Hydrocarbon charge history of the Paleogene reservoir in the northern Dongpu Depression,Bohai Bay Basin,China

The hydrocarbon charge history of the Paleogene in the northern Dongpu Depression was analyzed in detail based on a comprehensive analysis of the generation and expulsion history of the major hydrocarbon source rocks, fluorescence microscopic features and fluid inclusion petrography. There were two main stages of hydrocarbon generation and expulsion of oil from the major hydrocarbon source rocks. The first stage was the main hydrocarbon expulsion stage. The fluorescence microscopic features also indicated two stages of hydrocarbon accumulation. Carbonaceous bitumen, asphaltene bitumen and colloidal bitumen reflected an early hydrocarbon charge, whereas the oil bitumen reflected a second hydrocarbon charge. Hydrocarbon inclusions also indicate two distinct charges according to the diagenetic evolution sequence, inclusion petrography features combined with the homogenization temperature and reservoir burial history analysis. According to these comprehensive analysis results, the hydrocarbon charge history of the Paleogene reservoir in the northern Dongpu Depression was divided into two phases. The first phase was from the late Dongying depositional period of the Oligocene to the early uplift stages of the late Paleogene. The second phase was from the late Minghuazhen period of the Pliocene to the Quaternary. Reservoirs formed during the first period were widely distributed covering the entire area. In contrast,reservoirs formed during the second period were mainly distributed near the hydrocarbon generation sags. Vertically, it was characterized by a single phase in the upper layers and two phases in the lower layers of the Paleogene.

System design and measurements of flux concentrator and its solid-state modulator for CEPC positron source

Positron sources are one of the most important components of the injector of a circular electron positron collector(CEPC).The CEPC is designed as an e^(+)e^(−)collider for a Higgs factory.Its accelerator system is composed of 100-km-long storage rings and an injector.The design goal of the positron source is to obtain positron beams with a bunch charge of 3 nC.The flux concentrator(FC)is one of the cores of the positron source.This paper reports the design,development,and measurements of an FC prototype system.The prototype includes an FC and an all-solid-state high-current pulse modulator.Preliminary tests show that the peak current on the FC can reach 15.5 kA,and the peak magnetic field can reach 6.2 T.The test results are consistent with the theoretical simulation.The FC system fulfills the requirements of the CEPC positron source as well as provides a reference for the development of similar devices both domestically and abroad.

Coupling relationship between reservoir diagenesis and hydrocarbon accumulation in Lower Cretaceous Yingcheng Formation of Dongling,Changling fault depression,Songliao Basin,Northeast China

The Lower Cretaceous Yingcheng Formation in the southern Songliao Basin is the typical tight oil sandstone in China.In order to better predict the petrophysical properties of the tight sandstone reservoirs in the Lower Cretaceous Yingcheng Formation,Songliao Basin,Northeast China,the diagenesis and porosity evolution was investigated using a suite of petrographic and geochemical techniques including thin section analysis,scanning electron microscopy,mercury intrusion and fluid inclusion analysis,on a set of selected tight sandstone samples.Combined with the histories of burial evolution,organic matter thermal evolution and hydrocarbon charge,the matching relationship between reservoir porosity evolution and hydrocarbon accumulation history is analyzed.The result showed that the tight sandstone reservoirs characterized of being controlled by deposition,predominated by compaction,improved by dissolution and enhanced by cementation.The hydrocarbon accumulation period was investigated using a suite of hydrocarbon generation and expulsion history,microfluorescence determination and temperature measurement technology.According to the homogenization temperature of the inclusions and the history of burial evolution,Yingcheng Formation has mainly two phases hydrocarbon accumulation.The first phase of oil and gas is charged before the reservoir is tightened,the oil and gas generated by Shahezi source rocks enter the sand body of Yingcheng Formation,influenced by the carrying capability of sand conducting layer,oil and gas is mainly conducted by the better properties and higher connectivity sand body and enriched in the east,which belongs to the type of densification after hydrocarbon accumulation.The second phase of oil and gas charge after densification,which belongs to the type of densification before the hydrocarbon accumulation.

Overpressure and gas charging in tight sandstone:Xujiahe Formation,northeastern Sichuan Basin

