深水浊积扇成藏地质条件及地震描述技术

传统观点认为负向构造单元深度大于3 500 m的深洼陷只是生油有利区，而对成藏条件不利，但通过近期对济阳坳陷车西地区车66井的钻探，发现在深洼陷的中央深度达4 300 m的深水浊积扇灰岩砾石中仍有较好的储层，试油获得日产上百吨高产工业油气流。对该类扇体进行了地质研究和地震预测：首先通过高分辨率层序地层学研究，划分出了该区沙河街组地层的9个三级层序；利用岩电特性和成像测井分析，确定了该类扇体为深水浊积扇的沉积特征，可划分为内扇、中扇和外扇，其中以中扇的储集条件最为有利；通过扫描电镜观察发现，该区储层物性受次生溶蚀孔隙和微裂缝双重孔隙介质的控制，同时形成了隐蔽输导体系；通过岩心包裹体分析、钻井密度和声波曲线统计分析，确定该区具有两期幕式成藏和异常高压封存箱成藏的特点。进而建立了深水浊积扇体的地震反射特征，利用高分辨率地震处理解释方法，采用古地貌分析、地震属性预测和反演等地震描述技术，预测了扇体的有利发育区。

RESERVOIRING GEOLOGIC CONDITIONS AND SEISMIC DESCRIPTION OF DEEP WATER TURBIDITE FAN

It is generally accepted that a sag over 3500 m deep in a negative structure unit may be only favorable for hydrocarbon generation but unfavorable for hydrocarbon accumulation. However, the well Che 66 recently drilled in Chexi area of Jiyang depression encountered relatively good reservoirs in deep turbidite fan limestone gravel deposited in the central part of the deep sag with a depth of 4300 m, and tested industrial oil flow of around 100 t/d. Geologic research and seismic prediction are performed on this kind of turbidite fan. Nine third order sequences are recognized in the Shahejie Formation in the study area through high resolution sequence stratigraphy research. The sedimentary features of this kind of deep turbidite fan are defined through analyses of their lithologic and electric properties and image log data, and deep turbidite fan can be divided into inner, middle and outer fans, of which the middle fan has the most favorable reservoir conditions. Scanning electronic microscopic observation reveals that the reservoirs are characterized by the control of double porosity system consisting of secondary dissolved pores and micro fissures, and subtle transport systems. Analysis of inclusions in cores and statistical analysis of density log and acoustic log show that this area is featured by two phase episodic pooling and abnormal pressure compartments. The seismic reflectance signatures of deep turbidite fan are defined, and the favorable zones of turbidite fan development are predicted by using high resolution seismic processing methods, palaeogeomorphology analysis methods, seismic attribute prediction and inversion methods.