Comparison of well log and welltest data in a naturally fractured formation

摘要

Three primary sources of information available for reservoir description are cores, well logs, and welltest data. In this work, a comparison of formation storage capacity is made between well log and welltest information for a dual porosity, naturally fractured formation. Over the years, two independent parameters, the partitioning coefficient in well logging and the fracture storage coefficient in well testing, have been available to characterize these types of reservoirs. A relationship will be developed between these two parameters. By definition, well log and welltest data investigate different volumes of the formation; i.e., a variation in scale exists. Therefore, it is likely that when both parameters are within reasonable agreement the fracture storage (Fracture intensity?) is equal within the two test volumes and may be extrapolated as being representative of the given reservoir, However, if the parameters are different, then fracture storage is a function changing with distance from the wellbore. Application of these principles was tested on a known naturally fractured, sandstone reservoir in the Rocky Mountains. Analysis of this field example resulted in agreement between the two parameters; suggesting a widespread fracturedd volume. This conclusion confirms the geologic analysis of the area which was described as tectonically active and highly faulted.