Factors Influencing Electrical Resistivity of Drilling Fluids

Abstract

THE relation between the properties of electric logs and the fluid used in drilling a well is briefly discussed in this paper, and the fact that the resistivity of the drilling mud and its filtrate can appreciably affect such logs is shown.Apparatus was designed and a procedure established to determine the effect of various factors on the resistivity of drilling mud. Five muds commonly employed in California were tested and the following observations were made:1. The effect of raising the temperature from 80°F. to 180°F. is to decrease the resistivity of the mud or filtrate approximately SO per cent.2. The resistivity of the mud in most cases closely approximates that of its filtrate.3. The change in the resistivities of muds caused by ithe:addition of chemical is not the same function of the amount of chemical added for each mud.4. The effect produced by increased sodium chloride content is to reduce markedly the resistivity of the mud and its filtrate.5. Weighting materials, such as Baroid and limestone, tend to increase the resistivity of drilling mud.6. Cement and counteracting reagents reduce mud resistivity.

Sensitivity analysis from single-well ERT simulations to image CO2 migrations along wellbores

“…For this reason, oil-based drilling fluids are not recommended. Therefore, the drilling-mud resistivity is assumed to be 0.18 Ωm, which corresponds to a water-based mud with addition of a strong electrolyte to make it more conductive (Sherborne and Newton, 1942). The brine resistivity is 0.05 Ωm, while the formation resistivity without CO 2 is 1.5 Ωm in the mudstone and 0.46 Ωm in the reservoir (Kiessling et al, 2010).…”

Estimating Hydraulic Conductivity Profiles Using Borehole Resistivity Logs

“…Concerning the relationship between the resistivity of drilling mud R m and that of the mud filtrate R mf there are contradictory opinions. Sherborne and Newton [8] found experimentally that the resistivity of the drilling mud in most cases closely approximates the resistivity of the mud filtrate. Patnode [9] concludes that it is erroneous to substitute drilling mud resistivity for mud filtrate resistivity and Lamont [10] found experimentally the relationship: R mf = 0.88R m .…”

Techniques of Electric Log Interpretation

“…where Ee' = K' log Rxo/ R, (7) Ee' = reduced electrochemical potential of a shaly oil sand, and K' = slope of line through a point with co-ordinates Ee' and Rxo/ R, and through the point…”

“…The effective diameter of invasion of mud filtrate is two to five times the hole diameter. 7. Departure curves can be used to obtain R, from apparent resistivity measurements.…”