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Integration of Sequence Stratigraphy and Elastic Inversion Improved Understanding on Reservoir Characterizations in a Gas Field, Offshore Sabah

Mohamud, Nurhakimah; Mahmud, Othman A.; Razali, Noor Aznida; Handi, M.; Nor, M.; Amin, Mohd Khairil; Mohamed, M. Fairuz
PETRONAS Carigali Sdn. Bhd., Kuala Lumpur City Centre, Malaysia.

Understanding the geological model is important throughout the exploration, appraisal and development phase of hydrocarbon. A good geological model requires integration and manipulation of all available seismic, well logs, geology and engineering data. Such models are best derived in the context of sequence stratigraphic framework. It provides a platform to enable the interpretation of stratigraphic section that considers sedimentology and chronostratigraphy.

A case study in a gas field, Offshore Sabah of which sequence stratigraphy was used to reconstruct the geological model that best explained the recently drilled A-1 well result is presented. Shingled turbidite model deposited in the prograding complex during the Late Miocene Stage IVD is suggested in A field. Well log sequence stratigraphy was also utilized to validate seismic interpretation in building a realistic geological model and accurately tie well log to seismic.

An elastic impedance volume that integrates geological, petrophysical and engineering data was then generated to estimate the elastic impedance (EI) attributes for lithofacies discrimination and predicts the extension of hydrocarbon bearing sand in A field. The gas sands in the field were interpreted to have low EI values in comparison with the surrounding shale and brine sands. The EI volume enables interpretation of free water level in the reservoirs.

The integration of elastic impedance interpretation constrained by sequence stratigraphic derived model suggested better developed reservoirs are present away from A-1 well location. An iterative approach was carried out to establish the facies model and qualitatively interpret the net sand in the field. The interpretation of EI volume also suggested gas sands presence at the adjacent fault block. As a result, this integration enables more accurate resource estimation and quantification of risk and uncertainty in A field.

This paper will outline the pre-drill assumptions, well results and post drill sequence stratigraphy integrated with elastic impedance interpretation approach for reservoir characterizations and estimations in A field, Offshore Sabah.


AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012