An Assessment of Natural Fracturing in the Thamama Formation by Reservoir Surveillance

Abstract

The presence of natural fracturing in the Thamama Reservoir was postulated following its discovery in 1958. The performance of this reservoir was poorly understood being based on information gathered from a small number of well tests executed during the 1960’s and 70’s. An up to date assessment of this reservoir was sought utilising the latest reservoir monitoring technology. The objective was to confirm the existence, magnitude and orientation of any fracturing in the Thamama reservoir. A further objective was to evaluate their distribution within the zones of the Thamama reservoir. The surveillance programme included multi-well interference testing, pressure build-up testing, production logging and water saturation monitoring. It was concluded from this study that there were many small vertical fractures, predominantly located in the dense limestone intervals, which gave rise to a strongly anisotropic reservoir transmissibility.

Integrated Study of a Faulted and Fractured Reservoir

“…where Ka= fracture permeability in md S= fracture spacing in m A= aperture in I-1m (2) This equation enables the fracture permeability to be calculated throughout the field if S and A are known. An empirical constant, C, was introduced in order to obtain a close match with field data.…”