In order to identify fractured reservoirs and determine their fracture parameters with a high definition array laterolog,we built a fracture-induced anisotropic formation model with a parallel fracture group.The three...In order to identify fractured reservoirs and determine their fracture parameters with a high definition array laterolog,we built a fracture-induced anisotropic formation model with a parallel fracture group.The three-dimensional finite element method is used to simulate the responses of the array laterolog,and then the primary inversion method is utilized.Numerical simulation shows that when the fracture spacing is small,the array laterolog response of the fracture group is the same as that of a formation with macroscopic electrical anisotropy.The apparent resistivity of the array laterolog is approximately inversely proportional to fracture porosity.The anisotropy depends on the fracture porosity in the fractured formation,which accordingly results in response variation of the array laterolog.The higher the fracture dip,the larger the apparent resistivity.When the fracture dip is low the difference between the deep and shallow apparent resistivities is small,and when the dip is high the difference turns out to be positive.The fracture parameters were inverted using the Marquardt non-linear least squares method.The results,both fracture porosity and dip show a good match with parameters in the actual formation model.This will promote the application of the array laterolog in evaluating fractured reservoirs.展开更多
Based on the plane of weakness theory, a model for predicting borehole stability in fractured reservoirs under different stress states was estiblisted and the equations for solving borehole stability were developed. T...Based on the plane of weakness theory, a model for predicting borehole stability in fractured reservoirs under different stress states was estiblisted and the equations for solving borehole stability were developed. The minimum downhole pressures required to maintain borehole stability under different natural fracture occurrences were calculated by using the data from a well in the Tazhong （central Tarim） area, Tarim Basin, west China. Several conclusions were drawn for naturally fractured reservoirs with a dip angle from less than 10° to greater than 30°. Application in three wells in the Tazhong area indicates that this model is practically useful.展开更多
The high-resolution azimuthal resistivity laterolog response in a fractured formation was numerically simulated using a three-dimensional finite element method. Simulation results show that the azimuthal resistivity i...The high-resolution azimuthal resistivity laterolog response in a fractured formation was numerically simulated using a three-dimensional finite element method. Simulation results show that the azimuthal resistivity is determined by fracture dipping as well as dipping direction, while the amplitude differences between deep and shallow laterolog resistivities are mainly controlled by the former. A linear relationship exists between the corrected apparent conductivities and fracture aperture. With the same fracture aperture, the deep and shallow laterolog resistivities present small values with negative separations for low-angle fractures, while azimuthal resistivities have large variations with positive separations for high-angle fractures that intersect the borehole. For dipping fractures, the variation of the azimuthal resistivity becomes larger when the fracture aperture increases. In addition, for high-angle fractures far from the borehole, a negative separation between the deep and shallow resistivities exists when fracture aperture is large as well as high resistivity contrast exists between bedrock and fracture fluid. The decreasing amplitude of dual laterolog resistivity can indicate the aperture of low-angle fractures, and the variation of the deep azimuthal resistivity can give information of the aperture of high-angle fractures and their position relative to the borehole.展开更多
基金supported by Shandong Natural Science Foundation(Y2007F25)Fundamental Research Funds for the Central Universities in China(09CX04001A)
文摘In order to identify fractured reservoirs and determine their fracture parameters with a high definition array laterolog,we built a fracture-induced anisotropic formation model with a parallel fracture group.The three-dimensional finite element method is used to simulate the responses of the array laterolog,and then the primary inversion method is utilized.Numerical simulation shows that when the fracture spacing is small,the array laterolog response of the fracture group is the same as that of a formation with macroscopic electrical anisotropy.The apparent resistivity of the array laterolog is approximately inversely proportional to fracture porosity.The anisotropy depends on the fracture porosity in the fractured formation,which accordingly results in response variation of the array laterolog.The higher the fracture dip,the larger the apparent resistivity.When the fracture dip is low the difference between the deep and shallow apparent resistivities is small,and when the dip is high the difference turns out to be positive.The fracture parameters were inverted using the Marquardt non-linear least squares method.The results,both fracture porosity and dip show a good match with parameters in the actual formation model.This will promote the application of the array laterolog in evaluating fractured reservoirs.
文摘Based on the plane of weakness theory, a model for predicting borehole stability in fractured reservoirs under different stress states was estiblisted and the equations for solving borehole stability were developed. The minimum downhole pressures required to maintain borehole stability under different natural fracture occurrences were calculated by using the data from a well in the Tazhong （central Tarim） area, Tarim Basin, west China. Several conclusions were drawn for naturally fractured reservoirs with a dip angle from less than 10° to greater than 30°. Application in three wells in the Tazhong area indicates that this model is practically useful.
基金co-funded by the National Natural Science Foundation of China(41174099,41474100)the Fundamental Research Funds for the Central Universities (14CX06077A)National Major Science & Technology Projects of China(2011ZX05003,2011ZX05009,2011ZX05020,2011ZX 05035)
文摘The high-resolution azimuthal resistivity laterolog response in a fractured formation was numerically simulated using a three-dimensional finite element method. Simulation results show that the azimuthal resistivity is determined by fracture dipping as well as dipping direction, while the amplitude differences between deep and shallow laterolog resistivities are mainly controlled by the former. A linear relationship exists between the corrected apparent conductivities and fracture aperture. With the same fracture aperture, the deep and shallow laterolog resistivities present small values with negative separations for low-angle fractures, while azimuthal resistivities have large variations with positive separations for high-angle fractures that intersect the borehole. For dipping fractures, the variation of the azimuthal resistivity becomes larger when the fracture aperture increases. In addition, for high-angle fractures far from the borehole, a negative separation between the deep and shallow resistivities exists when fracture aperture is large as well as high resistivity contrast exists between bedrock and fracture fluid. The decreasing amplitude of dual laterolog resistivity can indicate the aperture of low-angle fractures, and the variation of the deep azimuthal resistivity can give information of the aperture of high-angle fractures and their position relative to the borehole.
