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Drilling wells in potential Unconventional gas reservoirs is coupled with challenges that expose these wells to costly failures. Elevated formation pressure and pressure ramps create uncertainty in determining the mud weight to use in drilling UC wells. Also, various sources of gas influxes create confusion in analyzing well control situations and prolong handling kicks. This paper details the approach taken on an unconventional exploratory HPHT gas well onshore Abu Dhabi to mitigate these drilling hazards. After a thorough analysis of the drilling challenges that were encountered on a previous well drilled in the same field (Well-A), the drilling team has identified Managed Pressure Drilling (MPD) a key enabling technology that can help in mitigating the drilling hazards of (Well-A). A task force was formed with the MPD service provider to plan the MPD system deployment on Well-B. The task force came up with a detailed MPD program to address the anticipated drilling challenges in Well-B with multiple scenarios mitigation plan. MPD goal was to identify the right mud weight to drill the reservoir section, handle gas influxes and analyze the sources of the gas at surface to minimize well shut-in time and to enhance the overall safety of the operations by providing close-loop drilling. Drilling the reservoir section utilizing MPD has resulted in avoiding unnecessary well shut-in and raising the mud weight. Gas influxes were handled utilizing a dedicated MPD Mud Gas Separator (MGS) instead of the rig’s one, this approach enabled smoother drilling and coring operations. The pilot hole reached the planned Total Depth (TD) across high pressure ramps, coring program was implemented without interruption and full cores were recovered as planned. Non-Productive-Time (NPT) was reduced by 60% comparing to Well-A and no well control events occurred, saving cost and building confidence in the system. Therefore, a decision was made to continue utilizing the MicroFlux MPD system in the horizontal section of Well-B. The MPD implementation on Well-B proved that the reservoir pressure was less than anticipated by 3 ppg, thus the 15K psi BOP was not required as thought previously, resulting in reducing the drilling cost of the consecutive wells. The impact of using a lower mud weight is believed to have a positive impact on the reservoir productivity. This paper show-cases the utilization of the Full-Automated MPD on well-B as the first application of this technology in ADNOC onshore fields. It sets a stepping-stone for future implementations and capture important lessons learned and best practices that will certainly facilitate the development of Unconventional resources fields in the United Arab Emirates. Even more, the knowledge management process applied on Well-B can support tackling similar drilling challenges in mature fields. |
