RE: Brx4z flowtest9 Jun 2019 14:43
Alexios
"Anyone remember Broadford Bridge? And what was the issue they failed to flow?"
IIRC UKOG summarized the issue in their statement in March denying they were going to Acid Frac Dunsfold:-
"UK Oil & Gas PLC would like to emphasise that it has no plans or intention to inject any dilute acid
into either the gas-bearing Portland sandstone reservoir (our primary Dunsfold objective) or the
underlying naturally fractured Kimmeridge Limestone rocks, situated at depths of around a
kilometre or more below Dunsfold.
Similarly, we have no intention to use this process, known as matrix acidisation, in the future at
Horse Hill, Broadford Bridge or other Weald Basin wells with the same targets.
Recent studies of our nearby Broadford Bridge-1 well show that, because of the chemical
composition of the rocks, the acidisation process can have a significantly detrimental effect on the
ability of oil and gas to flow into the well.
However, we reiterate that this process, which was fully permitted and approved by the
Environment Agency, has been used safely and widely for over 100 years to improve the fluid flow
from wells in limestone rocks (“lime” rich rocks made primarily from calcium carbonate) that
produce public drinking water and hydrocarbons.
The process, which attempts to enlarge flow pathways in limestones by dissolving lime, utilises
exactly the same chemistry as household lime scale removal from sinks, baths, showers and toilets,
using similar acid concentrations of up to 15%. The lime and acid is converted into water, carbon
dioxide and highly soluble calcium chloride, a naturally occurring significant constituent of the fossil
salt water already present within the Weald’s underground sedimentary rock sequence.
Crucially, the Portland and Kimmeridge rocks also contain significant amounts of microscopic clay
particles bound within the rock. Consequently, as the lime dissolves, some of these clay particles are
released into flow paths within the rock. The “free” clay particles then migrate towards the well and
combine, forming a clay “sludge”, restricting or blocking some of the flow pathways, which can
significantly reduce the well’s performance. Once blocked the flow pathways cannot be reopened.
It makes neither commercial or technical sense for UKOG to utilize this acidisation process, as its
future use could seriously reduce the significant natural flow potential and the good flows of
hydrocarbons we expect."
So basically they filled up all the holes in the rock with sludge = no flow = very expensive lesson learnt I guess
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