Sichuan Basin Of China Research Articles

Application of NMR logs in tight gas reservoirs for formation evaluation: A case study of Sichuan basin in China

Permeability, irreducible water saturation and other information associated with the pore size, such as capillary pressure, are very important input parameters in tight gas reservoir evaluation. Fortunately, those parameters can be well estimated from field NMR logs, if the proper calibrations between NMR relaxation time and capillary pressure were established with measurements from core samples. In this study, a novel calibration technique, which is used for constructing capillary pressure curve from NMR logs by combining the classical SDR model with J function, is proposed and the corresponding model is established. Based on the laboratory measurements of 54 plug samples taken from the Upper Triassic sandstone formation (Xujiahe Formation) in Anlu district, Sichuan basin, Southwest China, the model parameters are calibrated. With the calibrations established and procedures proposed in this paper, the synthetic capillary pressure curves of reservoir can be constructed from field NMR spectrum. Also from those laboratory measurements, the parameter of Kϕ (defined as the pore structure index) can be well related to the Swanson's parameter derived from capillary pressure curve. This correlation could then be used for estimating reservoir permeability from the synthetic capillary pressure curve. After formation is classified into three types by using the pore structure index, the pore throat radius cutoffs can be acquired to calculate irreducible water saturation from the pore throat radius distribution. The proposed techniques and procedures are applied in field logs and the estimated information and parameters are well verified by core and drill stem testing data. By combining with the information of reservoir pore structure, permeability and irreducible water saturation, potential low resistivity contrast gas bearing reservoirs can be identified from water layers.

Overviews of Failure Mode and Reconstruction of Road Traffic Facilities in Wenchuan Earthquak-stricken Areas

On 12 May 2008, the devastating magnitude 8.0 (Wenchuan, Sichuan Province) struck the Longmen Shan and neighboring region, which are located at the eastern edge of the Tibetan plateau and the western Sichuan basin in China. In the earthquake-stricken areas, road traffic facilities, especially bridge structures, were also destroyed heavily under the action of seismic waves. Because the secondary geological disaster of Wenchuan events were also serious, how to analyze damage modes of highway traffic facilities scientifically and organize rebuilding of transportation and construction of emergency road network in the earthquake-stricken areas have become an urgent topic to decisionmakers and engineers. According to geological structure and seismic features, damage modes of highway traffic facilities were analysed, and restoration and reconstruction of transportation would be characterized by its long-running works. It is concluded from the field investigations that the wrecked pavements in the seismic region are with extrusion and tenso-shear failure characteristics, and the destroyed side slopes of roadbed have the wrecking modes which collapse on the coseismic responses or damage because of the secondary geological disaster, and the destroyed bridges are characterized by abutment subsidence, piers damage, impact extrusion damage, bridge span damage and so on. In accordance with the damage modes of highway traffic facilities above, some attentive problems about the road traffic restoration and reconstruction of the earthquake-stricken areas are preliminarily discussed. Language: en

Allelopathic Effects of Twelve Hedgerow Plant Species on Seed Germination and Seedling Growth of Wheat (<i>Triticum astivum L.</i>)

In laboratory bioassay, conducted to study the allelopathic influence of aqueous extracts (0, 2.5, 5.0, 7.5, 10.0% concentration) of twelve hedgerow plant species (Amorpha fruticosa L., Citrus reticulate Banco., Coronilla varia L., Eriobotrya japonica Thunb., Eulaliopsis binata Retz., Gynura bicolor DC., Hemerocallis citrine Baroni., Medicago sativa L., Morus alba L., Toona sinensis Roem., Vetiveria zizanioides L., Zanthoxylum schinifolium Sieb.) which planted in the purple hilly area of Sichuan basin in China was on the germination and seedling growth of wheat (Triticum astivum L.). At 10.0% concentration, The aqueous extracts of twelve hedgerow plant species significantly inhibited the seed germination and seedling growth of wheat except that A. fruticosa, E. binata and V. zizanioides extracts had no effect or slight inhibition on germination of wheat, but the degree of inhibition was species dependent. The allelopathic effect of aqueous extracts from hedgerow plants on wheat was maximum with G. bicolor, H. citrine, C. varia and M. sativa in terms of germination, and G. bicolor , M. sativa, M. alba and H. citrine in terms of shoot length, root length and dry weight, respecitively. The degree of inhibition increased with increase in concentration. Duplication of this work under field conditions is needed, for which the results of this study will form a valuable base.

