The Experts below are selected from a list of 2151 Experts worldwide ranked by ideXlab platform
Pengfei Ren - One of the best experts on this subject based on the ideXlab platform.
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geological conditions of deep coalbed methane in the eastern margin of the ordos basin china implications for coalbed methane development
Journal of Natural Gas Science and Engineering, 2018Co-Authors: Dazhen Tang, Zhejun Pan, Shu Tao, Yanfei Liu, Pengfei RenAbstract:Abstract Deep coalbed methane (CBM) resource potential is enormous in China, and has become a new field for unconventional natural gas exploration and development. This work discusses the geological conditions (reservoir pressure, formation temperature and ground stress) of deep coal reservoirs in the Eastern margin of the Ordos Basin and their implication on CBM development. Various field Test data of CBM wells, including injection/Drawdown Test data, well temperature Test data, and hydraulic fracturing Test data were collected from this work and literature to describe the geological conditions of the deep CBM in the study area. From the results, it is found that deep CBM in this area is characterized by high reservoir pressure, high formation temperature, and high ground stress. However, there are diverse geological particularities in the different depth range: (1) Having a wide range of pressure gradient, vast majority of coal reservoirs in the study area are under abnormally low-pressure state, which is more significant in deeper coal seams. (2) Due to the impact of surface runoff, the distribution of geothermal gradient is discrete when the burial depth is less than 700 m, and relatively concentrated when the burial depth is greater than 700 m. (3) In shallow coal reservoirs, ground stress is strongest in the horizontal direction; while in deep coal reservoirs, the strongest ground stress is in the vertical direction. Because of the complex geological conditions associated with deep burial, the balance between CBM adsorption-desorption-seepage and the rheological behavior of coal reservoirs is complex, which has significant influence on the exploration and development of deep CBM in the study area. High pressure in deep coal reservoir often leads a long inefficient desorption stage and a long draining and depressurizing process, which increases production costs. Moreover, the negative temperature effect on gas adsorption indicates that CBM content decreases with increasing depth in deep conditions, and thus the evaluation of deep CBM resources needs to be reconsidered. In addition, different stress states govern fracture patterns, and in deep environments, high ground stress greatly reduces the fracturing improvement of the coal reservoir and significantly affects the deep CBM development.
Rajandrea Sethi - One of the best experts on this subject based on the ideXlab platform.
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a dual well step Drawdown method for the estimation of linear and non linear flow parameters and wellbore skin factor in confined aquifer systems
Journal of Hydrology, 2011Co-Authors: Rajandrea SethiAbstract:Summary In this study a method based on dual-well step Drawdown Test (i.e. a combination of an aquifer and a well performance Test) for the determination of hydrodynamic parameters (namely storage coefficient and hydraulic conductivity), mechanical wellbore finite thickness skin factor, non-linear wellbore and non-linear aquifer parameters in an homogeneous confined aquifer is presented in order to put together aquifer and well Tests. The interpretation procedure is based on the application of superposition principle to a large time logarithmic approximation of the solution. The advantages of this method, that can be considered an extension of Jacob step-Test (1947) and Cooper–Jacob approximation (1946) , are that: (I) it is possible to determine simultaneously aquifer and well properties in a single Test; (II) the method is based on a large time approximation and it is therefore independent from wellbore storage; (III) if the well skin is absent, the aquifer parameters (storage coefficient and hydraulic conductivity) can be derived just from a single-well Test; (IV) the interpretation procedure is easy to apply and robust and does not require any specific numeric code or software. The same procedure can be easily adapted to gas well Testing. It is also shown that, even in the presence of linear and non-linear flow, skin effect and wellbore storage, the hydraulic conductivity (and not the storage coefficient) of the aquifer can be correctly estimated by the Cooper and Jacob (1946) method applied to a single-rate pumping Test, using exclusively the large time Drawdown data measured at the pumping well.
Collin R Dudgeon - One of the best experts on this subject based on the ideXlab platform.
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new insight into the step Drawdown Test in fractured rock aquifers
Hydrogeology Journal, 1994Co-Authors: Lee C Atkinson, John E Gale, Collin R DudgeonAbstract:Review of the historical development of the step-Drawdown pumping Test and interpretations of well Test data using the step-Drawdown method indicates considerable differences in the importance attributed to head losses in the artificial environment (e.g., the gravel pack and screen) in the immediate vicinity of the wellbore and the losses resulting from non-laminar flow in the aquifer itself. These differences appear to be greaTest when attempts have been made to apply the step-Drawdown analysis to data from wells in fractured rock aquifers. The empirical flow-head loss relationship for a single, hydraulically-rough, open fracture have been incorporated into a mathematical expression for two-regime, radial, convergent flow. The resulting equation estimates the laminar and non-laminar head losses resulting from flow to a well over a range of flow rates. Combining these head loss components yields a non-linear relationship between production, Q, and Drawdown, s, that is similar to those observed for actual step-Drawdown Tests in fractured rock aquifers. These Test data are well approximated by:
Dazhen Tang - One of the best experts on this subject based on the ideXlab platform.
