TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSome of the older oil fields in Malaysia can be characterized as mature water floods. Schemes for enhancing and prolonging the already declining production and diminishing reserves strategically call for timely implementation of Enhanced Oil Recovery, EOR applications.Among various Enhanced Oil Recovery (EOR) processes and techniques, Malaysia's reservoirs appear especially amenable to gas injection. Feasibility studies showed that immiscible Water-Alternating-Gas (WAG) injection is potentially the most practical and viable option. Laboratory studies and numerical simulation study conducted on the applicability of immiscible WAG injection using high CO 2 content gas indicated that an additional 5-7% of OOIP can be recovered [1]. Such a gain will result in reserves growth and extended producing life of these reservoirs. WAG application is being field tested by implementing a pilot in a sub-block, South-3 of the Dulang field, which is isolated from other subblocks, by major faults. One in-fill well was drilled specifically for the current pilot. Upon drilling this infill well, several geological complexities were uncovered, that called for a thorough revisit of modelling and pilot conceptual plans. The pilot area contains 6 wells, three of which are being used as producers during WAG operations.This paper discusses detail of our first ever EOR pilot implementation (Immiscible WAG in Dulang oil field). It describes progression from conceptual design to various challenges, results and the lessons learnt during early periods of implementation.