Spatial distributions and seasonal cycles of aerosols in India and China seen in global climate-aerosol model

Abstract. A climate-aerosol model is employed to study spatial and temporal variability of aerosol properties over India and China for recent (year 2006) and future conditions (year 2020) under different emission pathways. We present results for aerosol mass concentration in different size classes and optical properties for the five different aerosol species treated by the model. Aerosol mass concentration and optical depth have significant contributions from both anthropogenic and natural aerosols. Different species have maxima in different regions, with the highest anthropogenic aerosol concentrations found in Kolkata and elsewhere in the Ganges basin in India and on the northern part of the east coast and in the Sichuan basin in China. In India, natural aerosols have a maximum in the summer due to higher wind speeds, whereas anthropogenic aerosols have a maximum in the winter due to less efficient wet removal. Surface concentrations also tend to be higher in winter due to the additional reason of lower average boundary layer height. In China, seasonal cycles are weaker with natural aerosols having a maximum in the spring and sulfate contribution to the aerosol optical depth (AOD) being higher in the latter half of the year. MODIS AOD spatial distributions are reproduced well by the model, except for the Ganges valley with high absorption and for the Thar desert with high dust concentrations. Seasonal cycles compare qualitatively well with MODIS measurements.

Multi-scale frequency and absorption attributes of seismic signals

Seismic absorption is sensitive to gas saturation, and this can lead to a number of observable features, such as low dominant frequency, absence of high frequencies and dimming of reflections. We obtain the time–frequency distribution of seismic signals at different scales based on wavelet decomposition and try to analyse the response of high-frequency sections for the characterization of hydrocarbon reservoirs. We present a case study using multi-scale (dominant) frequency and multi-scale absorption, and demonstrate that the method is effective in recognizing a deep tight-sandstone gas reservoir. By this study, we can draw the conclusion that multi-scale frequency and absorption attributes may indicate the gassy areas in reservoirs, and we have obtained many good applications in the Sichuan basin of China.

Effects of Conservation Tillage on Organic Carbon and Carbon Management Index in Paddy Soil

Effects of different tillage systems on organic carbon and carbon management index (CMI) in paddy soil of long-term experiment site (since 1990) were studied. The experiment included three tillage treatments: conventional tillage with rotation of rice and winter fallow (CT-r) system, no-tillage and ridge culture with rotation of rice and rape (RT-rr) system, and conventional tillage with rotation of rice and rape (CT-rr) system. Soil labile organic carbon measured by oxidation of KMnO4 respond rapidly to carbon supply changes, and it is considered as an important indicator of soil quality. Compared with CT-r system, long-term RT-rr system significantly increased total organic carbon and labile organic carbon in surface soil (0-10 cm and10-20 cm). The proportion of labile organic carbon to total organic carbon under RT-rr system was higher than other tillage systems. The carbon management index (CMI) is derived from the total soil organic carbon pool and carbon lability and is useful to evaluate the capacity of management systems to promote soil quality. The CMI increased in each layer under RT-rr system, while it decreased under CT-rr system. This indicated that conservation tillage improved the capacity of the management system into promoting soil quality in Sichuan Basin of China.

