EVALUATION METHOD OF THE MUD RESISTIVITY ACCORDING TO MULTIZONDE LATEROLOG CURVES

Abstract

The article proposes and discusses a method for estimating or clarifying the specific electrical resistance of drilling mud according to the indica tions of multisonde laterolog tool. The technique can be used in the absence of data resistivimetry or incorrect data. This is especially true for horizontal wells, since full resistivity measurement is difficult, and data on the electrical resistivity of the drilling mud should be measured on the surface by conductometer. The proposed technique is based on the trial and error method and reference bed method. To analyze the electrical resistiv- ity of the drilling mud, two specially selected reference beds are required. For them, the search for successive correction for borehole effect on the multisonde laterolog curves is carried out. According to the specific expansions in the reference layers, correctness of the choice of the corre- sponding electrical resistivity of the drilling mud is estimated. The deter- mination error of electrical resistivity of the drilling mud according to the introduce method be enough to correction borehole effect on the data of the multisonde Laterolog tool. The proposed method is exemplified by well materials from a five-sondes laterolog tool 5BK, issued by SPC «Geofizika», JSC, Ufa. Correction borehole effect is carried out through the pre-calculated departure curves for this type of tool. Also in the article present the definition of the contrast ratio for resistivity logging tools, the main factors affecting on the tool’s contrast ratio and the range of variation limits for contrast ratio for five-sondes laterolog tool 5BK.