JANTZEN, RONALD E., SVEIN OLA SYRSTAD, IAN STOCKDEN, and MICHAEL TAYLOR, Exlog, Inc., Houston, TX

ABSTRACT: Answering Geological Questions from Slimhole Coring Exploration

Slimhole exploration wells have been proposed as a cost-efficient method of exploring inaccessible and remote areas. Such areas often have limited geological control, and the use of wireline-retrieved, continuous coring methods adapted from the solid minerals industry can greatly improve the geological knowledge

of a prospect or basin. However, there are geological concerns which may hinder the spread of slimhole exploration.

The availability of core from long continuous sections of the well requires a rethink of geological knowledge acquisition at the wellsite. Market analysis among explorationists confirmed the critical answers required from the core before it leaves the wellsite. These include the presence or absence of hydrocarbons, reservoirs, seals, source rock and maturity, lithologies and depositional environments. To provide answers, a conceptual core screening operation was developed around key variables which answer these geological questions. Throughput analyses, followed by time and motion studies were performed to ensure wellsite suitability.

A series of analysis systems have been built and assembled into a fit-for-purpose, heli-transportable wellsite core logging facility which has successfully completed a four well field trial in Africa. The purpose of this facility is to digitally preserve these key variables from the core, through the use of a fully integrated data set, encompassing mud, core and wireline logs, together with high-resolution digital images of the core. Data transmission from the wellsite to the project explorationists will ensure rapid answers from a cost-effective novel exploration method.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.