Generation processes of mesoscale convective systems following midlatitude troughs around the Sichuan Basin

[1] The generation processes of mesoscale convective systems (MCSs) that occurred over the Sichuan Basin in China were revealed in the early 2008 monsoon season. MCS occurrences detected in METEOSAT geostational satellite images are associated with the traveling of midlatitude troughs after the onset of the Indian monsoon. Three episodes of large-scale MCSs were generated under synoptic conditions of merging southwesterly low-level monsoon flows with a northerly midlatitude air mass following the trough in the leeward of the Tibetan Plateau without direct migration of the vortex generated from the plateau surface. Numerical simulations using a weather research and forecast (WRF) model showed that the MCS was triggered in the evening by strengthening of the low-level wind convergences with horizontal shear between the southerly monsoon flow, with large convective available potential energy, and the northerly dry intrusion. A sudden increase in the northerly winds was confirmed by sonde observation data in the western basin, and the winds were simulated as intrusions passing over the Qinling Mountains when the daytime clouds over the mountain were diminished. Sensitivity experiments by a WRF simulation revealed that the topography of the Sichuan Basin was able to capture the dry intrusion at the bottom to prevent the propagation of disturbances from the plateau and to cause the sudden onset of MCSs apart from the plateau with a heavy precipitation zone.

One‐year follow‐up analysis of cognitive and psychological consequences among survivors of the Wenchuan earthquake

The catastrophic Wenchuan earthquake measuring 8.0 on the Richter scale occurred on May 12, 2008 in the West of the Sichuan basin in China and caused severe damage. A project was undertaken to examine the cognitive and psychological effects one year after the disaster among 2080 individuals in the local area. We evaluated the influence of gender, age, education level, and ethnic group on five aspects: work satisfaction, living satisfaction, health self-perception, psychological pressure, and psychological recovery. Male subjects had a better performance in all five aspects, which indicated that women were more affected. Subjects of different ethnic groups showed significantly different attitudes with respect to psychological pressure and psychological recovery. Significant differences for all the five aspects were also found in education level and age. The results showed that older people and those with a lower education level probably had more psychological problems. There were significant correlations between work satisfaction and living satisfaction, living satisfaction and health self-perception, living satisfaction and psychological recovery, and psychological pressure and psychosocial recovery. Living satisfaction and education level were significant predictors of psychological pressure. For psychological recovery, significant predictors were living satisfaction, age, work satisfaction, education level, and gender. The study findings indicated that government programs should provide more support for females, older people, those with a lower education level, and those in lower living conditions. Attention should be given not only to the psychological effects on each victim, but also to related issues such as work and living conditions to promote psychological wellbeing. Limitations of this study are addressed.

Characterization of Vegetative Insecticidal Protein vip Genes of Bacillus thuringiensis from Sichuan Basin in China

Vegetative insecticidal proteins (Vip), the second generation of insecticides, are produced during the vegetative growth stage of Bacillus thuringiensis (Bt). To perform a systematic study of vip genes in Bt strains from different ecological regions of Sichuan Basin, 1,789 soil samples were collected from this basin, which is situated in the western region of China. The basin has a complicated geomorphology and contains mountains, forests, highlands, hursts, and plains. A total of 2,134 Bt strains have been screened from the 1,789 soil samples. According to the results, three vip-type genes were found in this basin, namely the vip1, vip2, and vip3-type genes. Strains containing vip3-type genes were the most abundant in our collection (67.4%), followed by vip2-type genes (14.6%) and vip1-type genes (8.1%). The three types of vip genes were distributed in most of the regions, but E Mei Mountain and the Ba Lang Mountains only contained vip3 genes in environments with high elevation, low temperature, insufficient oxygen, and abundant snow. Moreover, five novel vip3 genes were found, and these Vip proteins were toxic for Chilo suppressalis. All the results mentioned above suggest that Sichuan Basin is a rich resource for vip genes.

Environmental factors of road slope stability in mountain area using principal component analysis and hierarchy cluster

Nine environmental factors of 147 roadside soil samples were administered in Sichuan Basin of China and principal component analysis was conducted using the Pearson correlation matrix. The results show that the first four principal components whose eigenvalue is over 1.00 can be extracted. The first principal component which is consisted of rock type, soil type, weathering degree, and soil depth is the most important factor of all. The geographical position which is consisted of altitude, longitude, and latitude is included in the second and the third principal components. The fourth principal component shows that the terrain factor influences the rock slope stability. The hierarchy cluster shows that rock type and soil type play the maximum positive correlation, while the slope and the aspect present the maximum negative correlation.

