Volume fracturing technology has been widely applied in the development of coalbed methane(CBM)reservoirs.As for the stimulated reservoir volume(SRV)created by volume fracturing,the seepage laws of fluids are describe...Volume fracturing technology has been widely applied in the development of coalbed methane(CBM)reservoirs.As for the stimulated reservoir volume(SRV)created by volume fracturing,the seepage laws of fluids are described more accurately and rationally in the rectangular composite model than in the traditional radial composite model.However,the rectangular composite model considering SRV cannot be solved using the analytical or semi-analytical function method,and its solution from the linear flow model has larger errors.In view of this,SRVareas of CBM reservoirs were described by means of dual-medium model in this paper.The complex CBM migration mechanisms were investigated comprehensively,including adsorption,desorption,diffusion and seepage.A well testing model for rectangular composite fracturing wells in CBM reservoirs based on unsteady-state diffusion was built and solved using the boundary element method combined with Laplace transformation,Stehfest numerical inversion and computer programming technology.Thus,production performance laws of CBM reservoirs were clarified.The flow regimes of typical well testing curves were divided and the effects on change laws of production performance from the boundary size of gas reservoirs,permeability of volume fractured areas,adsorption gas content,reservoir permeability and SRV size were analyzed.Eventually,CBM reservoirs after the volume fracturing stimulation were described more accurately and rationally.This study provides a theoretical basis for a better understanding of the CBM migration laws and an approach to evaluating and developing CBM reservoirs efficiently and rationally.展开更多
To satisfy the terminal position and impact angel constraints,an optimal guidance problem was discussed for homing missiles. For a stationary or a slowly moving target on the ground,an extended trajectory shaping guid...To satisfy the terminal position and impact angel constraints,an optimal guidance problem was discussed for homing missiles. For a stationary or a slowly moving target on the ground,an extended trajectory shaping guidance lawconsidering a first-order autopilot lag（ ETSG L-C FAL） was proposed. To derive the ETSG L-C FAL,a time-to-go- nth power weighted objection function was adopted and three different derivation methods were demonstrated while the Schwartz inequality method was mainly demonstrated.The performance of the ETSG L-C FAL and the ETSG L guidance laws was compared through simulation.Simulation results showthat although a first-order autopilot is introduced into the ETSG L-C FAL guidance system,the position miss distance and terminal impact angle error induced by the impact angle is zero for different guidance time.展开更多
基金supported by the National Natural Science Foundation of China“Basic Research on Reservoir Anhydration and Gas Flow Capacity Improvement in Tight Gas Reservoir”(No.:51534006)the Scientific Research Starting Project of Southwest Petroleum University(No.:2015QHZ003)the Development Fund for Young Scholars of Southwest Petroleum University(No.:201599010088).
文摘Volume fracturing technology has been widely applied in the development of coalbed methane(CBM)reservoirs.As for the stimulated reservoir volume(SRV)created by volume fracturing,the seepage laws of fluids are described more accurately and rationally in the rectangular composite model than in the traditional radial composite model.However,the rectangular composite model considering SRV cannot be solved using the analytical or semi-analytical function method,and its solution from the linear flow model has larger errors.In view of this,SRVareas of CBM reservoirs were described by means of dual-medium model in this paper.The complex CBM migration mechanisms were investigated comprehensively,including adsorption,desorption,diffusion and seepage.A well testing model for rectangular composite fracturing wells in CBM reservoirs based on unsteady-state diffusion was built and solved using the boundary element method combined with Laplace transformation,Stehfest numerical inversion and computer programming technology.Thus,production performance laws of CBM reservoirs were clarified.The flow regimes of typical well testing curves were divided and the effects on change laws of production performance from the boundary size of gas reservoirs,permeability of volume fractured areas,adsorption gas content,reservoir permeability and SRV size were analyzed.Eventually,CBM reservoirs after the volume fracturing stimulation were described more accurately and rationally.This study provides a theoretical basis for a better understanding of the CBM migration laws and an approach to evaluating and developing CBM reservoirs efficiently and rationally.
基金Supported by the National Natural Science Foundation of China(61172182)
文摘To satisfy the terminal position and impact angel constraints,an optimal guidance problem was discussed for homing missiles. For a stationary or a slowly moving target on the ground,an extended trajectory shaping guidance lawconsidering a first-order autopilot lag（ ETSG L-C FAL） was proposed. To derive the ETSG L-C FAL,a time-to-go- nth power weighted objection function was adopted and three different derivation methods were demonstrated while the Schwartz inequality method was mainly demonstrated.The performance of the ETSG L-C FAL and the ETSG L guidance laws was compared through simulation.Simulation results showthat although a first-order autopilot is introduced into the ETSG L-C FAL guidance system,the position miss distance and terminal impact angle error induced by the impact angle is zero for different guidance time.