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geological conditions of deep coalbed methane in the eastern margin of the ordos basin china implications for coalbed methane development
Journal of Natural Gas Science and Engineering, 2018Co-Authors: Dazhen Tang, Zhejun Pan, Shu Tao, Yanfei Liu, Pengfei RenAbstract:Abstract Deep coalbed methane (CBM) resource potential is enormous in China, and has become a new field for unconventional natural gas exploration and development. This work discusses the geological conditions (reservoir pressure, formation temperature and ground stress) of deep coal reservoirs in the Eastern margin of the Ordos Basin and their implication on CBM development. Various field Test data of CBM wells, including injection/Drawdown Test data, well temperature Test data, and hydraulic fracturing Test data were collected from this work and literature to describe the geological conditions of the deep CBM in the study area. From the results, it is found that deep CBM in this area is characterized by high reservoir pressure, high formation temperature, and high ground stress. However, there are diverse geological particularities in the different depth range: (1) Having a wide range of pressure gradient, vast majority of coal reservoirs in the study area are under abnormally low-pressure state, which is more significant in deeper coal seams. (2) Due to the impact of surface runoff, the distribution of geothermal gradient is discrete when the burial depth is less than 700 m, and relatively concentrated when the burial depth is greater than 700 m. (3) In shallow coal reservoirs, ground stress is strongest in the horizontal direction; while in deep coal reservoirs, the strongest ground stress is in the vertical direction. Because of the complex geological conditions associated with deep burial, the balance between CBM adsorption-desorption-seepage and the rheological behavior of coal reservoirs is complex, which has significant influence on the exploration and development of deep CBM in the study area. High pressure in deep coal reservoir often leads a long inefficient desorption stage and a long draining and depressurizing process, which increases production costs. Moreover, the negative temperature effect on gas adsorption indicates that CBM content decreases with increasing depth in deep conditions, and thus the evaluation of deep CBM resources needs to be reconsidered. In addition, different stress states govern fracture patterns, and in deep environments, high ground stress greatly reduces the fracturing improvement of the coal reservoir and significantly affects the deep CBM development.
Gianpietro Summa - One of the best experts on this subject based on the ideXlab platform.
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a new approach to the step Drawdown Test
Water SA, 2010Co-Authors: Gianpietro SummaAbstract:In this paper a new approach to perform step-Drawdown Tests is presented. Step-Drawdown Tests known to date are performed strictly keeping the value of the pumping rates constant through all the steps of the Test. Current technology allows one to let the submerged electric pumps work at a specific revolution per minute (r/min) and to suitably modify the rotation velocity at every step. The new approach presented in this paper is based on the idea of keeping the value of r/min fixed at every step of the Test, instead of keeping constant the value of the discharge. This technique has been experimentally applied to a well and a description of the operations and results are presented in detail. This approach, in this unique case, made possible an understanding of how the discharge Q varies as a function of the Drawdown sw. It also enables one monitor the approaching of the equilibrium between Q and sw, using both the variation of Q and sw with time. Moreover, it was observed that for the well in question the ratio Qsw remains almost constant within each step.
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a new approach to the step Drawdown Test
SA Journal of Radiology, 2010Co-Authors: Gianpietro SummaAbstract:In this paper a new approach to perform step-Drawdown Tests is presented. Step-Drawdown Tests known to date are performed strictly keeping the value of the pumping rates constant through all the steps of the Test. Current technology allows one to let the submerged electric pumps work at a specific revolution per minute (r/min) and to suitably modify the rotation velocity at every step. The new approach presented in this paper is based on the idea of keeping the value of r/min fixed at every step of the Test, instead of keeping constant the value of the discharge. This technique has been experimentally applied to a well and a description of the operations and results are presented in detail. This approach, in this unique case, made possible an understanding of how the discharge Q varies as a function of the Drawdown s w . It also enables one monitor the approaching of the equilibrium between Q and s w , using both the variation of Q and s w with time. Moreover, it was observed that for the well in question the ratio Q/s w remains almost constant within each step. Keywords: characteristic curve, pumping Test, equipment/field techniques, hydraulic Testing
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a new approach to the step Drawdown Test
arXiv: Geophysics, 2009Co-Authors: Gianpietro SummaAbstract:In this paper a new approach to perform step-Drawdown Tests in presented. Step-Drawdown Tests known so far are performed strictly keeping the value of the pumping rates constant through all the steps of the Test. Current technology allows us to let the submerged electric pumps work at a specific revolution per minute (rpm) and allows us to suitably modify the rotation velocity at every step. Our approach is based on the idea of keeping the value of rpm fixed at every step of the Test, instead of keeping constant the value of the discharge. Our technique has been experimentally applied to a well and a description of the operations and results are thoroughly presented. Our approach, in this peculiar case, has made possible to understand how actually the discharge Q varies in function of the Drawdown s_w. It has also made possible to monitor the approaching of the equilibrium between Q and s_w, using both the variation of Q and that of s_w with time. Moreover, we have seen that for the well studied in this paper the ratio Q/s_w remains almost constant within each step.
