Abstract
The underbalanced drilling (UBD) technology has been widely implemented due to its advantages in drilling efficiency improvement and cost reduction. However, this advanced technology requires very special equipment and operational mechanism, which raises multiple challenges to traditional well logging techniques. In this study, a real-time logging system (MWD/LWD and mud logging) was developed and utilized during underbalanced drilling, to quickly identify and evaluate gas formation. This advanced system enables fast detection of gas formation and determining the formation type while drilling, by monitoring the changes in gas production. This real-time logging system provides a powerful technical support to the gas reservoir drilling and development. A case study has clearly shown that the interpretation and evaluation results based on the real-time logging data agree well with the results of conventional well logging. Therefore, this advanced real-time logging technique can be utilized as an effective guidance for field operation.
Highlights
Underbalanced drilling (UBD) is a process by which the bottom pressure of the well is maintained below the formation pressure and causes the formation fluid to flow into the wellbore and to the surface under control [1]
When drilling into hydrocarbon reservoirs, especially gas reservoirs, kicks or blowout accidents may be caused if well control is handled poorly [2, 3]
The data signals are transferred to computer terminal wirelessly, and the interpretation results in the form of charts and diagrams can be visualized in real-time manner. This data processing and control system provides to field personnel capability of real-time monitoring and preventing the fluid loose/kick situation during UBD [12, 13]
Summary
Underbalanced drilling (UBD) is a process by which the bottom pressure of the well is maintained below the formation pressure and causes the formation fluid to flow into the wellbore and to the surface under control [1]. The most common approach is to monitor the changes of total hydrocarbon value and gas production in the real-time logging [7]. Xu et al (2007) put forward the comprehensive discriminating and evaluating method of recognizing the gas formation by monitoring the drilling time, gas logging values, and the gas flow rate, observing the variation of drilling parameters, the change of the mud ditch surface, and the state of the torch combustion with UBD. Separator Mud tank established a novel approach to identify and evaluate gas formation with underbalanced drilling. This new approach has provided significant improvement to the conventional well logging techniques. It is critical to a robust drilling program by rapidly evaluating gas formation and effectively guiding the site operation
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