Mudlogging while drilling is a combination of three pre-existing individual types of surveys – gas logging, express petrophysical analysis and measurement while drilling. Efficiency and safety of drilling are mainly determined by quality of mudlogging that has taken a more important role over the last years. On many occasions, mudlogging results helped discover new deposits of hydrocarbons in unconventional traps and reservoirs. A distinctive feature of mudlogging is that it examines core, cuttings, drilling mud, and gas that carry direct geological information about the studied section, which gives special significance and importance to this type of work. Accuracy of obtaining and processing mudlogging data will determine the order of pay zone penetration that, in turn, affects efficiency of oil production and overall future operation of the field. In comparison with classical geophysical methods, mudlogging while drilling gives an opportunity to get close to real-time information.
The article describes key objectives, methods and technologies of mudlogging while drilling and presents a structure of mudlogging methods from standard to high-tech logs. Special attention is paid to the integrated approach to forming a mudlogging program based on well type and preset geological and technical objectives. The authors give a specific example to illustrate introduction of modern technologies to improve control and safety of drilling operations at the Rosneft Oil Company license areas.
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