新生代辉绿岩岩体识别及油气地质意义——以中国东北地区方正断陷为例

利用钻井、测井和地震资料,通过地震剖面解释和地震属性分析等手段,对中国东北地区方正断陷新生代辉绿岩岩体进行了系统识别并探讨了其油气地质意义。方正断陷东北部广泛发育新生代辉绿岩岩株和岩床等侵入体,在测井上表现为自然伽马和声波时差值低、电阻率值高等特征;在地震剖面上表现为杂乱反射,岩体边部则以强反射和高振幅异常为特征。这些侵入体空间形态不规则但总体呈NE向延伸,与同时期活动的NE向大断裂近于平行,形成于伸展或张扭构造背景,可能与渐新世中期(约30 Ma)或中新世中期(约13 Ma)两期基性岩浆热事件有关。泥岩镜质体反射率数据显示断陷东北部的热演化存在明显的高值异常,结合构造演化分析,认为是新生代辉绿岩的侵入显著提升了局部的地温场,从而导致烃源岩加速成熟的异常热演化。此外,辉绿岩的侵入可能形成多种相关的油气圈闭,应是今后中国东北地区新生代盆地潜在的油气勘探目标。

Identification and hydrocarbon geological significance of Cenozoic diabase rock: a case study of Fangzheng faulted sag,NE China

Based on drilling, logging and seismic data, as well as seismic profile interpretation, seismic attribute analysis and other means, this study performs a systematical identification of the Cenozoic diabase rock in Fangzheng faulted sag, NE China, and also discusses its hydrocarbon geological significance. Cenozoic diabase rock stocks, sills and other intrusive mass are widely developed in the northeastern Fangzheng faulted sag, characterized by low values of natural gamma and acoustic transit time as well as high value of electrical resistivity in logging. Chaotic reflection occurs on the seismic profile, whereas the boundaries of rock are often featured by strong reflection and high amplitude anomaly. These intrusive mass has irregular spatial shape, but overall extending in a NE direction, and approximately parallel to the sync-activating NE-trending major faults, which is formed under extensional or transtensional tectonic setting. This might be related to the Mid-Oligocene (about 30 Ma) and Mid-Miocene (about 13 Ma) basic-magma thermal events. The vitrinite reflectance (R_o) data of mudstone show that the thermal evolution in the northeastern faulted sag had a significant high-value anomaly. In combination with the analysis of structural evolution, it is suggested that the intrusion of Cenozoic diabase significantly elevated the local geothermal field, which leads to the fact that the maturing of source rocks is accelerated by abnormal thermal evolution In addition, the diabase intrusion can result in multiple related hydrocarbon traps, which may be potential hydrocarbon exploration targets in Cenozoic basins of NE China in the near future.