The prediction of reservoir quality and producibility from petrophysical measurements in carbonates is a well-known challenge. A detailed reservoir characterization requires a suite of petrophysical logs, including imaging, nuclear magnetic resonance, capture spectroscopy for mineralogy, and formation testing logs. These logs are integrated with and often calibrated to measurements made from core analyses. Conventional cores that are cut while drilling are typically time consuming and expensive to acquire; they also require good geological control to pick the required coring depths. Conversely, wireline coring is faster; it provides precise depth control, and core plugs can be selected from a wide range of formations, which would not be practical for conventional coring.

In this paper, we introduce a new wireline rotary sidewall coring tool (RSCT™) device that can be used to selectively drill lateral core plugs from the formation. These core plugs are of sufficient size and quality for conventional and SCAL analyses. Recent improvements in the technology enable better core plug quality by providing digital interactive control of the downhole drilling process, which makes the new tool more reliable and less dependent on the experience of the operator.

This paper reviews experience and examples in which wireline acquired cores were drilled in various carbonate and silica-clastic reservoirs of the Middle East. The cases include carbonates with oomoldic porosity and brittle-fissile shales.

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