Exploration progress of the Paleogene in Jiyang Depression,Bohai Bay Basin

With increased exploration in the faulted basins of eastern China,petroleum exploration in this region has been challenged by unclear remaining petroleum resources distribution,complex reservoir and hydrocarbon enrichment patterns,and lacking of suitable exploration techniques.Aiming at resolving these problems,studies on source rocks,reservoirs,hydrocarbon accumulation and geophysical prospection were carried out by laboratory analysis,reservoir anatomy,and seismic analysis.A highlyefficient hydrocarbon generation/expulsion model of source rocks in saline environment was established,which aided in the discovery of a new set of source rocks in the Jiyang Depression.This study also reveals the formation process of high-quality reservoir by alternating acid and alkaline fluids during deposition and diagenesis,and pattern of secondary pores development in deep clastic rocks.Through the fine anatomy of the oil reservoirs,an orderly distribution pattern of the oil reservoirs is established,and the potential exploration targets in the undrilled area are identified.In addition,single-point highdensity seismic acquisition and high-resolution imaging technologies are developed,enabling fine and efficient exploration in areas with high exploration maturity.The research result plays a leading and demonstrative role in the fine and efficient exploration of faulted basins in eastern China.

聚糖的合成及其在糖疫苗研究中的应用

糖类在各种生命活动过程中发挥着重要的作用,但聚糖的获得性问题和其相对较弱的免疫原性一直限制了糖化学生物学尤其是糖疫苗研究的发展.近年来,聚糖和糖复合物化学合成技术的进步很大程度上促进了糖疫苗(包括抗菌疫苗、抗肿瘤疫苗、抗HIV疫苗等)研究的兴盛.其中,寡糖一釜合成策略和固相合成策略大大提高了聚糖合成的效率;聚糖与载体蛋白偶联的复合物也成功提高了糖抗原的免疫原性.本文将结合本课题组的相关研究工作,简述糖类化合物化学合成的方法和策略方面的研究进展及其在糖疫苗研究中的应用,希望对更好地理解糖化学生物学特别是糖疫苗有所帮助.

Main Mechanism for Generating Overpressure in the Paleogene Source Rock Series of the Chezhen Depression,Bohai Bay Basin, China

The Chezhen depression,located in the south of Bohai Bay Basin,is an oil-producing basin in China. The third and fourth members of the Shahejie Formation(E(s3) and E(s4)) are the main source rock series in the Chezhen depression. Widespread overpressures occurred in the E(s3) and E(s4) from the depths of approximately 2 000 to 4 600 m,with the maximum pressure coefficient of 1.98 from drillstem tests(DST). Among the sonic,resistivity and density logs,sonic-log is the only reliable pressure indicator and can be used to predict the pore pressure with Eaton's method. All the overpressured mudstones in the source rock series have higher acoustic traveltimes compared with normally pressured mudstones at a given depth. The overpressured mudstones in the E(s3) and E(s4) units are characterized by a normal geothermal gradient,high average density values up to 2.5 g/cm^3,strong present-day hydrocarbon generation capability,abundant mature organic matter and high contents of residual hydrocarbons estimated by the Rock-Eval S1 values and chloroform-soluble bitumen "A" values. All suggest that the dominant mechanism for overpressure in the mudstones of source rock series in the Chezhen depression is hydrocarbon generation. A comparison between the matrix porosity of the normally pressured sandstones and overpressured sandstones,the quantitative evaluation of porosity loss caused by compaction and the conventional thin section inspection demonstrate that the sandstones in the Chezhen depression were normally compacted. The high contents of hydrocarbons in the overpressured reservoirs prove that the overpressure in the sandstones of the source rock series was caused by pressure transmission from the source rocks.

Shale Oil Reservoir Characteristics and Enrichment in the Jiyang Depression, Bohai Bay Basin, East China

Based on the observation of the well cores, thin section and FESEM, combined with X-ray diffraction, physical property testing and geochemical indicators, the reservoir characteristics and the controlling factors of the shale oil enrichment of the Ess 4-Esx 3 shale in the Jiyang depression were detailed analyzed. Studies show that carbonate and clay minerals are dominated in the shale. According to the triangle chart, the TOC content（2% and 4%）, carbonate and clay minerals, nine lithofacies have been identified. The reservoir space types are rich in the shale, in which, the laminated fractures, recrystallization intracrystalline pores and organic pores are high-quality reservoir spaces. The shale oil enrichment is mainly determined by the hydrocarbon-producing potential and reservoir capacity. The hydrocarbon-producing capacity is controlled by the organic geochemistry indicators, especially the TOC content for the study area, and the thickness of the organic-rich shale. The reservoir capacity is mainly affected by the lithofacies, the TOC content and the structural activities. In addition, the shale oil production is influenced by the fracability of the shale, which is mainly controlled by the lithofacies, structural activities, formation pressure, etc. The shale oil reservoir evaluation should focus on the TOC content, the thickness of the organic-rich shale, lithofacies and structural factor.

