柴达木盆地东部地区石炭系泥页岩生烃条件及选区

Shale gas formation conditions and potential area selection in Carboniferous strata in eastern Qaidam Basin

柴达木盆地石炭系露头、钻井资料均揭示,其为海相沉积烃源岩,且石炭系泥页岩气展现出良好的勘探前景。对柴达木盆地东部石炭系泥页岩沉积环境、有机质丰度、类型和演化程度进行综合评价,利用野外露头、探井、地震、非震等资料证实了石炭系的残留及分布。研究认为,柴东地区石炭系泥页岩主要集中在上石炭统滨岸潮坪沉积的克鲁克组,发育炭质泥页岩、暗色泥岩2种烃源岩,有机碳均值为3.08%,有机质类型为Ⅱ—Ⅲ型,处于成熟-高成熟演化阶段,73%的样品达到中等-好烃源岩。平面上主要分布于尕丘、欧南、霍布逊和德令哈凹陷,分隔性较强,具有多个厚度中心,其中以欧南凹陷石灰沟地区和霍布逊凹陷落实程度高、资源潜力大,是泥页岩气最有利的发育区。

Drilling data and outcrops have both revealed marine source rocks in Qaidam Basin, and gas in claystone and shale of Car-boniferous strata has exhibited great exploration potential. Based on an integrated study of sedimentary environment, organic mattertype, abundance, and maturity, combined with outcrop data, drilling data, seismic data and non-seismic data, the authors determinedresidual thickness of the Carboniferous strata in eastern Qaidam Basin. The results indicate that claystone and shale are mainly concen-trated in the Keluke Formation of tide flat facies in the upper part of Carboniferous strata. There are mainly two kinds of sourcerocks, namely carbonaceous mudstone and dark-colored mudstone with TOC of 3.08%, and the organic matter is classified as typeII-III. Evaluation shows that about 73% of the matured-high matured samples are moderate-good source rocks, and they are mainlyscattered in Gaqiu, Ounan, Huobuxun and Delingha sags, forming several thickness centers. Source rocks in Shihuigou area of Ounansag and Huobuxun sag have most promising high resource potential, and possess favorable conditions for generating shale gas.