Polycyclic aromatic hydrocarbons in soils of Beijing and Tianjin region: Vertical distribution, correlation with TOC and transport mechanism

The contents and distribution of 20 polycyclic aromatic hydrocarbons （PAHs） and heterocyclic aromatic hydrocarbons （HAHs） were investigated in 16 soil profiles of Beijing and Tianjin region. Transport of high molecular weight PAHs （HMWPAHs） and the correlation between total organic carbon （TOC） and their concentrations were also discussed. The results indicated that highly contaminated sites were located at urban or wastewater irrigation areas and pollutants mainly accumulated in topsoil （〈 40 cm）, with a sharp content decrease at the vertical boundary of 30-40 cm. Total PAHs/HAHs concentrations in soils from Tianjin were markedly greater than those from Beijing. Even the contents at bottoms of soil profiles in Tianjin were higher than those in topsoils of Beijing soil profile. HMWPAHs dominated the PAH profiles, exhibiting a uniform distribution of pyrogenic origin between topsoils and deep layers. Furthermore, the percentages of HMWPAHs remained relative constant with the depth of soil profiles, which were consistent with the distribution of particulate matter-associated PAHs in the local atmospheric environments. Therefore, HMWPAHs transport with particulates might be the predominant source found in soil profiles.

Effects of temperature and surfactants on naphthalene and phenanthrene sorption by soil

Adsorption experiments were carried out to investigate the sorption behaviors of naphthalene and phenanthrene in six different soils and to determine the effects of temperature, linear alkylbenzene sulfonate （LAS） and cetylrimethyl ammonium bromide （CTAB） on sorption. The results show that for a given sorbent phenanthrene exhibited greater nonlinear and stronger sorption than naphthalene. There was a strong negative correlation for the Koc values with organic carbon content （foc）. The increase of temperature was not favorable to sorption. Sorption decreased along with the increasing aqueous LAS concentration from 0 to 1000 mg/L. At low CTAB concentration （〈 100 mg/L）, the adsorption increased as CTAB hemimicelles formed on the soil surface. At high concentration, CTAB decreased the adsorption by occupying active hydrophobic adsorption sites and solubilization of naphthalene and phenanthrene.

Polygonal faults in the Sanzhao sag of the Songliao basin:their significance in hydrocarbon accumulation

Polygonal faults,generally distributed in fine-grained sediments,are layer-bound faults and are important in hydrocarbon accumulation.Using 3D seismic data,we analyzed the plane and profile features of faults developed in the Qingshankou formation of the Sanzhao sag.We identified these faults as having typical features of polygonal faults:1) layer-bound;2) normal faults;3) slight fault displacements and steep in dip angles;4) multi-directional in strike and 5) a single fault has a short horizontal extension.In addition,these faults intersect each other and form polygons.These polygonal faults are the result from the combined action of compaction,volume contraction and episodic hydraulic fracturing,conditions favorable for oil/gas accumulation.They are the dominant channels for migration of fluids in the Qingshankou mudstone,forming a large number of fault-lithologic oil traps.Polygonal faults improve reservoirs.

Geochemical characteristics and origin of reservoir bitumens from Well Zhong 1 in the Katake Uplift,Tarim Basin

The source of marine crude oils from Tarim Basin is still disputed.However,research on the reservoir bitumens may provide a piece of new evidence to elucidate oil source.Geochemical characteristics of reservoir bitumens from different strata from Well Zhong 1 in the Katake Uplift were discussed here in detail.Pr/Ph ratios of reservoir bitumen from Well Zhong 1 range from 1.14 to 1.39,CPI ratios from 1.01 to 1.08,which indicates no odd-even predominance of normal alkanes,with OEP ratios ranging from 0.98 to 1.05.The contents of gammacerane and C28 sterane of reservoir bitumen from Well Zhong 1 are low,while dibenzothiophene series are abundant.Ster-ane isomerization maturity parameter and Ts/(Ts+Tm) ratio indicate that the reservoir bitumen from Well Zhong1 is mature to highly mature.Based on the differences in biomarker distribution,it is concluded that reservoir bitumen from Well Zhong 1,of which molecular parameters are contrary to those in Cambrian oil from Well Tadong 2,origi-nated from the Upper Ordovician source rocks.

Effect of Faulting on Ordovician Carbonate Buried-Hill Reservoir Beds in Hetianhe Gas Field, Tarim Basin

Ordovician carbonate buried-hill reservoir beds in the Hetianhe （和田河） gas field, located in the Mazhatage （玛扎塔塔） structural belt on the southern margin of the Bachu （巴楚） faulted uplift, southwestern Tarim basin, were studied. Based on field survey, core and slice observation, the general characteristics of carbonate buried-hill reservoir beds and specifically Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were discussed. The karst zone of the reservoir beds in Hetianhe gas field was divided into superficial karst zone, vertical infiltration karst zone, lower subsurface flow karst zone, and deep sluggish flow zone from top to bottom. The effects of faulting on Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were obvious. The faulting intensified the karstification and increased the depth of denudation. Faulting and subsequent fracture growth modified the reservoir beds and improved the physical property and quality of the reservoir beds. Moreover, faulting enhanced the development of the dissolution holes and fractures and increased the thickness of the effective reservoir beds. Meanwhile, faulting made the high porosity-permeability carbonate belts, which created conditions for the hydrocarbon accumulation, develop near the fault zone.

Segment, Linkage, and Extensional Fault-Related Fold in Western Liaodong Bay Subbasin, Northeastern Bohai Sea, China

The western Liaodong （辽东） Bay subbasin displays examples of segment, linkage of extensional fault, and fault-related folds. The Liaoxi （辽西） extensional fault system consists of a series of NNE- and NE-trending segments that were linked through relay ramps. The fault hanging walls are characterized by a series of en echelon synclines with axial traces sub-parallel to the faults. The synclines are doubly plunging located on the hanging wall of normal faults, with the strata dip sub-parallel to the fault. These folds result from along-strike displacement variations of the individual fault segments, as well as from extensional fault-related folding. In the study area, the synclines are separated by transverse intra-basin highs and relay ramps that formed where segment linkage occurred. These hanging wall synclines and their relation to fault displacement variations indicate that they are formed by extensional fault-related fold.