Better success rates from North Sea exploration drilling could be achieved if historical well data was stored and shared better, according to the results of a review of well data published.
The Oil and Gas Authority says a lack of quality geoscience and geophysics work, inconsistent de-risking, better regional play-based work, improved seismic data quality and high staff turnover were all also impacting the low exploration success rate in the basin.
The well failure analysis study, which covered the Moray Firth and Central North Sea, looked at 98 wells, currently owned by 24 companies, with a focus on wells that were either dry or a technical success, rather than commercial success. It found that between 2003–2013, the overall technical success in the Moray Firth and Central North Sea amounted to 40%.
The study found several of the prospects relied too heavily on geophysical analysis, missing the geological picture. Several prospects also relied too heavily on seismic anomalies. After analyzing 104 segments belonging to 97 wells, it found 39% of the well failures were due to three clear causes; lack of lateral seal (27%) followed by the absence of target reservoir (23%) and the lack of trap (17%).
“Even more strikingly, 36% of the main pre-drill risk was not accurately predicted,” the study says.
Some 12.6% of the analyzed segments failed for one clear reason (e.g. absence of target reservoir): in these cases, only the drill bit could check and test the segment.
The study said: “The poor storage of historical well data has been a recurring theme all through this study. This data issue is highlighting the questions about how companies store information, companies’ ability to retrieve information post staff movements (knowledge management is a real concern during company take overs), transfer of information from asset sales to purchasing companies and the balance between documentation of regional studies versus well justification documentation.”
Transparency of data is high on the list of the OGA’s objectives. Once the new organization is given new powers, through the Energy Bill - legislation due to be passed into Law during 1H 2016 – the OGA says it will improve the data storage and the way it is made available to the industry.
In its conclusion of feedback from operators the study says: “The lack of quality G&G work, ineffective peer review, and inconsistent de-risking were key points in a number of well failures. The importance of doing more regional play based work for setting and context were repeatedly missed.
“Fully linking the geophysicists and geologists was highlighted, as well as better collaboration /communication with other key functions: drilling and development and ultimately management.
“Regarding the Moray Firth it was observed that the quality of seismic was generally poor, causing challenges in picking the top Captain and Top Punt reservoirs.
“It was observed that the pre-drill analyses often excluded the full range of possible outcomes: when describing a prospect, we should take on-board a wide range of parameters; during the interpretation process we shall stay open minded and consider different scenarios.
“It was observed that the industry has a poor understanding of shales, seals and how to map them.
“Overall, firm well commitments were drivers for one third of the analysed wells. As a consequence, one must ask the key question “how rigorous is the bid work and what is the data quality to hang a commitment on”?”
The OGA adds: “The need to keep a fresh view of the UKCS /NCS was highlighted: it is still worth looking at gaps and where is yet to be explored and understanding the exploration significance of finds such as Johan Sverdrup right across the UK-Norwegian border.
“The value of end of well / post well information acquired even though the well is dry (pressure data, shear sonic logs / fluid Inclusion studies…etc…) can be key both to learn why a well failed and to better understand the Basin.”
The OGA says it acknowledges that a decision must be made to decide whether it should ask for a minimum standard set of logs / data.
Finally, it also highlighted staff turnover as an issue. “Quite often, people move on to another posting / company so that they don’t see the whole history from prospect maturing to post well analysis. This too fast turn-over is detrimental not only to build individual in-depth knowledge of the basin but also to keep this knowledge within companies as it can lead to disconnects in prospect generation, post well analysis and regional integration.”
The well failure analysis study was the first key project undertaken under the 21st Century Exploration Road Map, a project first recommended by the Exploration Task Force, aligned with the Wood Review.
Read the full report: Post well analysis report
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