Despite the unconventional geology currently targeted by Angus Energy, the company describes itself as a ‘conventional’ oil & gas company at every opportunity, and re-iterates that there will be no hydraulic fracturing because the Kimmeridge is naturally fractured.
However, in his expert commentary on Brockham, David Smythe – Emeritus Professor of Geophysics in the University of Glasgow – points out that the natural fractures (which are visible in the outcrop at the Kimmeridge Bay) are vertical, so it is difficult to see how lateral drainage (from a near vertical well) of the reservoir can be achieved. Elsewhere, Prof Smythe notes that, prior to the Horse Hill discovery in 2016, some 55 or so wells had been already drilled through the Kimmeridge in the wider Wealden area, and that none of them had free-flowing oil anywhere in the Kimmerigian layers.
From another expert source, we understand that it is not possible to conclude that a naturally fractured reservoir will flow oil based only on borehole imaging. The fractures might be closed due to overburden pressure, or they might not be connected enough to enable flow of oil. No tests have been done yet on the Kimmeridge at Brockham. Angus continues to tout the Horse Hill (nick-named the Gatwick Gusher) reportedly successful test flow rates, but forgets to mention the disappointing results at Broadford Bridge in Q4 2017/Q1 2018, where UKOG concluded that the Kimmeridge “appears to be unproductive due to low reservoir permeability” and that new completion and other reservoir stimulation techniques will need to be considered on future wells. In any case, even if an unconventional reservoir is naturally fractured, it will still require the drilling of back-to-back wells in order to drain the fractures efficiently, and it will likely require acid stimulation.
Acid stimulation* is a type of fracking performed on limestone or sandstone-rich shale that dissolves the rock enlarging or creating new fractures. We believe that this is the process Angus Energy’s MD, Paul Vonk, describes in this podcast talking about the plans at Brockham (from c.4 to 5 min).
Acid stimulation, which the industry sometimes refers to as an “acid squeeze”, includes matrix acidising (fluid pumped below formation fracture pressure) and acid fracking (fluid pumped above formation fracture pressure). It uses less water than high volume hydraulic fracturing, but because it’s an acid-based method, the concentrations of acid and other chemicals are higher. In addition to high strength hydrochloric or hydrofluoric acids (used on limestone and sandstone respectively), other chemicals are added, similar to those used in the hydraulic fracturing process.
Unlike hydraulic fracturing, acid stimulation has not been researched widely, but the available studies, as well as common sense, suggest that the expected risks of this process are the same as of hydraulic fracturing: risk of pollution to groundwater, surface water and air, stress on water supplies, toxic and potentially radioactive wastewater, and industrialisation from drilling multiple wells in close intervals, both in space and time. (1,2)
* Acid stimulation should not be confused with acid wash – decades-old and widely used method of cleaning of the wellbore by circulating small volumes of acid in the wellbore (but not pumping it under pressure into the formation).
Legislative & Regulatory Framework
Unfortunately, acid stimulation, like hydraulic fracturing that doesn’t meet the arbitrary thresholds of injected fluid volume set out in the Infrastructure Act 2015, is exempt from the Government definition of associated hydraulic fracturing, and from the regulations introduced by the IA2015.
The Environment Agency (EA) clarified how they view acid stimulation only in January 2018. It is a welcome step; however, there is no meaningful regulation behind it, the de minimis exclusion criteria are unclear, as are the monitoring methods to ensure that only operations that are permitted within the scope of permit are actually performed.
Specifically at Brockham, Surrey County Council (the relevant Minerals Planning Authority) operate according to an outdated minerals plan that doesn’t include any specific policies for unconventional hydrocarbons.
What’s even more concerning is that the site operates under an old-style environmental permit, which is clearly inadequate, and it appears to be another loophole in the system. The EA is in the process of assessing the operations proposed by Angus and deciding whether to permit them under a modern-style permit, which will also include much better monitoring. This process is taking longer than expected and creates uncertainty because the applicant is not sharing the information required. We think that Angus should not be allowed to progress operations, especially on new formations, until the new permit is in place. This is not however what the system prescribes.
For comparison, in California all acid-based stimulation is regulated within the state’s fracking regulations (in the same way as hydraulic fracturing) that follow the framework set out in Senate Bill No. 4 of 2013. In Florida, a bill seeking to ban all types of fracking, “including hydraulic fracking, acid fracking and matrix-acidizing” is currently going through the state legislature.
(1) Abdullah, K. (2016). Acidizing Oil Wells, a Sister-Technology to Hydraulic Fracturing: Risks, Chemicals, and Regulations. UCLA.
(2) Toxicity of acidization fluids used in California oil exploration, Khadeeja Abdullah, Toxicological & Environmental Chemistry Vol. 99, Iss. 1, 2017