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Logging while drilling

Nov 08, 2018

Logging while drilling

In the exploration and development of oil and gas fields, logging must be performed after drilling to understand the hydrocarbon content of the formation. However, the acquisition of logging data is always done by cable placing the instrument into the well after completion of the drilling. However, in some cases, such as high-angle wells or even horizontal wells where the slope of the well exceeds 65 degrees, It is difficult for the cable to put the instrument down; in addition, the well wall condition is not easy to collapse or block and it is difficult to obtain logging data. As the drilling fluid is circulated during the drilling process and the drilled cuttings are taken out, the drilling fluid filtrate always invades the formation. Therefore, after drilling and logging, the various parameters of the formation are different from those when the formation was just drilled. So people are thinking, if you put the logging instrument on the drill bit, let the drill bit grow "eyes", and get a variety of information on the formation while drilling into the side, this is the logging while drilling. In this way, wells can be drilled not only for wells in any situation, especially horizontal wells, but also with the measured drilling parameters and formation parameters, and the drill trajectory can be adjusted in time to make it drill along the target layer. Since the formation parameters obtained by logging while drilling are the parameters of the newly drilled formation, it is closest to the original state of the formation, and the evaluation of oil and gas for complex formations is more advantageous than general cable logging. The logging while drilling tool is placed in the drill collar. In addition to measuring conventional resistivity such as resistivity, sound velocity, neutron porosity, density, and some imaging logs, it also measures the weight, torque, speed, annulus pressure, and temperature. , drilling parameters such as chemical composition. Due to the harsh environment during the drilling process, the temperature is very high, the pressure is extremely high, and the vibration is strong. Therefore, the reliability of the logging while drilling tool is still the most important issue for the merchants.


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