松辽盆地古龙页岩油资源潜力及勘探方向

Resource potential and exploration direction of Gulong shale oil in Songliao Basin

以松辽盆地北部青山口组古龙页岩油为研究对象,通过大量岩心实验数据分析,研究了古龙页岩油形成的地质条件,优选了页岩油发育有利区评价,在此基础上分层、分类明确了页岩油资源量,探讨了松辽盆地北部古龙页岩油下一步勘探方向。结果表明,松辽盆地北部古龙页岩是在温暖潮湿、藻类发育、水体厌氧的还原环境下的沉积产物,发育了面积广、厚度大的中—高有机质页岩层,奠定了古龙页岩油规模发育的物质基础。在优质古水体沉积环境下,页岩内有机质富集,在埋藏演化过程中,热演化程度逐渐增高,当R o≥0.75%,有机质开始大量生排烃,良好的烃源岩条件是页岩油形成的关键;古龙页岩岩相类型主要为页岩、泥岩、粉砂质岩、灰质岩、云质岩5种岩相的储层,层状、纹层状页岩占比厚度大,有效孔隙度高、水平渗透性好,是页岩油优势储集岩相;广泛分布的微—纳米级储集空间为页岩油聚集提供必要的场所。通过对厚度、成熟度、有机质丰度、游离烃等特征分析,古龙页岩油纵向上主要发育在青山口组一段、青山口组二段下部,平面上主要发育在齐家—古龙凹陷、大庆长垣南部和三肇凹陷。依据页岩油评价标准,应用体积法分级、分层和分区开展了古龙页岩油资源潜力评价,w(TOC)≥1.0%、R o≥0.75%的页岩油总资源量为89.31×10^8 t;资源级别上w(TOC)为1%~2%的资源量为44.27×10^8 t,w(TOC)≥2%的资源量为45.04×10^8 t;层位上青山口组一段页岩油资源量为55.93×10^8 t,青山口组二段页岩油资源量为33.38×10^8 t;平面上齐家—古龙地区资源量为60.58×10^8 t,大庆长垣、三肇地区资源量为28.73×10^8 t。在有利区资源评价的基础上,进一步评价了R o≥1.0%、w(TOC)>2.0%的“甜点”区资源量为32.46×10^8 t。综合古龙页岩油形成的地质条件及资源潜力分析,松辽盆地北部青山口组页岩油勘探方向为:纵向上,主攻青山口组一段下部“甜点”段、探索中上部“甜点”段;平面上,主攻齐家—古龙地区、拓展三肇地区。

This paper takes the Gulong shale oil of Qingshankou Formation in North Songliao Basin as the research object.Based on the analysis of a large number of core experimental data,the geological conditions for the formation of Gulong shale oil were studied,and the favorable areas for shale oil development were evaluated.On this basis,the shale oil resource by the methods of stratification and classification was identified and the next exploration direction of Gulong shale oil in Songliao basin was discussed.The research shows that Gulong shale in Songliao Basin is a sedimentation product under warm-humid reducing environments with developed algae and anaerobic waterbody,where medium-high organic shales with wide area and large thickness are developed,which has laid the material foundation for the development of Gulong shale oil.In the sedimentary environment of high-quality ancient waterbodies,the organic matter in shale is enriched.During the burial evolution,the degree of thermal evolution gradually increases.The organic matter begins to produce and expel a large number of hydrocarbons with R o≥0.75%,and good source rock conditions are the key to the formation of shale oil.The lithofacies of Gulong shale is mainly composed of five types of reservoirs:shale,mudstone,silty rock,calcareous rock and clolomitic rock.The layered shale and laminated shale are characterized by a large proportion of thickness,high effective porosity and good horizontal permeability,and are the dominant reservoir facies of shale oil.The widely distributed micro-nanometer storage space provides the necessary place for the accumulation of shale oil.Combined with the analysis of thickness,maturity,organic matter abundance and free hydrocarbon,the favorable areas of Gulong shale oil are mainly distributed in the first member and the lower part of the second member of Qingshankou Formation vertically,and on the plane distribution,they are mostly seated in the Qijia-Gulong Sag,South Placanticline and Sanzhao Sag.According to the evaluation standard of shale oil,the volume method was applied for evaluating the resource potential of Gulong shale oil by grading,layers and zones.It is concluded that the total shale oil resource is respectively 89.31×10^8t with w(TOC)≥1.0%and R o≥0.75%,44.27×10^8t when w(TOC)ranges in 1.0~2.0%,and 45.04×10^8t with w(TOC)≥2%.Vertically,the shale oil resource of the first member of Qingshankou Formation and the second member of Qingshankou Formation is 55.93×10^8t and 33.38×10^8t,separately;horizontally,the shale oil resource of Qijia-Gulong area and that of Daqing Changyuan and Sanzhao area is 60.58×10^8t and 28.73×10^8t,respectively.On the basis of the resource evaluation of the favorable area,the resource of the sweet spots with R o≥1.0%and w(TOC)>2.0%is furtherly evaluated to be 32.46×10^8t.Through the comprehensive analysis of geological conditions of the formation of Gulong shale oil and the resource potential,the shale oil exploration direction of Qingshankou Formation in North Songliao basin is shown as follows.Vertically,its primary target is the sweet-spot interval in the lower part of the first member of Qingshankou Formation and the explore area is the sweet-spot interval in the upper-middle part;horizontally,its main target is the Qijia-Gulong area and the extension target is the Sanzhao area.