Bulletin of Earth Sciences of Thailand

Geology and geochemistry of The Nang Ann prospect, Noen Maprang District, Phitsanulok Province, Central Thailand

Tanapoom Khositanont — 2023-12-29

The Nang Ann prospect is situated approximately 35 km northeast of the Chatree gold-silver deposit in central Thailand. It is located in Ban Mung Subdistrict, Noen Maprang District, Phitsanulok Province. The mineralization at this site primarily consists of iron-copper reduced skarn, which is hosted in Late Permian-Early Triassic volcaniclastic rocks belonging to the Chatree volcanic complex. The oldest rock formation in the central part of the prospecting area is Permian limestone. In the northern part, there is a prevalent occurrence of polymictic rhyolitic sandstone and breccia, while the central part mainly contains unmineralized microdiorite. The host volcaniclastic rocks primarily comprise polymictic rhyolitic sandstone and breccia. Additionally, siltstone and quartz-phyric rhyolite intercalate within the sequence of host rocks. These rocks exhibit varying degrees of alteration, particularly in the sections intersected by diamond drill cores. The geochemistry of the intrusives in the area can be classified into two suites: the intermediate to mafic suite and the felsic suite. The intermediate to mafic suite includes andesite/basalt and basaltic andesite/andesite, suggesting a primitive magma source associated with within plate or ocean ridge origin. The felsic suite comprises dacite, trachy-andesite, and rhyodacite/dacite, indicating a magma source related to fractional crystallization in a volcanic arc setting. Both suites are identified as part of the calc-alkaline magma series.

Sweet spot Identification of shale gas from 2D modeling at Sinphuhorm field, onshore Thailand

Kanaporn Kulananpakdee — 2023-12-29

This research aimed to enhance the understanding and assessment of the shale gas potential of the Huai Hin Lat Formation in the Sinphuhorm Field, located in the Khorat Basin, northeastern onshore Thailand. The Huai Hin Lat Formation is recognized as a significant rock source in this region deposited in rifted basin during Triassic. To achieve the research objectives, geological, geophysical, and geochemical characteristic interpretations were integrated using published reports, well data and seismic data. The results of one- and two-dimensional petroleum system models can identify the shale gas sweet spot areas and estimate the potential gas-in-place resources of the Huai Hin Lat Formation. The geological analysis was derived from existing well data, including the final well report, mudlogging data and wireline logging data. These data facilitated a comprehensive understanding of the lithological characteristics and depositional environment in terms of both vertical and lateral dimensions. A composite seismic line was selected for geophysical analysis and two-dimensional (2D) petroleum system modeling. This seismic line was extracted from the crest structure of the Sinphuhorm field, extending from the production wells in the east to the basin center in the western part of the field. Seismic facies analysis was applied to identify lithological variations in the seismic profile. Results from the 2D petroleum system modeling indicated that the Huai Hin Lat Formation in the study area is in the late stage of the dry gas generation window at the present-day temperature model giving a high hydrocarbon transformation ratio. However, despite favorable rock properties suitable for shale gas production through hydraulic fracturing, the Formation exhibited lower potential for unconventional resources due to less promising hydrocarbon generation, poor hydrocarbon qualification, a high degree of maturation, and restricted hydrocarbon migration.

Micro-CT Imaging for Shale Pore Networks from Huai Hin Lat Formation

punnaya lertsrisunthad — 2023-12-29

Shale gas has emerged as a significant energy resource globally due to its abundance, cost-effectiveness, and environmental advantages. Understanding the geological and physical properties of shale formations, particularly porosity, is crucial for optimizing production and recovery rates. This study focuses on investigating the porosity characteristics of mudstone samples from the Sap Phlu Basin and the Na Po Song Basin in Thailand's Huai Hin Lat Formation, a potential shale gas prospect. Micro computed tomography (micro-CT), X-ray fluorescence (XRF), and X-ray diffractometer (XRD) techniques were employed to analyze the porosity and mineral composition of the samples. The results revealed distinct differences in porosity between the two basins, with porosity levels ranging from 0.05% to 0.07% in the Sap Phlu Basin and 0.12% to 0.17% in the Na Po Song Basin. The dominant mineral composition, primarily calcite, contributed to denser matrices and potentially lower porosity. However, the presence of quartz, albite, and dolomite influenced porosity variations within the samples. Fracture porosity, observed particularly in samples cut parallel to the bedding plane, highlighted its beneficial role in enhancing fluid flow within the mudstone formations, indicating its potential significance in shale gas extraction. These findings provide valuable insights into the porosity characteristics, mineral composition, and fracture porosity dynamics in mudstone reservoirs, essential for assessing shale gas reservoir potential and informing production strategies.

