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Petrography and geochemistry analyzing Dat Yai section can describe paleoproductivity and past-redox condition. Paleoproductivity proxies consisted of AOM, phytoclast, TOC, excess SiO2, Ba/Al, and P/Al as high values through sections which similarly indicate high productivity. High productivity in Beds 3 and 27 showed lower peak TOC which is explained by poorer preservation. Lower productivity of Bed 18 showed a high TOC peak indicating good preservation. Paleoredox condition was evaluated using Ni/Co, U/Th, V/Cr, V/(V+Ni), Ni/V, and (Cu+Mo)/Zn. Values for V/(V+Ni) ranged from 0.67 to 0.85 exceeding the cutoff value of 0.46 for a reducing environment. The average value of V/Cr (2.07) exceeded 2.0 of anoxic. Bed 9 consisted of the highest peak of TOC that does not reflect the excellent preservation resulting from dominantly high paleoproductivity. Bed 21 exhibited lower productivity and lowest TOC which indicated a poverty-reducing effect. AOM and phytoclasts were supplied and kept in the benthic floor by extreme redox. Sediments became black shale which expelled oil and some gas. [ABSTRACT FROM AUTHOR]

In this article, pore characteristics were studied in the exposed fine-grained sediments of the Huai Hin Lat Formation, Sap Phlu Basin in northeastern Thailand. The proxies of a variety of pore types which are important for shale gas reservoir evaluation were presented and classified using field emission scanning electron microscopy. The proxies represent a variety of pore shapes and sizes, dominantly of nano- to micrometer scale, which are dispersed in the rock matrix. The detected pore types can be classified into 10 types, which include organic matter pores, flocculation pores, intergranular pores, pores between crystals, pores at the rim of rigid grains, intercrystalline pores, intraplatelet pores, pores within fossil fragments, pores within a covering of pyrite crystal, and microfracture and microchannel-related pores. Most pores are associated with the organic and inorganic constituents formed by diagenetic alterations and thermal maturity (Ro). However, the microfracture and microchannel-related pores were formed by external forces. Overall, the micropores can contribute to good gas storage in the Huai Hin Lat Formation of the Sap Phlu Basin. The microfracture and microchannel- and other microstructure-related pores are also considered to be good migration pathways for generated hydrocarbon. [ABSTRACT FROM AUTHOR]