松辽盆地中部扶余油层相对湖平面变化定量研究

A QUANTITATIVE ANALYSIS RESEARCH ON RELATIVE LACUSTRINE LEVEL CHANGES IN THE LOWER CRETACEOUS FUYU RESERVOIR IN THE SONGLIAO BASIN

相对湖平面变化研究,不如相对海平面变化研究那么普遍和深入,一直是层序地层学研究的一个薄弱环节,而其定量研究更是少有涉及。在松辽盆地中央坳陷红岗北地区下白垩统扶余油层(泉四段)研究中,对相对湖平面变化定量研究的方法进行了总结和说明,并成功应用于研究区,取得了以下成果:通过定量的测井小波分析和以定性研究为主的经典地质学分析,将扶余油层(泉四段)定量地划分出1个长期(Ⅲ级)层序、4个中期(Ⅳ级)层序、22个短期(Ⅴ级)层序和69个超短期(Ⅵ级)层序;以69个超短期(Ⅵ级)层序为单元,对其进行了压实校正和Fischer图解的定量分析;Fischer图解分析与对比显示,相对湖平面变化具有级别性,长期(Ⅲ级)旋回级别的相对湖平面,受全球海平面变化影响,经历了湖侵→湖退的变化过程,而中期(Ⅳ级)旋回级别的相对湖平面,受全球海平面变化和湖盆内部因素共同影响,经历了(Ⅳ亚段)湖侵→湖退→(Ⅲ亚段)湖侵→湖退→(Ⅱ亚段)湖平面稳定、来回振荡→(Ⅰ亚段)湖退的变化过程。相对湖平面变化的定量研究依赖于测井数据的提取、应用和高分辨率层序地层的定量研究,有利于层序地层学和沉积学定量研究的发展和提高。

This paper presents a quantitative method to study relative lacustrine level changes,with a case study of the Fuyu reservoir in the 4th member of the late Cretaceous Quantou Formation in the northern Honggang area,central depression,Songliao Basin.The Fuyu reservoir can be divided into 1long-term sequence cycle（LSC1）,4middle-term sequence cycles（MSC1-4）,22short-term sequence cycles（SSC1-22）and 69super short-term sequence cycles（SSSC1-69）,on the basis of quantitative wavelet analysis of logging curves and classical sequence stratigraphic analysis of geologic data.The original sedimentary thickness of the 69super short-term sequence cycles was restored after correction for compaction.These cycles were then Fischer plotts.Analysis of the Fischer plots shows that relative lacustrine level changes were hierarchical.The long-term cycle of relative lacustrine level change was controlled by global sea level changes,and it experienced a lacustrine transgression →lacustrine regression cycle.The middle-term cycles were controlled by both global sea level changes and internal factors within the basin,and consist of lacustrine transgression→lacustrine regression→lacustrine transgression→lacustrine regression→lacustrine level oscillation→lacustrine transgression cycles.Quantitative analysis of relative lacustrine level changes can improve the resolution of stratigraphic correlation and have important implications for exploration geology,sequence stratigraphy,and sedimentology.