天然气勘探与开发2025，Vol.48Issue(4)：15-26,12.DOI:10.12055/gaskk.issn.1673-3177.2025.04.002
川西—川中地区侏罗系沙溪庙组一段浅水三角洲沉积特征及油气勘探意义
Sedimentary characteristics and hydrocarbon exploration significance of shallow-water delta in the first member of Jurassic Shaximiao Formation,western-central Sichuan Basin
摘要
Abstract
To clarify the sedimentary characteristics and hydrocarbon exploration significance of shallow-water delta in the first member of Middle Jurassic Shaximiao Formation(hereinafter referred to as Sha-1 Member)in the western-central Sichuan Basin,the sedimentary setting,sedimentary microfacies types,sand-body distribution patterns,and geophysical response features of Sha-1 Member were analyzed systematically,and a sedimentary model was established,using the core,logging and contiguous 3D seismic data.Research results are shown as follows:(i)During the sedimentation period of Sha-1 Member,the paleotopography was gentle,with shallow water body that rose and fell frequently,a large shallow-water delta was developed under the alternating humid-arid climates,contributing the subaqueous distributary channel sand bodies with the cumulative thicknesses ranging 15-40 m,the widths of 300-8 000 m,and the maximum extension up to 200 km.(ii)The subaqueous distributary channel sand bodies are distributed in a reticulate pattern,enclosed within interdistributary bay mudstones,possibly forming large-scale lithologic traps,and accounting for more than 50%of the front sedimentary area.In contrast,the reverse-graded river mouth bars are sporadically developed and small in scale(with individual layer thickness not exceeding 6 m).(iii)The seismic responses reveal the bright spot of"trough at the top and peak at the bottom"with medium to strong amplitude.Strong amplitude continuous reflection is observed along the channel,while the amplitude weakens to both sides of the channel in the transverse direction.High-resolution 3D seismic data are crucial for the fine characterization of sand bodies.(iv)The shallow-water delta front sand bodies of Sha-1 Member show good physical properties(with the porosity of 7%-13%,and the permeability of 0.01-1.00 mD),and form an efficient source-reservoir assemblage with the underlying source rocks of the Upper Triassic Xujiahe Formation,supporting the discovery of large-scale gas reservoirs such as the Tianfu Gasfield in the central Sichuan Basin(with proven reserves of 1 500×10⁸ m³).In conclusion,the shallow-water delta is the main contributor to the current increase in continental tight gas reserves in the Sichuan Basin;besides,its sedimentary model featuring wide channel,thick sand body and optimal configuration provides a reusable geological model and technical paradigm for hydrocarbon exploration of similar reservoirs in the Xujiahe Formation and the Middle Jurassic Lianggaoshan Formation within the basin.关键词
四川盆地/侏罗系中统沙溪庙组/浅水三角洲/水下分流河道/沉积模式/地震响应/岩性圈闭/致密气Key words
Sichuan Basin/Middle Jurassic Shaximiao Formation/Shallow-water delta/Subaqueous distributary channel/Sedimentary model/Seismic response/Lithologic trap/Tight gas分类
能源科技引用本文复制引用
吴长江,张晓丽,贾敏,杨棵,王自剑,李兰..川西—川中地区侏罗系沙溪庙组一段浅水三角洲沉积特征及油气勘探意义[J].天然气勘探与开发,2025,48(4):15-26,12.基金项目
中国石油西南油气田公司科学研究与技术开发项目"四川盆地中生界陆相含油气系统及气藏分布规律研究"(编号:20230301-08). （编号:20230301-08）
