Complex Gas Bearing Carbonate Reservoir Evaluation – A Case Study From Saudi Arabia

S. Mahiout¹, E. Clerke¹, A. Belowi¹, K. Qubaisi¹, and A. Qatari¹

Abstract

Most of the Middle East gas reserves are found in carbonate reservoirs. As a result of their origin and post depositional transformation, the pore space is quite complex in structure, pore geometry and pore size aspects. The dominant carbonate minerals are dolomite and calcite, commonly associated with a variable content of anhydrite and episodic presence of minor siliciclastics. The anhydrite content, if improperly accounted for, negatively impacts the well log interpretation and ultimately affects the reservoir production and development plans. Anhydrite nodules, smaller than the tool resolution, can be detected but not quantified nor resolved. Disseminated anhydrite, however, requires spectroscopy logging tool input for volumetric determinations. These gas-bearing complex carbonate reservoirs commonly contain layered, nodular and disseminated anhydrite, the latter as either matrix-replacive or as a pore filling cement.

AAPG Search and Discovery Article #90188 ©GEO-2014, 11th Middle East Geosciences Conference and Exhibition, 10-12 March 2014, Manama, Bahrain