Wan Yuqing, Lv Jun-e Tan Furong, Liu Zhuo, Qiao Junwei
03 Sep 2012 to 03 Sep 2012
Gas hydrate is ice-like solid material forming by gas and water in the low temperature and high pressure, it’s better known as "flammable ice". It is an unconventional energy with high density and clean energy sources. Therefore, from 2011 to 2012 China coal geology administration bureau entrusted Aerial Photogrammetry and Remote Sensing Bureau (ARSC) to carry out natural gas hydrate exploration method research under the Qinghai-Tibet plateau mainly with remote sensing and GIS technology.
After Summarizing and analyzing the previous research results, the work group selected Muli coal field where natural gas hydrate had been found and Qiangtang basin which had a bright prospect in natural gas hydrate as the research areas. We followed the following process to research.
First, we used remote sensing technology as an important means to analyze image features in visible-near infrared and thermal infrared bands over working areas to search direct and indirect interpretation marks for gas hydrates for reference of defining the target areas.
The second step was to do the field investigation over the target and adjacent areas specially the place where natural gas hydrate had been found, and carry out geological survey to observe the strata, tectonics, occurrence environment. Simultaneously collected samples from strata and drilling holes to analyze the existence of hydrocarbon (gas) source in rocks, studied the material foundation of natural gas hydrate formation and accumulation, identified and determined the position of hydrocarbon source rocks, petrological characteristics, the structure background of the development and sedimentary environment, the exhibition character of research area in space and time, and the evolution rule. These were the fundamental and precondition for evaluating and predicting natural gas hydrate resource in sedimentary basin, and were major geological questions to be answered for exploration. By test and analysis organic type of hydrocarbon source rocks, organic matter and the thermal evolution level, they were elements for comprehensive analysis, we selected the most advantageous distribution areas as hydrocarbon source target areas, which located in Jurassic strata in MuLi coal field?
Based on the previous work, combined with the analysis of the existing data about geological construction, geophysical and geochemical data over research area, and using natural gas hydrate reservoiring elements as marginal condition, We quantified all factors and finished digital processing. Then we used GIS platform to make comprehensive analysis with ground elevation, permafrost thickness, geothermal gradient, inversion temperature from thermal image within MuLi coalfield, and then defined the final target areas.
In the paper, the validity analysis about remote sensing and GIS technology for natural gas hydrate had been discussed, which also provided a new technology for gas hydrates exploration over Qinghai-tibet plateau.
In the study, the authors also found some signs over gas hydrates areas, such as lots of hot abnormalities over water bodies on thermal infrared band of ETM+ image; there were a lot of mud volcanoes in Qiangtang basin; and longtime continuous bubbles and orange sediment in about 50% marsh puddles during field survey, etc. The formation mechanism of these phenomena were worth researching.
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