陆相湖盆深水块体搬运体优质储层的主控因素以松辽盆地英台地区青山口组为例

深水储层已成为增储上产的重要领域,传统观点认为此类储层物性差,但近年来的勘探实践表明,陆相湖盆深水块体搬运体可形成优质储层,其储层物性甚至优于三角洲前缘。以岩心观察、铸体薄片、扫描电镜、实测孔隙度、地层水有机酸含量、地层超压等资料为基础,对松辽盆地青山口组深水块体搬运体优质储层的主控因素进行了分析。分析认为青山口组深水块体搬运砂岩为高结构成熟度的岩屑长石砂岩,储集空间主要包括原生粒间孔和次生溶蚀孔,碎屑颗粒以点接触为主,方解石胶结物和石英次生加大现象少见。深水块体搬运优质砂岩储层的发育主要受沉积作用和超压旋回的控制。块体搬运作用是形成优质储层的基础,使其继承了三角洲前缘高能环境砂岩的原始孔渗特征;超压抑制破坏性成岩作用是核心,使原始孔隙得以保存、胶结物含量少;有机酸溶蚀是补充,促进次生孔隙发育。青山口组深水块体搬运砂岩呈透镜状分布于源岩内部且具有良好的物性,是有利的勘探目标。

Main Controlling Factors of High Quality Deep-Water Mass Transport Deposits (MTDs)Reservoir in Lacustrine Basin:An Insight of Qingshankou Formation,Yingtai Area,Songliao Basin,Northeast China

Deepwater sandstone,viewed as poor reservoir traditionally,is now the potential target for increasing reserves and production.However,the exploration practice in recent years showed that deepwater mass transport deposits (MTDs)in lacustrine basin can form high-quality reservoir.Its reservoir properties are even superior to a delta front.Based on the data of core observation,casting thin sections,scanning electron microscope,measured porosity,organic acid content of formation water,and formation overpressure,the main controlling factors of high quality deep-water MTDs in Qingshankou Formation,Yingtai area,Songliao basin have been analyzed.According to the analysis,it can be concluded that MTDs sandstone of Qingshankou Formation is debris-feldspar sandstone with high texture maturity,where the reservoir space is dominated by primary intergranular pores and secondary dissolution pores,and the detrital grains are dominated by point-contacted with low calcite cement and quartz overgrown. The development of a good deepwater sandstone reservoir is controlled by sedimentary process and overpressure cycles.Sedimentary process of MTDs is the foundation,which makes the deepwater sandstone inherit the primary characteristics of porosity and permeability of sandstone in delta front (deposited in high energy environment).Inhibition of destructive diagenesis caused by overpressure is the core factor,which can preserve the primary pores and lead to a low content of cement.Organic acid dissolution can be a supplement to promote the development of secondary pores. MTDs deepwater sandstone of Qingshankou Formation is distributed inside the source rock as lenticulars with good physical properties,which can be treated as favorable exploration targets.