Based on previous studies on the internal structures of fault belts, the fault belts in the Laoyemiao Oilfield of the Nanpu Sag can be divided into three units, a crushed zone, an upper induced fracture zone and a low...Based on previous studies on the internal structures of fault belts, the fault belts in the Laoyemiao Oilfield of the Nanpu Sag can be divided into three units, a crushed zone, an upper induced fracture zone and a lower induced fracture zone according to the log response characteristics. The upper induced fracture zone is characterized by the development of pervasive fractures and has a poor sealing or non-sealing capability. It therefore can act as pathways for hydrocarbon migration. The lower induced fracture zone consists of fewer fractures and has limited sealing capability. The crushed zone has a good sealing capability comparable to mudstone and can thus prevent lateral migration of fluid. Through physical modeling and comparing laboratory data with calculated data of oil column heights of traps sealed by faults, it is concluded that the fault-sealing capability for oil and gas is limited. When the oil column height reaches a threshold, oil will spill over from the top of reservoir along the lower induced fracture zone under the action of buoyancy, and the size of reservoir will remain unchanged. Analysis of the formation mechanisms of the fault-sealed reservoirs in the Nanpu Sag indicated that the charging sequence of oil and gas in the reservoir was from lower formation to upper formation, with the fault playing an important role in oil and gas accumulation. The hydrocarbon potential in reverse fault-sealed traps is much better than that in the consequent fault-sealed traps. The reverse fault-sealed traps are favorable and preferred exploration targets.展开更多
In the calibration of hydrological models, evaluation criteria are explicitly and quantitatively defined as single-or multi-objective functions when utilizing automatic calibration approaches.In most previous studies,...In the calibration of hydrological models, evaluation criteria are explicitly and quantitatively defined as single-or multi-objective functions when utilizing automatic calibration approaches.In most previous studies, there is a general opinion that no single-objective function can represent all important characteristics of even one specific hydrological variable(e.g., streamflow).Thus hydrologists must turn to multi-objective calibration.In this study, we demonstrated that an optimized single-objective function can compromise multi-response modes(i.e., multi-objective functions) of the hydrograph, which is defined as summation of a power function of the absolute error between observed and simulated streamflow with the exponent of power function optimized for specific watersheds.The new objective function was applied to 196 model parameter estimation experiment(MOPEX) watersheds across the eastern United States using the semi-distributed Xinanjiang hydrological model.The optimized exponent value for each watershed was obtained by targeting four popular objective functions focusing on peak flows, low flows, water balance, and flashiness, respectively.Results showed that the optimized single-objective function can achieve a better hydrograph simulation compared to the traditional single-objective function Nash-Sutcliffe efficiency coefficient for most watersheds, and balance high flow part and low flow part of the hydrograph without substantial differences compared to multi-objective calibration.The proposed optimal single-objective function can be practically adopted in the hydrological modeling if the optimal exponent value could be determined a priori according to hydrological/climatic/landscape characteristics in a specific watershed.展开更多
Beibuwan B asin is an important offshore oil and gas bearing basin of China.However,the distribution of oil and gas in different sags is uneven,and the rule of hydrocarbon accumulation and main controlling factors hav...Beibuwan B asin is an important offshore oil and gas bearing basin of China.However,the distribution of oil and gas in different sags is uneven,and the rule of hydrocarbon accumulation and main controlling factors have not been clearly understood in this basin.Based on abundant seismic,well and analytical data,the differences and main controlling of tectonic evolution,sedimentary filling and source rock quality in sags are analyzed,and combined with the study of geothermal filed,the main controlling factors of differential hydrocarbon generation in sags of the Beibuwan Basin are clarified.On the basis of the research above,the hydrocarbon enrichment of the basin is clarified through the systematic analysis of reservoir-caprock assemblage and accumulation characteristics of different structural units.The results show that there are four NE-trending sag zones in the basin,and under the influence of fault activity,the scale of sags is regularly distributed.The scale of rifts in different sag zones decreases gradually from northwest to southeast and the scale of rifts in the middle of a single sag zone is normally larger than that at two ends.Under the control of the sag-controlling faults activity,paleoproductivity and organic matter preservation conditions,the quality of source rocks in sags of the Beibuwan Basin decreases from northwest to southeast.The hydrocarbon-rich sags in the Beibuwan Basin were formed under the control of source rocks and geothermal field,and the distribution of large-medium scale fields is controlled by the favorable structural traps in the rift strata of inner gentle slope zone.The understanding of the hydrocarbon enrichment and main controlling factors in the Beibuwan Basin also provides a significant guidance for the oil and gas exploration in other rift basins.展开更多
基金the Key Project of Chinese National Programs for Fundamental Research and Development (973 Program, No. 2006CB202308)the National Natural Science Foundation of China (Grant No. 40472078)
文摘Based on previous studies on the internal structures of fault belts, the fault belts in the Laoyemiao Oilfield of the Nanpu Sag can be divided into three units, a crushed zone, an upper induced fracture zone and a lower induced fracture zone according to the log response characteristics. The upper induced fracture zone is characterized by the development of pervasive fractures and has a poor sealing or non-sealing capability. It therefore can act as pathways for hydrocarbon migration. The lower induced fracture zone consists of fewer fractures and has limited sealing capability. The crushed zone has a good sealing capability comparable to mudstone and can thus prevent lateral migration of fluid. Through physical modeling and comparing laboratory data with calculated data of oil column heights of traps sealed by faults, it is concluded that the fault-sealing capability for oil and gas is limited. When the oil column height reaches a threshold, oil will spill over from the top of reservoir along the lower induced fracture zone under the action of buoyancy, and the size of reservoir will remain unchanged. Analysis of the formation mechanisms of the fault-sealed reservoirs in the Nanpu Sag indicated that the charging sequence of oil and gas in the reservoir was from lower formation to upper formation, with the fault playing an important role in oil and gas accumulation. The hydrocarbon potential in reverse fault-sealed traps is much better than that in the consequent fault-sealed traps. The reverse fault-sealed traps are favorable and preferred exploration targets.
