Insights into moisture content in coals of different ranks by low field nuclear resonance

The moisture occurrence in coal reservoirs has important significance in the evaluation of gas-bearing properties and production of coalbed methane(CBM).In order to investigate the occurrence mechanism of moisture content of coals,a series of experiments including mercury intrusion porosimetry(MIP),low temperature nitrogen gas absorption/desorption(N_(2)GA)and nuclear magnetic resonance(NMR)are conducted in this study to characterize and quantify pore structure properties.The nature of occurrence of moisture content in coal reservoir pores is then divided into four categories by NMR saturation and centrifugation experiments.The bound water content in the adsorption pore accounts for the highest proportion.Based on the relevance of bound water content and its influencing factors,moisture occurrence in coal reservoirs of different ranks is revealed by SPSS statistical methods.The moisture content of low-rank coal is mainly controlled by elemental oxygen and specific surface area,whereas for medium-and high-rank coals,this is controlled mainly by minerals.Our study finds application in CBM evaluation and development.

Micropaleontology and palaeoclimate during the early Cretaceous in the Lishu depression,Songliao basin,Northeast China

Diverse and abundant microfossils, such as palynomorphs, algae and Ostracoda, were collected from lower Cretaceous strata of Lishu depression, located in southeastern Songliao basin, and were identified and classified in order to provide relevant, detailed records for paleoclimate research. The early Creta- ceous vegetation and climate of southeastern Songliao basin have been inferred from the analysis of palynomorph genera, algae and Ostracoda of the LSI and SW110 wells. The lower Cretaceous strata include, in ascending stratigraphic order, the Shahezi, Yingcheng and Denglouku formations. Palyno- logical assemblages for each formation, based on biostratigraphic and statistical analyses, provide an assessment of their longitudinal variations. During deposition of the Shahezi Formation, the climate was mid-subtropical. Vegetation consisted of coniferous forest and herbage. During deposition of the Ying- cheng Formation, the climate was south Asian tropical. Vegetation consisted mainly of coniferous forest and herbal shrub. In addition, fresh and saline non-marine water dominated the lacustrine setting during deposition of these formations. Deposition of the Denglouku Formation, however, occurred under a hot and dry tropical climate. The vegetation was mostly coniferous forest and lake waters became saline. Palaeoclimate variation is correlated by the lake level change and the development of sedimentary facies. Palaeoclimate contribute to the formation of hydrocarbon source rocks and reservoir.

Effects of uranium on hydrocarbon generation of hydrocarbon source rocks with type-Ⅲ kerogen

Organic-inorganic interaction exists universally and is important in the process of mineral resources formation.It is the essential reason why organic oil,gas,coal and inorganic uranium coexist,accumulate,and mineralize in the same sedimentary basins.Hydrocarbon-generating simulation experiment was conducted using low-mature hydrocarbon source rock containing kerogen type III with uranium(UO2CO3 solution)added to study the effects of uranium on the hydrocarbon generation of hydrocarbon source rocks.Experiment results show that uranium can enhance the yield of gas hydrocarbon,promote the total gas output,and increase the total hydrocarbon production(mass or volume).Uranium may lower the hydrocarbon generation threshold temperature and lead to the generation of liquid hydrocarbon in the relative low temperature of hydrocarbon source rock.Uranium can enhance the yield of saturated hydrocarbon,promote the low molecular weight hydrocarbons generating,and in turn increase the content of CH4 and the content of dry gas of the generated hydrocarbons.Uranium is one of the potential inorganic accelerating factors of the immature hydrocarbons.