大情字井地区上白垩统青山口组沉积相与岩性油藏

Sedimentary facies and lithologic oil pools of the Upper Cretaceous Qingshankou Formation in Daqingzijing area,Changling Sag,southern Songliao Basin

大情字井地区位于长岭富油凹陷的中部,呈向斜型构造形态,以青山口组一段为主要目的层发现亿吨级油田。沉积相带研究表明,区内储集层主要发育于通榆-保康三角洲沉积体系,青一段至青三段沉积环境由“深湖型”过渡到“浅湖型”。青一段与青二段沉积环境相似,均发育“深湖型”三角洲前缘亚相砂体,储集体平面展布为多个独立的、顺源窄条带状的河控坝体及水下分流河道微相砂体,且多期次储集体错叠连片分布,为形成大面积岩性油藏提供了条件。岩性油藏综合分析得出,该区青二段具有与青一段相似的相带展布特点,有利于形成自生自储和下生上储型的生储盖组合方式,尚具有5000万t的勘探潜力,是下一步岩性油藏勘探的主要方向。

Daqingzijing area is a synclinal structure in the central part of Changling Sag. With the Qing-1 member of Qingshankou Formation as the main target zone, Daqingzijing oilfield is discovered with reserves of 100m tons. The reservoirs are mainly derived from Tongyu to Baokang deltaic depositional system, and the sedimentary environmem from Qing-1 to Qing-3 members transforms from deep-lake type to shallow-lake type. The sedimentary environments of Qing-1 and Qing-2 members are similar, and with the deep-lake type delta front subfacies developed. The fades belts are fluvial-dominated sandbars and underwater distributaries channel micro-facies with their distributions being multiple and independent in plane as well as narrow-banded in source direction, which is favorable for forming large-scale lithologic deposits. Comprehensive analysis indicates that Qing-2 member has a potential of 50m tons reserves, and is the main target for exploration of the next step.