--> Abstract: Horizontal Drilling in South Oman, by A. P. Heward; #91012 (1992).

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ABSTRACT: Horizontal Drilling in South Oman

HEWARD, ALAN P., Petroleum Development Oman, Muscat, Sultanate of Oman

Fourteen medium-radius horizontal wells have been drilled to date in South Oman with encouraging results. Two horizontal "plays" in sandstone reservoirs are being pursued, which aim to reduce bottom-water coning through the typically viscous oils and increase the productivity of moderate-permeability layered reservoirs. Both improve the economics of already attractive development activity.

The reservoirs are Cambrian-Ordovician continental sediments and Permian-Carboniferous glacial deposits. Porosities range from 27 to 30% and permeabilities from 500 to more than 5000 md. The fields are faulted and fractured as a result of the removal of underlying salt, and fractures may enhance bottom-water coning. The reservoir sandstones are only partly consolidated, and most vertical wells require gravel packs to prevent sand production.

In the first play, 400-500 m drainholes are located as far as possible above the oil-water contact. Where reservoir quality is uncertain, wells are inclined subhorizontally over a 5-20 m interval. They are inclined through a greater interval of strata in the second play to increase productivity. Wells are orientated parallel to the trends of faults mapped from 3-D seismic to minimize the number of fractures intersected. FMS logs confirm that wells drilled oblique to the fault pattern encounter more fractures than those that parallel one of the fault sets. The requirement for sand exclusion and the method (predrilled liner, slotted liner, or wire-wrapped screens) appears likely to depend on geological formation and depth. The Tertiary and Mesozoic geology of the top-hole and build-up s ctions are significant to well design and to reducing well costs.

 

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