Sichuan-Chongqing Region Research Articles

Vibration Analysis of a Drillstring in Horizontal Well

The complicated geological conditions will bring great challenges to the drillstring of horizontal wells for the reason that the increase of the well depth in SichuanChongqing region. Since drillstring failure and friction during drilling are generally caused by drillstring vibration, great importance must be attached to computer simulation methods for the prediction of drillstring vibration. A finite element model considering axial, lateral and torsional vibration is established. In order to verify the established numerical model, an indoor experimental device based on the similarity principle was established. The vibration characteristics of three shale gas horizontal wells drillstrings are described. The reasons for the large difference in vibration characteristics between the three wells were discussed by changing the well structure, BHA(bottom hole assembly) and drilling parameters. The simulation results show that the depth of ultra-deep well 3 is only 1.27 times of that of medium-deep well 2, but the fluctuation of WOB (weight on bit) is 2.8 times. The primary factor for the great difference of WOB fluctuation is the change of vertical section depth, the secondary factor is the change of the horizontal section length. Additionally, the reasonable range of speeds has been proposed and applied in the field. The advantage of this numerical analysis method is that it can judge the vibration and friction torque of drillstring in horizontal wells with arbitrary structure, drilling parameters and BHA. This method has certain guiding significance to the field practice.

Changes in Haze Trends in the Sichuan-Chongqing Region, China, 1980 to 2016

This study analyzed the long-term variations and trends of haze pollution and its relationships with emission and meteorological factors using the haze days (HDs) data derived from surface observation stations in Sichuan-Chongqing (SCC) region during 1980–2016. The results showed that the multi-year mean number of HDs were 68.7 and 4.9 days for the Sichuan-Basin (SCB) and the rest of SCC region, respectively. The seasonally averaged HDs over SCB reached its maximum in winter (34.7 days), followed by autumn (17.0 days) and spring (11.6 days), and with the minimum observed in summer (5.5 days). The inter-annual variations of HDs in 18 main cities revealed that Zigong, Neijiang, and Yibin, which are located in the southern of SCB, have been the most polluted areas over the SCC region in the past decades. A notable increasing trend in annual HDs over the majority of SCC region was found during 1980–1995, then the trend sharply reversed during 1996–2005, while it increased, fluctuating at some cities after 2006. Seasonally, the increased trend in spring and autumn seems to be the strongest during 1980–1995, whereas the decreased trend in spring and winter was stronger than other seasons during 1996–2005. In addition, a remarkable increasing trend was found in winter since 2006. Using correlation analysis between HDs and emission and meteorological factors during different periods, we found that the variability of local precipitation days (PDs), planetary boundary layer height (PBLH), near-surface wind speed (WS), and relatively humidity (RH) play different roles in influencing the haze pollution change during different historical periods. The joint effect of sharp increase of anthropogenic emissions, reduced PDs and WS intensified the haze pollution in SCB during 1980–1995. In contrast, decreased HDs during 1996–2005 are mainly attributable to the reduction of PM2.5 emission and the increase of PDs (especially in winter). In addition, the decrease of PDs is likely to be responsible for the unexpected increase in winter HDs over SCB in the last decade.

Study on the Instability Mechanisms and Monitoring Control of Stratified Rock Slope with Water-Rich Strata

Water is one of the leading factors in the sliding geological disasters of rock slope, and the harm of fissure water to slope rock mass more and more becomes one of the hotspot research problems in transportation infrastructure construction in mountainous area. Based on the current research status quo of effect of fissure water on rock mass, the interaction mechanisms of water and rock in stratified rock slope were analyzed by related theories such as rock mass mechanics, fluid mechanics and soil mechanics including softening dissolution, scour hole enlargement and padding effective stress, and the influence of water–rock interaction on slope sliding disasters. Then, the influence of rainfall on the displacement field distribution of slope was analyzed during one year of monitoring a typical,natural slope in the Sichuan–Chongqing region. Observations include surface displacement, deep displacement, water level and rainfall. Finally, a targeted reinforced disposal scheme was proposed that considered the rainfall effect. The results provide reference for the instability theory and treatment measures for a high-risk stratified slope.

Comprehensive drought index as an indicator for use in drought monitoring integrating multi-source remote sensing data: a case study covering the Sichuan-Chongqing region

ABSTRACTNumerous meteorological drought-monitoring indices and remote-sensing-based spatial drought monitoring indices have been developed and applied to monitor drought in different ways. However, individual indices have obvious deficiencies in terms of their responses to drought, and they do not comprehensively reflect the available information on drought. To overcome issues with the data themselves and improve drought monitoring techniques, we use a comprehensive drought index (CDI) derived from the vegetation condition index, the temperature condition index, and the precipitation condition index to monitor meteorological or agricultural drought for the Sichuan-Chongqing region. To assess CDI performance, monthly CDI values for Sichuan-Chongqing region were used to analyse the spatial and temporal variations of the 2006 drought. The results indicated that all aspects of the drought were monitored, and the results were in agreement with related research. Meanwhile, an extreme drought was accurately explored using the CDI in the Sichuan-Chongqing region from 2000 to 2011. Finally, a validation was performed, and the results show that the CDI is closely related with the standardized precipitation index calculated using a 3-month time scale (SPI3), as well as variations in crop yield and drought-affected crop area. These results provide further evidence that the CDI is an indicator that can be used in integrated drought monitoring and that it can simultaneously reflect meteorological and agricultural drought information.

