渤海海域蓬莱9-1油田花岗岩潜山储层成因机制及石油地质意义

Reservoir forming mechanism of Penglai 9-1 granite buried-hills and its oil geology significance in Bohai Sea

蓬莱9-1油田作为中国最大的花岗岩潜山油田,储层成因演化复杂,展布范围变化大。利用地球化学、地球物理、实验模拟等手段,结合野外地质观察,深入探讨了蓬莱9-1油田花岗岩潜山储层的成因机制及油气成藏模式。研究表明:蓬莱9-1油田花岗岩潜山为华北板块板内裂解背景下沿断裂主动侵入形成,其侵入时期为侏罗纪160~170 Ma,属于环太平洋构造域的燕山构造幕岩浆活动产物。表生岩溶和构造改造两大主要作用控制了花岗岩储层的形成,燕山期风化剥蚀控制储层宏观发育,新生代构造运动形成的断裂与节理则加速花岗岩内幕储层改造。横向上花岗岩储层厚度展布范围与断裂发育密度呈现正相关性;垂向上可划分为黏土带、砂质带、碎裂带、裂缝带和基岩带,花岗岩潜山中上部的砂质带、碎裂带和裂缝带为有利储层带和主力含油层段。蓬莱9-1油田花岗岩潜山为"似层状"油藏模式,其成功发现丰富了火山岩领域的油气勘探实践,对渤海海域相似地区花岗岩类潜山油气成藏规律研究及勘探具有重要参考价值。

The Penglai 9-1 oilfield is the largest granite buried-hill oilfield in China at present,but the reservoir forming mechanism and its evolution is complex,it causes the reservoir distribution varies in large ranges.Based upon geochemical,geophysical,experimental simulation and other methods,and combined with field geological observation,this paper has discussed the reservoir forming mechanism of Penglai9-1 granite buried-hills and its hydrocarbon accumulation model.The results show that the granite buried-hills intruded along deep faults under North China plate crack background,the intrusion period for the Jurassic 160-170 Ma,and the Middle-Late Mesozoic granite belongs to Circum-Pacific Tectonic Region.In the paper,we propose that reservoir forming are controlled mainly by epigenic karstification and tectonic reconstruction;the weathering and denudation in Jurassic affects the reservoir macroscopic development;the faults and joints formed in Cenozoic strengthen the transformation of granite reservoir.Laterally,there is a positive correlation between the fracture density and granite reservoir thickness;Vertically,the granite rock can be divided into five zones：soil zone,sand weathering zone,broken zone,fracture zone and base-rock zone,The upper-middle parts（sand weathering zone,broken zone,fracture zone）of the granite buried-hill are the high-quality reservoir and the main oil reservoir.Penglai9-1is the near-beded reservoir model,the successful discovery of the oil-field has enriched the oil and gas exploration in the field of volcanic rock,and also have important reference value for other granite buried-hills research and exploration in similar areas.