Overpressure is a key factor for oil and gas charging in tight reservoirs,but it is still a challenge to evaluate the overpressure evolution and its control on oil and gas charging.Taking Xujiahe Formation in the northeastern Sichuan Basin as an example,this paper presented a method for evaluating overpressure and its effect on natural gas charging in tight sandstone in compressional basin.The abnormally high pressure and its causes were analyzed by measured data and logging evaluation.Theoretical calculation and PVT simulation were used to investigate the amounts of overpressure resulted from hydrocarbon generation and tecto nic compression,respectively.Then the source rock-reservoir pressu re differences were calculated and the characteristics of natural gas charging during the natural gas charging periods were analyzed.It was revealed that hydrocarbon generation and tectonic compression were the main causes of the overpressure.The overpressure of both source rocks and reservoir exhibited a gradually increasing trend from Middle Jurassic to Early Cretaceous(J2-K1),then decreased since Later Cretaceous(K2),and some of that preserved to now.The contributions of the hydrocarbon generation and tectonic compression to overpressure were different in different periods.The residual pressure difference between the source rocks and the reservoir is the major driving force for tight sandstone gas charging.The main hydrocarbon generating area of the source rocks and the area of high driving force were major natural gas enrichment areas,and the driving force determined the natural gas charging space in the pore throat system of the reservoir.This research helps evaluate the overpressure and pressure difference between source rocks and reservoir in compressed basin,as well as investigate the effective pore throat space of tight gas charging by the driver of overpressure.

Waveguide distribution system of the HEPS linac

Purpose The High-Energy Photon Source(HEPS)is a 6 GeV storage ring-based light source under construction in Beijing,China.Its accelerator consists of a 6 GeV storage ring,a full-energy booster,an S-band normal-conducting 500 MeV linac,and three transport lines.As the beginning of HEPS,a stable linac is quite important,which needs a qualified waveguide distribution system to transmit microwave power from klystrons to accelerating structures.Methods Installation and high-power conditioning of the HEPS linac were performed from February to September 2022.The assembly and conditioning of the waveguide distribution system were completed in April and July,respectively.The design of the waveguide distribution system began in 2018 and was finalized at the end of 2020 after multiple iterations.Results Owing to careful design,fabrication,and assembly preparation,the assembly and conditioning of the system proceeded smoothly and considerable time was saved.Conclusion The entire process from the design to the ultimate realization of the system is introduced in detail in this paper.Satisfactory measurement results were obtained for some waveguide components.

Research on the measurement and shielding methods of the spatial electromagnetic radiation of the BEPCⅡLinac

Purpose The research focuses on the related measurement and shielding works for solving the spatial electromagnetic radiation and interference problems of the BEPCⅡLinac.Methods The radiation frequency and intensity can be determined by using a set of antennas connected with a spectrum analyser.Results The source of the radiation is located on the cable connectors of some device panels.The radiation intensity is significantly reduced after wrapping the connectors with the radiation shielding tape.Conclusions The entire research process includes the selection of a domestically made ultra-wideband antenna,the proposal of the measurement methods,the locating of the radiation source,the performance measurement of the radiation shielding tape and the shielding of the radiation.It provides a whole set of feasible solutions for similar problems in accelerators.

RF design and test of a high-directivity high-power waveguide directional coupler for the HEPS

Purpose A novel high-directivity high-power waveguide directional coupler(DC)working at 2998.8 MHz is developed for the High Energy Photon Source.It can help the phase control system to obtain a very accurate microwave signal,which is very important to minimize the beam emittance.Methods The novel reversely placed T-type coupling piece helps to obtain a high directivity.The N-type high-vacuum feedthroughs for vacuum sealing instead of the traditional ceramic plate is beneficial to holding a higher peak power.The simulation and the high-power commissioning are accomplished in the Institute of High Energy Physics(IHEP),while the fabrication and the low-power test are conducted in cooperation with the manufacturer.Results Both the single-coupler and the dual-coupler DCs are developed with a directivity of more than 35 dB while keeping the coupling factor within 60±0.5 dB.Finally,69.4%of all the fifty-two mass produced DCs have got a directivity of more than 40 dB.Conclusion:The mature manufacturing process for mass production is obtained.The novel high-directivity high-power waveguide DC can be mass produced with an actually internationally leading performance.

Radio-frequency design and commissioning of a flexible waveguide for high-vacuum S-band applications

Purpose Flexible waveguides,which allow for greater deformation as compared to traditional hard waveguides,are highly useful for simplifying waveguide system assemblies.However,the peak powers of these waveguides have been limited to several megawatts in non-vacuum environments.Herein,a novel flexible waveguide was developed for the S-band(2856 MHz)with the aim of facilitating the interconnection of two hard waveguides.Methods The flexible waveguide was composed of brass,and its surface was plated with oxygen-free high-conductivity copper for brazing with stainless steel flanges in a vacuum furnace.By connecting the stainless steel flanges together,it can be applied to a high-vacuum environment.Results The prototype exhibited good measurement results in low-power microwave tests;the results of a 72-h vacuum leak test showed satisfactory vacuum performance as well,and no obvious surface collapse was observed.High-power microwave commissioning was conducted between June and July 2019;the waveguide showed a maximum average power of approximately 2.7 kW.Conclusion Unfortunately,the prototype was damaged after reaching that power level,which indicates the need for further optimization of the fabrication process.From our experiment,it is clear that the flexible waveguide cannot be used in large accelerators because of its average power limit.