Performance Analysis of SegFormer for Fault Prediction

Ekapost Meenak — 2023-12-29

Accurately identifying faults in seismic images is critical to reservoir characterization, structural geological interpretation, and well placement. While traditional methods rely on horizontal discontinuities in seismic reflectivity, they are often plagued by artifacts and require manual correction as post-processing. SegFormer, based on a backbone transformer, has successfully tackled this challenge by utilizing the open-source dataset from the Thebe gas field located in Australia's Carnarvan basin. The experiment involved comparing three primary backbone models, namely, MiT-B1, MiT-B3, and MiT-B5, along with hyperparameter tuning. Tests demonstrate that the lowest cross-entropy loss is MiT-B5 with 98.8% accuracy. In addition, it is noteworthy that SegFormer displays a high degree of accuracy in predicting faults through inference in 3D post-stack seismic migration while producing minimal artifacts, suggesting that the technology has the potential to supplant traditional seismic attributes in fault interpretation processes.

Stratigraphy and depositional environment of Permian clastic rocks in Ko Phi Phi Don, Krabi, Thailand with implications for reservoir quality

Adam Elzner — 2023-12-29

This study is a preliminary sedimentological analysis of the potential reservoir quality of the Kaeng
Krachan Group that crop out on Loh Dalum Beach on Ko Phi Phi Don, Krabi Province, Thailand, encompassing
field observations, stratigraphic interpretations based on field measurements, depositional environment
interpretations, and thin section petrography. The objective is to understand depositional environments and their
impact on reservoir properties. Discrepancies in stratigraphic thickness and sedimentation patterns across various
studies reflect the complexities inherent in this sedimentological analysis, which carry implications for
understanding reservoir quality. The presence of mudstones and shales with dropstones between the sandstone
successions, along with findings of cool water brachiopods linking the rift infill to the separation of the Sibumasu
block from Gondwana in the Early Permian, could indicate a likely distal glaciomarine or deltaic depositional
environment with longshore currents creating the long tabular sandstones. Thin section analyses show the
predominance of very fine to fine-grained quartz arenites with generally low porosity, leading to potentially minimal
permeability. However, fracture presence could enhance fluid migration depending on infill conditions. Further
research will refine these interpretations, providing a more comprehensive understanding of the Kaeng Krachan
Group and its reservoir potential at depth.

Characterization of Transpressional Structure in Moattama Basin, Gulf of Moattama, Myanmar

Wongsakorn Choowala — 2023-12-29

Moattama Basin in the Gulf of Moattama is underlaid by the southern branch of Sagaing Fault, a major active strike-slip fault of Myanmar. According to 3D & 2D seismic reﬂection data, the basin has undergone faulting by the interaction between dextral transtension and gravity-driven deformation. In the basin center, synchronous normal faults and anticlines are formed by the dextral reactivation of an earlier structure with an N-S trend, that anticline is a high potential prospective for hydrocarbons. To assess this potential, structural analysis using 3D seismic data and well data was carried out to determine the evolution and distribution of anticline that related to positive flower structure in the strike-slip fault zone. Understanding the relationships between anticline and positive flower structure is very useful in exploration within the oil and gas industry. Based on all data, anticline structures were interpreted by 3D seismic data. As a result, the three anticlines in the study area were mapped at Top Pliocene. This analysis shows all anticline structures interpreted as the upper part of positive flower structures that are related to dextral transtension and gravity-driven deformation from the Sagaing Fault. This anticline structure is very good trapped for hydrocarbon and flower structure movement can provide migration pathways for hydrocarbon.