金坛储气库阜宁组四段含盐层系沉积特征及成盐模式

Sedimentary Characteristics and Salt-Forming Model of Salt-Bearing Sequence of Member 4 of Funing Formation in Jintan Gas Storage

为了解决金坛储气库的安全平稳运行及下一步开发建设等问题,在综合利用岩心、薄片、测井、地震以及分析化验等资料的基础上,对该区含盐层系沉积特征、控制因素及沉积模式进行了研究.结果表明:阜宁组四段含盐层系发育石盐岩、硫酸盐岩、碳酸盐岩、泥岩、粉砂岩5种岩石类型,具有6种层理构造和2种化学成因构造;沉积时气候干旱炎热,盐度较高.研究区含盐层系在测井上表现为箱形、钟形、齿形、漏斗形及平直形5种形态,地震上表现为平行状、杂乱丘状、舌形孤立状3种反射特征;含盐层系属于盐湖沉积,可识别出中心膏盐岩、过渡带碳酸盐岩、边缘带砂泥岩3种亚相及7种微相,含盐层系在不同层序内部沉积特征和分布规律各异,沉积中期高位体系域盐岩厚度最大;古地貌控制含盐层系沉积微相类型和分布特征,水体开放程度控制沉积序列演化和岩性组合,湖平面变化控制含盐层系岩石类型和发育规律.研究区存在局限型和广覆型两种成盐模式,湖盆中心的低洼区域为下一步开发建设的有利区域.

For the safe and continuous operation,further development and construction of Jintan gas storage,based on the observations of core and thin sections,the analysis of well logging and seismic and testing data,the sedimentary facies characteristics,development characteristics,controlling factors and sedimentary pattern of salt-bearing sequence in the study area were studied.The results showed that the salt-bearing sequence rocks can be divided into five categories:salt rocks,sulphate rocks,carbonated rocks,and silt rocks,six types of bedding structures,and two types of chemical genesis structures,and their sedimentation was in arid,hot and high salinized water.The salt-bearing sequence has the characteristics of box-shaped,bell-shaped,tooth-shaped,funnel-shaped and flat-shaped on logging curves,and there are three types of seismic reflection characteristics in the seismic profile of the salt-bearing sequences:parallel,irregular hummocky,and lobate isolation.The salt-bearing sequences in the study area are salt lake sediments,which can be divided into three sub-facies,including depocenter of gypsum-halite,transitional zone of carbonatite and edge zone of sand shale,and seven micro-facies are identified.The salt-bearing sequences have different sedimentary characteristics and distribution pattern in each sequence.The highstand system tract is characterized by the biggest salt thickness in the middle stage of depositional progress.The paleogeomorphology controls the type and distribution of the sedimentary microfaces,the openness of water body controls the sedimentary sequence evolution and lithological combination,and the alternation of lake level controls the rock type and distribution law of the salt-bearing sequences.A salt-forming model of localization and superposition is established in the study area,and the low-lying area in the lake-basin center is favorable for further development and construction.