--> --> New Plays and New Reservoirs - Reviving Untapped Potential in the Northern Malay Basin, Southern Gulf of Thailand

2018 AAPG International Conference and Exhibition

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New Plays and New Reservoirs - Reviving Untapped Potential in the Northern Malay Basin, Southern Gulf of Thailand


Recent appraisal drilling in Block A-18, Northern Malay Basin, has revived interest in hitherto untapped resources within the Malaysia-Thailand Joint Development Area. Block A-18 encompasses several prolific, but mature gas fields situated in the center of the basin that first came on-stream in 2005. Hydrocarbons were also known from the undeveloped western flank of the basin, but were originally considered to be sub-economic. To ascertain future potential of the block, the area was re-assessed, and an appraisal drilling campaign conducted across the three main western fields, A, B and C. The western flank resources were originally discovered in Oligocene to Miocene sandstones by exploratory drilling in the 1990s. Following 3D seismic acquisition and subsequent assessment, these resources were considered sub-economic. However, recent re-evaluation, using fresh techniques and reprocessed 3D seismic data, indicated resources were potentially larger than originally thought. Remapping of the bounding faults to Fields A and B increased the areas of closure for both fields, while additional up-dip potential had been identified in Field C. An appraisal program was therefore drawn up to test the potential of these three fields. Post-drill evaluation of Fields A and B confirmed the increased resource estimates, with gas – and some oil – encountered in stacked fluvial sandstones down to around 10,000 ft subsea. Conventional core and wireline pressure data shows permeability is generally higher than in the central part of the basin, and is frequently well preserved at depth. Furthermore, reprocessed seismic provides evidence of both stratigraphic and structural trapping, and several clearly imaged, but as-yet undrilled stratigraphic traps provide additional upside potential. Unfortunately, appraisal drilling results from Field C failed to find the hypothesized up-dip resource. However, the field remains of interest and will be further assessed. The recent appraisal drilling campaign has increased resource estimates for Block A-18, and has reduced geological uncertainty. This has led to revived interest in the area, and could pave the way towards a future economic development.