I attended the Buru presentation on Wednesday at the AEP Conference in Perth. Thomas and Eric were in attendance up the front and although I was sitting quite far from them, they seemed to be enjoying the presentation by their speaker Kurt Chambers, nodding away in agreement from time to time. Thomas in particular seemed happy with it all and was taking happy snaps throughout the presentation on his phone. My notes from the presentation are below for your info. Kurt seemed extremely knowledgeable and spoke very engagingly.
“The Rafael gas-condensate discovery – a potentialgame-changer in the Canning Basin”
Kurt Chambers
Speaker Bio: “Kurt Chambers joined Buru in July 2018 and has 19 years of technical experience in exploration and production. He has spent the last four years getting his head around the Paleozoic geology, including the Devonian dolomites, of the Canning basin. He was previously located overseas with Total Energies located in France and then Singapore. He spent eleven years with Total Energies working on international and Australian exploration opportunities and the subsequent appraisal of several discoveries. He has also worked on the Ichthys field development and has experience in seismic inversion and reservoir characterization. He is a Geophysicist with an honour’s degree from Curtin University and an MBA (Finance) from the Australian institute of Business.”
In this slide you can see an inversion on the basin-bounding fault on the edge of the main Fitzroy trough and you can also see the salt-related structures that formed e.g. Rafael and the Frome Rock salt diapir just to the south. Buru is looking to basically focus on two main plays, firstly the regionally extensive Devonian, Dolomitic and vuggy reservoirs which are proven firstly at Blina in the north, then in Ungani and subsequently with the Rafael-1 well; and secondly, the permacarboniferous plastics, under that regional seal (the Nookanbah top seal) which is thick and extensive and covers across the basin.
Rafael-1 was drilled in 2021. It was a deep well targeting a faulted four-way closure. And basically as soon as they entered structural closure they started to have hydrocarbon shows wherever they saw a reservoir. Firstly in the Anderson sandstones at 3290 metres, they had really high significant drill gas with some, up to C5s and some weak fluorescence. Secondly, they went into the Upper Laurel Dolomite which also had really strong gas peaks of up to 4%. And analysis of the mud gas ratios from the isotubes and also the GC while drilling suggests that that's actually a wetter hydrocarbon phase than what was subsequently tested in the deeper Ungani Dolomite. Another interesting thing about the upper Laurel Dolomite is that's the first time that that interval has been seen dolomitised on the southern flank of the basin. So it's a new play.
Re the T20, you can see the clean gamma rays, 165 metre gross section of carbonate there. What was quite a surprise for them compared to Ungani is its actually two dolomitised zones separated by a 60 metre thick undolomitised limestone. The upper Dolomite was the first indication that they had high pressure gas; they took a kick as they entered into that upper Dolomite zone.
Rafael-1 was drilled with 2D data – this 2D image was the only strike line that they had through the structure. The structure is really obvious but the faulting and the outer plane reflectors and the signal-to-noise is actually quite low.
So late last year they acquired the 200-square-kilometre 3D survey and they used the learnings from their continuous seismic operations since the company's inception to acquire a really focused 3D. The three main things that they did were they knew that at these depths putting more high frequencies into the ground was just going to be a waste so they really focused in the 3 to 20 Hz range with a low-dwell sweep. They realised that from their previous survey that they didn't need to have fleets of two or three vibes per VP so they could use single vibes and by doing single vibes they could have four going at the same time so they had a really highly efficient acquisition. The other thing that they realised was that because this is a really deep target, they didn’t need to have their source and receiver lines so close together. So historically they've always used 240 metres spacing (the conventional wisdom). They went out to 400 metres for this 3D which reduced line clearing and footprint by about 60%, and some costs associated with that as well. And this had no effect on the data quality for this deep target. The third thing that they did was in the field with close partnership with the TOs, where the north-western corner of the 3D was actually curtailed because of a tributary coming off the main Fitzroy River which is a zone of cultural significance so they couldn't go in there with the vibes (you can see this cut-off on the top-right image), but they were able to negotiate to go in and hand carry the nodes in which meant they got an additional 12 square kilometres of seismic that they otherwise wouldn't have got if they hadn't gone in and hand carried those nodes. Luckily too, because there's a big fault that sets up the structure on that side and without that hand-carry data they wouldn't have had the data to migrate in to understand it.
