Two-thirds of the UK’s first horizontal shale gas well was not fracked during a nine-week operation last autumn, according to reports that the company, Cuadrilla, tried to keep secret.
The documents reveal that the Preston New Road site near Blackpool experienced mechanical problems and lost equipment.
They show that quantities of frack fluid used in the operation were too low to qualify for the legal definition of associated hydraulic fracturing. They also confirm for the first time that a majority of earth tremors around the site were on days when fracking was carried out.
The reports are daily logs sent by Cuadrilla to regulators, giving information about operations, induced seismicity, frack fluid volumes, proppant and fracture lengths.
They are marked confidential and were not published on the company’s website, despite a recommendation by the industry organisation, UK Onshore Oil and Gas (UKOOG).
Cuadrilla did not reveal most of the contents to local residents or councillors and it sought to prevent release under freedom of information legislation (FOI).
The Environment Agency did release the logs recently in response to an FOI request by a member of the public. Analysis by DrillOrDrop has revealed:
Cuadrilla carried out just 15 main fracks between mid-October and mid-December 2018
Just 36% of the planned stages of the well had a main frack
Whole sections of the well were not fracked at all
On two-thirds of the fracking days there was at least one seismic event
Fracking used a fraction of the expected volume of fluid and proppant
Fracking paused for more than a month
Fracking equipment suffered a mechanical failure
The well had to be cemented and milled to solve the problem
Equipment became stuck in the well and was abandoned
Despite this, Cuadrilla said it had enough data to predict “a potential initial flow rate range of between 3 million and 8 million standard cubic feet per day”. Based on Cuadrilla’s figures, UKOOG upgraded its UK production estimates by 70% and predicted that at peak levels domestic shale gas could wipe out the need for gas imports.
First UK high volume frack for seven years
Cuadrilla announced the start of fracking at Preston New Road on 15 October 2018. There was intensive interest from the media, onshore gas industry and opposition groups. The well, known as PNR1z, would see the first high volume hydraulic fracture in the UK since 2011 and the first ever frack of a UK horizontal shale gas well.
The operation continued until 17 December 2018. The following day, the company issued a statement that it was moving equipment off the site for Christmas.
Equipment began to return three weeks ago but there has been no public statement that fracking has resumed. In February 2019, Cuadrilla indicated that it would not frack again at Preston New Road until there had been a relaxation of regulations on induced seismicity.
41% of days fracked
Cuadrilla had permission to frack on weekdays and Saturday mornings. This gave it 56 available days between 15 October and 17 December.
The logs show that the company fracked on just 23 (41%) of these available days.
The operation was most intensive in the first fortnight when there were mini and/or main fracks on every available day.
But from 3 November to 17 December, Cuadrilla fracked on just seven of the 39 (18%) available days.
36% of stages fracked
Cuadrilla’s hydraulic fracturing plan said the company would frack up to 41 stages of the well. It planned to start at stage 1, the toe of the well, furthest from the site, and continue progressively towards stage 41, nearest the well head.
According to the daily logs, the company carried out main fracks on just 15 of the 41 stages (36%).
Fracking began at stage 1, as planned, and continued in the first week to stages 2 and 3. It then moved on to stages 12, 13 and 14, before jumping to the stages closest to the well head.
According to the logs, a total of 24 stages, making up entire sections of the well, were not fracked. These included stages 4-11, 15-17, 19-21 and 23-29.
Two stages, 18 and 25, had a mini frack only.
The company told the community liaison group of residents and councillors on 12 November 2018 that it had changed the order of the fracks to “further understand seismicity and obtain data”. It did not say it had missed out entire sections of the well.
17 main fracks
During the operation, Cuadrilla carried out 17 main fracks. Of these, 11 were in October.
There were no main fracks in November or the first week in December. There were six main fracks from 8-17 December 2018.
Two stages of the well each had two main fracks: stage 3 on 18 and 20 October and stage 37 on 8 and 10 December. 12 mini fracks were carried out during the operation.
Fracking and tremors
Cuadrilla’s chief executive, Francis Egan, told BBC Radio 4’s Today programme on 15 October 2018 that fracking at Preston New Road would not cause earthquakes.
Very small tremors began on 18 October 2018, three days after fracking started. They continued until 14 December 2018. The British Geological Survey recorded a total of 56 seismic events, ranging from minus 0.8ML to 1.5ML on the local magnitude scale. Just two tremors were felt at the surface but opponents of the operation expressed concerns about the risks of seismic activity to the well.
The company never suggested that the tremors were unrelated to fracking. But until the release of the daily logs it had not been possible to see how closely they corresponded with pumping operations because Cuadrilla would not reveal all the days that it fracked.
We now know there were tremors on 15 of the 23 days (65%) when there were main or mini fracks. With one exception, there were no tremors on Sundays when Cuadrilla did not have permission to frack.
