Natural Gas Exploration Prospect of the Platform Marginal Zone of the Fourth Member of Sinian Dengying Formation in Southeastern Sichuan Basin

doi:10.19657/j.geoscience.1000-8527.2022.194

Abstract

Abstract:

The platform marginal zone of the Sinian Dengying Formation on both sides of Mianyang-Changning extensional trough is an important exploration target for natural gas in Sichuan Basin. Since Anyue natural gas field, located in the platform marginal zone of Dengying Formation on the eastern side of the extensional trough, was discovered at the core of central Sichuan paleo-uplift, more and more attention has been paid to the deep to ultra-deep platform marginal zone of Dengying Formation on the south and north side of the paleo-uplift. However, it is unclear about its distribution, geometrical features and hydrocarbon accumulation conditions of the platform marginal zone of Dengying Formation and exploration potential, especially in southeastern Sichuan Basin. Therefore, the platform marginal zone of the fourth member of Dengying Formation in the southern slope of central Sichuan paleo-uplift and its adjacent depression was systematically studied by using the latest seismic and drilling data in southeastern Sichuan Basin. It was shown that the distribution direction of the platform marginal zone of the fourth member of the Dengying Formation extends from NE to NNW from south to north, and shows the characteristics of gentle slope platform marginal zone, which is significantly different from those in the central Sichuan paleo-uplift and its northern slope to depression. There exist three sets of source rocks developed in the Sinian Doushantuo Formation, the third member of Dengying Formation and the Cambrian Qiongzhusi Formation, which laid the sound resource basis for large and medium-sized oil and gas fields. Reservoir has a good quality. The traps are mainly lithologic traps, developed in large numbers, and have good self-sealing characteristics in the updip direction. There are three kinds of accumulation assemblages of “lower generation and upper reservoir, side generation and side reservoir, and upper generation and lower reservoir”. Two sets of regional cap rocks, Qiongzhusi Formation shale and Middle-Lower Cambrian gypsum rock, provide a good preservation condition for hydrocarbon accumulations. All of the above mentioned indicate that there are good exploration prospect and great potential for natural gas in the platform marginal zone of the fourth member of the Dengying Formation in southeastern Sichuan Basin.

Key words: platform marginal zone with gentle slope, exploration prospect, the fourth member of the Deng-ying Formation, Sinian System, southeastern Sichuan Basin

CLC Number:

TE122

SUN Ziming, BIAN Changrong, ZHANG Rongqiang, SUN Wei, WU Chongyang, LIN Juanhua. Natural Gas Exploration Prospect of the Platform Marginal Zone of the Fourth Member of Sinian Dengying Formation in Southeastern Sichuan Basin[J]. Geoscience, 2022, 36(04): 979-987.

Figures/Tables 6

Fig.1 Platform marginal zone of the fourth member of Sinian Dengying Formation,central Sichuan paleo-uplift and the location of study area in Sichuan Basin (a) and the stratigraphic column (b)

Fig.2 Seismic sections flattened along the bottom of the third member of the Dengying Formation, showing the middle and the north segment of the eastern side of Mianyang-Changning extensional trough of the platform marginal zone of the fourth member of the Dengying Formation in the Sichuan Basin and its relationship to the Cambrian (Section locations are shown in Fig.1(a))

Fig.3 Seismic sections flattened along the bottom of the third member of the Dengying Formation, showing the south segment of the eastern platform marginal zone of the fourth member of the Dengying Formation in the Sichuan Basin(Section locations are shown in Fig. 1(a))

Fig.4 Interpreted E—E' seismic section(a) and impedance inversion section(b), flattened along the bottom of Dengying Formation(Section location is shown in Fig.1)

Fig.5 Maps showing the superposition of the platform marginal zone of the fourth member of Dengying Formation with the thickness(a) and hydrocarbon generation intensity(b) of source rocks of Qiongzhusi Formation in southeastern Sichuan Basin

Fig.6 Accumulation pattern of the fourth member of Sinian Dengying Formation in southeastern Sichuan Basin

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