Log Evaluation of Nonmetallic Mineral Deposits

Abstract

Well logs can be used to locate and evaluate deposits of various commercially important minerals. It is only necessary that the mineral of interest represent a significant fraction of the formation bulk volume, and that it exhibit characterizing properties measurable by logs. Because modern logging methods measure electrical, density, acoustic, radioactivity, and certain nuclear characteristics of formations, they may be used to identify many minerals. For evaluation of sulfur deposits, either density or sonic logs provide good resolution when compared with porosity computed from neutron or resistivity logs. Trona beds are identified by a sonic reading of approximately 65 μsec/ft, neutron porosity index of about 40 percent, low natural radioactivity, and pronounced hole enlargement. Gamma‐ray logs provide important information in the location, identification, and evaluation of potash mineral deposits. Neutron, sonic, and density logs, in various combinations, augment the gamma‐ray data in such studies. Coal beds are characterized by high resistivities, and by high apparent porosities on sonic, neutron, and density logs. Density logs are particularly suited for evaluation of yield from oil shales. In all such explorations for nonmetallic mineral deposits, well‐logging methods provide a fast, detailed, and economical reconnaissance of the entire length of drilled hole. Results compare well with core assays.

Salt deposits in Los Medanos area, Eddy and Lea Counties, New Mexico

“…The geophysical logs contain the most reliable information, so that lithologic and driller's logs were used in the present study only in areas where geophysical data were lacking. The use of geophysical logs in the study and analysis of salt deposits and other evaporites has been discussed by several authors (Jones and others, 1960;Alger and Grain, 1966;Edwards and others, 1967;Tixier and Alger, 1967) and is not within the scope of this report.…”

Gas Content Evaluation of Coalbed Methane Reservoir in the Fukang Area of Southern Junggar Basin, Northwest China by Multiple Geophysical Logging Methods

“…Coals can be easily distinguished by geophysical logging [36]. RLLS (shallow laterolog, Ω·m) and RLLD (deep laterolog, Ω·m), reflecting the formation resistivity, can be used to calculate porosity of the formation.…”

EMSE: Synergizing EM and seismic data attributes for enhanced forecasts of reservoirs

“…Research has however shown that although the original equation is valid, the parameters m and n strongly depend on the formation under consideration and may significantly deviate from the original form. In order to study the robustness of the algorithm with respect to different forms of Archie's equation, we have implemented several empirical relationships based on the models of Archie (1942), Winsauer (1952), Tixier and Alger (1970), Carothers (1968), Timur et al (1972) and Hill and Milburn (2003). The differences in the conductivities obtained from these models between two consecutive update steps are then incorporated into the observation operator of the different EnKFs.…”