A gap in fracking corresponded with a gap in seismic activity. When fracking resumed, earth tremors began two days later.
Of the 23 days when there were main or mini fracks, eight days (35%) had no seismic activity. Three of these dates were when the company carried out mini fracks only. Three of the dates were at the start of the operation (15-17 October) and two were at the end (15 and 17 December). On 2 days, there was seismic activity but no fracking.
The strongest earth tremors happened when Cuadrilla was carrying out main fracks on the stages of the well closer to the well pad. For example, the 1.5ML tremor on 11 December was on the day that stage 38 was fracked. The second strongest tremor, 1.1ML, on 29 October, was the day that stage 32 was fracked. This was followed by a 39-day gap in main fracks.
The daily logs don’t provide information on the timing of fracturing so it is not possible to see how soon after injection there was seismic activity. This means it is not possible to check the number of red events under the traffic light system regulations. These are defined as seismic activity above 0.5ML that happen during fracking.
There does not appear to be a close relationship between the strength of seismic activity and the volume of frack fluid or proppant.
Frack fluid and proppant
Cuadrilla’s hydraulic fracturing plan, which describes how fracking will be carried out at the Preston New Road site, said up to 756m3 of fluid would be used per fracking stage.
If the company had used the maximum volume on all 41 proposed stages, the fluid would have amounted to just under 31,000m3. This would have complied with the definition of associated hydraulic fracturing under the 2015 Infrastructure Act: fracking of shale involving the injection of more than 1,000 cubic metres of fluid at each stage or more than 10,000 cubic meters of fluid in total.
The logs show that the total volume of fluid injected at Preston New road for the 17 main fracks and 12 mini fracks was 3,869m3. The average volume for the main fracks was 218m3.
According to the logs, there were just three dates when the operation used at least half the proposed maximum volume: 417m3 on 17 December, 393m3 on 18 October, 384m3 on 22 October.
On three dates, main fracks each used less than 100m3: 19 October 33.9m3; 8 December 78.4m3; 10 December 99.5m.
The hydraulic fracturing plan said each frack stage would use up to 75 tonnes of proppant – the material used to prop open fractures. Cuadrilla later said it had expected to use 50 tonnes per stage but because of the seismicity regulations it had achieved this on only two dates.
The logs confirm this statement. Fracks using about 50 tonnes were on 17 December, the final injection of the 2018 operation, and 18 October, the third main frack.
According to the logs, seven fracking stages used proppant weights below 10 tonnes.
Month long fracking gap and mechanical failure
The logs showed there was no fracking between 3 November and 7 December 2018. This gap largely coincided with a mechanical failure with fracking equipment and efforts to solve the problem.
We asked Cuadrilla whether the fracking pause was caused by the equipment problem. The company replied that on this, and our other questions, it had nothing to add to the information in the logs.
We do know from the logs that the problem concerned mechanical sleeves surrounding the well that open during fracking.
Two sleeves, at stages 30 and 31, became stuck in the open position. These sections of the well had been fracked on 26 October and 27 October 2018.
There were seismic events on both these dates. Cuadrilla confirmed that the tremor on 26 October, measuring 0.8ML, counted as a red event under the regulations. This meant fracking had to pause for 18 hours. There was also a 0.8ML event on 27 October, which was described as a trailing event.
On 1 November, the log recorded that fluid from fracking both these stages of the well was flowed back. The following day, the company announced that it had begun to see gas reach the surface and it released a 12-second video of gas being burned in the flare.
Stages 30 and 31 were flowed back again on 2 November, according to the logs. Two days later, on 4 November, the log recorded:
“Coiled Tubing ran in hole to try to close sleeves 30 and 31.”
The following day, 5 November, Cuadrilla tried again to solve the problem. The log said:
“Coiled Tubing finished a logging run, came to surface, switched the BHA, ran in hole, tried to close sleeves, came to surface, re-dressed the BHA [bottom hole assembly on surface.”
According to the logs, the company tried again on 6 November:
“Coiled Tubing run into the well to attempt to close sleeves 30 and 31, pull coiled tubing to surface, and close well head master valve.”
The log recorded that the well was cleaned on 7 November and a day later prepared for a cement job to solve the sleeve problem. The record for 9 November said:
“Equipment maintenance and preparedness for the upcoming cement job.”
On three days, from 10-12 November, the logs reported:
“Waiting for equipment and material for the upcoming cement job”.
Cuadrilla told the High Court in October 2018, a day’s delay would cost £94,000. If this rate were applied to the sleeve problem, the cost by mid-November would have topped £1m. Cuadrilla did not respond to our question about delays.
On 12 November, there was a monthly meeting of the community liaison group (CLG) for Preston New Road.
The minutes, written by Lexington Communications for Cuadrilla, recorded that Cuadrilla’s then technical director, Mark Lappin, “provided an overview of operational activity”. There was no reference to the sleeve problems or the upcoming cement job.
