Geochemical characteristics and genetic types of crude oils from the Tertiary system in the southern part of western Qaidam Basin,Northwest China

Crude oil samples taken from the southern part of western Qaidam Basin were analyzed with GC/MS in order to understand the geochemical characteristics of crude oils.The results reveal that most crude oils are characterized by high abundance of gammacerane and C35 homohopane,which are the representative characteristics of saline lacustrine crude oils.Based on the variation of the ratios of gammacerane/C30 hopane(G/H) and C35 homoho-pane/C34 homohopane(C35/C34H),two crude oil groups,A and B,are identified.Group-A crude oils mainly occurr in the north of the study area,with higher ratios of G/H(>0.8) and C35/C34H(>1.2),whereas group-B crude oils,selected from the south of the study area,show lower ratios of G/H(<0.8) and C35/C34H(<1.0).In addition,group-A crude oils are distinguished into three subgroups in accordance with their different ratios of G/H and C35/C34H and different distribution characteristics of n-alkanes,isoprenoids and steranes.These may be helpful for understanding the distribution characteristics of crude oils in the southern part of western Qaidam Basin and providing clues to the forthcoming exploration of crude oils and gas.

Structural Evolution of the Eastern Qiulitagh Fold and Thrust Belt,Northern Tarim Basin,China

东方 Qiulitagh 褶层和戳带(EQFTB ) 是活跃 Kuqa 褶层的部分和北 Tarim 盆的戳带。地震思考侧面与地质的表面和练习数据是综合的检验变丑和 EQFTB 的结构风格，特别地第纳干扰器的 deformational 历史 2 煤气的地。地震解释建议 Dongqiu 8 是双结构在被动房顶戳下面开发了的外套，它在中新世的 Jidike 形成从一根尖端线产生了，并且脚底推进从在 Kuqatawu 背斜下面向西延长的一样的 Jidike 形成 evaporite 地区被开始。Dongqiu 5 是在 EQFTB 的西方的部分的弹出式结构，也在 Jidike 形成 evaporite 下面发展了。在 EQFTB 的很轻轻的地下室剧降和陡峭的蘸的地志的斜坡建议 Jidike 形成盐提供有效去耦。在 EQFTB 的强壮的变丑向南显得发展了进一步，在 evaporite 可能正在缺乏的一个区域。自从上新世， EQFTB 在 evaporite 上向南远移动了并且到达了 Yaken 区域。恢复一张平衡剖面图建议越过 EQFTB 的最小的弄短是超过 7800 m。假设这弄短发生在 5.3 妈期间预定平底锅，弄短的率是约 1.47 公里 / 年。

Rhus laccase catalysis and product characterization of 1,2-dimethoxyphenol in organic solutions

Dimethoxyphenol was a widely used substrate in determination of laccases activity.It was surprised,however,that the products of it had not been completely determined until now.Studies were thus conducted on Rhus laccase (RL) and immobilized Rhus laccase (IRL)-catalyzed oxidation of 2,6-dimethoxyphenol (DMP) in water-organic solvent systems.Only one product,3,3′,5,5′- tetramethoxy-1,1′-biphenyl-4,4′-diol (TMBP),was produced by RL catalysis,and it was thoroughly characterized by FT-IR,NMR and GC-MS,etc.

Formation and evolution of petroliferous basins in African continent and their hydrocarbon distribution

There are eighty sedimentary basins in five different types in African continent,i.e.craton sag basin,foreland basin,intermountain basin,passive margin basin and rift basin,which underwent the stress environment of stable depression-compression-extension.The first three types of basins had been intensely influenced by Hercynian and Alpine tectonic movement,while the later two types of basins always exist in a stable extension environment.Different basin evolution caused the obviously hydrocarbon distribution difference.In North Africa,marginal craton sag and rift basins show great expedition potential of hydrocarbon,marginal craton sag basins had good formation and preservation of Lower Silurian hot shale,tectonic-strata traps and migration pathway formed by Hercynian unconformity,and rift basins had excellent Upper Cretaceous marine source rocks and good hydrocarbon preservation with little tectonic activity.Meanwhile,in the salt-containing passive margin basins and delta basins of West Africa,thick strata containing high quality source rocks and plastic strata were well developed.Source rocks of high maturity,good hydrocarbon preservation,growth faults and deformational structure traps were formed by abundant overlying sediments and sources supplied from Tertiary large water system.

