Natural Gas Characteristics And Accumulation Models Of Typical Gas Pool Of Bozhong Area

The dissertation is written on the base of the project 《oil-gas characterictics and conformation models of typical oil-gas formation of Bozhong Area 》prosided by China Ocean Petroleum Company . The main subject in the dissertation include petroleum system theory and dynamics of petroleum . During the researching ,we use some new methods and new theories on petroleum geology and petroleum exploration ,for example ,we use ray-tracing technique to posit conformation history and its times ,use base model to research oil-gas migration .All these works are importance for oil-gas formation research and exploration of Bozhong area .The dissertation based on natural gas formation and analyses gas geochemical characteristics ,genesis type and distinguish sign. The dissertation analysis "Four type history " and fluid inclusion about source rock and to posit hydrocarbons migration netwok ,filling times and formation history . The HC charging history was semi-quantitatively calculated based on reservoir fluid inclusion homogenization temperatures plus buried history curves and geotemperature ones. Also, the reservoir-filling history with HCs was inferred from interreservoir fluid compositional heterogeneities. The main conclusions are followings:Geology Factors of Gas formation1,Source rock distributing: From the geology factors sight ,Bozhong area and its surround include several depressions ,which are Bozong sag of middle ,Qinnan sag of north ,Qikou sag of west ,Huanghekou sag of south ,Miaoxi sag of east . The main source rock include Shahejie(Sh) formation and Dongyingzu(DY) formation . It is indicated that Sh3 and Sh1-2 source rocks in all the sags had been maturated in different levels. These three formation's organic matter are mix type Ⅱ, and besides it ,Sh3 formation's organic matter is better with type ⅡA－Ⅰ,but lower DY formation's organic matter is little worse ,its type isⅡB－ Ⅲ;2,Tectonic surround : Fluid drain skeleton constitutes unconformities, fault system and sandstones. Palaeozoic and pre-Cambrian unconformities have been playing a key role of regional lateral conduit, and fluid can mingrate vertically along faults which have been active since early Eogene, in particular, strong new tectonic movement. Sandstone bodies ,most of which are alluvial fan, fan-delta and delta front sandstone, made up mainly regional and local lateral pathway system. Two of the major reservoir-seal combination were constructed beneath two regional mudstone seals, i.e. lower MF and lower DF, respectiely. Beneath the tow seals, unconformities and laterally continual sandstone bodies formed not only lateral carrier, but also most of reservoirs that have been found in the studied area.3,Conformation history and its times :Nearly 50 thin sections of reservoir rock sampleshave been observed and measured with both microscope added a cooling-heating platform and Raman System for fluid inclusion identification and homogenization temperature (Th). It is suggested that a great deal of hydrocarbon inclusions had been enclosed within fractures and diagenetic minerals such as quartz, calcite and gypsum, with most of liquid phase or/and qas-liquid two phase HC inclusions plus less gas phase HC inclusions, indicating oil being dominantly generated and accumulated rather than gas in Bozhong Depression. The stages of HC migrating and charging into reservoirs could be divided early and late ones, corresponding to early and late HC inclusions with Th in range of 80-130℃and140-190℃,respectively. By homogenization temperatures plus buried history curves and geotemperature ones, the time of reservoir-filling was dated later than 15Ma or so, main filling stage not earlier than 5Ma. Geochemical Characteristics, Genesis and its Distributing rule of Natural GasThe gas can be classified two groups, continental organic gases and petroliferous gases, according to isotopic signatures ofδ13C1 andδ13C2. The former group distributes peripheral highs around Bozhong Sag, stemmed out of lower DF which contains...