According to the minutes:
“Mark Lappin advised that [gas flow] is now being analysed and confirmed that Cuadrilla intends to commence hydraulic fracturing over the coming days.”
The daily logs show that the next main frack would not be for nearly a month.
Calls for information release
The CLG minutes also recorded a question about why the daily logs were not published on Cuadrilla’s website.
“Mark Lapin confirmed that daily reports are issued to the OGA [Oil & Gas Authority], EA [Environment Agency] and HSE [Health & Safety Executive], but advised that it is not a requirement to publish on the operator’s website. Clarifying this, he noted that the United Kingdom Onshore Oil and Gas (UKOOG), the representative body for the industry, had recommended this, but that was not a requirement.”
The minutes also suggested that the Environment Agency may be required to provide the logs if there was a freedom of information request.
According to the minutes, the Environment Agency officer at the CLG suggested:
“it may be beneficial for Cuadrilla and the regulators to be on the front foot by providing information that would be useful for the community.”
“No stage-by-stage fracking updates”
At around this time, people started to notice that seismic activity around Preston New Road had stopped. The British Geological Survey (BGS) last recorded earth tremors in the area on 4 November 2018. There were also rumours about why fracking had stopped (DrillOrDrop report).
On 11 November, DrillOrDrop asked Cuadrilla whether it had fracked in the week before the CLG meeting. The company told us:
“We are continuing to test our exploration well in Preston New Road, Lancashire, including testing the responsiveness of the shale to fracturing. We are also analysing the recent natural gas flow at the surface and other data which is available to us following the start of our hydraulic fracture fracturing programme last month. However, we are not giving a stage by stage update on each frac.”
After the CLG meeting, the logs for the next three days recorded more waiting for the cement job on the well.
On 15 November, DrillOrDrop asked Cuadrilla about suggestions that the well had been damaged. The company replied:
“There are no integrity issues with the PNR1z well”.
The next day, we asked:
“Are there any other problems with the well that might be considered to be damage but which don’t involve well integrity with PNR1z?”
Cuadrilla responded on 22 November with a statement:
“We are continuing to test the shale gas exploration well in Preston New Road, Lancashire, and the coiled tubing remains clearly and visibly attached to the coiled tubing tower on site above the well.
“We have completed a series of smaller fracks along the length of the horizontal well to gather data to assess the micro-seismic response of the shale rock 2km below the surface.
“We have said many times in recent days and weeks, to both local people and any media who have asked for an update, that we are now analysing that data as well as drawing on expert advice to determine how we can further optimise our hydraulic fracturing programme within the very rigorous operating boundaries of the micro-seismic traffic light system.”
A freedom of information request by DrillOrDrop revealed that the Environment Agency had been asked for the daily logs. A heavily-redacted email showed that Cuadrilla told the agency:
“We believe that all the data contained in our daily reports is commercially confidential”.
It also said:
“Please would you confirm that the Environment Agency will not be releasing any of these reports to the public without our consent.”
The company’s lawyers later asked for more time to respond to the request.
Cement job, cleaning and lost equipment
On 16 November, the logs recorded the cement job had been carried out on sleeve 30. The work on sleeve 31 took place on 17 November. The next day, the company waited for the cement to harden.
On 19 November, the log recorded:
“Ran coiled tubing into the well to mill to stage # 31.”
According to the logs, milling took place from 20-22 November. Four days of cleaning then began on 23 November.
On 26 November, the log recorded:
“Pulled coiled tubing to surface. Boot basket was empty. Upon inspecting BHA [bottom hole assembly], the mill, crossover, and bottom piece of the motor were left in the well.”
The solution, reported in the log for 27 November, was to push the equipment to the end of the well:
“Ran in hole with the bullnose BHA on coiled tubing and pushed the missing part of the previous BHA to TD.”
Fracking resumed on 8 December and continued for another eight days.
Relaxation of regulations
Since last year’s operation, Cuadrilla has called for a raising of the seismicity limit at which fracking must pause.
In a statement in February, the company said it had acquired 40,000 micro-seismic data points during fracking the PNR1-z well.
The company’s chief executive, Francis Egan, said:
“We believe there is more than ample evidence to justify an expert technical review of the TLS [traffic light system] and, based on the outcome of that review, a revision at the PNR site, without compromising on safety.”
But Sir Edward Davey, the former energy secretary who approved the 0.5ML threshold, said in a parliamentary debate last week that any review must be based on “a significant amount of evidence”.
“So far we have had very few fracking experiences in this country, so we do not have anywhere near the number of data points or the amount of evidence that we would need to possibly allow anything to go forward.”
Information from the company’s logs raises questions about the limitations of last year’s operation at Preston New Road and whether the data meets the requirement of “a significant amount of evidence”.
DrillOrDrop acknowledges the help of Refracktion with data assembly. If you would like to see the daily logs please get in touch