Use Of Geophysical Logs Research Articles

Applications of Geophysical Logs to Coal Mining—Some Illustrative Examples

Geophysical logs can be used not only for qualitative interpretation such as strata correlation but also for geotechnical assessment through quantitative data analysis. In an emerging digital mining age, such a use of geophysical logs helps to establish reliable geological and geotechnical models, which reduces safety and financial risks due to geological and geotechnical uncertainty for new and existing coal mining projects. This paper presents some examples of geological and geotechnical characterizations from geophysical logs at various coal mines in Australia and India. The applications include rock strength and coal quality estimations, automated lithological/geotechnical interpretation and geophysical strata rating, all based on geophysical logs. These derived parameters could provide input to modelling, control, even ‘digital twin’ generation in a form of geological and geotechnical models as part of the future digital mining. The outcomes can be visualized in 3D space and used for identifying the key geotechnical strata units that are responsible for caving behaviors during longwall mining. This could assist site geologists and planning and production engineers predict and manage mining conditions on an ongoing basis. Both conventional logs such as density, natural gamma and sonic and less common logging data, such as full waveform sonic, televiewer and SIROLOG spectrometric natural gamma logging data are examined for their potential applications. The geotechnical strata classification and rock strengths predicted from the geophysical logs match the laboratory tests, drill core geotechnical strata classification, core photos and the mining condition/behavior observed. These illustrate the usefulness and effectiveness of using geophysical logs for geological and geotechnical characterizations.

Use of geophysical logs in hydrogeological studies and borehole designs: case study of Apapa coastal area, Lagos, Nigeria

The hydrogeological study of Apapa, a coastal part of Lagos, Nigeria, has been investigated using combined geophysical borehole logs, consisting of natural gamma and electrical resistivity components and ditch cutting samples. This study utilized data from 10 boreholes to delineate freshwater aquifer and proposes the best borehole design and construction for optimum groundwater developments in the study area. The electrical resistivity log data show that the depth to the freshwater interface varies across the study area occurring between 150 and 160 m and as shallow as 110 m in a borehole. The variations in depth of the freshwater interfaces are attributed to the extent of saline/brackish water contamination and distribution of rock types. Based on these differences and the inability to identify water quality from ditch cuttings, borehole geophysical logging is a vital tool in providing in situ subsurface information of the rock types and fluid contents in groundwater studies. This further demonstrates that geophysical borehole logs play an important part in borehole design for development of water wells.

Use of geophysical logs to estimate water quality of basal Pennsylvanian sandstones, southwestern Illinois : Ground WaterV27, N5, Sept–Oct 1989, P682–688

Use of geophysical logs to estimate water quality of basal Pennsylvanian sandstones, southwestern Illinois : Ground WaterV27, N5, Sept–Oct 1989, P682–688

DISCUSSION OF “Use of Geophysical Logs to Estimate Water Quality of Basal Pennsylvanian Sandstones, Southwestern Illinois,” by V.L. Poole, K. Cartwright, and D. Leap, September‐October 1989 issue, v. 27, no. 5, pp. 682–688

GroundwaterVolume 28, Issue 1 p. 118-119 DISCUSSION OF “Use of Geophysical Logs to Estimate Water Quality of Basal Pennsylvanian Sandstones, Southwestern Illinois,” by V.L. Poole, K. Cartwright, and D. Leap, September-October 1989 issue, v. 27, no. 5, pp. 682–688 John Logan, John Logan P.O. Box 2096, Carmel, California 93921Search for more papers by this author John Logan, John Logan P.O. Box 2096, Carmel, California 93921Search for more papers by this author First published: January 1990 https://doi.org/10.1111/j.1745-6584.1990.tb02241.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume28, Issue1January 1990Pages 118-119 RelatedInformation

REPLY TO the preceding Discussion by John Logan of “Use of Geophysical Logs to Estimate Water Quality of Basal Pennsylvanian Sandstone, Southwestern Illinois”

REPLY TO the preceding Discussion by John Logan of “Use of Geophysical Logs to Estimate Water Quality of Basal Pennsylvanian Sandstone, Southwestern Illinois”

Use of Geophysical Logs to Estimate Water Quality of Basal Pennsylvanian Sandstones, Southwestern Illinois

ABSTRACTFresh water is found at depths up to 1000 feet in basal Pennsylvanian sandstone aquifers along the southern margin of the Illinois Basin. These aquifers, though not highly productive, represent a significant potential source of ground water in a region of very limited ground‐water supplies. A pilot study was undertaken in southwestern Illinois using geophysical logs and limited hydrologic data to evaluate the potential of these aquifers. Water quality, porosity, and permeability were estimated from the geophysical logs; these data were then used in conjunction with data from aquifer performance tests to delineate zones of potable water. The data indicate that fresh‐water lenses extend basinward in sandstone paleochannels.

The Use of Geophysical Logs for Determining Formation Water Quality

ABSTRACTIn situ water‐quality measurements, with respect to various ion and dissolved solids concentrations, have been closely approximated using open‐hole borehole geophysical logs. Analyses have shown good correlation between water resistivity (Rw, as determined from the logs) and dominant ion concentrations sampled from a wide range of water quality in Tertiary carbonate and granular formations.Rw can be accurately determined by cross‐plotting saturated formation resistivity (Ro), obtained from normal or lateral resistivity logs, against formation bulk porosity from neutron, density, or acoustic velocity logs. Plotting these data on Hingle Resistivity‐Porosity Cross Plot (RPCP) paper with the proper matrix cementation factor (m, commonly 1.4 for unconsolidated sands or 1.6 for noncompacted Tertiary carbonates), will yield a graphical solution for Rw based upon the relationship Rw=φm Ro. The graphical technique also provides information concerning water‐quality variations with depth, true matric resistivity, location of confining beds, and vertical changes in formation porosity.Once Rw has been determined, other ion concentrations can be estimated based upon chemical analyses of water samples from adjacent wells tapping a similar type water mass (i.e., calcium‐bicarbonate, sodium‐chloride water, etc.). Total dissolved solids (TDS), chloride, sulfate, potassium, sodium, magnesium, and hardness (as CaCO3) concentrations have consistently shown a high correlation with Rw.

Role of Geophysical Logging in Coal Exploration and Discrimination: ABSTRACT

Geophysical logging has become an important phase of coal exploration. Electric logs that were run in wells drilled for oil and gas can be used to make preliminary studies of structure, coal thickness, depth, and sedimentological anomalies that affect coal continuity. They can be used to locate the best areas for local exploration coring. Radioactivity logging has become standard procedure in most areas in exploration drilling and coring programs. Thickness (and therefore tops and bottoms of seams) can be determined with great precision on density and neutron logs. Interpretation of radioactivity logs allows the predictions of local geological, structural, stratigraphic, and sedimentological anomalies that will influence mining programs. Ash content calculations which compares favorably with core analyses can be made with the use of density logs. With the use of sonic logs in conjunction with density logs, calculations can be made which will give an indication to the strength of roof and floor rocks. This paper presents case studies of the successful use of geophysical logs in regional and local phases of exploration and the discrimination of coal seams in several geographic locations. End_of_Article - Last_Page 526------------