准南西段清水河组底部砂砾岩体成因机制及发育模式^*

Genesis and development model of glutenite body at the bottom of Qingshuihe Formation, western section of southern Junggar Basin

摘要

准南清水河组底部砂砾岩段油气勘探获重大突破,但砂砾岩的沉积特征、成因机制和发育控制因素仍不明确,成为制约下一步油气勘探的关键。以准南西段清水河组下段砂砾岩体为研究对象,运用沉积学理论,结合测井、录井、岩心、野外露头及实验分析数据,对砂砾岩体的岩相、岩相组合及沉积展布进行分析,并探讨砂砾岩体沉积发育的主控因素及成因机制。研究表明,准南西段清水河组低位及湖侵域识别出6种岩相及6种岩相组合类型。不同部位砂砾岩成因类型不同,西段南部高泉地区清水河组低位及湖侵域以冲积扇—扇三角洲沉积体系为主,北部卡因迪克地区以辫状河三角洲沉积为主。清水河组沉积期准南西段砂砾岩沉积受源区母岩性质、供源强度及古气候影响,其中,物源区母岩性质及供源强度控制砂砾岩体的沉积类型及规模,古气候影响母岩区风化剥蚀程度及沉积搬运环境。结合控制因素和沉积特征建立准南西段清水河组低位及湖侵域的南部冲积扇—扇三角洲及北部辫状河三角洲前缘的沉积发育模式,可为砂砾岩体的成因判别以及类似盆地的油气勘探提供地质依据。

Abstract

Despite significant breakthroughs in oil and gas exploration in the glutenite section of the Qingshuihe Formation in the southern Junggar Basin,the sedimentary characteristics,genetic mechanism and controlling factors of the glutenite remain unclear,which has become a key restricting factor for hydrocarbon exploration. As such,we investigated the lower Qingshuihe Formation glutenite body in the western section of the southern Junggar Basin based on wireline logs,cores,outcrops and experimental data,with a focus on the lithofacies,lithofacies assemblage and distribution of the glutenite body,as well as their main controlling factors and genetic mechanism. Six types of lithofacies and lithofacies assemblages and genetically different glutenites are identified in the lowstand and transgression systems tracts of the Qingshuihe Formation in the western section of the southern Junggar Basin. The lowstand and transgression systems tracts of the Qingshuihe Formation in the southern Gaoquan area of the western section are dominated by alluvial fan and fan delta depositional systems,and braided river delta depositional system predominates the northern Caindic area. During the depositional period of the Qingshuihe Formation,glutenite sedimentation in the south western section of the Junggar Basin was affected by the nature of the parent rock in the provenance area,sediment supply and paleoclimate. Among them,nature of the parent rock in the provenance area and sediment supply control the sedimentary type and scale of the glutenite body. While paleoclimate affects the weathering and denudation degrees of the parent rock area and the sedimentary transport environment. Based on the controlling factors and sedimentary characteristics,a sedimentary model for the southern alluvial fan-fan delta and the northern braided river delta front of the Qingshuihe Formation lowstand and transgression systems tract in the western section of the southern Junggar Basin has been established,which can provide a geological basis to aid discrimination between different glutenite bodies and hydrocarbon exploration in similar settings.

关键词

准南西段 / 清水河组 / 砂砾岩体 / 成因机制 / 发育模式

Key words

western section of southern Junggar Basin / Qingshuihe Formation / glutenite body / genetic mechanism / development mode

基金资助

*国家自然科学基金面上项目(编号: 42072115)、黑龙江省博士后基金(编号: LBH-Z20045)和新疆维吾尔自治区自然科学基金(编号: 2022D01B141, 2022D01B145)联合资助