琼东南盆地深水区宝岛——长昌凹陷火山/岩浆底辟分布及CO_2充注风险分析

琼东南盆地深水区石油勘探面临的幔源CO_2风险主要集中于其东区的宝岛—长昌凹陷,目前已在宝岛凹陷北缘发现多个高CO_2含量气层。文章基于地震火山地层学原理,利用地震相分析技术,识别火山/岩浆底辟分布,分析其分布规律和控制因素。结果表明,宝岛—长昌区的火山/岩浆底辟呈串珠状集中分布在(潜伏)深大断裂附近,凹陷中心的火山分布集中且规模大;中新统为火山最活跃时期,其控制因素主要为地幔上涌、断裂活动、沉积盖层厚度等。通过分析火山/岩浆底辟类型及分布、输导体系、宝南断阶带成藏之间的时空配置关系,认为宝南断阶带整体来看CO_2风险较小,特别是主要目的层陵三段。

Volcano/magma diapir distribution and analysis of CO2 injection risk in Baodao-Changchang Sag of deepwater area in Qiongdongnan Basin

At present,the exploration in deepwater of Qiongdongnan Basin is facing with mantle-derived CO2 risk,especially in Baodao-Changchang Sag,the eastern deepwater area.Multiple high CO2-bearing gas layers have been found in northern margin of Baodao Sag.This paper is based on seismic volcanic stratigraphic theory and uses seismic phase analysis technique to recognize volcano/magma diaper distribution and analyze the distribution pattern and the control factors.The result shows that in Baodao-Changchang Sag the volcano/magma diapers occur as bead in strings along deep fault;in center of the sag are concentrated big volcanoes;upwelling of the mantle,fault activity and thickness of sediment cover during peak active volcanism in Miocene epoch are the main control factors.Based on spatial-temporal relationship analysis of the volcano/magma diapir types and the distribution pattern carrier systems and accumulation conditions,the risk in Baonan step-fault zone is lower,especially in the major target,3rd member of Lingshui Formation.