Assessing the application of ultradeep azimuthal electromagnetic resistivity tools in detecting igneous formations ahead of the transmitter

Abstract

The Faroe–Shetland basin (FSB) is considered challenging for oil and gas exploration due to its complex geological structure and limited exploration drilling activity. The costs of drilling in the basin are the most expensive within the United Kingdom Continental Shelf (UKCS) due to varying geological and engineering challenges. The prevalence of igneous sill complexes within the basin present drilling hazards that contribute to drilling nonproductive time (NPT) and are documented in multiple studies. Recent advancements in ultradeep azimuthal resistivity (UDAR) technology which utilizes the look-ahead portion of the electromagnetic (EM) signal presents an opportunity to assess its suitability as a derisking tool to ‘look-ahead’ and detect igneous intrusions in volcanic basins. This paper utilizes resistivity log data from Well 214/28-1, which encountered multiple igneous intrusions and is used to validate the ability of these tools to detect the intrusions. The EM look-ahead technology detected with good confidence the top of an igneous intrusion 72 ft (22 m) true vertical depth (TVD) ahead of the transmitter and once drilled, detect the base of the intrusion 54 ft (16 m) TVD ahead of transmitter. The detection of the intrusions prior to drilling and information on intrusion thickness can enable proactive drilling decisions to reduce nonproductive time.