Management of geologic risk, uncertainty defines accurate horizontal well placement

More than 40% of horizontal wells encounter major unexpected structural geologic/ stratigraphic changes during drilling that result in wells being sidetracked or serious consideration given to this option. As the hole angle increases and measured depth of bed thickness becomes more distorted, correlation between predicted and actual geologies proportionately increases in difficulty. Therefore, real-time correlation must be systematically planned in advance, and must identify key marker beds and decision points. Failure to recognize individual parameters within the reservoir of interest, such as stratigraphy, rock type, reservoir geometry and structure, fluid content, and formation petrophysical properties, can result in costly mistakes. As witnessed during planning and executing horizontal drilling programs in the Hawiyah and Haradh fields of Saudi Arabia, the industry’s ability to drill horizontal and high-angle boreholes has improved with the aid of proper geological planning, execution and evaluation.