The National Gas Hydrate Program expeditions(NGHP-01 and-02)have conclusively proven the presence of hydrate deposits on the eastern coast of India.The novelty of the present study lies in its investigation of the ric...The National Gas Hydrate Program expeditions(NGHP-01 and-02)have conclusively proven the presence of hydrate deposits on the eastern coast of India.The novelty of the present study lies in its investigation of the richest gas hydrate deposit(hydrate saturation[Sh]>0.75),NGHP-01-10D,in the Krishna-Godavari(KG)Basin,India.The study presents a first look at the long-term gas production viability using a single vertical well,subjected to variations in production interval and bottom hole pressure.Specifically,we compared the gas production at bottom hole pressures of 3-6 MPa and production intervals of 20-40 m.The results indicate production rates that are technically feasible but lower than commercially acceptable standards.Increasing the bottom hole pressure drawdown from 6 MPa to 3 MPa increased the gas production from 1297 m^(3)/d to 4902 m^(3)/d(i.e.,more than tripling the average daily gas production).Meanwhile,while expanding the production interval from 20 m to 40 m led to an increase in gas production,it also resulted in higher water production.As a result,the average gas-to-water ratio(RGW)decreased from 9.5 to 5.3 with the expansion of the production interval,thereby highlighting the need to optimize the interval length.Furthermore,the spatial evolution of certain thermodynamic parameters,including pressure,temperature,and phase saturation(methane,water,and hydrate),underscores the critical role of heat transfer from the UB.Our study findings offer valuable insights for long-term production forecasting,the delineation of phase evolution patterns,and the identification of potential flow barriers that may impede deliverability.展开更多
The microstructure and corrosion behavior of as-cast and friction stir processed in-situ Al-TiB2 based composite in 3.5 wt.% sodium chloride solution were investigated. The microstructure was characterized using X-ray...The microstructure and corrosion behavior of as-cast and friction stir processed in-situ Al-TiB2 based composite in 3.5 wt.% sodium chloride solution were investigated. The microstructure was characterized using X-ray diffractometry, scanning electron microscopy and electron backscattered diffraction technique while corrosion behavior was evaluated using linear/cyclic potentiodynamic, electrochemical impedance spectroscopy and ASTM–G67 tests. The composite contains sub-micron TiB2 particles in an aluminum matrix with both blocky and fine clusters of Al3Ti agglomerated around TiB2 and displays a low uniform corrosion rate. It is also resistant to pitting as substantiated by the absence of a positive loop in cyclic potentiodynamic tests. This is due to the non-conductive nature of TiB2 particles and a controlled amount of blocky Al3Ti phase. However, both friction stir processed and as-cast composites are susceptible to inter-granular corrosion where Al3Ti and TiB2 at grain boundaries provide initiation sites for corrosion. Electrochemical impedance study attributes this to the adverse effect of Al3Ti and TiB2 on the protective oxide surface film, which increases with immersion time.展开更多
Due to improper acquisition settings and other noise artifacts,the image degraded to yield poor mean preservation in brightness.The simplest way to improve the preservation is the implementation of histogram equalizat...Due to improper acquisition settings and other noise artifacts,the image degraded to yield poor mean preservation in brightness.The simplest way to improve the preservation is the implementation of histogram equalization.Because of over-enhancement,it failed to preserve the mean brightness and produce the poor quality of the image.This paper proposes a multi-scale decomposi-tion for brightness preservation using gamma correction.After transformation to hue,saturation and intensity(HSI)channel,the 2D-discrete wavelet transform decomposed the intensity component into low and high-pass coefficients.At the next phase,gamma correction is used by auto-tuning the scale value.The scale is the modified constant value used in the logarithmic function.Further,the scale value is optimized to obtain better visual quality in the image.The optimized value is the weighted distribution of standard deviation-mean of low pass coefficients.Finally,the experimental result is estimated in terms of quality assessment measures used as absolute mean brightness error,the measure of information detail,signal to noise ratio and patch-based contrast quality in the image.By comparison,the proposed method proved to be suitably remarkable in retaining the mean brightness and better visual quality of the image.展开更多
The gas hydrate formation in pipelines of industries and chemical plants can cause various operational damages and can increase economic risks.Hence,the knowledge of hydrate formation conditions has become a critical ...The gas hydrate formation in pipelines of industries and chemical plants can cause various operational damages and can increase economic risks.Hence,the knowledge of hydrate formation conditions has become a critical research study to overcome the problems arising from the formation of hydrates.In this study,we applied an algorithm to develop an LSSVM model to predict the formation temperature of natural gas hydrate for a comprehensive range of data points.Total 188 experimental data points were applied from the literature for the development of the LSSVM model.The input parameter was finalized based on the structure of hydrates by each gas species.The results obtained by the LSSVM model have good accuracy as compared with empirical correlations available in the literature.This model gave the squared correlation coefficient(R2),and root mean square error of 0.9901 and 0.59974,respectively.The composition of gases may affect the phase equilibrium condition of gas hydrates.The applied algorithm revealed that the developed LSSVM model could become a good alternative for calculating the formation temperature of hydrate for the range of all data sets.The results showed that the proposed LSSVM model could be applicable for the prediction of hydrate formation temperature for all data points.展开更多
