As an important pilot target for shale gas exploration and development in China,the Longmaxi Formation shale in the Dianqianbei Area is characterized by high content of nitrogen,which severely increases exploration ri...As an important pilot target for shale gas exploration and development in China,the Longmaxi Formation shale in the Dianqianbei Area is characterized by high content of nitrogen,which severely increases exploration risk.Accordingly,this study explores the genesis of shale gas reservoir and the mechanism of nitrogen enrichment through investigating shale gas compositions,isotope features,and geochemical characteristics of associated gases.The high-nitrogen shale gas reservoir in the Longmaxi Formation is demonstrated to be a typical dry gas reservoir.Specifically,the alkane carbon isotope reversal is ascribed to the secondary cracking of crude oil and the Rayleigh fractionation induced by the basalt mantle plume.Such a thermogenic oil-type gas reservoir is composed of both oil-cracking gas and kerogen-cracking gas.The normally high nitrogen content(18.05%-40.92%) is attributed to organic matter cracking and thermal ammoniation in the high-maturity stage.Specifically,the high heat flow effect of the Emeishan mantle plume exacerbates the thermal cracking of organic matter in the Longmaxi Formation shale,accompanied by nitrogen generation.In comparison,the abnormally high nitrogen content(86.79%-98.54%) is ascribed to the communication between the atmosphere and deep underground fluids by deep faults,which results in hydrocarbon loss and nitrogen intrusion,acting as the key factor for deconstruction of the primary shale gas reservoir.Results of this study not only enrich research on genetic mechanism of high-maturity N_@ shale gas reservoirs,but also provide theoretical guidance for subsequent gas reservoir resource evaluation and well-drilling deployment in this area.展开更多
In this paper, it is proved that the direction of the node-voltage difference vector, which is the difference between the node-voltage vector at faulty state and the one at the nominal state, is determined only by the...In this paper, it is proved that the direction of the node-voltage difference vector, which is the difference between the node-voltage vector at faulty state and the one at the nominal state, is determined only by the location of the faulty clement in linear analog circuits. Considering that the direction of the node-voltage sensitivity vector is the same as the one of the node-voltage difference vector and also considering that the module of the node-voltage sensitivity vector presents the weight of the parameter of faulty element deviation relative to the voltage difference, fault dictionary is set up based on node-voltage sensitivity vectors. A decision algorithm is proposed concerned with both the location and the parameter difference of the faulty element. Single fault and multi-fault can be diagnosed while the circuit parameters deviate within the tolerance range of 10 %.展开更多
基金financially supported by the National Science and Technology Major Project (2017ZX05063002–009)National Natural Science Foundation of China (41772150)+1 种基金Sichuan Province’s Key Project of Research and Development (18ZDYF0884)Qian Ke He Platform Talents [2017]5789-16。
文摘As an important pilot target for shale gas exploration and development in China,the Longmaxi Formation shale in the Dianqianbei Area is characterized by high content of nitrogen,which severely increases exploration risk.Accordingly,this study explores the genesis of shale gas reservoir and the mechanism of nitrogen enrichment through investigating shale gas compositions,isotope features,and geochemical characteristics of associated gases.The high-nitrogen shale gas reservoir in the Longmaxi Formation is demonstrated to be a typical dry gas reservoir.Specifically,the alkane carbon isotope reversal is ascribed to the secondary cracking of crude oil and the Rayleigh fractionation induced by the basalt mantle plume.Such a thermogenic oil-type gas reservoir is composed of both oil-cracking gas and kerogen-cracking gas.The normally high nitrogen content(18.05%-40.92%) is attributed to organic matter cracking and thermal ammoniation in the high-maturity stage.Specifically,the high heat flow effect of the Emeishan mantle plume exacerbates the thermal cracking of organic matter in the Longmaxi Formation shale,accompanied by nitrogen generation.In comparison,the abnormally high nitrogen content(86.79%-98.54%) is ascribed to the communication between the atmosphere and deep underground fluids by deep faults,which results in hydrocarbon loss and nitrogen intrusion,acting as the key factor for deconstruction of the primary shale gas reservoir.Results of this study not only enrich research on genetic mechanism of high-maturity N_@ shale gas reservoirs,but also provide theoretical guidance for subsequent gas reservoir resource evaluation and well-drilling deployment in this area.
基金supported by Program for New Century Excellent Talents in University under Grant No.NCET-05-0804
文摘In this paper, it is proved that the direction of the node-voltage difference vector, which is the difference between the node-voltage vector at faulty state and the one at the nominal state, is determined only by the location of the faulty clement in linear analog circuits. Considering that the direction of the node-voltage sensitivity vector is the same as the one of the node-voltage difference vector and also considering that the module of the node-voltage sensitivity vector presents the weight of the parameter of faulty element deviation relative to the voltage difference, fault dictionary is set up based on node-voltage sensitivity vectors. A decision algorithm is proposed concerned with both the location and the parameter difference of the faulty element. Single fault and multi-fault can be diagnosed while the circuit parameters deviate within the tolerance range of 10 %.
