中国石油陆上中-高成熟度页岩油勘探现状、进展与未来思考

Current status,advances,and prospects of CNPC’s exploration of onshore moderately to highly mature shale oil reservoirs

中国石油天然气集团公司(简称中国石油)矿权区陆相页岩油地质资源丰富,“十三五”资源评价,中国石油陆上中-高熟页岩油(简称页岩油)地质资源量201×108t,占中国页岩油地质资源总量的71%。鄂尔多斯盆地延长组7段、松辽盆地青山口组和准噶尔盆地芦草沟组等重点层系的产量显著增长,中国石油页岩油年产量从2010年的2.5×10^(4)t增至2023年的391.6×10^(4)t,勘探潜力巨大。研究表明:近年来由于陆相不同类型页岩油具有地质特征非均质性强、富集高产因素明显差异的特点,其效益勘探存在地质认识与勘探技术的双重挑战。特别是:(1)夹层型页岩油虽在鄂尔多斯盆地长71+2亚段(延长组7段1+2亚段)实现规模勘探,但勘探靶体钻遇率变化大,深湖区细粒沉积体系研究薄弱,靶体空间展布刻画技术的准确性仍需提升;(2)混积型页岩油地层垂向厚度大、岩性频繁变化、发育多套地质甜点,在柴达木盆地、渤海湾盆地虽然实现了勘探突破,但垂向地质甜点产量差异明显,页岩油高产主控因素不清,主力靶体评价优选技术、方法仍需完善;(3)页岩型页岩油在松辽盆地青山口组实现了古龙页岩油勘探突破,但陆相湖盆不同类型页岩生、排烃差异明显,页岩原位滞留烃特征变化大,地质-工程一体化靶体评价技术、方法仍需深化研究。总体上中国石油页岩油勘探开发仍处于快速推进阶段,未来应:(1)加强淡水湖盆深湖区多类型砂体成因机制研究,实现薄层浊积砂体等夹层型页岩油效益勘探;(2)加强咸化湖盆富碳酸盐混积型页岩油源-储组合评价,优选主体靶体实现混积型页岩油高效勘探;(3)加强淡水、咸化湖盆优质源岩生、排烃差异性评价,优选最佳靶体,实现不同湖盆页岩型页岩油地质-工程一体化精细勘探。

China National Petroleum Corporation(CNPC)boasts abundant continental shale oil resources in areas covered by its mineral rights.The national hydrocarbon resource evaluation of the 13th Five-Year Plan reveals that CNPC’s geological resources of onshore moderately to highly mature shale oil(hereinafter referred to as shale oil)are estimated at 201×108 tonnes,accounting for 71%of the national total.Shale oil production has increased significantly in key plays such as the 7th member of the Yanchang Formation in the Ordos Basin,the Qingshankou Formation in the Songliao Basin,and the Lucaogou Formation in the Junggar Basin,rising from 2.5×10^(4)tonnes in 2010 to 391.6×10^(4)tonnes in 2023,suggesting enormous potential for shale oil exploration.The study results reveal that CNPC’s commercial exploration of continental shale oil is facing challenges in both geological understanding and techniques due to the highly heterogeneous geological characteristics and significantly different factors determining the enrichment and high productivity across various types of continental shale oil reservoirs.Notably,despite large-scale exploration in the 1st and 2nd submembers of the 7th member of the Yanchang Formation in the Ordos Basin,intercalated shale oil reservoirs exhibit greatly varying drilling ratio for targets under exploration,limited research on fine-grained sedimentary sequences of deep lacustrine facies,and the low accuracy of techniques for characterizing the spatial distribution of targets.Shale oil reservoirs of the mixed type exhibit great vertical thicknesses,frequent lithological variations,and multiple suites of sweet spots.Despite breakthroughs in the Qaidam and Bohai Bay basins,the exploration of these reservoirs is constrained by greatly different vertical shale oil production in geological sweet spots,ambiguous major factors contributing to high shale oil production,and imperfect techniques and methods for evaluating and selecting dominant targets.For the exploration of shale oil reservoirs of the pure shale type,breakthroughs have been achieved in the Gulong shale oil reservoirs of the Qingshankou Formation in the Songliao Basin.Nevertheless,due to greatly different hydrocarbon generation and expulsion characteristics and significantly varying in-situ hydrocarbon retention across various types of shales in continental lacustrine basins,it remains necessary to further investigate the geo-engineering integrated techniques and methods for target evaluation.Overall,CNPC’s exploration and exploitation of shale oil reservoirs are still rapidly advancing.In the future,it is necessary to intensify research on the genetic mechanisms of various sand bodies in deep parts of fresh lacustrine basins to achieve the commercial exploration of intercalated shale oil reservoirs such as thinly laminated turbidite sand bodies.For shale oil reservoirs of the mixed type,there is a need to enhance the evaluation of source rock-reservoir assemblages of these reservoirs enriched in carbonate in saline lacustrine basins.This will enable the preferential selection of primary targets for efficient exploration.Furthermore,differential evaluations of hydrocarbon generation and expulsion should be underlined for high-quality source rocks in both fresh and saline lacustrine basins to identify the optimal targets.The purpose is to achieve geo-engineering integrated,fine-scale exploration of shale oil reservoirs across various types of lacustrine basins.