The damages of different drilling modes to reservoirs are different in types and degrees.In this paper,the geologic characteristics and types of such damages were analyzed.Then,based on the relationship between reserv...The damages of different drilling modes to reservoirs are different in types and degrees.In this paper,the geologic characteristics and types of such damages were analyzed.Then,based on the relationship between reservoir pressure and bottom hole flowing pressure corresponding to different drilling modes,the experimental procedures on reservoir damages in three drilling modes(e.g.gas drilling,liquid-based underbalanced drilling and overbalanced drilling)were designed.Finally,damage simulation experiments were conducted on the tight sandstone reservoir cores of the Jurassic Ahe Fm in the Tarim Basin and Triassic Xujiahe Fm in the central Sichuan Basin.It is shown that the underbalanced drilling is beneficial to reservoir protection because of its less damage on reservoir permeability,but it is,to some extent,sensitive to the stress and the empirical formula of stress sensitivity coefficient is obtained;and that the overbalanced drilling has more reservoir damages due to the invasion of solid and liquid phases.After the water saturation of cores rises to the irreducible water saturation,the decline of gas logging permeability speeds up and the damage degree of water lock increases.It is concluded that the laboratory experiment results of reservoir damage are accordant with the reservoir damage characteristics in actual drilling conditions.Therefore,this method reflects accurately the reservoir damage characteristics and can be used as a new experimental evaluation method on reservoir damage in different drilling modes.展开更多
基金Project supported by the Scientific Research and Innovation Team Fund of Universities Affiliated to Sichuan Province(No.2014TD0006)“Research on downhole safety risk and control methods of gas drilling”in Sichuan outstanding young academic technology leader training plan(No.2014JQ0045)Device and software development for quantitative evaluation of low-permeability gas reservoir damages(No.2016ZX05021-004-005).
文摘The damages of different drilling modes to reservoirs are different in types and degrees.In this paper,the geologic characteristics and types of such damages were analyzed.Then,based on the relationship between reservoir pressure and bottom hole flowing pressure corresponding to different drilling modes,the experimental procedures on reservoir damages in three drilling modes(e.g.gas drilling,liquid-based underbalanced drilling and overbalanced drilling)were designed.Finally,damage simulation experiments were conducted on the tight sandstone reservoir cores of the Jurassic Ahe Fm in the Tarim Basin and Triassic Xujiahe Fm in the central Sichuan Basin.It is shown that the underbalanced drilling is beneficial to reservoir protection because of its less damage on reservoir permeability,but it is,to some extent,sensitive to the stress and the empirical formula of stress sensitivity coefficient is obtained;and that the overbalanced drilling has more reservoir damages due to the invasion of solid and liquid phases.After the water saturation of cores rises to the irreducible water saturation,the decline of gas logging permeability speeds up and the damage degree of water lock increases.It is concluded that the laboratory experiment results of reservoir damage are accordant with the reservoir damage characteristics in actual drilling conditions.Therefore,this method reflects accurately the reservoir damage characteristics and can be used as a new experimental evaluation method on reservoir damage in different drilling modes.
