| dc.description.abstract | Most commonly used resistivity tools for well logging measure the horizontal resistivity of the formation. A problem appears when you want to measure the true resistivity in a sand reservoir which also contains multiple thin layers of shale. When the layer thickness is below the tool s vertical resolution, the thin shale layers make the measured resistivity value lower than the actual resistivity value of the hydrocarbon-saturated sands. As a result, the calculated water saturation is higher than the real value, and the estimation of the volume of oil is lower than the real volume. The resistivity of the sand can be calculated if the vertical resistivity is measured too, and this can be done with a triaxial induction tool, however, this is rarely done due to the additional cost.
The objective of this project is to investigate methods to estimate the vertical resistivity from the horizontal resistivity in the absence of triaxial measurements. The work began by reviewing the published literature related to this topic, and identifying some methods that achieved something similar. The paper from \cite{tabanou2002thinly} was used as a reference for the development of one of the methods; estimating Rv using a convolution average filter.
Three algorithms were programmed and tested with resistivity data from six different wells, half of them water based mud, and the other half oil based mud. The results were satisfactory, not finding a general method that works in every case, but concluding that if the method chosen is the best option for the well and formation conditions, a high probability of success is achieved. | |
