WIRELINE LOGGING
In the oil and gas industry, the term wireline logging usually refers to a cabling technology used by operators of oil and gas wells to lower equipment or measurement devices into the well for the purposes of well intervention and reservoir evaluation. Also a continuous measurement of formation properties with electrically powered instruments to infer properties and make decisions about drilling and production operations.
This book is a basic introduction to open hole logging. Study of the properties of rocks by petrophysical techniques using electric, nuclear, and acoustical sources is as important to a geologist as the study of rock properties by more conventional means using optical, x-ray, and chemical methods. Nevertheless, despite the importance of petrophysics, it is frequently underutilized by many geologists who are either intimidated by logging terminology and mathematics, or who accept the premise that an in-depth knowledge of logging is only marginally useful to their science because, the feel, it more properly belongs in the province of the log analyst or engineer. |
As logging tools and interpretive methods are developing in accuracy and sophistication, they are playing an expanded role in the geological decision- making process. Today, petrophysical log interpretation is one of the most useful and important tools available to a petroleum geologist. Logging data are used to identify productive zones, to determine depth and thickness of zones, to distinguish between oil, gas, or water in a reservoir, and to estimate hydrocarbon reserves. |
The continuous recording of a geophysical parameter along a borehole produces a geophysical well log. The most appropriate name for this continuous depth-related record is a wireline geophysical well log, conveniently shortened to well log or log. It has often been called an ‘electrical log’ because historically the first logs were electrical measurements of electrical properties. However, the measurements are no longer simply electrical, and modern methods of data transmission do not necessarily need a wire line so the name above is recommended. This book therefore concerns wireline geophysical well logs. |
Downhole logging is the process of measuring physical, chemical, and structural properties of penetrated geological formations using logging tools that are either lowered into the borehole on a wireline cable (wireline logging) or placed just behind the drill bit as part of the drill pipe itself (logging-while-drilling). The tools employ various acoustic, nuclear, and electrical measurement techniques to acquire downhole logs of properties such as sonic velocity, density, and electrical resistivity. The wireline cable provides real-time communication between the tools and the surface; logging-while-drilling tools typically record the logs in downhole memory devices, which are subsequently downloaded when the tool returns to the ship.
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This handbook is designed for explorationists who work in the real world and who, therefore, aren’t always lucky enough to have textbook-type evaluation problems in their everyday work, especially when working in carbonate reservoirs. This book is largely devoted to explaining and then illustrating a variety of techniques which can be brought to bear on carbonate-related problems. This book is useful but should apply these techniques with caution. They may not work every time. |
Resistivity of a water sample is 0.3 ohm-m at 25°C; what is the resistivity at 85°C? Enter the chart with 25°C and 0.3 ohm-m. Their intersection indicates a salinity of approximately 20,000 ppm. Moving along this constant salinity line yields a water sample resistivity of 0.13 ohm-m at 85°C. |
This document presents a review of well logging methods and interpretation techniques. The various openhole services offered by Schlumberger are discussed in some detail, together with essential methods of interpretation and basic applications. The discussion is kept as brief and clear as possible, with a minimum of derivational mathematics. |
Introduction to Wireline Log Analysis is intended for those who have little or no experience in log analysis methods, petrophysics, and perhaps the petroleum industry. The material contained in this book is not intended to be used as a self-teaching course, but instead contains practical questions / problems that are intended to be used as a review of the material being presented. The text is intended to introduce well log analysis to entry-level logging engineers, or whomever has an abiding interest in learning about formation evaluation. |
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