AAPG Bulletin; November 2007; v. 91; no. 11;
p. 1637-1661; DOI: 10.1306/06280707014
© 2007 American Association of Petroleum Geologists (AAPG)
Degradation of a footwall fault block with hanging-wall fault propagation in a continental-lacustrine setting: How a new structural model impacted field development plans, the Sirikit field, Thailand
Christopher K. Morley1,
Yarick Ionnikoff2,
Nantavan Pinyochon3 and
Krongpol Seusutthiya4
1 PTT Exploration and Production, 555 Vibhavadi-Rangsit Road, Chatuchak, Bangkok 10900, Thailand; chrissmorley{at}gmail.com
2 PTT Exploration and Production Siam Ltd., 10 Soonthornkosa Road, Bangkok 10110, Thailand
3 PTT Exploration and Production Siam Ltd., 10 Soonthornkosa Road, Bangkok 10110, Thailand
4 PTT Exploration and Production Siam Ltd., 10 Soonthornkosa Road, Bangkok 10110, Thailand
Chris graduated from Swansea University in 1980, and received his Ph.D. in 1983. After working for Amoco, Elf Aquitaine, and the University of Brunei Darussalam, he is currently working for PTT Exploration and Production as a senior geophysicist. He has worked as an exploration geologist and structural geologist. Geographic areas of work have included East Africa, Morocco, the Norwegian Caledonides, Carpathians, northwestern Borneo, and Thailand. His research interests have focused on the structure and tectonics of rifts; fold and thrust belt structural styles; the characteristics of transpressional deformation; and the evolution, fault displacement characteristics, and structural geology of mobile shale provinces.
Yarick graduated in geosciences and geotechniques from the University of Paris VI in 1997 and joined Shell Research and Technical Services in 1998 as a structural geologist. Initially working on developing structural modeling solutions, he then moved to the reservoir modeling team to work on the next-generation integrated reservoir modeling environment while at the same time being involved in reservoir modeling projects in the Middle East, Nigeria, and in the North Sea. He joined Thai Shell in 2002 as a production geologist and worked on several primary and secondary development projects in the Sirikit oil fields. He is now working as a principal geologist and team leader for development projects onshore Thailand with PTT Exploration and Production.
Nantavan joined Thai Shell Exploration and Production 20 years ago and held positions in various operation environments, including well services and drilling. For the past 5 years, she has moved to production technology and has joined development study teams aiming at improving recovery in several blocks of the mature Sirikit oil field.
Krongpol joined PTT Exploration and Production in 2002 and has been mostly involved in the exploration and development of joint venture projects as an associate geophysicist. In 2005, he was assigned to join the S1 Asset (the onshore Thailand asset) as a geophysicist and seismic interpreter. In close cooperation with the exploration team, he was responsible for defining the geologic and tectonic setting, structural style, petroleum system-related prospectivity, and well planning. Currently, he is working for PTT Exploration and Production Oman Company Limited on the exploration team. He holds a B.Sc. degree in geology from Chulalongkorn University and an M.Sc. degree in petroleum geosciences from University of Brunei Darussalam.
The Sirikit field is a large field developed in a complex tilted fault block. The relatively simple stratigraphy on the tilted fault block flank becomes difficult to trace onto the tilted fault block crest. A recent reinterpretation of the reprocessed three dimensional seismic reflection data revealed that the difficulties of correlating reservoirs toward the crest are caused by features associated with degradation of the footwall, particularly (1) the prevalence of low-angle detachment faulting and (2) the development of discordant stratigraphic sections resulting from multiple episodes of erosion at the tilted fault block crest, followed by the eastward onlap of the section onto the eroded footwall surface. The main characteristic of this structure is the preservation of the onlapping sections through periodic propagation of the main bounding fault toward the hanging wall, which resulted in the accretion of former hanging-wall rocks to the footwall. This propagation sequence appears to be atypical for most degraded footwalls described in the literature. The degraded footwall model replaced earlier splaying bounding fault models used for development planning. Implementing this new structural model opened up new appraisal opportunities as the compartmentalization and reservoir distribution pictures changed. Appraisal of the reservoir now present above the hydrocarbon-water contacts following the new structural model led to a 15% increase in recoverable hydrocarbon volumes.
Copyright © 2009 by American Association of Petroleum Geologists (AAPG)
