Publications

Tunu is a mature and giant gas field in Mahakam Delta with enormous multilayer sand-shale series deposited within a deltaic environment. This field has been produced morethan 9847 Bscf of cumulative gas production and 1300 drilled wells. It consists of stacked fluvial-deltaic sand bodies deposited as channel fill or mouth bars between the surface and 5000 mTVDss. The series is divided into Tunu Shallow Zone (SZ) and and Tunu Main Zone (MZ). Since the field going mature and the reserves going marginal, alternative potential should be unlocked from existing reserves portfolio to sustain Mahakam hydrocarbon production safely and efficiently. The transition zone which defined as Intrabeta and SU1 subzone reservoirs are located between SZ & SU2 MZ at the interval of 1800 - 2500 mTVDss. It has distinctive-multi-characteristics of reservoirs from Tunu field perspective: the presence of various driving mechanisms, various reservoir fluids, and less-consolidated sand formation. This transition zone become the latest phase of MZ well perforation portfolio since adequate reservoir management is applied where adaptive bottom-top reservoir perforation is performed. Therefore, delayed production usually occurred during the reservoir management cycle. Apart for producing gas, producing very light oil potential from these zones are challenging considering the limitation of surface equipment to handle the severe emulsion of gas-oil-water-solid phase fluids and the requirement to optimize gas production as the main field objective.
This report presents:1). Subsurface study & information of transition zone reservoirs; 2). Producing reservoirs in transition zone with various reservoir characteristics and its challenges; 3) Portfolio management, reserves mapping, planning strategy and surveillance; 4). Solving the presence of severe emulsion problem by chemical treatment. Implementation of this initiative has been contributed significantly for the last two years of Tunu field oil production in order to support Mahakam oil production. Oil production increased more than 100% above expectation and produced with main gas production.