柴达木盆地阿尔金东段基岩气藏盖层特征及控藏机制

基于对阿尔金山前东段古近系岩心相、测井相、地震相等分析，发现该地区古近系沉积早期发育一套区域性含膏盐岩盖层。该套含膏盐岩盖层岩性主要为膏质泥岩、含膏泥岩等，纯膏盐发育较少。含膏盐岩盖层发育特征表现为纵向主要分布于路乐河组底部，横向主要发育于尖北、坪西、东坪、牛中等4个局部厚度较大区，且含膏盐岩盖层整体厚度自尖北斜坡区向牛东方向具有逐渐减薄趋势。该地区多类型含膏盐岩的形成及分布特征主要受古近系沉积前的古地貌条件及路乐河组沉积时期的古物源条件、古气候条件联合控制。经综合研究发现该套含膏盐岩盖层的发育程度与油气分布具有良好的匹配关系：含膏盐岩盖层累计厚度较大时，下伏基岩地层油气藏富集，形成构造、岩性、地层油气藏；盖层累计厚度较小时，含膏盐岩盖层相对缺乏，油气向浅层逸散，形成古近系局部盖层和构造控制的多层系构造油气藏。该研究提出阿尔金东段路乐河组含膏盐岩盖层发育特征有效控制气藏纵横向富集规律，并为柴达木盆地下步煤型气有利区预测指明方向。

Caprocks characteristics and their control on hydrocarbon accumulation of bedrock gas reservoirs in eastern segment of Alkin Piedmont，Qaidam Basin

Based on the analysis of core facies，logging facies and seismic facies of Paleogenlulehee in the eastern part of Alkin Piedmont，it is found that regional gypsum-salt cap rocks developed in the Early Paleogene.The lithology was mainly gypsum mudstone and creaming mudstone，and with little gyprock.The gypsum-salt rocks mainly developed in the bottom of Lulehe Formation in vertical，and formed 4 areas with largest thickness in horizon，including northern Jiandingshan，western Dongping，Dongping and Niuzhong，and thinned gradually from west to east.In the study area，the formation and distribution of gypsum-salt rocks was jointly controlled by palaeogeomorphology，paleoclimate and sediment supply before the Paleogene deposits.A well match between development degree of gypsum-salt rocks and hydrocarbon distribution was proved:Gypsum-salt rocks with lager thickness formed structural，lithologic and stratigraphic reservoirs in underlying bed rocks，with well hydrocarbon preserving and accumulative conditions；and those with less gypsum-salt rocks formed regional cap rocks and structural reservoirs with multiple layers.Above all，the gypsum-salt cap rocks developed in Lulehe Formation in the eastern part of Alkin Piedmont controlled natural gas enrichment effectually，pointing out a direction for predicting favorable areas of coal-type gas in Qaidam Basin.