松辽盆地长岭断陷盆缘陡坡带中性火山岩相模式及其对储层的控制作用

Faces Model of Intermediate Volcanic Rocks in Steep Slope and Its Control on Resevoirs:A Case Study in Changling Fault Depression,Songliao Basin

松辽盆地长岭断陷盆缘斜坡带岩性以中基性火山岩为主,目前对中性火山岩岩性、岩相分布模式和优质储层发育规律尚缺乏深入认识.以长岭断陷盆缘斜坡带龙凤山地区为例,综合利用钻井、测井和地震资料,刻画该区中性火山机构、火山岩相的空间分布特征,进而建立中性火山岩相模式和喷发模式,探讨优质储层发育规律.研究结果表明:该区火山喷发中心分布在盆缘斜坡带靠近盆地边缘高部位,沿盆地边缘断裂分布,火山机构中心相带以喷溢相和爆发相互层为典型特征;向盆方向,火山机构中源相带以厚层爆发相热碎屑流亚相堆积为主,火山碎屑喷发物进一步向盆地凹陷中心搬运,与盆地水体互相作用,过渡为火山沉积相.这种火山岩相模式由多期亚普林尼式喷发作用、火山喷发物的搬运和就位方式等因素共同控制.该区优质火山岩储层以溶蚀强烈的火山凝灰岩和气孔安山岩为主,位于斜坡中部的火山机构中源相带和发育辫状熔岩流的近火山口相带是该区火山岩储层发育的有利部位.

The basin edge slope area of Changling fault depression in Songliao basin is mainly composed of intermediate-basic volcanic rocks.At present,there is a lack of in-depth understanding of the lithology,lithofacies distribution pattern,and high-quality reservoir stratum development law of the intermediate volcanic rocks in the basin edge slope area.By taking Longfengshan area in Changling fault depression as an example,the spatial distribution characteristics of volcanic edifice and volcanic facies were described by making a comprehensive use of well drilling,well logging,and seismic data,the volcanic facies model and eruption model were established,and the development law of the high-quality reservoir stratum was discussed.The research results indicate that the volcanic eruption center is located in the basin edge slope zone near the high place of the basin edge and distributed along the fault.The proximal facies belt of the volcanic edifice is featured with interlayers of effusive facies and explosive facies.The central facies belt of the volcanic edifice is mainly composed of pyroclastic flow of thick explosive facies.The pyroclastic flow is further advanced to the sub-concave center of the basin and then transformed into volcanic deposit facies.The volcanic facies is jointly controlled by multi-stage Plinian eruptions,the transport and placement of volcanic eruptions,and other factors.High-quality volcanic rock reservoirs are dominated by volcanic tuff and vesicular andesite with strong dissolution,which are located in the medial facies belt of the volcanic edifice on the basin edge slope.The proximal facies belts with lava flow developed are the favorable development parts of the volcanic reservoir stratum in the area.The research has certain directive significance in the oil-gas exploration of intermediate-basic volcanic rocks in the slope belt of the basin margin of a fault depression basin.