Effects of vegetation cover on phosphorus loss from a hillslope cropland of purple soil under simulated rainfall: a case study in China

Nutrients and sediment lost through runoff to surface and ground water represents a risk to human and environmental health. In order to understand the mechanisms of nutrient and sediment loss under different levels of vegetation cover, we conducted a simulated rainfall experiment on hillslope cropland in the Sichuan Basin of China. The experiment was performed on a 4.5 m long × 1.5 m wide × 0.6 m deep plot to analyze the mechanisms of overland flow, subsurface flow, sediment yield, and P loss for bare soil, and soil with 25, 50, 75, and 90% vegetation coverage. The results showed that total sediment loss and total bioavailable P (BAP) loss by overland flow decreased with increasing coverage; the rate of P release from fertilizer decreased with increasing time during a rain event and increasing coverage; and the growth in vegetation shoots and roots improved soil physical properties around roots, thus increasing P absorbance and the infiltration rate. Hence, we suggest increasing vegetation coverage to conserve soil and reduce BAP loss by sediments, and paying more attention to groundwater affected by pollutant transport through subsurface flows.

Simulation of direct effects of black carbon aerosol on temperature and hydrological cycle in Asia by a Regional Climate Model

The simulation of direct radiative effect of black carbon (BC) aerosol over Asia is carried out with application of Regional Climate Model RegCM3 over the period of 1993–2003 based on BC emission inventory in 2000. Major findings are as follows. The column burden of BC exceeds 1 mg/m2 in central, eastern, and southern China with the highest value of 2.5 mg/m2 over Sichuan Basin of China, and is of 1–2 mg/m2 in India subcontinent. The column averaged advection field of BC shows an eastward tendency in north of 20° N, whereas an opposite trend is found in south of 10° N. Off-line radiative forcing (RF) induced by BC, which is due to direct absorption or scattering of BC, is positive at the top of the atmosphere (TOA), while maximum effect is found over Sichuan Basin. The RF is of 1–1.5 W/m2 in areas such as the middle and low reaches of the Yangtze River, East China Sea, South China Sea, Indo-China Peninsula and most parts of Indian subcontinent. Surface RF is found to be negative and its absolute value is larger than that at TOA. Based on simulation results, BC’s impacts on temperature, stratification stability, water vapor, precipitation and evaporation etc., are primarily characterized by cold-and-wet change in southern and northwest China, cold-and-dry change in northern and northeast China, warm-and-wet change of India subcontinent, as well as warm-and-dry change of Central Asia.

Mitochondrial DNA Diversity of Monopterus albus from the Sichuan Basin of China

Genetic diversity of Monopterus albus in a wild population in the Sichuan Basin was investigated by employing mtDNA polymorphisms. The mitochondrial control region was sequenced for a total of 59 individuals collected from four localities. These sequences (553 bp) belonged to 13 haplotypes defined by eight polymorphic sites. The haplotypes were clustered into one lineage, suggesting that Monopterus albus from the Sichuan Basin might originate from a single ancestor in maternal lineages. The genetic differentiation between the population from Zhongxian in Chongqing city and the other three populations, from Mianyang, Longchang, and Ya'an in Sichuan province (F (ST): 0.29167-0.55126), was higher than that among the latter three (F (ST): -0.04196 to 0.05984). Little genetic differentiation was found in the three populations from Sichuan province (Nm: -6.21 to 3.93), and the Zhongxian population also showed lower genetic heterogeneity (P (i): 0.00077 +/- 0.00027; H (d): 0.404 +/- 0.130). The combination of limited variation and weak phylogenetic structure revealed that the Monopterus albus from the Sichuan Basin exhibited lower mtDNA diversity and should probably be treated as a monogroup genetically.

