鲁西豫东地区奥陶纪岩相古地理特征及其演化*

鲁西豫东地区奥陶系碳酸盐岩地层是重要的石油和地下热水储集层。受限于基础地质资料,前人对鲁西豫东地区奥陶系层序划分存在争议,缺少对岩相古地理演化的精细刻画。为明确奥陶系层序地层特征与各期岩相古地理演化特征,通过对鲁西豫东地区周缘野外地质剖面考察、19口井岩心观察以及测井曲线特征分析,在层序地层格架内,对奥陶纪岩相古地理展布及其演化特征进行了研究。结果表明,根据层序界面类型和最大海泛面发育位置,研究区奥陶系可划分为SSQ1-SSQ2共2个二级层序和SQ1-SQ4共4个三级层序; 沉积相类型为海相碳酸盐岩台地,包括局限台地、开阔台地和蒸发台地3种亚相,并进一步细分为灰坪、颗粒滩、泥灰坪、灰-云坪、云坪、潟湖、含膏云坪和膏云坪8种沉积微相; 岩相古地理单元整体表现出陆表海的沉积建造特征,各期旋回性沉积为储集层叠置发育奠定了物质基础,云坪、膏云坪、含膏云坪、颗粒滩微相易于形成有利储集空间,是区域地热资源勘探开发的重点领域。

Lithofacies palaeogeographic characteristics and evolution of the Ordovician in western Shandong-eastern Henan area

The Ordovician carbonate strata in western Shandong-eastern Henan represent important oil and hot water reservoirs. Limited by the basic geological data,there is controversy over sequence classification of Ordovician carbonate in western Shandong-eastern Henan,the lack of detailed investigation of sedimentary facies and lithofacies palaeogeography. Through the field geological profile investigation of the perimeter of the study area,the core observation of 19 wells in the study area and the analysis of the shape of the logging curve,the lithofacies palaeogeography of Ordovician and its evolution characteristics in the study area were reconstructed,in order to clarify the characteristics of sequence stratigraphy and lithofacies palaeogeography feature in each period of the Ordovician in the study area. Results from the current study suggest that according to the sequence boundaries and the output position of the maximum flooding surface,the Ordovician sedimentary strata were divided into two second-order sequences of SSQ1-SSQ2 and four third-order sequences of SQ1-SQ4. The Ordovician carbonate strata of study area were formed in the marine carbonate platform sedimentary environments,including three subfacies,including restricted platform,open platform and evaporate platform. They were further subdivided into eight sedimentary microfacies,including carbonate flat,grain beach,muddy carbonate flat,carbonate-dolomite flat,dolomite flat,lagoon,gypsum-dolomite flat and gypsum-bearing dolomite flat. The lithofacies palaeogeographic units of SQ1-SQ4 show the sedimentary construction characteristics of land surface seas as a whole,and seawater mainly inflows from the northeast. Dolomite flat,gypsum-dolomite flat,gypsum-bearing dolomite flat,and grain beach microfacies are favorable for the formation of reservoir space,which are the focused areas of regional hydrocarbon and hot water exploration and development.