Basic characteristics and evaluation of shale oil reservoirs

Shale oil refers to liquid hydrocarbons existing in free,dissolved or adsorbed states in the effective source rock of mudstones or shales,where some residual oil is retained after hydrocarbon generation and expulsion from the mudstones or shales.Basically shale oil experiences no migration or only undergoes some primary,short-distance migration within the source rocks.So far,there is no consensus on the exact definition of shale oil in China.Researches on the reservoir-controlling factors and evaluation elements are also far from sufficient.In this study,shale oil reservoirs are defined as mudstones or shales excluding the interbedded or adjacent layers of coarser siliciclastic or chemical-biogenic lithofacies(e.g.siltstone,carbonate,salt or chert layers)in the source rocks.According to different reservoiring mechanisms,shale oil reservoirs are classified into“fracture type”and“matrix type”.The general features of shale oil reservoirs include:rich in organic matters,dominated by Type I and II_(1) kerogen(with Ro=0.6%-1.2%and total organic content(TOC)>2.0%),complex mineral compositions and laminated structures,tight storage space,low porosity and ultra-low permeability,and as well as the requirement for reservoir fracturing.This paper emphasizes the critical role of organic matter in the formation and evaluation of shale oil reservoirs,and its critical control on the oil generation potential and storage capacity of shale,which eventually determine the oil content and productivity of shale oil reservoirs.Besides,a set of reservoir evaluation criteria is also put forward with a focus on the TOC content,in which the threshold values of TOC are set to be 2%and 4%,and a variety of indicators are taken into account including the type and maturity of organic matter,the thickness of organic-rich shale,mineral compositions and rock types,porosity and permeability,and fracturing ability.The evaluation criteria divide shale oil reservoirs into three grades,i.e.,target reservoir,favorable reservoir and invalid reservoir.

Pressure field characteristics of petroliferous sags in Bohai Bay Basin: Implication for hydrocarbon enrichment

Pressure fields of different sags in a petroliferous basin were significantly different,and it was related to hydrocarbon enrichment.Based on pressure data of different sags in Bohai Bay Basin,types of pressure field and its distribution characteristics were well discussed,and relationships between overpressure and hydrocarbon generation,pressure field and hydrocarbon enrichment were also investigated.Results showed that the Paleogene pressure fields of different sags in Bohai Bay Basin could be divided into three types:normal pressure type,single overpressure type and double overpressure type.These three types of pressure fields had the zoned features in their distributions.The normal pressure fields were mostly distributed in peripheral sags of the basin,while the single overpressure fields were widespread in the basin,and the double overpressure fields were concentrated in the areas around the Bohai Sea.Hydrocarbon generation had a significant effect on overpressure formation,thus overpressure horizons generally were corresponded to major source rock horizons,and differences of filling evolution history and main hydrocarbon-generation strata of different sags might be important factors for the formation of these three types of pressure fields.Overpressure in source rock horizons was closely related to hydrocarbon enrichment.Horizontally,hydrocarbons were mainly distributed around the overpressure center,and the secondary migration distance of hydrocarbons was affected by the degree of overpressure.Vertically,hydrocarbon distributionwas controlled by the type of pressure fields.Hydrocarbons in the normal pressure sags were mainly enriched in the major hydrocarbon-generation horizons and their adjacent horizons,hydrocarbons in the single overpressure sags were mainly distributed in the hydrocarbon-generation horizons and its upper and lower horizons,while in the double overpressure sags,the hydrocarbon enrichment degree in Neogene was high.Hydrocarbon enrichment in sags was controlled by the degree of overpressure in hydrocarbon-generation horizons,and these oil-rich sags had relatively large overpressure degree.

An evaluation workflow for shale oil and gas in the Jiyang Depression, Bohai Bay Basin, China: A case study from the Luojia area in the Zhanhua Sag

Shale oil and gas plays in continental rift basins are complicated and have not been reported elsewhere.In the Luojia area of the Jiyang Depression,an evaluation workflow for shale oil and gas in this continental rift basin is proposed.Based on analysis of oil-and gas-related geological conditions,a favorable area of shale oil and gas can be identified,and a high-frequency sequence stratigraphic framework of the target area can be established,therefore,the spatiotemporal distribution of shale has been elucidated in the Luojia area.According to the rock texture,structure,composition and color,petrographic classification criteria for shale are determined,and well log data are used to demarcate,track and predict high-quality lithofacies.Based on geochemical analyses and physical simulations of hydrocarbon generation,abundance,types and maturity of organic matter are analyzed,furthermore,geochemical parameters criteria of hydrocarbon generation and the characteristics of oil and gas occurrence in shales can be determined.Storage space types,assemblages and evolution characteristics of shale reservoirs are studied through core observation,thin-section analysis,electron microscopy examination and fluorescence spectrometry.Combined with analysis of reservoir physical properties,the reservoir performance is evaluated.A saturation model is established based on core analysis,well-log interpretation and well-test production data.The model is further used for evaluation of the movable hydrocarbon contents and integrated assessment of the oil potential.Finally,the shale oil and gas production capacity and exploration prospects in the Luojia area are forecasted based on the analyses of factors controlling production capacity and the rock fracability.Through an integrated analysis of multi-factors(including the lithofacies,source rocks,reservoir properties,oil saturation,and production capacity),the shales in the Luojia area can be divided into three categories,i.e.,Class I(high porosity-high resistivity),Class II(medium porosity-medium resistivity),and Class III(low porosity-medium resistivity).