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Fault Framework Construction and Fault Seal Analysis of the Lanta Field, Gulf of Thailand.

Narongsirikul, Sirikarn

Geoscience Masters Degree, 2010

University of Adelaide

Abstract

This study evaluates and risks the sealing potential of N-S striking normal faults in the Lanta Field, Gulf of Thailand. The fault sealing potential is examined using analysis of structures in 3D, the development of seal potential through juxtaposition or shale gouge mechanisms and the risk of seal breach by recent fault reactivation. The first stage of this project involved using seismic data, petrophysical logs and existing studies on the geology, tectonic history and present-day stress to build a robust 3D geological model. The geological model developed herein reveals that fault geometry, sedimentary and fault zone architecture, and burial depth during deformation are key controls on fault seal development and are essential for highlighting uncertainty in seal assessment. In particular, this study reveals that faults in the Lanta Field are likely to have a high seal capacity due to the high potential for the development of a membrane seal by clay smear/shale gouge. The overall low net-to-gross of the field suggests that fault sealing by juxtaposition is also likely to also occur in many regions. Analysis of the risk of fault reactivation in the present-day stress regime indicates that the faults, whilst being favourably oriented for reactivation, are currently unlikely to be active or breached.

All of these factors were used to undertake an integrated quantitative probabilistic analysis of the fault seal potential, which revealed that the target fault in the Lanta Field has a 67% chance of sealing. Key uncertainties in fault seal potential remain due to the complex 3D stratigraphic architecture and capabilities of the software used herein. However, the results indicate that fault seal capacity is a low exploration risk in the Lanta Field and have key implications for platform placement and water-flood design.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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