Revealing the Uncertainty of Heterogeneities in Fractured Basement: A Case Study from the South Malay Basin Offshore Peninsular, Malaysia

Abstract

Fractured basement reservoirs represent more than 20% of the world's oil and gas reserves. Because of their heterogeneity and complex, unconventional natures, the process of mapping the reservoir properties presents a monumental task. The identification of the high productivity zones in basement reservoirs presents a major challenge because of the drastic vertical and temporal variation in porosity and permeability.Reservoir characterization in terms of rock-forming minerals, multipore system analyses, hydrocarbon typing and quantification, and textural variations can be performed by combining quad-combo, elemental spectroscopy, and resistivity-imaging measurements, regardless of the conveyance technique, in an integrated workflow.Because fractures play a major role in hydrocarbon production, rapid reservoir decline, and undesirable fluids breakthrough, fracture description is crucial. Aside from conventional techniques to quantify matrix porosity and permeability, a workflow has been designed to provide additional unconventional techniques for multipore system analyses using high-resolution resistivity imaging. With one technique, the resistivity image is sculptured using an object-oriented filter that produces fracture density, aperture, and porosity. The other technique is based on a transformation of image conductivity to porosity that is classified into a matrix and secondary pores to estimate their contribution to permeability.The multipore system analysis is then used to determine the cementation exponent parameter needed for hydrocarbon quantification. Finally, critically stressed fractures are identified, using geomechanical analyses, to determine the production-contributing fractured zones.Although the technique/workflow used is relatively new and uncommon for data acquired while drilling, its results successfully met the objectives of the study with quality deliverables.This paper presents a basement reservoir characterization study with a discussion of the technologies used in the workflow, study results, conclusions, and recommendations for future work. Data used in this work were obtained from a well in Malacca, Malaysia.