A Basement Play In Mature Sirikit Oilfield, Phitsanulok Basin

Abstract

Basement play is an interesting remaining potential in Mature Sirikit Oilfield, Phitsanulok Basin, where was proven since 1991 with 1.64 MMSTB of cumulative production gained until 2015 only from Sirikit Main Area. With the variation of basement behaviors, subsurface team has revisited geological setting and petroleum system of basement to strengthen play concept and identify sweet spot. Multidisciplinary team integration then collaborates to target additional production from this unconventional reservoir. To understand geological setting, surrounding exposed rock units of Phitsanulok Basin are observed to be compared and correlated with existing cutting and core data. Tectonic history and basin evolution has been modeled to explain 1) Trap configuration and 2) Lithology. These two factors influence the most the brittleness and fracture generation behavoir. Detailed works of petrography are initiated along with production data review and seismic attribute analysis. Potential area ranking then can be stated and aimed to prove. The strategy of production well deepening to basement is a key process to reduce the uncertainties and risk for encountering basement. Six lithologies are preliminarily identified with the results of the initiated works. The highest ranking areas are located at Central Sirikit High (CSH): alomost 90% of the production gained from this trend, Greater Sirikit East (GSE) and Nong Saeng - Pra Da (NSG-PDA) area. They are underlied with Triassic - Jurassic Rock Units (Lampang Group/Huai Hin Lat Formation - Khorat Group) being the most relatively brittle compared with others. Production data from CSH trend confirm the dual porosites: matrix and fracture, which is aligned well with brittleness of these rock units. Seismic data are investigated on their characteristics, amplitude attributes and edge detecting attributes (coherence and ant tracking) to specify lithological boundaries and possible fractured zone to support well target deepening. Phitsanulok basement revisit is one of the interesting remaining potential that might be significantly rejuvenated in Mature Sirikit Oilfield. Its processes and workplans can be an example to inspire how to set new paradigm of hydrocarbon investigation from inactive play type of mature field. To achieve company' goal, remaining potential in mature field is a key of success of PTTEP sustainability.

AAPG Datapages/Search and Discovery Article #90331©2018 AAPG Asia Pacific Region GTW, Back to the Future – The Past and Future of Oil and Gas Production in the Asia Pacific Region, Bangkok, Thailand, September 26-27, 2018