Relationship between atmospheric heat source over the Tibetan Plateau and precipitation in the Sichuan–Chongqing region during summer

NCEP–NCAR reanalysis data and a 47-yr daily precipitation dataset from a network of 42 rain gauges are used to analyze the atmospheric heat source ( ) anomaly over the Tibetan Plateau (TP) and its influence on the summer precipitation anomaly in the Sichuan–Chongqing region. Results show that the vertical advection of over the central TP is a major factor affecting summer precipitation in the Sichuan–Chongqing region. When the vertical advection of over the central TP is strengthened, the South Asian high shifts further than normal to the south and east, the western Pacific subtropical high shifts further than normal to the south and west, and the Indian low weakens. This benefits the transport of warm moist air from the low latitude oceans to the Sichuan–Chongqing region. Correspondingly, in the high latitudes, two ridges and one trough form, which lead to cool air moving southward. These two air masses converge over the Sichuan–Chongqing region, leading to significant precipitation. In contrast, when the vertical advection of over the central TP is weakened, the South Asian high moves to the north and west, the subtropical high moves eastward and northward, and the Indian low strengthens. This circulation pattern is unfavorable for warm air advection from the south to the Sichuan–Chongqing region, and the cool air further north cannot move southward because of the presence of two troughs and one ridge at high latitude. Thus, ascent over the Sichuan–Chongqing region is weakened, resulting in less precipitation.

Thinking on Sichuan-Chongqing gas pipeline transportation system reform under market-oriented conditions

The gas pipeline networks in Sichuan and Chongqing (Sichuan-Chongqing) region have formed a fully-fledged gas pipeline transportation system in China, which supports and promotes the rapid development of gas market in Sichuan-Chongqing region. In the circumstances of further developed market-oriented economy, it is necessary to carry out further the pipeline system reform in the areas of investment/financing system, operation system and pricing system to lay a solid foundation for improving future gas production and marketing capability and adapting itself to the national gas system reform, and to achieve the objectives of multiparty participated pipeline construction, improved pipeline transportation efficiency and fair and rational pipeline transportation prices. In this article, main thinking on reform in the three areas and major deployment are addressed, and corresponding measures on developing shared pipeline economy, providing financial support to pipeline construction, setting up independent regulatory agency to enhance the industrial supervision for gas pipeline transportation, and promoting the construction of regional gas trade market are recommended.

乡土植物生活型构成对川渝地区边坡植被水土保持效益的影响

乡土植物生活型构成对川渝地区边坡植被水土保持效益的影响

Applicability analysis of the TRMM precipitation data in the Sichuan-Chongqing region

Precipitation data is often needed for hydrological, meteorological, ecological, and other environmental and geographic applications. Currently there are mainly two sources of precipitation estimates: observation at meteorological stations and remote sensing data. However, a large number of studies has demonstrated that measurements at conventional meteorological stations are point data and they cannot reflect the spatial variation of precipitation effectively, especially in areas of more complex terrain. Remote sensing technology, on the other hand, is able to produce reasonably high resolution gridded precipitation fields. Precipitation products obtained by satellites have been widely used in previous studies in the world. The Sichuan-Chongqing region is a typical area with complicated terrain and climate characteristics. The meteorological stations are very unevenly distributed in this region, especially in the western area. Precipitation estimation using satellite data provides potential alternatives to precipitation measurements in this region. In this study,the performance of the TRMM(Tropical Rainfall Measurement Mission) 3B43 monthly precipitation data over 2000-2011 was evaluated in the SichuanChongqing region with rainfall records from 72 meteorological stations at different time intervals. The influence of elevation and slope on the verification result was analyzed at the monthly scale. Finally, principal component analysis was used to compare the effects of elevation and slope on the accuracy of TRMM 3B43 precipitation estimates. The results show that:(1) Regional average annual precipitation estimated by TRMM 3B43 is higher than the observed data from meteorological stations by 5.38%, and the eastern area estimation results are less accurate than the western plateau. Goodness of fit of seasonal precipitation between TRMM 3B43 estimates and observed data is high, but varies between the seasons—the goodness of fit of spring precipitation is higher than other seasons. Correlation between observations at the 72 stations and TRMM 3B43 estimates is high and shows little numerical biases in the whole study area at the monthly scale.(2) For individual stations, at most stations the correlation coefficients are reasonably high and the estimation biases are small, but the correlation coefficient at the Xuyong Station is comparatively low and the estimation biases at the Xiaojin Station, Yaan Station, Leibo Station, Yanyuan Station, and Panzhihua Station are comparatively high.(3) Compared with slope, elevation has greater influence on the accuracy of TRMM 3B43 estimates, which can be characterized by a cubic nonlinear relationship. With the increase of Elevation, R shows an increasing trend and |Bias(%)| increases-decreases-increases.(4) The influence of slope on the accuracy of TRMM 3B43 estimates is more complicated. Generally speaking, slope significantly affects the accuracy of TRMM 3B43 estimates

