扇三角洲高分辨率层序地层分析——辽河油田D区块兴Ⅰ油层组

High-Solution Sequence Stratigraphy in Fan Delta:A Case Study From Xing Ⅰ Oil-Bearing Interval in D Block of Liaohe Oilfield

辽河油田D区块兴Ⅰ油层组稠油油藏储层为扇三角洲沉积,采用蒸汽辅助重力泄油(SAGD)技术,获得了良好的经济效益。但该油田仍面临剩余油分布分散等问题,亟待对其扇三角洲储层内部结构作进一步分析。为此,以高分辨率层序地层学理论为指导,以中期基准面旋回为格架,分析辽河油田D区块兴Ⅰ油层组扇三角洲基准面旋回变化与扇三角洲沉积复合体储层内部结构的关系。研究表明,兴Ⅰ油层组中期旋回层序界面以河道冲刷面为主,可据此将该油层组划分为4期中期基准面旋回,即MSC1、MSC2、MSC3和MSC4中期旋回。自MSC1至MSC4中期旋回,兴Ⅰ油层组扇三角洲沉积复合体呈退积结构,中期旋回的有效可容纳空间逐渐缩小,大量的沉积物转移堆积至向陆一侧。在SAGD开发区中,MSC1中期旋回下部物性较差,而MSC1中期旋回中部物性较好。而在MSC2至MSC4中期旋回时,纵向上高物性段与低物性段或泥岩段交互出现。进行SAGD方式开发时,位于最顶部的MSC4中期旋回砂体内的稠油较难采出,易形成剩余油富集,而MSC1和MSC2中期旋回内的稠油可得到有效动用。

The Xing I oil-bearing interval of Block D is a heavy oil reservoir in Liaohe Oilfield and its facies is mainly fan delta deposits. The steam assisted gravity drainage( SAGD) technology has achieved good economic benefits,but it is needed to analysis the reservoir structure of fan delta reservoir to solve the problem of residual oil distribution. Based on the theory of high resolution sequence stratigraphy,the relationship between fan delta base-level cycles and the internal structure of fan-delta sedimentary complexes of Xing I group in Block D of Liaohe Oilfield is analyzed in the framework of mid-term base-level cycles. The study shows that the sequence interface type of the mid-term base-level cycles is channel scouring surface in Xing I oil-bearing interval. Based on the sequence interfaces,the Xing I oil-bearing interval is divided into four middle-term base-level cycles,including MSC1,MSC2,MSC3 and MSC4. From MSC1 to MSC4,the fan delta sedimentary complexes of Xing I oil-bearing interval is a retro gradation structure. In this process,the effective accommodation space of the middle-term base-level cycle decreases gradually,and a large number of sediments are transferred toward the land. In SAGD development,the reservoir physical property is poor at bottom of the MSC1,while the property is well in the middle of the MSC1. From MSC2 to MSC4,the high reservoir physical property layer and low reservoir physical property layer or mudstone layers appear alternately. During the development by SAGD,the heavy oil located in the MSC4 is hardly produced,and residual oil is enriched relatively in MSC4,while heavy oil in MSC1 and MSC2 could be well produced.