ABSTRACT: Use of Horizontal Drilling in International Exploration

BAGNALL, ALASTAIR C., Oryx U.K. Energy Company, Uxbridge, England, and J. B. BLANCHE, Independent Geologist, Dunblane, Scotland

Internationally (outside the United States) approximately 200 horizontal wells were drilled in 1991. Horizontal well reservoir targets generally consist of a preponderance of clastic reservoirs over carbonates in the ratio of approximately 65% to 35%.

The concept of using horizontal wells as an exploration tool can be defined as a means not only of proving new reserves in undrilled plays, but as a means of re-exploring previously drilled and poorly productive terrains. The Austin Chalk play in southeast Texas is the prime example of this concept in action. Re-exploration in this case can be defined as the adding of significant additional reserves value, significant in this context meaning multiple orders of additional ultimate recoverable reserves.

International basin selection criteria are discussed that can optimize the chances of proving large value additions in the initial stages of an exploration campaign by using horizontal drilling (often with the important help of slim-hole pilot drilling).

These criteria include the presence of self-sourcing carbonate reservoirs, the presence and predictability of regional fracturing, the presence of significant original oil or gas-in-place, and the reservoir depth criteria in which HD drilling technology is practicable and cost-effective.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)