Tectonic evolution of the Leshan-Longnüsi paleo-uplift and its control on gas accumulation in the Sinian strata

Organic geochemistry of marine source rocks and pyrobitumen-containing reservoir rocks of the Sichuan Basin and neighbouring areas, SW China

“…The main Paleozoic marine source rocks in the Sichuan Basin include the Lower Sinian Doushantuo Formation (Z1ds, e.g., Xu et al, 2012;Yang et al, 2012;Wei et al, 2013), the third section Cross section AB modified from Xu et al, 2012; Cross section CD modified from Zhao et al, 2011. of the Upper Sinian Dengying Formation (Z2dn3, e.g., Xu et al, 2012;Wei et al, 2013), the Lower Cambrian Jiulongdong Formation (Є1j) and its age-equivalents, i.e., Niutitang Formation (Є1n) and Qiongzhusi Formation (Є1q, e.g., Zhu et al, 2006;Liang et al, 2008Liang et al, , 2009, the Lower Silurian Longmaxi Formation (S1l, e.g., Zhu et al, 2006;Liang et al, 2008Liang et al, , 2009, the Lower Permian Liangshan Formation (P1l, e.g., Liang et al, 2008Liang et al, , 2009 Modified from Ma et al, 2007Ma et al, . 2008Ma et al, , 2009, and the Upper Permian Dalong Formation (P2d, e.g., Wu et al, 2012;Chen et al, 2013a).…”

“…Among them, the Lower Cambrian strata (Є1j, Є1n and Є1q), Lower Silurian Longmaxi Formation (S1l) and Upper Permian Longtan Formation (P2l) are generally considered the three major marine source rocks in the Sichuan Basin, and have been extensively studied (Cai et al, 2006;Zhu et al, 2006;Ma et al, 2008;Liang et al, 2008Liang et al, , 2009. Recently, the Sinian source rocks, especially those within the third section of the Dengying Formation (Z2dn3), have gained attention increasingly due to the finding of gas pools and bitumen-containing reservoir rocks from both the fourth and second sections of the Upper Sinian Dengying Formation (Z2dn4 and Z2dn2, Xu et al, 2012;Wei et al, 2013).…”

“…According to geological conditions as demonstrated in crosssections AB and CD of Figure 1, in central Sichuan, hydrocarbon gases in reservoirs within the fourth section of the Upper Sinian Dengying Formation were derived from Lower Cambrian and Upper Sinian source rocks Xu et al, 2012;Wei et al, 2013). In eastern Sichuan, hydrocarbon gases in the Middle Carboniferous reservoirs were mainly derived from Lower Silurian Longmaxi Formation source rocks, while those in the Upper Permian and Lower Triassic reservoirs were mainly derived from the Upper Permian and Lower Silurian source rocks (Fig.…”

“…Several marine source rocks have been identified from Sinian to Permian in the Sichuan Basin. The major source rocks are within the Upper Sinian, Lower Cambrian, Lower Silurian and Upper Permian strata (e.g., Zhu et al, 2006;Liang et al, 2008Liang et al, , 2009Ma et al, 2010;Zhao et al, 2011;Xu et al, 2012;Wei et al, 2013). All of the marine hydrocarbon gases are very dry, with dryness (C 1 /SC 1e 4 ) ratio values >0.975 and mostly >0.99 due to high maturities of the marine source and reservoir rocks Liu et al, 2013).…”

Formation conditions, accumulation models and exploration direction of large-scale gas fields in Sinian-Cambrian, Sichuan Basin, China

“…A large scale palaeo-uplift developed in Sichuan Basin, namely the Leshan Longnvsi palaeo-uplift, which has been recognized as a large inherited palaeo-uplift by the industry consensus [24]; which has controlled the Sinian-Cambrian basin natural gas gathering and accumulation [25]. Before the Cambrian Longwangmiao Formation deposited, the top surface area of the Sinian in mid-Sichuan was expressed as the "uplift" structural framework, and its core part of the uplift is located in Gaoshiti-Moxi area; before the Ordovician was deposited, the Sinian top surface was still developing to be a palaeo-uplift.…”