三角洲沉积微相特征及其地震识别方法-以委内瑞拉卡拉高莱斯地区为例

东委内瑞拉盆地卡拉高莱斯地区主要目的层为一套海陆过渡环境的三角洲相沉积,三角洲平原河道、三角洲前缘水下分流河道、河口坝及决口扇构成区内主要沉积骨架砂体,各种微相砂体单层厚度薄,分布面积小,在地震剖面上无法直接识别.首先对该地区的主要目的层梅雷库莱组和奥菲西纳组的沉积微相类型及其地质特征进行了分析.针对该地区北部断裂发育、构造破碎以及钻井密度大等特点,采用了测井约束反演方法来预测砂体的分布特征.但该区的声波资料少,为此分析了各种测井曲线对储层响应的敏感性,选择了对薄砂层分辨能力较高的自然伽马曲线进行声波曲线重构.反演结果较好地反映了区内的储层分布特点,对河道砂、决口扇等沉积微相的分布范围进行了预测.部署的I-GV井在梅雷库莱组钻遇河道砂体5.2 m,测试产油82m^2/d.针对该地区中部和南部构造简单、断裂相对不发育且测井数量少等特点,采用地震属性分析方法对三角洲各沉积微相的分布特征进行了预测,边缘特征和调谐振幅特征很好地描述了河道、废弃河道等沉积微相体.经钻井验证,预测结果与实际地质情况吻合率较高.

The characteristics of delta sedimentary microfacies and their diagnosis seismic methods: A case study in the CARACOLES area, Venezuela

The main target zone of the CARACOLES area in eastern Venezuela basin is a series of delta facies sedimentation in ocean-land transitional environment. The predominant sedimentary matrix sand body in the area consists of river channel on the delta plain, underwater distributaries channel of delta front, channel mouth bar and the crevasse-splay. The character of microfacies sand body is thin, small distribution area and cannot be identified directly by the seismic section. According to the responsive of the reservoir on well logs, GR possesses the higher vertical resolution than other logs to the thin sand. The GR is used to imitate the DT to constraint seismic inversion; the results sounds good and the thin sand can be identified in the northern area. This method can be used to predict the microfacies distribution of river channel and the crevasse-splay etc. In the middle and southern area, edge detection technique and spectra interference pattern in frequency can detect the river channel, abandoned channel and other microfacies. The prediction result by methods listed above tally with drill highly.