Abstract: Horizontal Well Application for Development of a Thin Oil Column Within Multiple Discontinuous Lower Coastal Plain Sand Units, Lower Miocene Cycle II, Offshore Sarawak, East Malaysia
Boniface Bait, George Canjar, Norazlam Norbi
The Balingian province, offshore Sarawak, holds multiple challenges to economic oil-field development. Discontinuous primary gross geometries of the lower coastal plain objective sand bodies and a strong structural overprint can combine to isolate hydrocarbon accumulations and make drainage planning difficult. The case of north Bayan development from BYDP-C illustrates these difficulties. Initial development by conventional wells encountered irregular sand distribution and thinner oil columns than expected from appraisal well drilling. The latter part of the campaign used dip-oriented horizontal completions of between 2000 and 3000 ft to salvage development of a 45 to 69 ft oil accumulation within the S7 sands.
The benefits of horizontal well trajectory to exploit this reservoir geometry are many. The gently dipping structure, constant fluid contacts, and dip orientation of the well path allowed intersection of multiple sand units while remaining consistently positioned at the optimum location relative to the OWC and GOC. The effect of lateral sand thickness and quality variations is minimized by the relationship of the well bore to the reservoir geometry. Each sand unit is gradually penetrated from the base to the top, maximizing the opportunity for a well-developed genetic unit to be traversed.
Attempts to characterize lateral relationships such as sand continuity and amalgamation using discreet data from exploratory, appraisal, and conventional wells are generally non-unique and poorly predictive. Horizontal wells maximize potential contact with objective reservoirs and production potential amidst rapid sand-body thickness change and local discontinuities.
AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994