珠江口盆地惠州凹陷岩性圈闭预测及识别

Prediction and Identification of the Lithologic Trap in Huizhou Sag of Pearl River Mouth Basin

惠州凹陷是目前珠江口盆地勘探程度最高的地区,通过对本区构造演化及层序地层格架下沉积相研究,证实了惠州25鼻状构造带是岩性圈闭发育的有利位置,能够形成岩性上倾尖灭圈闭。本次通过层序地层格架研究,将珠江组晚期-韩江组早期划分为三个三级层序,本区处于凹陷缓坡高位区,主要以海侵体系域和高位体系域为主,未见低位域沉积。该时期主要以三角洲前缘沉积为主,物源来自西北部古珠江三角洲,海侵体系域三角洲退积砂体是本区最有可能形成岩性圈闭的沉积载体,受到大套海相泥岩包裹,自东向西部鼻状构造带上倾方向形成岩性尖灭。在落实岩性圈闭有利位置及有利层段的基础上,综合分析各种属性特征,挑选出与储层岩性变化相关性最强的均方根振幅及波形分类两种敏感属性参数,建立地震属性与沉积微相平面展布的关系,落实砂体上倾尖灭点的位置,同时基于地震分辨率不足造成的实际砂体尖灭点与地震尖灭点的不同,建立正演地质模型,进行模拟,最终落实岩性圈闭。

Huizhou sag is the region with the highest level of exploration in Pearl River Mouth Basin at pre- sent.Through the research of sedimentary facies of the structural evolution and sequence stratigraphic frame- work,Huizhou 25 nose structural belt is proved as the favorable position of the lithologic traps,which is ca- pable of forming lithologic up-dip pinch-out traps.Later Zhujiang formation to early Hanjiang formation is di- vided into three third-order stratigraphic sequences after the research of the sequence stratigraphic framework, which is mainly composed of delta front depositional system whose provenance is the Ancient Pearl River Delta in the northwest.This area is located in the highland of the gentle slope in the Huizhou sag with transgressive system tract and highstand system tract mainly and no lowstand system tract seen.Retrograding delta sand of TST is the depositional body most likely to form lithologic traps in this region ,which is en- veloped by a large set of marine mudstones and forms lithological pinch out in the updip direction of the nose structure belt from east to west.Based on identifying the favorable prospects and layers of the lithologie traps ,we pick out two kinds of sensitive attribute parameters RMS amplitude and waveform classification most related to reservoir lithology changes by means of comprehensive analysis of each attribute characteristic.The relationship between seismic attributes and depositional microfacies distribution is established,and the up-dip pinch-out of the sand layer is identified.At the same time based on the different position between the actual sand pinch-out point and that in the seismic event resulted from low resolution of the seismic data,forward geological model is established for modeling and identifying lithologic traps eventually.