沉积模式约束的蚀源区砂砾岩分布预测研究

Prediction of Sand and Conglomerate Distribution in Erosion Source Areas Constrained by Sedimentary Patterns

古潜山油气藏表面普遍发育一套准原地沉积成因的砂砾岩储层,物性好、产能高但展布规律复杂,亟需开展储层分布预测,支持潜山油气藏开发。该文以渤海A油田太古界潜山为例,采用“将今论古”思路,建立蚀源区砂砾岩沉积原型模式。基于微古地貌恢复,充分利用三维地震资料的低频响应特征,实现了古潜山蚀源区砂砾岩储层分布预测,取得以下认识:(1)蚀源区砂砾岩沉积受局部地形地貌控制,在山地区、山间洼地、山间沟谷形成不同沉积组合模式;(2)在印模法基础上,采用层面斜率属性差异放大技术实现了微古地貌精细刻画,基于低频地震数据开展地震属性分析,利用属性分布与微地貌单元的对应关系,进一步判断储层分布预测结果的合理性。A油田研究结果显示,其蚀源区砂砾岩分布符合山地区发育的“山间侵蚀河道-山前冲积扇”组合模式,山间沟谷内砂砾岩呈连续条带状,山峰山脊区砂砾岩发育程度低、呈不连续斑块状分布,山前斜坡地貌单元砂砾岩呈连片分布。

A set of sand and gravel reservoirs with quasi in-situ sedimentary genesis are commonly developed on the surface of ancient buried mountain oil and gas reservoirs,which have good physical properties and high productivity but complex distribution patterns.It is urgent to carry out reservoir distribution prediction to support the development of buried mountain oil and gas reservoirs.This article takes the Archean buried hill in Bohai A oilfield as an example and adopts the approach of“discussing the present and the past”to establish a prototype model of sand and gravel sedimentation in the source area.Based on the restoration of micro ancient landforms and fully utilizing the low-frequency response characteristics of 3D seismic data,the distribution prediction of sand and gravel reservoirs in the ancient buried hill erosion source area has been achieved.The following understanding has been obtained:(1)The sedimentation of sand and gravel in the erosion source area is controlled by local terrain and landforms,forming different sedimentary combination patterns in mountain areas,inter mountain depressions,and inter mountain valleys;(2)On the basis of the impression method,the fine characterization of micro paleogeomorphology is achieved using the technique of amplifying the difference in layer slope attributes.Based on the low-frequency seismic data,seismic attribute analysis is carried out,and the corresponding relationship between attribute distribution and micro geomorphic units is used to further judge the rationality of reservoir distribution prediction results.The research results of Oilfield A show that the distribution of sand and gravel in its erosion source area conforms to the“mountain eroded river front alluvial fan”combination model developed in mountainous areas.The sand and gravel in the mountain valleys are in a continuous strip shape,while the sand and gravel in the peak and ridge areas are poorly developed and distributed in discontinuous patches.The sand and gravel in the geomorphic units of the mountain slope are distributed in continuous patches.