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Bualuang Oilfield, Gulf of Thailand: A Successful Development Using Geosteered Horizontal Wells

Comrie-Smith, Nick; Lawlor, Michael; Virdy, Manjeet Kaur; Khanna, Mohit
Exploration, Salamander Energy, Bangkok, Thailand.

The Bualuang field is located in Block B8/38, in the Western Basin of the Gulf of Thailand, water depth 60 meters. The field is operated by Salamander Energy (Bualuang) Ltd, which holds a 100% interest.

The field was discovered in 1993 by Sun Oil (B7/32-2 well) and subsequently appraised by SOCO in 1997 with two further wells. The discovery was then known as the Pornsiri field. Although the field was initially developed using a high density 2D seismic grid, 3D was acquired in 2010, which has facilitated further development drilling and exploration of surrounding satellite potential.

The development plan for the field was approved by the DMF in 2006 and was fast-tracked in 2007. A single well head platform was installed and production connected via pipeline to an FPSO. Phase I/II of development drilling consisted of five sub-vertical producers and one water injector/disposal well. The wells were completed in June 2008 with gravel packs and electrical submersible pumps. The field came on stream in August 2008 and a month later had reached production of 17,000 bpd.

The Bualuang oil has a gravity of 27°API, viscosity of 8.5 cp and GOR of only 4 scf/stb. The primary T4 reservoir of Middle Miocene age consists of amalgamated fluvial channel sandstone exceeding 50 meters in thickness. Reservoir net-to-gross is in excess of 90%, porosity approaches 30% with permeability averaging 1.8 darcys . The top T4 sand is at 1100 meters subsea and the oil column is a maximum 32 meters in height.

Post Phase II log analysis and routine core analysis in relation to PVT properties indicated that water coning would be a key concern. Indeed the reservoir net-to-gross in the development wells was higher than expected, resulting in an even higher Kv/Kh ratio than initially observed. In response future drilling phases have utilized horizontal drilling technology, combined with geosteering to locate production wells as close as possible to the roof of the reservoir to maximize standoff from the OWC and minimize water coning.

At year-end 2011, 16 development and 2 water disposal wells have been drilled. All produced water is re-injected. EUR stands at 27 MMBO, almost double pre-development figures. Cumulative oil production is 10MMBO. Further appraisal drilling has identified oil in shallower and deeper horizons, and in a separate fault block to the east. A second production platform will be installed in mid-2012, with subsequent drilling of 16 development wells into 2013.

 

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012