【作者】 高胜利；

【导师】 任战利；

【作者基本信息】 西北大学 ， 地球探测与信息技术， 2007， 博士

【摘要】 生物气是在还原条件下有机质经生物化学作用形成的天然气，与常规的天然气相比，具有埋藏深度浅，勘探开发成本低，效益好的特点。我国已在柴达木、渤海湾、松辽、苏北、百色等盆地发现生物气藏。河套盆地第四系、新近系具有与柴达木盆地相似或近于相似的地质背景，有形成浅层生物气的地质条件，加强对河套盆地生物气成藏地质条件、成藏机理及生物气勘探前景研究，对于河套地区生物气勘探具有重要的现实指导意义。本论文以天然气成藏理论为指导，将微生物学、地球化学、地震地层学、沉积学、古生物学等多学科相结合，运用现代分子地球化学、有机与无机化学组成和同位素等分析测试技术、微生物鉴定与培养技术以及生物气生成模拟试验技术等，在分析大量样品及基础地质资料的基础上，对河套盆地生物气成藏地质条件、生物气模拟实验、生物气富集影响因素及资源量等进行了深入研究，取得了以下重要认识：通过对河套盆地浅层气组分分析，明确指出该区浅层气属于生物成因气，气体组分以甲烷、氮气、二氧化碳、氢气为主，四者含量之和大于97％，乙、丙、丁、戊烷的含量之和小于3％，甲烷的碳同位素含量为（-74.183～-77.57）‰。运用翔实的、系统的古生物（孢粉）资料，研究了河套盆地古气候演化特征，认为河套盆地早更新世气候从干冷-温干-略温干-偏凉湿变化，中更新世气候从偏凉湿-偏暖湿-干冷变化，晚更新世又从略暖向干燥寒冷变化，古气候演化特征为生物气藏的形成奠定了基本条件。通过对第四系更新统地震反射特征的分析，识别出4种地震相类型，结合岩心、测井等资料将地震相转变为沉积相，认为本区主要发育浅湖、半深湖、滨（浅）湖相等，沉积相分布特征指出了烃源岩的有利位置。本区气源岩以灰色泥岩、砂质泥岩为主，另有腐植土、碳质泥岩，生气区面积2.3891×10⁴km²，气源岩厚123-1300m，占地层厚度的（16.4-59.8）％。气源岩有机碳（0.18-15.4）％，平均0.41％，有机质含量（1.13-3.23）％，平均2.1％；氯仿沥青“A”（0.0021-1.424）％，平均0.011％；烃含量（3.4-234.96）ppm，平均53.48ppm；有机质类型以Ⅱ型、Ⅲ型为主，未成熟，目前正处于生物化学生气阶段。第四系更新统、新近系上新统为本区生物气勘探的目的层系，气源、储层、盖层配置良好，成藏模式应为互层式自生自储组合，该模式生、储层以及储、盖层接触面积大，为该区的最佳组合。河套盆地本源细菌以发酵性细菌和厌氧纤维素分解菌这两大类功能菌群为主，同时有产甲烷菌的检出，说明河套盆地地质环境中生化产甲烷过程的客观存在并且仍然在进行。通过对不同深度段微生物、有机组分和甲烷产率变化规律研究，结合试气资料，建立了河套盆地生物气生成演化新模式。河套盆地具有独特的“二带式”生物化学分带，纵向上具有2个主产生物气带，即200-800m带和1200-1800m带。系统分析了该区影响生物气赋存、富集的构造及环境因素，经与柴达木盆地类比，认为河套盆地成藏条件与柴达木盆地相似，资源量计算结果表明，呼和坳陷总生气量13.8433×10¹²m³、临河坳陷总生气量26.5697×10¹²m³、乌前坳陷总生气量1.4×10¹²m³。呼和坳陷北部凹陷南缘、南部斜坡北缘及临河坳陷北部凹陷中南部处于生气中心，为岩性圈闭发育区，该区地层水含盐量高，保存条件好，是生物气勘探的最有利区。更多还原

【Abstract】 Biogenic gas, whose buried depth is shallow, exploration cost is lowliness and has a characteristic of finer benefit comparing to conventional natural gas, is generated by organic matter under reduction condition, with biochemical action. Biogenic gas reservoir are found in Qaidam Basin, song liao Basin, northern area of Jiangsu and Baise area. Having a similarity geologic background about quaternary and tertiary formation comparing to Qaidam Basin ,and the shallow gas having the characteristic of biogenetic gas, therefore, the research about geological condition of shallow gas （biogenic gas ） accumulation in HETAO Basin is carried out in order to find added reserves in new area. The research must be creative of great meanings to HETAO area or even china about biogenic gas exploration field.Applying synthetically Microbiology, geochemistry, geology of natural gas（natural gas genesis theoretics, gas accumulations theoretics）, seismic stratigraphy, sedimentology and palaeobiology, using modern geochemical analysis testing technology, microorganism identification and culture techniques and biogenic gas generating simulating testing technique, geological condition of shallow gas （biogenic gas ） accumulation is researched , biogenic gas stock size is calculated and favorable biogenic gas area is selectd in HETAO Basin.It is approved that shallow gas has a characteristic of biogenetic gas. The main Gases constituent are methane, nitrogen, carbon dioxide and hydrogen, these four Gases constituent is above and beyond 97%, the content of ethane, propane, butane and pentane less than 3%, the content of methane carbon isotope ranges from -74.183‰to-77.57‰.The sedimentary facies types of shallow lake facies, semi- deep lake facies and shore lake facies have an intimate relation to biogenic gas. The main gas source rocks its thickness ranging from 123m to 1300m are grey mudstone, sandy mudstone, humus soil and carbon mudstone. The source rocks thickness ratio ranges from 16.4% to 59.8% and the generation gas province area is 2.3 891×10⁴km². Organic carbon ranges from 0.18% to 15.4% and its average is 0.41%. Chloroform bitumen "a" ranges from 0.0021% to 1.424% and its average is 0.011%. The thermal evolution of those organic matter, which mostly contains kerogen Type I and II ,was speculated to have primarily been at the immature mature and biochemistry stage.The palaeoclimate of Pleistocene in Hetao basin is changed during different period: dry and cold-warm and dry-little warm and dry-little cold and damp during eopleistocene、cold and dam-little warm and damp-dry and cold during mid-pleistocene and little warm-dry and cold during epipleistocene.There is a good allocation among the source rock, reservoir and cap rock, the accumulation model is self-producing and self-reserving primary reservoir ,which is optimum combination form in HETAO Basin.There is no obvious correlativity between zymogenic bacteria, cellulose-decomposing microorganisms and buried depth, as well that of organic components.Biochemistry methanogenesis process is of outwardness and its evolution is still processed possibly because of the detection of methanogen. It is reasonable that Organisms methanogenesis function maybe already has been processed, or it will processed.The two main methanogenesis belt on the vertical were proved, one ranges from 200m to 800m,another ranges from 1200m to 1800m. Gas generating center where are lithologic trap, high salinity in formation water and favorable area, lie in south edge of north depressed of HUHE sag, north edge of south slope of HUHE sag and the central and southern parts of north depressed of LINHE sag.It is considered that there are similarity geologic background about quaternary and tertiary formation between Qaidam Basin and HUHE Basin, and having a favourable exploration prospect. The Common gas production is 13.8433×10¹²km³ in HUHE sag, 26.5697×10¹²km³ in LINHE sag and 1.4×10¹²km³ in WUQIAN sag.更多还原