The contribution of different polyphenol compositions from chokeberry produced in China to cellular antioxidant and antiproliferative activities

Abundant polyphenols make chokeberry have beneficial antioxidant and antiproliferative activity. In order to explore the contribution of different polyphenols in chokeberry to these activities, this study was conducted to determine polyphenol composition from 7 chokeberry varieties produced in China. Totally, 11 kinds of main polyphenol monomers were identified and quantified by UPLC-Q-TOF-MS and UPLC-PDA. HepG2 cells were used to evaluate their cellular antioxidant and antiproliferative activities. Partial least squares method was utilized to analyze multivariate correlations between proportion of different composition and monomers in total polyphenols with these activities. The results showed that the highest proportion in chokeberry polyphenols was proanthocyanidins. In comparing the bioactivities of 7 varieties of chokeberry, ‘Viking' and purple chokeberry had the strongest antioxidant activity, while 'Fukangyuan 1#' had the strongest antiproliferative activity. In terms of the contribution sources of these bioactivities, the total antioxidant activity of chokeberry mainly depended on the contribution of free polyphenols. As the main source of cellular antioxidant activity, anthocyanins and neochlorogenic acid can provide more contribution. The antiproliferative activity mainly depended on the proportion of free polyphenols and proanthocyanidins in total polyphenols. The results may provide some new possibilities for the comprehensive utilization of polyphenols from chokeberry.

Spontaneous imbibition characteristics of shale oil reservoir under the influence of osmosis

The spontaneous imbibition(SI)process in shale oil reservoirs is not only infuenced by capillary force,but also by the osmotic pressure between the fracturing fuid and formation water in the nanopores media.In this study,experimental methods are used to investigate the mechanisms of osmosis in the SI,taking into account the presence of initial formation water in shale oil reservoirs.To investigate the efect of osmosis,SI experiments were performed on the fne-grained felsic shale of the Qikou sag of Dagang oilfeld.Low-feld NMR testers and high-precision electronic balances are utilized for the measuring of oil–water migration.The results show that,when Sw≠0,high-salinity fuid SI can be divided into four stages:initial imbibition stage,drainage stage,secondary imbibition stage and stationary stage;when Sw=0,there is no drainage stage of high-salinity fuid SI;when Sw≠0 or Sw=0,low-salinity fuid SI can be called the“osmosis-enhanced SI”;and we have found that“newly formed pores or microfractures”as well as reducing salinity can promote SI.This article presents a systematic study of SI of shale oil reservoirs under the infuence of osmosis,which provide useful information for reservoir numerical simulation and development program design.

Micropore structure characteristics and quantitative characterization methods of lacustrine shale-A case study from the member 2 of Kongdian Formation, Cangdong sag, Bohai Bay Basin

To better understand the micropore characteristics of lacustrine shale and develop quantitative methodsfor characterizing lacustrine shale, the reservoir space types, structures and spatial distribution patternsof effective pores in the shale of Member 2 of Kongdian Formation in Cangdong sag are studied usingcores, thin sections, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM),nuclear magnetic resonance (NMR), whole-rock X-ray diffraction (XRD) data, etc. Various shale porositycalculation methods are evaluated. The study results show that the reservoir spaces of the shale mainlyinclude three types, i.e., matrix pores, organic pores and fractures. Flaky pore throats formed bydissolution-induced pores and mould pores can improve the pore connectivity. NMR effective porosity ofthe shale varies from 0.59% to 4.42% with an average of 2.38%, accounting for 49.54% of the total NMRporosity and 34.53% of the gas porosity. The shale is divided into the unimodal-type felsic shale, bimodaltype felsic shale, carbonate shale and mixed shale. The different lithologies exhibit linear correlationsamong NMR, gas and effective porosities. The shale has effective porosity of 0.56%-4.53% with an averageof 2.12%. Furthermore, the shale reservoir is divided into four classes: Class I reservoir with effectiveporosities of more than 2.5%;Class II1 reservoir with effective porosity of 2.0%-2.5%;Class II2 reservoirwith effective porosity of 1.5%-2%;and Class III reservoir with effective porosity of less than 1.5%.