文摘The National Gas Hydrate Program expeditions(NGHP-01 and-02)have conclusively proven the presence of hydrate deposits on the eastern coast of India.The novelty of the present study lies in its investigation of the richest gas hydrate deposit(hydrate saturation[Sh]>0.75),NGHP-01-10D,in the Krishna-Godavari(KG)Basin,India.The study presents a first look at the long-term gas production viability using a single vertical well,subjected to variations in production interval and bottom hole pressure.Specifically,we compared the gas production at bottom hole pressures of 3-6 MPa and production intervals of 20-40 m.The results indicate production rates that are technically feasible but lower than commercially acceptable standards.Increasing the bottom hole pressure drawdown from 6 MPa to 3 MPa increased the gas production from 1297 m^(3)/d to 4902 m^(3)/d(i.e.,more than tripling the average daily gas production).Meanwhile,while expanding the production interval from 20 m to 40 m led to an increase in gas production,it also resulted in higher water production.As a result,the average gas-to-water ratio(RGW)decreased from 9.5 to 5.3 with the expansion of the production interval,thereby highlighting the need to optimize the interval length.Furthermore,the spatial evolution of certain thermodynamic parameters,including pressure,temperature,and phase saturation(methane,water,and hydrate),underscores the critical role of heat transfer from the UB.Our study findings offer valuable insights for long-term production forecasting,the delineation of phase evolution patterns,and the identification of potential flow barriers that may impede deliverability.
基金financial support from the Board for Research in Nuclear Sciences (BRNS) (Project number 36(2)/20/02/2014-BRNS/)
文摘The microstructure and corrosion behavior of as-cast and friction stir processed in-situ Al-TiB2 based composite in 3.5 wt.% sodium chloride solution were investigated. The microstructure was characterized using X-ray diffractometry, scanning electron microscopy and electron backscattered diffraction technique while corrosion behavior was evaluated using linear/cyclic potentiodynamic, electrochemical impedance spectroscopy and ASTM–G67 tests. The composite contains sub-micron TiB2 particles in an aluminum matrix with both blocky and fine clusters of Al3Ti agglomerated around TiB2 and displays a low uniform corrosion rate. It is also resistant to pitting as substantiated by the absence of a positive loop in cyclic potentiodynamic tests. This is due to the non-conductive nature of TiB2 particles and a controlled amount of blocky Al3Ti phase. However, both friction stir processed and as-cast composites are susceptible to inter-granular corrosion where Al3Ti and TiB2 at grain boundaries provide initiation sites for corrosion. Electrochemical impedance study attributes this to the adverse effect of Al3Ti and TiB2 on the protective oxide surface film, which increases with immersion time.
文摘Due to improper acquisition settings and other noise artifacts,the image degraded to yield poor mean preservation in brightness.The simplest way to improve the preservation is the implementation of histogram equalization.Because of over-enhancement,it failed to preserve the mean brightness and produce the poor quality of the image.This paper proposes a multi-scale decomposi-tion for brightness preservation using gamma correction.After transformation to hue,saturation and intensity(HSI)channel,the 2D-discrete wavelet transform decomposed the intensity component into low and high-pass coefficients.At the next phase,gamma correction is used by auto-tuning the scale value.The scale is the modified constant value used in the logarithmic function.Further,the scale value is optimized to obtain better visual quality in the image.The optimized value is the weighted distribution of standard deviation-mean of low pass coefficients.Finally,the experimental result is estimated in terms of quality assessment measures used as absolute mean brightness error,the measure of information detail,signal to noise ratio and patch-based contrast quality in the image.By comparison,the proposed method proved to be suitably remarkable in retaining the mean brightness and better visual quality of the image.
文摘The gas hydrate formation in pipelines of industries and chemical plants can cause various operational damages and can increase economic risks.Hence,the knowledge of hydrate formation conditions has become a critical research study to overcome the problems arising from the formation of hydrates.In this study,we applied an algorithm to develop an LSSVM model to predict the formation temperature of natural gas hydrate for a comprehensive range of data points.Total 188 experimental data points were applied from the literature for the development of the LSSVM model.The input parameter was finalized based on the structure of hydrates by each gas species.The results obtained by the LSSVM model have good accuracy as compared with empirical correlations available in the literature.This model gave the squared correlation coefficient(R2),and root mean square error of 0.9901 and 0.59974,respectively.The composition of gases may affect the phase equilibrium condition of gas hydrates.The applied algorithm revealed that the developed LSSVM model could become a good alternative for calculating the formation temperature of hydrate for the range of all data sets.The results showed that the proposed LSSVM model could be applicable for the prediction of hydrate formation temperature for all data points.