Stress changes from the 2008 Wenchuan earthquake and increased hazard in the Sichuan basin

On 12 May 2008, the devastating magnitude 7.9 (Wenchuan) earthquake struck the eastern edge of the Tibetan plateau, collapsing buildings and killing thousands in major cities aligned along the western Sichuan basin in China. After such a large-magnitude earthquake, rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. The mainshock of the 12 May earthquake ruptured with as much as 9 m of slip along the boundary between the Longmen Shan and Sichuan basin, and demonstrated the complex strike-slip and thrust motion that characterizes the region. The Sichuan basin and surroundings are also crossed by other active strike-slip and thrust faults. Here we present calculations of the coseismic stress changes that resulted from the 12 May event using models of those faults, and show that many indicate significant stress increases. Rapid mapping of such stress changes can help to locate fault sections with relatively higher odds of producing large aftershocks.

Halomonas saccharevitans sp. nov., Halomonas arcis sp. nov. and Halomonas subterranea sp. nov., halophilic bacteria isolated from hypersaline environments of China

Three strains of Gram-negative, aerobic, neutrophilic and halophilic bacteria were isolated from samples of a salt lake on the Qinghai-Tibet Plateau and a subterranean saline well in the Si-Chuan Basin of China. These isolates, designated AJ275(T), AJ282(T) and ZG16(T), were investigated using a polyphasic approach. Based on 16S rRNA gene sequence analysis, the isolates could be affiliated to the genus Halomonas. Genomic DNA G+C contents were 65.9 mol% for AJ275(T), 56.7 mol% for AJ282(T) and 57.6 mol% for ZG16(T). The results of DNA-DNA hybridizations, fatty acid analysis and physiological and biochemical tests allowed the isolates to be differentiated genotypically and phenotypically from closely related species. It is proposed that strains AJ275(T) (=CGMCC 1.6493(T)=JCM 14606(T)=LMG 23976(T)), AJ282(T) (=CGMCC 1.6494(T)=JCM 14607(T)=LMG 23978(T)) and ZG16(T) (=CGMCC 1.6495(T)=JCM 14608(T)=LMG 23977(T)) represent the type strains of three novel species in the genus Halomonas: Halomonas saccharevitans sp. nov., Halomonas arcis sp. nov. and Halomonas subterranea sp. nov., respectively.

Application of Stepwise Discriminant Analysis for the Identification of Salinity Sources of Groundwater

Statistical analysis can be an important tool to identify and classify different sources of groundwater salinisation. This paper refers to the application of Stepwise Discriminant Analysis (SDA) as an effective technique for the identification of major constituent ratios which can be used for efficiently identifying various salinity sources. The effectiveness of the SDA method was tested on five groups of groundwater samples known for their salinisation. Three were taken from the brackish groundwater of the Nestos River delta, from the geothermal field of Nea Kessani and the brackish groundwater of the western coastal area of Rhodope, in Greece. The remaining two groups were taken from bibliographic sources and they refer to the degraded groundwater of the Wittmund area in coastal NW Germany as well as from the underground brines of Sichuan Basin in China. The method of SDA has demonstrated its effectiveness of classifying different groundwater groups, and its usefull contribution to the groundwater contamination. In this way, possible expensive field investigations and analyses of chemical parameters can be eliminate.

Methane-dominated thermochemical sulphate reduction in the Triassic Feixianguan Formation East Sichuan Basin, China: towards prediction of fatal H 2S concentrations

