Revealing New Potentials in Mahakam Mature Fields through Reducing Petrophysical Uncertainty with Innovative Fluid Interpretation Techniques

Abstract

Mahakam Delta in Kutai Basin Indonesia hosts significant oil and gas resources within Miocene deltaic systems. Fluid interpretation in mature fields located in such deltaic area is very challenging due to thin & multi layers of reservoir geometry, wide range of water salinity and water-rise phenomena in highly producing zones. In order to minimize the petrophysical and fluid interpretation uncertainty in Mahakam fields, new innovative techniques have been developed based on e-log and core analysis data. The innovative techniques include AutoFluid resistivity specific cutoff, water saturation gradient to salinity, resistivity – gamma ray cutoff, gas chromatograph dynamic baseline, dual log sliding average analysis, and Swirr core to Sw logs uncertainty analysis. These newly applied techniques have been developed, evaluated and calibrated with down-hole fluid analysis and production data with high success ratio. In its application, these methods are also integrated with conventional techniques such as quick look interpretation, true-wet Resistivity separation, gas volume from simultaneous solution, total gas chromatography, well correlation and production data. The integrated fluid interpretation methodology has successfully revealed some new alternatives of hydrocarbon potential coming from thin bed reservoirs, sand below conventional reservoir cutoff, low resistivity pay zones, hydrocarbon below thin shale break, and radioactive sand reservoirs. Most of those hidden potentials were previously by-passed because of thin layers/beds effects, bioturbation, conductive minerals, thin permeability barrier, or structural shale which make dubious in log response. Among these bypassed potentials, the thin bed reservoirs and low resistivity pay are very common in deltaic system and can be unfortunately overlooked in exploration and development phase. Observations and examinations on cores and outcrops have been the keys in understanding the presence and distribution of alternative hydrocarbon potentials. Some of those alternative potentials have been perforated and giving additional production gain in fighting the production decline in Mahakam mature fields. This paper gives detail of integrated petrophysical and innovative fluid interpretation techniques in reducing reservoir uncertainties and revealing new potentials in Mahakam. These techniques could be implemented in other fields outside Mahakam to find hidden potentials which not identified yet.

AAPG Datapages/Search and Discovery Article #90354 © 2019 AAPG Asia Pacific Technical Symposium, The Art of Hydrocarbon Prediction: Managing Uncertainties, Bogor, (Greater Jakarta), Indonesia, August 7-8, 2019