Petroleum exploration in the mature Phitsanulok Basin, Thailand: success and failure analysis, and characterization of source rocks and crude oils

Abstract

Finding new petroleum resources is one of the important tasks to sustain the future of energy consumption. Considerable petroleum resources can be added through exploration in frontier and emerging basins and plays. However, finding petroleum accumulations and proving new exploration concepts in the maturing and mature areas are also essential to prolong the consumption of energy from fossil fuels. The study area for this thesis is located in the Sirikit Oil Field, the Phitsanulok Basin, Northern Thailand. Sirikit Oil Filed has been explored and produced for almost 40 years. During all those times, PTTEP (the national petroleum exploration and production company based in Thailand) has performed several types of activities attempting to prolong the field life. Although there were several exploration campaigns to locate additional resources, especially in the eastern part of the Phitsanulok Basin in the past ten years, the success rate of the exploration wells is quite low. The objective of the thesis was to study the petroleum system and define additional petroleum potential of failure areas using post-mortem analysis and source rocks-crude oils characterization. The success and failure analysis indicates that the most common critical failure mode of the Eastern Flank area is the migration, especially in the most eastern part of the study area. This area might fail because of a great distance away from the kitchen area, limiting lateral hydrocarbon migration to the particular region. Characterization of source rocks and crude oils presents two source rocks facies in the Phitsanulok Basin, including lacustrine and terrestrial facies. These two source facies are located in different areas and charged petroleum into different regions. Lacustrine source facie is dominated by Type I kerogen, situated in the Sukhothai Depression and the south of the Basin. This source rock facie mainly charged hydrocarbon to the southern part of the Basin. On the contrary, terrestrial source facie mainly consists of Type III kerogen type and dominated in the Sukhothai Depression and the eastern part of the basin. Petroleum generated from the latter facie mostly migrated to the Eastern Flank area. Expected source rocks in both discovery and failed exploration areas are in an immature stage of the oil generation window. Therefore, hydrocarbons present in the successful area is migrated from the mature terrestrial facie from the kitchen area or mature local sources nearby. All of the results indicate that potential areas for future exploration activities are located in between proven hydrocarbon migration boundaries and none hydrocarbon show lines, especially in the Pratu Tao and the Lan Krabu plays.