Electrical Logging In Recent Sediments
Authors: Chmelik F.B. , Bouma A.H. 
Published: October 2008

Electrical logging technology offers, solutions to many problems involving recent sedimentary deposits. One of the more important of these concerns the time delay between the collection of a sample and the reduction and analysis to useable data. Electrical, logs produce results on a real-time basis thus allowing the operator to take quick action. Further, the availability of real-time data facilitates time-rate-of-change studies of sedimentary environments.

Subtle property differences between layers as thin as 0.5 cm can be easily resolved on both core and in situ logs. The ability to recognize these differences affords the operator a basis for choosing test and sample locations along cores. Comparisons of electrical logs and sever-al physical property tests indicate that:quantitative relationships exist between electrical and other properties of sediments,log scan be used for determining the "weight" to be given to sample points,logs can be used as a positive quality control on cores by identifying "missing" sections, andlogs can be used for the correlation of layers between core stations.

Electrical logging technology in sediment investigations find immediate application in several fields including:,pollution evaluation and control,foundation evaluation for drilling platforms, pipelines, and other sea-floor construction work, andevaluation of mining prospects.

The problems of resolution, both in terms of layer thickness and layer properties, are being investigated. In situ probes operated in the vertical-and horizontal modes are suggested as a means of reducing the, time-on-location for anyone job. Economically, the application of electrical logging technology, as an adjunct to present techniques in the investigation of sedimentary deposits, promises to significantly improve the cost effectiveness of such operations.

INTRODUCTION

The importance of understanding the properties of unconsolidated recent marine sediments has become magnified within the last decade. Information regarding these sediments is vital to many industries. Sea floor studies have traditionally been conducted with tools borrowed from technologies developed on land. Marine geophysics has been indispensable to deep exploration efforts. Soil mechanics' equipment and techniques adapted from civil engineering have enabled scientists to define many of the parameters needed to understand marine sediments. However, no one technology is capable of supplying all of, the answers needed. Every source of data must be exploited.

As techniques have improved and the demand for information has grown, certain problems emerged. The time-lag involved between acquisition of samples and generation of data, the adverse effects of removing samples from their environment, inaccuracies caused by sample and testing techniques and the overall economics of sample programs stand as major problem areas. In situ systems using real, time presentation of sediment property data and convenient, easily handled hardware will facilitate the solution of these problems.

Electrical logging, a technology well developed and widely accepted by the oil industry, appears to be such a system.