四川盆地东南部震旦系灯影组四段台缘带天然气勘探前景

doi:10.19657/j.geoscience.1000-8527.2022.194

摘要/Abstract

摘要：

四川盆地绵阳-长宁拉张槽两侧震旦系灯影组台缘带是重要的天然气勘探领域,自川中古隆起核部拉张槽东侧灯影组台缘带发现安岳气田以来,处于古隆起南、北两侧深层-超深层斜坡和深洼陷区的灯影组台缘带日益受到关注,但对其发育特征尤其川中古隆起南侧灯影组四段台缘带的发育特征和油气成藏条件等缺乏清晰的认识。基于此,充分利用最新地震和钻井等资料,选择四川盆地东南部绵阳-长宁拉张槽东侧灯影组四段台缘带进行了重点研究。结果表明,该区灯影组四段台缘带平面展布方向自南向北从北东向转为北北西向,剖面上与川中古隆起及其北斜坡至深洼区的陡坡型台缘带差异显著,以缓坡型台缘带为特征;该区油气成藏条件优越,发育陡山沱组、灯三段和筇竹寺组3套烃源岩,储层品质良好,发育系列由台缘丘滩体构成的岩性圈闭,空间上存在“下生上储、旁生侧储和上生下储”等多种源储配置样式,具有近源优储的显著特点,且保存条件好,勘探前景好。

关键词: 缓坡型台缘带, 勘探前景, 灯影组四段, 震旦系, 四川盆地东南部

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

中图分类号:

TE122

孙自明, 卞昌蓉, 张荣强, 孙炜, 武重阳, 林娟华. 四川盆地东南部震旦系灯影组四段台缘带天然气勘探前景[J]. 现代地质, 2022, 36(04): 979-987.

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.

图/表 6

图1 四川盆地震旦系灯影组四段台缘带、川中古隆起、研究区位置(a)及地层柱状图(b) 1.盆地边界;2.古隆起界线;3.灯影组四段台缘带;4.绵阳-长宁拉张槽;5.灯影组四段局限台地;6.安岳气田;7.地震剖面位置;8.砂岩;9.粉砂岩;10.泥质粉砂岩;11.泥页岩;12.白云岩;13.泥质白云岩;14.生屑白云岩;15.砂屑白云岩;16.灰岩;17.膏盐岩

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)

图2 灯影组三段底拉平地震剖面,示灯影组四段拉张槽东侧陡坡型台缘带北段和中段(剖面位置见图1(a)

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))

图3 灯影组底面拉平地震解释剖面,示灯影组四段东侧台缘带南段特征(剖面位置见图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))

图4 灯影组底面拉平地震解释剖面(a)和波阻抗反演剖面(b)(剖面位置见图1中的E—E')

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)

图5 四川盆地东南部灯影组四段台缘带与筇竹寺组烃源岩厚度(a)和生烃强度(b)叠合图

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

图6 四川盆地东南部灯影组四段台缘带成藏模式图

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

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