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Sometimes referred to as borehole logging, well logging is the action of creating an intricate written record of the data gathered during the process of creating a borehole. This record, known as a well log, makes it possible to get a better idea of the different types of matter that are encountered when drilling a hole into the ground in search of different minerals, oil or gas deposits, or even groundwater. The exact structure and content of the well log will vary, depending on the purpose for creating the record.
Well logging usually takes one of two different approaches to the task of detailing information about a particular drilling activity. One approach is known as a geological log. With this approach, samples are obtained from the borehole and physically brought to the surface for evaluation. An alternative method focuses on the creation of a geophysical log. In this instance, equipment is lowered into the borehole, and the sides of the shaft created by the drilling are examined in their natural environment.
When it comes to well logging involving evaluations of possible oil and gas deposits, the log will track findings that have to do with the amount of hydrocarbons found at various depths. In order to assess the hydrocarbon content, testing of both rock and fluid formations collected at different points is conducted, and the results recorded in the log. Generally, a device known as a logging tool is attached to a thin piece of wire called a wire line. The line is used to lower the tool to the correct depth, where the tool is used to gather the necessary data to assess the level of hydrocarbons present at that depth.
Accurate well log data is key to knowing whether there is a sufficient supply of oil or gas to merit attempting to drill any further. From this perspective, well logging can be seen as an important way of minimizing the chances of spending a great deal of time and money searching for underground deposits that will not yield enough return to justify the operation. If the testing does not indicate that enough hydrocarbons are present to suggest the presence of a large deposit, it is a simple task to move to another site and initiate another test before bringing in the heavy drilling equipment.
Well logging can also be used in scientific exploration of the makeup of earth in a given locale. By employing either a geological or geophysical approach to the task, it is often possible to use well logging as a means of discovering which events helped to shape the construction of the area under consideration. For example, the results obtained from a borehole can be properly arranged in a well log and allow researchers to determine if the current land formation came about due to shifts during earthquakes, flooding, or any number of other natural phenomenon.