Preliminary Prediction and Evaluation of Source Rocks in theLunpola Basin, Tibet, China

Liu Yiming; Ye Jiaren; Cao Qiang; Liu Zhongrong; Yang Baolin

doi:10.3799/dqkx.2017.047

Abstract：As the only one basin which oil has come to the industrial standard in Tibet, it is believed that the Lunpola basin extend into rich-oil area, but exploration and investigation activities were limited, so that the development of Niubao Formation, palaeogene, is not clear, which not only limited the evaluation of oil and gas ,but also the exploration strategy.Based on the drilling, logging and related laboratory test data, an integrated approach involving the logging regression equation model and basin modeling technique was used to investigate the distribution of source rock, organic matter abundance and types in main period of Niubao Formation, and to reconstruct the source rock thermal evolution history, so an evaluation system for source rocks was presented in Lunpola basin.The following conclusions can be drawn: the Lunpola basin is riched by the source rocks of Niubao Formation, and the middle of the second member of Niubao Formation is widely distributed with large thickness, the date indicates that the source rock thickness in Jiangriacuo sag can reach above 400m, what`s more, the thickness of excellent source rocks (TOC>1.0%) can reach more than 170m;in general, the type of source rocks of Niubao Formation is good, with highest proportion of good-excellent source rock in the upper of the second member of Niubao Formation and lower proportion in the middle of the second member of Niubao Formation;parent material types of source rocks in Niubao Formation are mainly mixed type of type Ⅱ1-Ⅰ and have oil-prone characteristic;the maturities of organic matters are mainly high in the midwest and low in the east, the results indicate that the middle of the second member of Niubao Formation is middle and late mature, the upper of the second member of Niubao Formation and the bottom of the third member of Niubao Formation are immature to early mature to present-day.Therefore, in Lunpola basin, the middle of the second member of Niubao Formation is major source rock and Jiangriacuo sag is the most important hydrocarbon generating sag.