Geological characteristics and key exploration technologies of continental shale oil sweet spots: A case study of Member 2 of Kongdian Formation in the Cangdong sag in the Huanghua depression, Bohai Bay Basin

Under the general trend of stepping-up oil and gas exploration and development in China,the unconventional oil and gas resources such as shale oil and gas have become an important alternative.Abundant continental shale oil resources are developed in Member 2 of Kongdian Formation(Ek2)of the Cangdong sag in the Huanghua depression of the Bohai Bay Basin which has complex structure,strong heterogeneity,and large buried depth,thus,the geological characteristic of shale oil accumulation and key exploration technologies are investigated on base of the system coring of 635.8 m,centimeter-level fine description and analysis of over ten thousand samples,therefore,the“four accurate”technologies have been developed,including the accurate selection of sweet spot areas,accurate drilling of sweet spot layers,accurate fracturing of sweet spot layers and accurate measure of fracture-rich sections.The results show that the continental shale strata in Member 2 of Kongdian Formation can be divided into three types:felsic shale,limy dolomitic shale and mixed shale.The Member 2 of Kongdian Formation is characterized by diverse mineral components,abundant laminae,good source rocks and medium thermal evolution degree,tight reservoir with rich micropore and microfractures,high oil saturation and brittle mineral content,indicating good prospect of shale oil exploration.Through sedimentological study,TOC and Ro evaluation,brittle mineral calculation,and seismic fusion inversion,a total of 126 km^(2) of Class I sweet spots in Member 2 of Kongdian Formation was delineated comprehensively,which guides horizontal well deployment(Well GD1701H and Well GD1702H).The drilling rate of sweet spot of these two horizontal wells is up to 96%by tracing thin layer through fine calibration,locating compartment through fine inversion,ensuring window entry through precise positioning,and tracking sweet spot through adjustment.The “one-excellent and five-highs”criterion is used to select perforation points to realize differential designs of fracturing intervals and clusters.Micro-seismic and potentiometry monitoring show that the artificial fractures formed by volumetric fracturing are 300e400 m long and 120 m high,and control a volume of about 0.07 km^(3).The maximum daily oil production of two horizontal wells is 48 t and 66 t respectively to realize the economic exploitation of shale oil reserves controlled by fractures.The shale oil exploration in Member 2 of Kongdian Formation shows that the continental shale oil has great potential of exploration and development,and the above technologies are critical and effective for shale oil efficient recovery.

Fine-grained rock fabric facies classification and its control on shale oil accumulation: a case study from the Paleogene Kong 2 Member, Bohai Bay Basin

Lacustrine shale oil resources in China are abundant,with remarkable exploration breakthroughs being achieved.Compared to marine shale oil in North America,efficient exploration of lacustrine shale oil is more difficult;thus,selecting favorable layer and optimization zone for horizontal wells is more important.In this study,based on systematic coring of approximately 500 m fine-grained deposits of the Kong 2 Member,combining laboratory tests and log data,source rock geochemistry and reservoir physical properties,the favorable rock fabric facies for oil accumulation was analyzed and classified.First,the dominant lithologic facies,organic facies,and bed combination facies were determined based on mineral composition from logging,total organic content(TOC),and sedimentary structure.Secondly,10 fabric facies were classified by combining these three facies,with 4 fabric facies were found to have high TOC content,high total hydrocarbon,and strong fluorescence features,indicating good shale oil enrichment.Thirdly,the distribution of the upon good fabric facies was identified to be located at the top of the Kong 2 Member,with evidences of seismic resistivity inversion,thermal maturity,structure depth,and strata thickness.And the favorable facies were found to be stably distributed lateral at the area of about 100 km2.High oil flow has been detected at this layer within this area by several wells,including horizontal wells.The exploratory study of fabric facies classification and evaluation provides a new research idea for lacustrine shale oil exploration and effectively promotes breakthroughs in lacustrine shale oil exploration in Bohai Bay Basin.