鄂尔多斯盆地海陆过渡相页岩气勘探理论与技术研究新进展

Research progress in exploration theory and technology of transitional shale gas in the Ordos Basin

鄂尔多斯盆地海陆过渡相页岩气资源丰富,是国内油气增储上产的重要战略接替新领域。为了探索形成海陆过渡相页岩气相关理论,促进技术进步,基于充分调研国内外海陆过渡相页岩气研究进展的基础上,明确了盆地海陆过渡相页岩气规模勘探所面临的理论与技术挑战,并以盆地东缘大吉区块作为先导试验区,形成了海陆过渡相页岩气勘探理论与技术。研究结果表明:①建立了四级层序约束下的2类海陆过渡相页岩发育模式,即“暖干、贫氧、地貌、海侵”四元耦合的“双源”模式和“潮湿”气候下的“单源”模式;②建立了海陆过渡相页岩“早生烃—长周期”双源宽幅生烃演化模式,并估算了先导区试验区海陆过渡相页岩气资源量约9×10^(12)m^(3);③形成了基于测井反褶积理论的海陆过渡相页岩岩性组合与富有机质页岩识别方法(U—SP曲线重叠法),建立了岩性约束下的页岩储层物性、地化参数、含气性测井定量评价模型;④创建了海陆过渡相多岩性组合页岩气甜点地球物理评价及预测技术体系,实现了海陆过渡相页岩气富有机质页岩发育特征空间定量表征及预测。结论认为,研究成果实现了地质—地球物理多信息融合的页岩气甜点预测与综合评价,并优选出了4个I类有利区,有力支撑了先导试验区井位部署和先导试验方案的编制,推动了我国海陆过渡相页岩气的勘探开发进程,拓展了天然气勘探开发新领域,有利于保障国家能源安全。

The Ordos Basin is rich in transitional shale gas resource,which is a new important strategic replacement area for increasing oil and gas reserves and production in China.In order to explore and form the theories related to transitional shale gas and promote technological progress,this paper clarifies the theoretical and technological challenges to the large-scale exploration of transitional shale gas in the Ordos Basin by fully investigating domestic and foreign research progresses in transitional shale gas.In addition,the transitional shale gas exploration theories and technologies are developed by taking the Daji Block along the eastern margin of the Ordos Basin as the pilot test area.And the following research results are obtained.First,two transitional shale development models under the constraint of fourth-order sequence are established,namely the"dual-source"model coupled with"warm and dry paleoclimate,poor-oxygen bottom water,geomorphology and transgression"and the"single-source"model under humid paleoclimate.Second,the"early hydrocarbon generation-long cycle"dual-source and wide-range hydrocarbon generation and evolution model of transitional shale is established,and the amount of the transitional shale gas resources in the pilot test area is estimated to be about 9×10^(12)m^(3).Third,the transitional shale lithology combination and organic-rich shale identification method based on the logging deconvolution theory(the U-SP curve overlap method)is formed,and the logging quantitative evaluation model of shale reservoir physical property,geochemistry and gas-bearing property under the constraint of lithology is established.Fourth,the geophysical evaluation and prediction technology system of sweet spot of transitional shale gas with multi-lithology combination is established,and the development characteristics of organic-rich shale in transitional shale gas reservoirs can be quantitatively characterized and predicted in space.In conclusion,the prediction and comprehensive evaluation of shale gas sweet spots based on the integration of geological and geophysical information is realized,and four Class I favorable areas are selected.The research results strongly support the deployment of well locations in pilot test areas and the preparation of pilot test plan,powerfully promote the exploration and development of transitional shale gas in China,and open up a new field of natural gas exploration and development,so as to provide favorable conditions for ensuring national energy security.