冀中坳陷武清凹陷新近系浅层生物气勘探潜力探讨

Discussion on exploration potential of shallow biogas in the Neogene of Wuqing Sag,Jizhong Depression

冀中坳陷武清凹陷是华北油田公司勘探与研究程度低、研究难度大的地区之一,多年来一直未取得重大进展。以武2井新近系馆陶组获得气流为线索,着重对武清凹陷的岩相古地理环境、有机地化特征、沉积特征、成藏条件、构造特征和资源评价等方面进行了阐述,从而表明武清凹陷浅层生物气具有巨大的勘探潜力。武清凹陷新近系为滨浅湖与河流沼泽相沉积,地层沉积巨厚,广泛发育暗色泥岩,具有浅层生物气形成的基础,有机地化指标良好,盆地模拟计算生物气资源量潜力巨大,天然气主要生成于新近纪,总生气量856×108m3,天然气资源量(150～200)×108m3。新近系馆陶组的河道砂体是生物气的良好储集层。新近系沉降速率快,厚度大,埋藏深,有利于生物气的形成和保存。后期构造反转形成的凹中挤压塌陷背斜是生物气聚集的有利场所。

Abstract Due to the low maturity of exploration and study of the Wuqing Sag in Jizhong Depression of Huabei Oilfield Company, no important exploration breakthroughs have been obtained for years. This study focuses on the lithofacies palaeogeography setting, organic geochemistry characters, depositional characters, petroleum reservoir forming conditions, tectonic features and resource assessment and investi- gates the great exploration potential for shallow biogas in the Wuqing Sag based on the gas production from the Neogene Guantao Formation in Well Wu 2. The Neogene in the Wuqing Sag is dominated by shore- shallow lacustrine and fluvial deposits with great thickness and dark color mudstones were widely developed which provided favorable conditions for formation of shallow biogas. The natural gas was mainly generated in the Neogene with good organic geochemistry indexes and great biogas resource potential calculated by basin simulation. The total gas production quantity is 856 × 10^8m^3 and the gas resource quantity is （ 150 -200） × 10^8m^3. The channel sandbody constitutes the favorable reservoirs of the Neogene Guantao Formation. It is easy for the biogas formation and preservation due to the quick subsidence, great thickness and deep burial of the Neogene. Biogas accumulated in the slumping anticlines which were induced by the tectonic inversion in the later period.