makarem-2 test indicated very tight formation with no flow. The estimated Gas-Initially In-Place (GIIP) volumes based on the assumption of mainly fracture porosity were insufficient to justify field development. The main goal of the study was to determine the potential for significant matrix flow which would be critical to the commerciality of the field. In this paper we focus on the method applied to develop multiple 3D static model realizations from the available, seismic, well log, geological and engineering information and the use of these models in the assessment of development scenarios. With multiple models available, uncertainty of reservoir parameters determined from static models may be quantified. Further, the P50 model (in terms of volumetrics) was taken into a flow simulator for dynamic modelling to evaluate the potential for matrix flow. The modelling study confirmed a high likelihood of a sufficient matrix porosity contribution to flow. As a result, Makarem-3 was re-tested specifically to address the fracture/matrix flow transition. The test was successful and proved a significant contribution of the matrix to flow, providing support for the reliability of the models. The reserves proved-up by this exercise form part of the long-term development planning for gas supply in the Sultanate.