So now with the same line on the 3D, with those low frequencies the contrast is boosted and you can quite clearly see the different reservoirs, the Upper and Lower Dolomite (the seal is in between), and then the Ungani Dolomite is this “booming reflector in here” (haha); prior to the 3D with the low signal-to-noise and the lack of low frequencies it just wasn't obvious.
- The Rafael -1 discovery proved that in the Canning Basin, contrary to conventional wisdom, you can have quite high hydrocarbon column height.
- To date in the past there's been no sustained naturally flowing gas condensate, so everything that's been flowed in the basin has been from the basin-centred tight gas. This was a naturally flowing, unstimulated flow test.
- It's a significant extension of the play (ref maps later on showing post- the well and the new 3D).
- Having that 60 metre limestone interval in the middle of the gross section is quite different to what they've seen in all the wells at Ungani, and it's going to help them improve their understanding of the depositional environment of the reservoir and also the diagenetic history.
The Ungani Dolomite is imaged nicely all across the structure (this is the relative acoustic impedance overlayed on the full stack). The well encountered a GDT and with that GDT they proved up a 165-metre gas column. That has implications for how they evaluate the potential of the rest of the exploration portfolio.
However on top of this, if you take the mapping on the 3D you can see that even though Rafael-1 was placed pretty well, there is an attic of about 50 metres and so the hydrocarbon column height proven up by Rafael is actually in excess of 200 metres..!
This was the first unstimulated gas condensate flow in the basin. The high reservoir pressure was confirmed during that test being more than 6,200 psi. So in conjunction with the kick they took as they entered the reservoir, that high reservoir pressure was confirmed. There was no pressure depletion seen on that test and in the two pressure build-ups and importantly there was no formation water observed during the flow test.
Encouraging flow rates were also achieved despite a sub-optimal testing configuration, as they were all geared up for an oil discovery and they were going to do a case and perforated flow test. In the end they scrambled to get a test away and got 7.6 mmcf/d. Quite encouraging flow rates despite not exactly the most ideal test.
Following Rafael-1, with the biostrat and the analysis of the 3D, it was clear that this was an Ungani Dolomite interval. And not only that, it's actually a complete Laurel section which is totally analogous with what was found at Ungani. And so that has really changed their understanding of this eastern part of the Basin. There's a number of surrounding structures; Udialla to the north, Salinas and even the uptick of Victory.
(Victory-1 was an interesting well because it took complete losses in the base of the well and they thought initially it was probably due to faults. But now with the 3D and the calibration of Rafael-1, it's just as likely that the well actually intersected some very vuggy, faulted carbonates at TD and that's the explanation for the complete losses.)
With the 3D now, the wavy characteristic at Rafael, these super-bright seismic facies (which is also seen at Ungani) are present on a number of surrounding structures. Pre-3D it wasn't obvious that they had the Laurel there. They've now got a few prospects that need to be worked up. They're looking to reprocess all the old seismic lines around here, and they're also planning for some future 2D acquisition over some of those structures.
The Devonian carboniferous succession at Ungani has undergone intensive dolomitisation. It's completely obliterated the initial micro-facies and this has always meant that there's some uncertainty on what the primary depositional environment was at the Ungani dolomite at the Ungani field. They’ve put together a couple of projects that they're going to launch very soon (now that they've been awarded some EIS incentive grants) with both Cambridge Carbonates in the UK and also at UWA, to get a better understanding of what the controls on reservoir quality are. They’re also going to take the 3D seismic and do a pre-stack seismic inversion reservoir characterisation study, because there is actually a change in elastic properties between limestone and dolomite (dolomite is denser, has slightly higher acoustic impedance and lower Poisson's ratio). With that they'll be able to have a better understanding of the 3D evolution of the limestone away from the Rafael-1 well.
The other pleasant surprise that came out of the 3D was that the Shallow prospect. The western fault shown here is the one where they needed to hand-carry on the left to be able to get some coverage. You can see the little rollover, a faulted four-way beneath a thick Nookanbah shale top seal with shallow permacarboniferous plastics.
In all, the results at Rafael-1 have really challenged Buru’s preconceived notions about the Canning Basin, and it highlights how underexplored the basin is “when you can drill a well like this and have your pre-drill geological model completely invalidated” (lol). Studies are ongoing to characterise the Rafael gas-condensate resource, and they have the new Shallow plastic prospect that's been illuminated by the appraisal 3D which they're planning to drill later in the year, and the team is also working to mature the surrounding structures adjacent to the Rafael discovery. So things are looking good for Buru shareholders IMO.
Cheers.
