塔里木盆地塔河地区南部志留系油气成藏特征

CHARACTERISTICS OF THE SILURIAN HYDROCARBON ACCUMULATION IN THE SOUTHERN TAHE REGION,THE TARIM BASIN

在分析塔里木盆地塔河地区南部志留系柯坪塔格组储集岩特征、油气成藏条件及控制因素的基础上,建立了塔河南部志留系油气成藏分布模式,预测了油气勘探方向。柯坪塔格组砂岩属于低孔、低渗储集岩,局部发育厚层滨岸相、三角洲分流河道、河口砂坝以及潮汐水道等优质储集岩。砂岩层具有深埋藏、大面积、低丰度、薄油气层、断层沟通、叠合连片的油气聚集特点。塔河地区南部寒武—奥陶系烃源岩生成的烃类,沿着断裂、裂隙、砂岩和不整合面经过上奥陶统桑塔木组泥岩运移到柯坪塔格组砂岩层聚集成藏。柯坪塔格组油气藏以喜山期成藏为主,发育背斜、地层不整合遮挡、地层超覆和岩性等油气藏。围绕志留系剥蚀尖灭线周围是地层不整合遮挡油气藏有利成藏区,往南是背斜、地层超覆及岩性油气藏有利成藏区。

The distribution pattern of the Silurian hydrocarbon accumulation in the southern Tahe region, the Tarim Basin has been established and the direction of oil and gas exploration in this region hasbeen predicted based on the research results of the reservoir characteristics, the accumulation conditions and the controlling factors of the hydrocarbons in the Silurian Kepingtage Formation. The sandstone reservoir of the Kepingtage Formation is of low porosity and low permeability, with some high quality thick layers of the shore phase, the delta distributary channel phase, the channel-mouth bar phase and the tidal channel phase developing locally. The Kepingtage Formation sandstone reservoir is characterized by deep burial, large area, low abundance, thin hydrocarbon layer, fault conduit, and superimposition of layers. Hydrocarbons generated from the Cambrian Ordovician source rocks in the southern Tahe region migrated through the faults, the fractures, the sandstones and the uncomformities in the Upper Ordovician Sangtamu Formation into the Kepingtage Formation and accumulated as hydrocarbon reservoirs. The hydrocarbon reservoirs in the Kepingtage Formation mainly formed during the Himalayan pe- riod and can be divided into four types, including anticline reservoir, stratigraphic unconformity reservoir, stratigraphical overlap reservoir and lithologic reservoir. The region around the Silurian erosional pinch-out line is favorable for developing stratigraphic unconformity reservoirs, whereas the area southward is favorable for developing anticline, lithologic and stratagraphic overlap reservoirs.