JANTZEN, RONALD E., BP Research, Sunbury-on-Thames, England; SVEIN OLA SYRSTAD, STATOIL Research, Trondheim, Norway; IAN STOCKDEN, BP Research, Sunbury-on-Thames, England; MICHAEL R. TAYLOR, EXLOG Inc., Houston, TX; and MICHAEL R. SAUNDERS, EXLOG (Services), Windsor, England

ABSTRACT: Answering Geological Questions from Slim-Hole Coring Exploration

Slim-hole exploration wells have been proposed as a cost-effective method of exploring inaccessible and remote areas. These areas often have limited geological control, and the use of wireline-retrieved, continuous coring methods adapted from the mining industry can greatly improve the geological knowledge of a prospect or basin.

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

performed to ensure well-site suitability.

A series of analysis systems have been built and assembled into a fit-for-purpose, heli-transportable well-site core logging facility, which successfully completed a four-well field trial in Africa during 1992. The purpose of the facility is to digitally preserve the key variables from the core. Core measurements made include natural gamma ray, density/porosity, caliper, permeability, total organic carbon, and Rock-Eval pyrolysis, together with high-resolution white light and U.V. digital images. A geological workstation allows for speedy, geologically-correct descriptions, preserving all geological data in digital form. Through the use of a fully integrated data set, encompassing mud, geological, core, and wireline logs, the key variables are combined and plotted to provide near-real time composite logs for the geologist and petrophysicist. Data transmission from the well site to the project explorationists ensure rapid answers from a cost-effective, novel exploration method.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.