测井技术2025，Vol.49Issue(5)：721-733,772,14.DOI:10.16489/j.issn.1004-1338.2025.05.008
准噶尔盆地腹部中1区侏罗系齐古组-三工河组地层界线探讨
Discussion on the Basal Boundary of Qigu Formation-Sangonghe Formation in Zhong1 Area of Junggar Basin Hinterland
摘要
Abstract
To demarcate the basal boundary between the Jurassic Qigu formation-Sangonghe formation in Zhong1 area of Junggar basin,solve the problem of ambiguous boundary and attribution confusion between the two formations caused by intense erosion,and provide geological theoretical support for deep sandstone reservoir prediction and oil-gas exploration in this area,a combined method of logging analysis(strati-graphic dip,natural gamma ray spectrum,acoustic time difference,Δlg R),wavelet transform,rock property analysis(lithology,sporopollen fossils,grain size,compositional maturity),seismic data analysis and astronomical cycle analysis is adopted to conduct a systematic study on the basal boundary of the two formation.And the research results are improved through multi-parameter integration and forward/inversion verification.The research results show that:①The basal boundary is located at the junction of the gray-green sandstone at the bottom of the Qigu formation and the gray mudstone at the top of the Sangonghe formation.The sedimentary environment transitions from the humid reducing deep-water environment of the Sangonghe formation to the arid oxidizing shallow-water high-energy environment of the Qigu formation.At the interface,Δlg R drops sharply(e.g.,5 178 m in well Z8 and 5 028 m in well Z3),the U content decreases from 2.27 μg/g to 1.67 μg/g,the Th content increases from 5.75 μg/g to 8.77 μg/g,Th/U increases from 2.50 to 5.25,and the jumping component of the grain size curve rises from 50%to 90%,all of which jointly confirm the interface characteristics.②Wavelet transform reveals an obvious cycle transition at the boundary(energy cluster changes from high energy to low energy),the sudden change in the slope of the acoustic time difference regression line and the absence of stratigraphic dip vectors clarify the vertical unconformity characteristics.Seismic profiles show strong amplitude continuity of the boundary,and the lateral distribution range of residual sand bodies in the Qigu formation is larger than traditionally recognized.Combined with astronomical cycle analysis(e.g.,dominant cycle thicknesses of 55.55 m and 36.36 m identified in well Z1-1),the vertical and lateral isochronism of the interface is confirmed.③The reservoir of the Qigu formation is dominated by fine sandstone(accounting for 65.37%),with an average porosity of 12.4%and an average permeability of 22.8×10-3 μm2.The physical properties are significantly controlled by sedimentary facies belts,with the best physical properties in the main channel deposits,followed by distributary channels and then channel margins,showing an overall low-porosity and low-permeability characteristic that gradually deteriorates from north to south.④The traditional understanding that the Qigu formation is widely missing in the study area is revised,and it is clarified that the two formations are in angular unconformity contact.The intense uplift of the Che-Mo paleo-uplift in the late Jurassic led to large-scale erosion(erosion area exceeding 2×104 km2),which is the main cause of the missing of the two formations and the ambiguous boundary.It is concluded that the basal boundary demarcation scheme integrating multiple methods effectively solves the problem of boundary identification between the Qigu formation and Sangonghe formation,clarifies the contact relationship and sedimentary-tectonic evolution background of the two formations,and provides a key basis for the prediction of reservoir sweet spots;combined with the fault-sandbody coupled migration system,the stratigraphic-lithologic composite traps around the underwater uplift belt are determined as favorable exploration targets.This result provides a high-resolution stratigraphic framework and theoretical support for Jurassic oil-gas exploration in the hinterland of the Junggar basin.关键词
地质评价/小波变换/地层界线/测井响应/沉积环境/储层预测/准噶尔盆地/侏罗系Key words
geological evaluation/wavelet transform/basal boundary/logging response/sedimentary environment/reservoir prediction/Junggar basin/Jurassic system分类
天文与地球科学引用本文复制引用
李国璞,宋璠,焦国华,张卫平,周晋科,田磊..准噶尔盆地腹部中1区侏罗系齐古组-三工河组地层界线探讨[J].测井技术,2025,49(5):721-733,772,14.基金项目
国家自然科学基金项目"成岩流体演化对致密砂岩气藏储层质量的控制作用研究"(41702158) （41702158）
山东省自然科学基金项目"超浅层成岩圈闭形成机理及对油砂成矿的影响作用研究"(ZR2017QD010) （ZR2017QD010）