New sour pools have recently found in the Lower Triassic Feixianguan Fm carbonate reservoirs in the East Sichuan Basin in China with H 2S up to 17.4% by volume. A recent blowout from a well drilled into this formation killed hundreds of people as a result of the percentage concentrations of H 2S. In order to assess the origin of fatal H 2S as well as the cause of petroleum alteration, H 2S concentrations and the isotopes, δ 34S and δ 13C have been collected and measured in gas samples from reservoirs. Anhydrite, pyrite and elemental sulphur δ 34S values have been measured for comparison. The high concentrations of H 2S gas are found to occur at depths >3000 m (temperature now at ∼100 °C) in evaporated platform facies oolitic dolomite or limestone that contains anhydrite nodule occurrence within the reservoirs. Where H 2S concentrations are greater than 10% its δ 34S values lie between +12.0 and +13.2‰ CDT. This is within the range of anhydrite δ 34S values found within the Feixianguan Fm (+11.0 to +21.7‰; average 15.5±3.5‰ CDT). Thus H 2S must have been generated by thermochemical sulphate reduction (TSR) locally within the reservoirs. Burial history analysis and fluid inclusion data reveal that the temperature at which TSR occurred was greater than about 130–140 °C, suggesting that the present depth-temperature minimum is an artifact of post-TSR uplift. Both methane and ethane were actively involved in TSR since the petroleum became almost totally dry (no alkanes except methane) and methane δ 13C values become significantly heavier as TSR proceeded. Methane δ 13C difference thus reflects the extent of TSR. While it is tempting to use a present-day depth control (>3000 m) to predict the distribution of H 2S in the Feixianguan Fm, this is an invalid approach since TSR occurred when the formation was buried some 1000–2000 m deeper than it is at present. The likelihood of differential uplift across the basin means that it is important to develop a basinal understanding of the thermal history of the Feixianguan Fm so that it is possible to determine which parts of the basin have been hotter than 130–140 °C.

Thermochemical sulphate reduction and the generation of hydrogen sulphide and thiols (mercaptans) in Triassic carbonate reservoirs from the Sichuan Basin, China

The Sichuan Basin in China is a sour petroleum province. In order to assess the origin of H2S and other sulphur compounds as well as the cause of petroleum alteration, data on H2S, thiophene and thiol concentrations and gas stable isotopes (δ34S and δ13C) have been collected for predominantly gas phase petroleum samples from Jurassic, Triassic, Permian and Upper Proterozoic (Sinian) reservoirs. The highest H2S concentrations (up to 32%) are found in Lower Triassic, anhydrite-rich carbonate reservoirs in the Wolonghe Field where the temperature has reached >130 °C. δ34S values of the H2S in the Wolonghe Triassic reservoirs range from +22 to +31‰ and are close to those of Triassic evaporitic sulphate from South China. All the evidence suggests that the H2S was generated by thermochemical sulphate reduction (TSR) locally within Triassic reservoirs. In the Triassic Wolonghe Field, both methane and ethane seem to be involved in thermochemical sulphate reduction since their δ13C values become less negative as TSR proceeds. Thiol concentrations correlate positively with H2S in the Triassic Wolonghe gas field, suggesting that thiol production is associated with TSR. In contrast, elevated thiophene concentrations are only found in Jurassic reservoirs in association with liquid phase petroleum generated from sulphur-poor source rocks. This may suggest that thiophene compounds have not come from a source rock or cracked petroleum. Rather they may have been generated by reaction between localized concentrations of H2S and liquid range petroleum compounds in the reservoir. However, in the basin, thiophene concentrations decrease with increasing vitrinite reflectance suggesting that source maturity (rather than source type) may also be a major control on thiophene concentration.

A NEW MODEL FOR DIURNAL FLUCTUATION IN SOIL TEMPERATURE: THE DAMPING WAVE EQUATION

Using an XQC-300 electronic temperature recorder, a continuous automatic record of the in situ diurnal changes in soil temperature under different weather conditions over several years was collected in a valley of the Sichuan Basin in China. A vast amount of experiment data was obtained. Analysis of the measurements of diurnal fluctuation in soil temperature showed that the fluctuation could be described by a damping wave equation. A comparison was made between the damping wave equation and the sine wave equation to describe the diurnal fluctuation under different weather conditions and in different seasons. The results showed that the damping wave equation was more accurate. Using given boundary conditions, a damping wave equation describing the diurnal fluctuation at different depths of the soil body was derived from the heat flow equation. The calculated result and the measured data at different depths in an upland and a paddy soil were found to be in good agreement. These results show that the damping wave equation is much better than the sine wave equation in describing the diurnal changes of soil temperature and that the sine wave equation is a special case of the damping wave equation when the damping coefficient equals zero.

Evaluation of Sichuan Basin in China: ABSTRACT

Evaluation of Sichuan Basin in China: ABSTRACT