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The Kinetic Experiment Of Hydrocarbon Generation And Primary Expulsion Of Coal And Marine Shale And Its Preliminary Application

Posted on:2008-09-28Degree:MasterType:Thesis
Country:ChinaCandidate:J TianFull Text:PDF
GTID:2120360215950771Subject:Institute of Geochemistry
Abstract/Summary:PDF Full Text Request
This paper is focusing on the following questions: What is the hydrocarbon generating capability of coal and marine shale? What are their main hydrocarbon generating stages and generating rates? What are the main hydrocarbon expulsion stages, mechanism and characteristics of coal and marine shale? What are the hydrocarbon generation potentials and their secondary cracking characteristics for coal and marine shale? The following chapters will answer these questions one by one. The kinetic experiments of primary hydrocarbon generation of coal and marine shale, whole rock expulsion and the gas generation kinetics of different precursors are performed in this paper.The kinetic experimental results of hydrocarbon generation indicate that the hydrocarbon generating capability of marine shale is larger than that of coal, not only in much higher hydrocarbon generating rate, but also in much longer hydrocarbon generating time. The main hydrocarbon generating stage of coal is Ro(%)=0.72-1.23%, while marine shale is Ro(%)=0.71-1.1%. In the geologic heating rate of 5℃/Ma, the corresponding geologic temperatures of main hydrocarbon generating period are 126-160.5℃for marine shale and 128-168.5℃for coal respectively, which shows that marine shale's main hydrocarbon generating period is narrower than that of coal.A lumpy rock sample is used in the generation-expulsion experiment in order to truly simulate the real geological condition. It can be found that both coal and marine shale reach hydrocarbon generation peak firstly and then hydrocarbon expulsion peak afterwards. The quantity of retained hydrocarbon in coal is larger than that of marine shale. This increases the difficulty of hydrocarbon generated in coal to be expulsed because coal's absorbability is stronger than marine shale's. The main hydrocarbon expulsion stage is Ro=0.7-1.26% for marine shale and Ro=0.71-1.3% for coal. The quantities of retained hydrocarbon in marine shale and coal are also affected by heating rate. In the case of fast heating rate, the expulsed quantity of the hydrocarbon will decrease which leads to the increase of retained hydrocarbon.The Hydrogen Index (HI) of marine shale is larger than that of coal, which indicates that the hydrocarbon generation capability of marine shale is larger than that of coal. In addition, marine shale's hydrocarbon expulsion rate is higher than coal's for the reason that coal has strong absorbability, which hinders its expulsion efficiency. The hydrocarbon expulsion rate is also affected by the heating rate. The results show that it changes quickly under faster heating rate. However, both fast and slow heating rates show the same change trend, which indicates that the precursor is the major control for causing different hydrocarbon expulsion efficiency fundamentally.It can be found after comparing the hydrocarbon generation, expulsion and secondary cracking to gas that the main source of natural gas is from secondary cracking of oil in the reservoirs and the conducting strata in high-over maturation marine strata, The coal-associated gas generated from hydrocarbon-expulsion has two resources before expulsion (Ro<1.3%): one is the gas generated by primary cracking of kerogen, another is from the generated liquid oil before expulsion. After the hydrocarbon expulsion (Ro<1.3%), the coal associated gases are mainly from the natural gas generated from cracking of oil.In view of generation, expulsion and secondary cracking gas, the lower Permian of northeast Sichuan was taken as an evaluation target. Calculating results show that the hydrocarbon generation and expulsion time is relatively late and the hydrocarbon expulsion efficiency is low. The secondary gas generation intensity is very larger due to the large quantity of retained hydrocarbons in marine source rocks, which is easier to form the good retained-hydrocarbon-type gas source kitchen. The high effective gas source kitchens are located in the areas along Kaixian, Daxian, Pingchang, Quxian and Liangping.
Keywords/Search Tags:Whole rock pyrolysis, Hydrocarbon generation kinetics, Retained hydrocarbon, Secondary cracking, Source rock of Permian in Northeastern Sichuan
PDF Full Text Request
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