基金Under the auspices of National Key Research and Development Program of China(No.2016YFC0402701)National Natural Science Foundation of China(No.51825902)
文摘In the calibration of hydrological models, evaluation criteria are explicitly and quantitatively defined as single-or multi-objective functions when utilizing automatic calibration approaches.In most previous studies, there is a general opinion that no single-objective function can represent all important characteristics of even one specific hydrological variable(e.g., streamflow).Thus hydrologists must turn to multi-objective calibration.In this study, we demonstrated that an optimized single-objective function can compromise multi-response modes(i.e., multi-objective functions) of the hydrograph, which is defined as summation of a power function of the absolute error between observed and simulated streamflow with the exponent of power function optimized for specific watersheds.The new objective function was applied to 196 model parameter estimation experiment(MOPEX) watersheds across the eastern United States using the semi-distributed Xinanjiang hydrological model.The optimized exponent value for each watershed was obtained by targeting four popular objective functions focusing on peak flows, low flows, water balance, and flashiness, respectively.Results showed that the optimized single-objective function can achieve a better hydrograph simulation compared to the traditional single-objective function Nash-Sutcliffe efficiency coefficient for most watersheds, and balance high flow part and low flow part of the hydrograph without substantial differences compared to multi-objective calibration.The proposed optimal single-objective function can be practically adopted in the hydrological modeling if the optimal exponent value could be determined a priori according to hydrological/climatic/landscape characteristics in a specific watershed.
基金The National Oil and Gas Major Project under contract Nos 2016ZX05024,2016ZX05026,2011ZX05025 and 2008ZX05025Key Project of Chinese National Programs for Fundamental Research and Development(973 Program)under contract No.2009CB219400Major Research Program of National Natural Science Foundation of China“The control effect of deep-sea geological evolution on oil and gas resources in South China Sea”。
文摘Beibuwan B asin is an important offshore oil and gas bearing basin of China.However,the distribution of oil and gas in different sags is uneven,and the rule of hydrocarbon accumulation and main controlling factors have not been clearly understood in this basin.Based on abundant seismic,well and analytical data,the differences and main controlling of tectonic evolution,sedimentary filling and source rock quality in sags are analyzed,and combined with the study of geothermal filed,the main controlling factors of differential hydrocarbon generation in sags of the Beibuwan Basin are clarified.On the basis of the research above,the hydrocarbon enrichment of the basin is clarified through the systematic analysis of reservoir-caprock assemblage and accumulation characteristics of different structural units.The results show that there are four NE-trending sag zones in the basin,and under the influence of fault activity,the scale of sags is regularly distributed.The scale of rifts in different sag zones decreases gradually from northwest to southeast and the scale of rifts in the middle of a single sag zone is normally larger than that at two ends.Under the control of the sag-controlling faults activity,paleoproductivity and organic matter preservation conditions,the quality of source rocks in sags of the Beibuwan Basin decreases from northwest to southeast.The hydrocarbon-rich sags in the Beibuwan Basin were formed under the control of source rocks and geothermal field,and the distribution of large-medium scale fields is controlled by the favorable structural traps in the rift strata of inner gentle slope zone.The understanding of the hydrocarbon enrichment and main controlling factors in the Beibuwan Basin also provides a significant guidance for the oil and gas exploration in other rift basins.
