惠州凹陷花岗岩潜山储层条件分析及石油地质意义

Reservoir condition analysis of a buried granite hill in the Huizhou Depression and its petroleum geological significance

南海珠江口盆地惠州凹陷经过近四十年的勘探、开发和生产,已经进入复式勘探阶段,急需开拓新的勘探领域。其中之一的花岗岩古潜山勘探由于一直没有钻遇油藏导致潜力受到学界质疑。为开拓火成岩油气藏勘探领域,优选惠州凹陷A构造作为靶区后成功钻探珠江口盆地第一口花岗岩潜山油藏发现井。对井壁取心、薄片和FMI(地层微电阻率扫描成像)成果进行分析,储层段裂缝有成组缝、网状缝和孤立缝3种类型,存在4个裂缝较为发育的层段;次生溶蚀主要包括沿裂缝溶蚀和溶蚀孔洞。垂向上受差异风化淋滤改造分为黏土带、碎裂-裂缝带和基岩带。储集空间以伴生缝为主,裂缝被方解石充填。应用RCI(储层表征仪)和MDT(模块式电缆储层动态测试器)测试油藏的情况并分析生、储、盖和运移条件,揭示其石油地质意义和领域性突破的科学价值。

After nearly forty years of exploration and production, the Huizhou Depression of the Pearl River Mouth Basin(PRMB) of the South China Sea has entered the stage of duplex exploration.It is urgent to open up new exploration areas. The buried granite hill, which is selected by some scholars as one of the succeeding areas, but questioned by others since no oil reservoir has been encountered so far, is selected in this paper as the research target.In order to open up the new exploration area of igneous reservoirs, therefore, a discovery well was drilled on the structure A of the Huizhou Depression of the PRMB.Specific analysis, such as thin sections and FMI(Formation Micro-Scanner Image)are made for the borehole cores. Three types of fractures are recognized in the reservoir i.e. group fractures, reticulated fractures and isolated fractures, and four segments are divided where fractures are more developed.Secondary dissolution includes those along cracks and dissolution voids. Vertical zonation, which includes the clay zone, fractured zone and bed rock zone, is observed due to differential weathering and leaching. The reservoir space is dominated by associated fractures, which are filled by calcite. RCI(reservoir characterization instrument) and MDT(modular cable reservoir dynamic tester) are adopted to test reservoir conditions, and the conditions for hydrocarbon generation, storage, capping and migration are analyzed individually for evaluation of petroleum geological conditions.