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UKOG reports positive initial oil flows from its BB-1/1z Kimmeridge Limestone test in Weald Basin licence PL234

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Oilfield Technology,


  • Oil flowed to surface from Kimmeridge Limestone 5 (KL5) throughout 96 hours of near-continuous rod-pumping. Fluid returns, measured as half-hourly instantaneous pumped rates, currently range from around 10 to 72 bpd.
  • Fluids flowed to surface consist of oil mixed with returned reactants (spent acid) from an acid-wash programme. Associated average oil percentages (oil-cut) exceed 30% with intermittent periods exceeding 50% by volume and continue to increase. To date, no obvious formation water has been observed in returns.
  • 24 hour pumping operations will continue to enable flow to stabilise, return all spent acid and achieve 100% oil (‘clean-up’).

UK Oil & Gas Investments PLC announces that oil has flowed to surface from the naturally fractured KL5 reservoir at its 100% owned BB-1/1z exploration discovery, located in licence PEDL234. Fluid returns to surface, measured as half-hourly instantaneous pumped flow-rates over a 96 hour near-continuous period, ranged between 10 to 72 bpd.

To date, fluid returns through the test equipment consist of a mixture of oil plus returned spent-acid from an acid wash treatment, with no observed obvious formation water component. Associated oil-cut steadily increased to over 30%, with intermittent periods exceeding 50% by volume. Flow continues to clean-up with an improving oil-cut trend.

The artificial lift programme, which commenced Friday 16th February, included several initial half-hour shut-downs to bleed off produced associated gas before it locked-up the pump. One short pressure build-up test was also undertaken.

As the KL5 zone's steel casing was not perforated during the original 2017 well completion programme, two new casing-perforation runs were undertaken prior to testing.

The current test, number 7, the first ever within the KL5 in the Weald's 100-year exploration history, straddles a discrete naturally fractured limestone interval close to the top of KL4, which corresponds to the previously reported occurrence of live oil in open natural fractures seen in BB-1 core.

General Testing Update and Future Plans

The KL5 24-hour rod-pumping programme is planned to continue until further notice to enable flow to stabilise and further clean-up with the aim of achieving 100% oil to surface. 

Prior to the KL5 test, oil and associated gas were recovered to surface from tests 5 and 6 within the uppermost KL3 and KL4, but with no sustained flow. Due to the limited time remaining on the planning consent, the decision was made to spend no further time on these zones and proceed ahead to the KL5 zone which, as reported in December, was known from core and geochemical analyses to contain oil in fractures and within the limestone rock matrix.

In the light of results and analyses from tests 5 and 6, together with learnings from test 7 in KL5, the Company and its consultants are currently investigating the possibility that zones 5 and 6, originally perforated in summer 2017 and acidised during the original test programme, were damaged by a combination of the long residence times of spent acid within the reservoir prior to current testing and the perforating technique utilised.

It is now thought that both fractures and perforated channels around the wellbore of KL3 and KL4 could be partially blocked by released clay particles and cement related debris, thus preventing sustainable fluid inflow.

In this respect, serious consideration is being given to a possible future short sidetrack and selective re-test of KL3 and KL4 which electric logs show as oil-saturated.

Existing planning consent time permitting, following completion of KL5 testing, the plan remains to test a 40 ft thick limestone zone in KL1 which, as per KL5, was not perforated or acid-washed in 2017.

About BB-1/1z

As previously reported, BB-1 was purposely drilled in a location where no conventional hydrocarbon trapping mechanism within the Kimmeridge reservoir section is evident. Therefore, in the Company's opinion, the now proven flow to surface of moveable, light Kimmeridge oil and associated solution gas at the BB-1z sidetrack, provides further proof that the Kimmeridge at Broadford Bridge contains a continuous oil deposit of up to 1400 ft gross vertical thickness.

The near identical Kimmeridge reservoir parameters and geology seen at BB-1/1z and the Horse Hill-1 Kimmeridge oil discovery, in which the Company holds a 32.435% interest, some 27 km to the northeast, demonstrates that the Kimmeridge oil accumulation is also laterally extensive across the Central Weald Basin and, consequently, a potentially significant national oil resource.

As previously reported in December, the integration of BB-1z petrophysical analyses with Geomark Research's in-depth geochemical analyses, strongly suggests that Broadford Bridge lies within the southern flank of the Kimmeridge continuous oil deposit, with the commercially viable extent of the play, determined by the presence of significant volumes of in-situ generated mobile oil within Kimmeridge shales and fractured limestones, terminating some few kilometres to the south of PEDL234.

UKOG, as the largest licence holder in the Kimmeridge oil accumulation's "sweet-spot" is well positioned to exploit this extensive and likely commercially viable oil resource. 

Stephen Sanderson, UKOG's Executive Chairman, commented:

"These positive and encouraging initial oil flows from the first-ever Kimmeridge Limestone 5 test provide further supporting evidence for the presence and significant spatial extent of a viable Kimmeridge continuous oil deposit within the PEDL234 Licence.

The KL5 test results, plus the many strands of technical evidence gathered from the well, now also indicate that the BB-1 location lies towards the southern edge of a thick, naturally-fractured, oil-saturated Kimmeridge "wedge", stretching around 30 kms to the north of BB-1 across the Weald. UKOG, as the largest licence holder in the thickest part of this ‘wedge’, is therefore ideally placed to exploit the potentially commercially viable recoverable resources that now likely underlie our Licences.

We look forward to further positive news from the ongoing KL5 test programme."  

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