A variety of recently developed techniques are available to improve carbonate rock characterization. This paper reviews the application of these techniques on an Eocene carbonate reservoir from the Gulf of Suez.
Spectroscopy data was a main driver of the formation evaluation. It allowed an accurate determination of clay, pyrite and siderite with a good match to core data, while the photoelectric factor could not be used because of high barite content in the mud. Magnesium from spectroscopy indicated small amounts of dolomite were present.
Since rock texture has a strong impact on porosity and permeability in carbonates, texture-sensitive tools must be included in the evaluation. Based on nuclear magnetic resonance (NMR) data, porosity partitioning analysis showed that the porosity is dominated by micro and meso pore sizes. While the default correlations used for NMR in carbonates considerably overestimate permeability, a modified SDR equation was applied to predict permeability more accurately, providing a good match to core data.
Hydrocarbon properties have been found to vary vertically. NMR fluid identification stations were used to characterize the variation, which was validated by the drillstem test (DST) results.
Tar was identified based on the comparison of total porosity and NMR porosity. This is an important parameter as tar can affect the reservoir producibility.
Fracture analysis was performed on a data set of microresistivity image and sonic Stoneley data. The analysis performed on the Oil-Base MicroImager (OBMI) identified the orientation of the fracture system. The Stoneley wave processing determined that the majority of the fractures encountered in the reservoir were healed. This conclusion was supported by the core analysis results.
The work presented in this paper demonstrates how integrating the measurements from various tools and sources provides a good understanding of reservoir producibility in carbonates. The integrated evaluation was validated with core and well test results.