Geologic Input to Enhanced Oil Recovery Project Planning in South Oman

N. L. Watts, D. Ellis, A. P. Heward, G. Maier, G. P. Marks

South Oman clastic reservoirs contain a combined stock-tank oil in place of more than 1.9 billion m³ of predominantly heavy oil distributed in almost 40 fields of varying size. Successful early application of such enhanced oil recovery (EOR) methods as steam flood, polymer drive, and steam soak could realize undiscounted incremental recoveries of 244 million m³ of oil. Target oil is contained in three reservoir intervals with distinct characteristics relevant to EOR. (1) The Cambrian-Ordovician Haima Group is a thick monotonous sequence of continental and coastal sands; major problems are steam-rock reactions, recovery factors, effective kv/kh (ratio of vertical to horizontal permeability), and aquifer strength. (2) The Permian-Carboniferous Al Khlat Formation is a glacial package showing severe heterogeneity, strong permeability anisotropy, and poor predictability. (3) The Permian Gharif Formation is a coastal to fluvial sequence with isolated and multilayer channel sands, smectitic clays, and anomalous primary production performance.

Several EOR pilot projects are either ongoing or in preparation as part of a longer term EOR strategy. Geologic input is important at four essential stages of pilot planning: initial project ranking, optimization of pilot location, definition of pilot size, and predictive/history match simulations. Each stage is illustrated using a specific project example from south Oman to show the diverse geologic and logistic problems of the area. Although geologic aspects are highlighted, EOR project planning in south Oman is multidisciplinary, with integration being aided by a dedicated EOR coordination department.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.