Organic Matter and Elemental Composition of Mudstones in the Member 3 of Paleogene Shahejie Formation in the Dongying Depression, Eastern China

The organic matter distribution and hydrocarbon generation potential as well as element distribution in the lacustrine mudstones of lower Member 3 of Paleogene Shahejie Formation in the Dongying depression, eastern China were investigated using methods of Rock-Eval pyrolysis, inductively coupled plasma emission spectrometer. The results show that most of the samples are high-quality source rocks with high TOC and?S2, and the oil shale samples are excellent source rocks with the TOC and?S2?greater than 5.0% and 20.0 mg/g, respectively. A freshwater depositional?environment in the deep lake for the mudstones was indicated by lower values of biomarker?ratios gammacerane/C30?Hopane and C35Hopane/C34?Hopane. With the lacustrine regression, the ratios Ca/U, Ca/Ba, Ca/Mg, Ca/B, Ca/Li, Ca/Sr and Sr/Ba decrease, while Fe/(Ca + Mg) increases. In the section 3330 - 3370 m with enrichment of oil shale, the organic matter and inorganic elements present strong fluctuation. The quantitative relations among U, U/Th and TOC,?S2, %Ca are divided into two parts at boundary values of 7.0%, 32 mg/g and 11% for TOC,?S2?and %Ca, respectively.

Geochemical characteristics of oils among real cores in displacement model

Physical simulation experiment on oil displacement is an important approach to understand the mechanism and efficiency of displacement. Physical simulation experiments on water-flooding and chemical flood-ing in real cores with different lithologies and physical properties, reservoir Rock-Eval, TLC-FID, GC of saturated hydrocarbon fractions and GC-MS of saturated and aromatic hydrocarbon fractions were performed to investigate differences in the geochemistry of residual oils in the cores processed by water-flooding and chemical flooding. After fine sandstone was displaced with the two methods, the preferable replacement efficiency was displayed by the chemical constitutions of residual oils. As to glutenite, water-flooding is less effective, while chemical flooding has excellent performance according to changes in chemical compounds in oils. The results showed that the geochemical characteristics of the reservoir oils and lithology and physical properties of reservoir bed need to be considered in selecting replacement methods. In addition, the geochemical parameters for residual oils slightly changed during water-flooding and chemical flooding, which suggested the water-flooding and chemical flooding could not affect the application of these parameters in geochemistry.

Study of NMR porosity for terrestrial formation in China

NMR logging is an effective method for porosity measurement. NMR-derived porosity only comes from the pore fluid and is, in principle, not affected by rock matrix. However, it is found that the difference between NMR-derived and conventional log-derived porosities is often between 2 to 6 pu, which is unacceptable, in terrestrial formation in China. In the paper, the theory of NMR porosity was reviewed. The influence factors on NMR porosity error were analyzed based on NMR core measurements. More than 30 core samples with a wide range of porosities including sandstone, limestone and artificial ceramic were chosen for the conventional and NMR porosity measurements. The current NMR data acquisition method was studied based on laboratory NMR core meas- urements and found to be not good for terrestrial formation. A new NMR data acquisition method suiting for terrestrial formation in China was proposed and much improved the accuracy of NMR porosity measurement. It is suggested that the analysis of core samples from different regions should be carried out before logging in order to obtain accurate NMR porosity.

Simulation experiments on the reaction system of CH_4-MgSO_4-H_2O

H2S-rich gas in carbonate reservoirs is usually attributed to thermochemical sulfate reduction (TSR). In this paper, thermal simulation experiments on the reaction system of CH4-MgSO4-H2O were carried out using autoclave at 425℃―525℃. The threshold temperature for initiating TSR is much lower than our previous studies (550 ℃ ). Properties of the reaction products were analyzed by microcoulometry, gas-chromatography (GC), Fourier transform-infrared spectrometry (FT-IR) and X-ray diffraction (XRD) methods. Thermodynamics and reaction kinetics of TSR processes were investigated on the basis of the experimental data. The results show that thermochemical reduction of magnesium sulfate with methane can proceed spontaneously to produce magnesium oxide, hydrogen sulfur, and carbon diox-ide as the main products, and high temperature is thermodynamically favorable to the reaction. Ac-cording to the reaction model, the calculated activation energy of TSR is 101.894 kJ/mol, which is lower than that by most previous studies. Mg2+ may have played a role of catalytic action in the process of TSR. The elementary steps of TSR and reaction mechanism were discussed tentatively. The study can provide important information on the explanation of geochemical depth limit for natural gas and on the generation of high H2S gas in deep carbonates reservoirs.