Corallian discovers oil and gas shows at Colter appraisal well

  • Exploration & Production

UK-based Corallian Energy has encountered oil and gas shows at its Colter appraisal well offshore UK, confirming a discovery in the Colter South Prospect.

Ensco-72 jack-up rig. Author: SP Mac

Corallian is the operator of offshore license P1918 which contains the Colter oil discovery located two kilometers south of Wytch Farm – Europe’s largest onshore oil field.

Corallian started drilling operations on the Colter appraisal well, using the Ensco-72 jack-up rig, on February 6, 2019.

According to the operator’s statement on Monday, the Colter well (98/11a-6) has been drilled as a vertical well and has reached a Total Depth of 1870m MD in the Sherwood Sandstone. The well is an appraisal of the 98/11-3 well, drilled in 1986 by British Gas, within the Colter Prospect.

Corralian said that the 98/11a-6 well unexpectedly remained on the southern side of the Colter Prospect bounding fault but encountered oil and gas shows over a 9.4m interval at the top of the Sherwood Sandstone reservoir. A petrophysical evaluation of the LWD data has calculated a net pay of 3m. Similar indications of oil and gas were encountered in the 98/11-1 well, drilled in 1983 by British Gas, within the Colter South fault terrace.

Provisional analysis of the new data indicates that the two wells may share a common oil-water-contact having both intersected the down-dip margin of the Colter South prospect, Corallian explained.

Corallian’s most recent assessment of the Colter South Prospect prior to drilling the 98/11a-6 well had estimated a mean recoverable volume of 15 mmbbls. Further work will be required to refine this assessment with the new well data, the company said.


Two weeks for side-track


The joint venture has started preparations to side-track the 98/11a-6 well. The side-track will be drilled directionally to a Sherwood Sandstone target within the Colter prospect on the northern side of the bounding fault, and will take approximately two weeks to complete.

“It is encouraging that the well has confirmed a discovery in the Colter South Prospect. More work will be required to determine the resource potential within the structure and we look forward to the results of the side-track to evaluate the Colter Prospect,” Corallian said.

United Oil & Gas and Baron Oil, Corallian’s partners in the license, on Monday commented on the Colter appraisal well results.

United Oil & Gas CEO, Brian Larkin, said: “Initial results from Colter have delivered a bonus in the form of an additional hydrocarbon structure, which has excellent initial oil and gas shows.  This offers opportunity for future appraisal and to increase the overall value of the Colter license for our shareholders. More work will be required to determine the resource potential within the structure, and we will update shareholders on the outcome of the side-track well in the coming weeks.”

Malcolm Butler, Chairman and CEO of Baron, commented: “The initial well bore has given valuable information on the potential of the Colter South Prospect, which will be integrated into our existing analysis of the structure in this area. We are now moving forward with the side-track into the Sherwood Sandstone reservoir in our main Colter Prospect target and look forward to updating shareholders in due course. Baron Oil has an 8% interest in Colter and Colter South.”

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