松辽盆地北部青山口组夹层型页岩油形成地质条件及勘探潜力

Geological conditions and exploration potential of interbedded shale oil in Qingshankou Formation of northern Songliao Basin

松辽盆地北部青山口组是大庆油田重要的页岩产油层,主要发育泥纹型和夹层型2种类型的页岩油,其中泥纹型页岩油已经在Q9油层取得效益勘探,夹层型页岩油近2年也受到了广泛关注,部分探井取得较好效果,展现了一定的资源规模,是大庆油田增储建产的重要接替领域。基于钻井、测井、岩心和实验分析资料,通过对青山口组沉积相、砂体分布、储层宏微观特征和含油性的系统分析,明确了松辽盆地白垩系青山口组夹层型页岩油形成的地质条件及勘探潜力。结果表明:青山口组沉积时期,主要发育北部和西部物源,沉积微相类型主要为水下分流河道、河口坝、远砂坝、席状砂、浊积砂和砂质碎屑流,夹层砂岩在全区大面积分布,沿着物源方向逐渐减薄;夹层型页岩油砂岩储层主要发育粒间孔和溶蚀孔,有效孔隙度一般为6%~12%,页岩储层主要发育粒间孔、晶间孔、有机生烃缝等,砂岩和页岩均具有较好的储集能力;青山口组夹层型页岩油源储一体近距离运移立体成藏,砂岩、页岩普遍含油,在成熟烃源岩内为纯油区,大规模连续成藏;按照有效烃源岩范围、砂岩分布范围、储层特征、黏土矿物含量、油水关系等地质条件,综合划分了青山口组夹层型页岩油发育的有利区带,初步估算资源量潜力为25×10^(8) t,展现出良好的勘探前景。主要参数对比结果表明,齐家南和古龙西地区夹层砂岩相对较厚、源岩品质相对较好,是近期增储建产的现实区带。

Qingshankou Formation in northern Songliao Basin is an important shale oil production layer in Daqing Oilfield,mainly developing 2 types of shale oil including mud laminae shale oil and interbedded shale oil.Among them,mud laminae shale oil in Q9 reservoir is beneficially explored,and interbedded shale oil is also widely concerned in recent 2 years.Some exploration wells achieved good results,demonstrating large resource scale,making it important replacement field for increasing reserves and production in Daqing Oilfield.Based on drilling,logging,core and experimental analysis data,geological conditions and exploration potential for the formation of interbedded shale oil in Cretaceous Qingshankou Formation of Songliao Basin are clarified through systematic analysis on sedimentary facies,sandbodies distribution,reservoir macro and micro characteristics and oil-bearing property of Qingshankou Formation.The results show that,mainly northern and western provenance developed in sedimentary period of Qingshankou Formation.The main sedimentary microfacies types are underwater distributary channels,mouth bars,distal sand bars,sheet sand,turbidite sand and sandy debris flow.Interbedded sandstone is widely distributed throughout the whole area,gradually thinning along provenance direction.Interbedded shale oil sandstone reservoirs mainly develop intergranular pores and dissolution pores,with effective porosity of 6%~12%.Shale reservoirs mainly develop intergranular pores,intercrystaline pores and organic hydrocarbon-generating fractures.Both sandstone and shale have high storage capacity.Interbedded shale oil in Qingshankou Formation demonstrates short-distance migration and 3D accumulation of integrated source-reservoir,with sandstone and shale widely containing oil,forming pure oil zones in mature source rocks and continuous large-scale accumulation.Favorable zones for interbedded shale oil development in Qingshankou Formation are comprehensively divided based on geological conditions of effective source rock range,sandstone distribution range,reservoir characteristics,clay mineral content and oil-water relationship.Preliminary estimated resource potential is 20×10^(8) t,showing good exploration prospects.Comparison of main parameters indicates that southern Qijia and western Gulong areas have relatively thick interbedded sandstone and relatively good source rock quality,making them realistic zones for recent increase in reserves and production.