Financial Geography in Xikang Region During the Late Qing and the Republic of China Era

After a series of economic and social changes in the late Qing era, a new scene emerged in Xikang-Tibetan region with Kangding (Dajianlu) as the commercial and trade center. The commercial and trade foundation was more solidified when Kangding became the regional financial center. Since the Republican era, with the radiation and drive of the new financial center in Sichuan-Chongqing region, partial modernization of financial instruments appeared in Xikang region, followed by gradual replacement of old currency by new currency. Through the establishment and expansion of Xikang provincial bank and the promotion and maturity of rural cooperative finance during the anti-Japanese war period, Kham’s finance when Kangding served as the regional financial center was fully incorporated into the new financial geographic landscape in Sichuan-Chongqing region.

Theoretical Foundation and Disciplinary Construction of Chinese Historical Financial Geography: A Case Study of Financial Geography in Sichuan- Chongqing Region During the Late Qing and the Republic of China Era

As a branch of economic geography, the theoretical origins of financial geography are multiple, which increasingly shows the vitality and advantages of interdiscipline. As an important component of economic geography, the research contents and measures of China’s historical economic geography have been continuously expanding in recent years with the development of times, which is a major feature of rising discipline. During its development process, China’s economic geography has been subject to many influences including the former Soviet Union and other Western economic geographical ideas, it is possible and also necessary to critically use the still growing Western economic geographical ideas for reference in China’s economic geographical research, scope of such research should include regional finance of historical periods, in this sense, the research of financial geography in Sichuan-Chongqing region in modern times, which has relatively strong regional change characteristics and practical reference value, is undoubtedly a valuable research content.

Comparative Analysis of Catechin and Caffeine Content of Wild Tea Plant in Sichuan-Chongqing Region

Comparative Analysis of Catechin and Caffeine Content of Wild Tea Plant in Sichuan-Chongqing Region

The characteristics of temperature variability with terrain, latitude and longitude in Sichuan-Chongqing Region

Using the daily temperature data of 95 meteorological stations from Sichuan-Chongqing Region and its surrounding areas, this paper adopted these methods (e.g., linear regression, trend coefficient, geographical statistics, gray relational analysis and spatial analysis functions of GIS) to analyze the relations of temperature variability with topography, latitude and longitude. Moreover, the rank of gray correlation between temperature variability and elevation, longitude, latitude, topographic position and surface roughness also was measured. These results indicated: (1) The elevation affected temperature variability most obviously, followed by latitude, and longitude. The slope of the linear regression between temperature change rate and elevation, latitude and longitude was 0.4142, 0.0293 and −0.3270, respectively. (2) The rank of gray correlation between temperature change rate and geographic factors was elevation > latitude > surface roughness > topographic position > longitude. The gray correlation degree between temperature change rate and elevation was 0.865, followed by latitude with 0.796, and longitude with 0.671. (3) The rate of temperature change enhanced with the increase of elevation. Especially, the warming trend was significant in the plateau and mountain areas of western Sichuan, and mountain and valley areas of southwestern Sichuan (with the warming rate of 0.74°C/10a during the 1990s). However, there was a weak warming trend in Sichuan Basin and its surrounding low mountain and hilly areas. (4) The effects of latitude on temperature change rate presented the specific regulation, which the warming rate of low-latitude areas was more significant than that of high-latitude areas. However, they were consistent with the regulation that the increasing of low temperature controlled most of the warming trend, due to the effects of terrain and elevation on annual mean temperature. (5) Basically, temperature variability along longitude direction resulted from the regular change of elevation along longitude. It was suggested that, in Sichuan-Chongqing Region, special features of temperature variability largely depended on the terrain complexity (e.g., undulations, mutations and roughness). The elevation level controlled only high or low annual mean temperature and the range of temperature change rate in the macro sense.

Calculation analysis of sustained casing pressure in gas wells

Sustained casing pressure (SCP) in gas wells brings a serious threat to worker safety and environmental protection. According to geological conditions, wellbore structure and cement data of gas wells in the Sichuan-Chongqing region, China, the position, time, environmental condition and the value of SCP have been analyzed. On this basis, the shape of the pressure bleed-down plot and pressure buildup plot were diagnosed and the mechanism of SCP has been clarified. Based on generalized annular Darcy percolation theory and gas-liquid two-phase fluid dynamics theory, a coupled mathematical model of gas migration in a cemented annulus with a mud column above the cement has been developed. The volume of gas migrated in the annulus and the value of SCP changing with time in a gas well in Sichuan have been calculated by this model. Calculation results coincided well with the actual field data, which provide some reference for the following security evaluation and solution measures of SCP.