松辽盆地古龙页岩油富集规律及有利区分布

Enrichment law and favorable areas distribution of Gulong shale oil in Songliao Basin

近年的勘探开发实践已经证实松辽盆地白垩系发育的页岩油资源潜力巨大,但页岩油富集规律不清、有利区分布不明的问题制约了古龙页岩油勘探开发的快速推进。基于古龙全区多口井的取心及全面实验分析,系统开展页岩油含油性、储集性以及动用条件分析,明确页岩油富集分布规律,建立有利区划分标准,系统评价了松辽盆地齐家−古龙凹陷页岩油有利区。结果表明:沉积背景控制了页岩矿物组分及薄夹层岩性纵向上的规律性;明确了烃源岩丰度及热演化程度控“油”,有机质生烃演化及成岩演化控“储”,核磁可动孔隙度和脆性矿物含量控“动用”的富集可动主控要素。古龙页岩油纵向上在下部的Q_(1)—Q_(4)油层以纯页岩为主,含油性最好,但黏土矿物含量最高,工程品质较差,一类有利区主要分布在齐家-古龙凹陷北部及南部的部分区域,二类有利区基本覆盖齐家-古龙凹陷,分布面积最大;中部的Q_(5)—Q_(7)油层为页岩夹薄层白云岩,含油性中等,工程品质中等,核磁可动孔隙度最低,一类有利区部分发育于齐家−古龙凹陷北部,面积最小,二类有利区分布与R_(o)>1.2%范围相近,面积小于Q_(1)—Q_(4)油层;Q_(8)—Q_(9)油层岩性为页岩夹薄层粉砂岩,含油性较好,黏土矿物含量相对最低,工程品质最好,核磁可动孔隙度最大,可动条件最好,一类有利区分布面积最大,R_(o)>1.2%范围内基本均有分布,二类有利区分布与Q_(8)—Q_(9)油层相似。研究成果可为古龙页岩油的下一步勘探开发提供理论指导。

In recent years,exploration and development practices have confirmed enormous potential of shale oil resources developed in Cretaceous strata of Songliao Basin.However,unclear enrichment law of shale oil and uncertain distribution of favorable areas hinder the rapid progress of exploration and development of Gulong shale oil.Based on coring and comprehensive experimental analysis of several wells in entire Gulong area,a systematic analysis is conducted on oil-bearing properties,reservoir properties and producing conditions of shale oil to clarify shale oil enrichment and distribution laws.Classification criteria for favorable areas is established to systematically evaluate favorable areas of Qijia-Gulong Sag in Songliao Basin.The results show that sedimentary background controls vertical regularity of shale mineral components and lithologies of thin interlayers.Main controlling factors for enrichment producibility are determined including source rocks abundance and thermal evolution degree controlling“oil”,evolution of organic matter generating hydrocarbon and evolution of diagenesis controlling“reservoir”,and NMR movable porosity and brittle mineral content controlling“producing”.Gulong shale oil in vertically lower Q_(1)-Q_(4) oil layers are dominated by pure shale,with the best oil-bearing properties but maximum clay mineral content and poor engineering quality,and Class Ⅰ favorable areas are mainly distributed in northern and part of southern Qijia-Gulong Sag,Class Ⅱ areas mainly cover Qijia-Gulong Sag,with largest distribution area.Middle Q_(5)-Q_(7) oil layers develop shale interlayered with thin dolomite,with moderate oil-bearing properties and engineering quality and minimum NMR movable porosity,and Class Ⅰ favorable areas partially develop in northern Qijia-Gulong Sag,with the smallest area,The scope of Class Ⅱ area is similar with R_(o)>1.2% range,with area smaller than Q_(1)-Q_(4) oil layers.Q_(8)-Q_(9) oil layers develop shale interlayered with thin siltstone,with good oil-bearing properties,relatively low clay mineral content,best engineering quality and maximum NMR movable porosity,providing the best production conditions,and Class Ⅰ favorable areas have the largest area distributing throughout the range of R_(o)>1.2%.The scope of Class Ⅱ area is similar with Q_(8)-Q_(9) oil layers.The research provides theoretical guidance for further exploration and development of Gulong shale oil.