Skip to main content

Lyceum 2021 | Together Towards Tomorrow

The baths of the Mornington Peninsula tap a low enthalpy aquifer at 47 degrees C and have grown in popularity since they opened in 2002.

One operating development has brought tremendous wellbeing and economic impact on the whole region. With another facility scheduled to open in winter 2022, long-term management of the low enthalpy geothermal reservoir is being encouraged by the regulators. This presentation will use Leapfrog visualisation tools to present geological modelling and reservoir modelling, highlighting the key characteristics of this area, and other regions of Victoria blessed with similar reservoirs that are ideal for direct use geothermal.



Martin Pujol
Principal Geothermal Hydrogeologist, Rockwater


30 min

See more Lyceum content

Lyceum 2021

Video transcript

(bright upbeat music)

<v ->Hi, my name is Martin Pujol.</v>

welcome to my talk.

We’re going to talk about geothermal in Australia,

more specifically the popular bath

of the Mornington Peninsula in Victoria.

Before I start, I’d like to acknowledge

the traditional owners on the land

on which I’m recording today,

the Whadjuk people,

of the Noon gar nation

and we are recording bullet in Perth.

This is a company I’m working from,

Rock water

is a boutique geothermal consultancy based in Perth,

in Western Australia,

we have project around Australia

in Europe and South America.

We have selected a small selection here,

and they cover different aspects of the geothermal industry.

Today we going to cover the direct-use projects

and more specifically the hot spring industry,

which is leisure and health.

So I’ve picked us a couple of graphics

from a great initiative from

Matt psychs that premiered last year,

which is a great Victorian based in trail.

So you can see some of the spectacular photos there,

and that’s a list of the geothermal hot springs

and bathing

facilities and experiences across Victoria

of which the bath of the Mornington Peninsula

is one of the most popular,

with half a million visitors per year.

Uhm that’s pre COVID, of course,

and the success of the bath in the Mornington Peninsula

has led to a number of projects being planned,

including Alba Thermal Springs &amp; Spa,

which is our client for this project.uhm..

and that particular project is due to open in 2022.


And as part of the process,uhm

we have to go through a series of licenses,uhm

which is set by the Victorian government

for geothermal direct-use projects in Victoria.

and it’s an amendment to the Water Act,

which is fairly recent.

So you can see the date there June, 2020.

So this is one of the first projects

to go through this process,

which includes three key licenses,

um…one license to construct the bore,

license to take the groundwater out of the reservoir

and one license to return it to the reservoir by injection.

This process requires um..

a good understanding

of the hydro geological context and some modeling

to support the licensing processing,

that’s what we’ll talk about today.

So starting with the left side is a slide,

we have a digital elevation model of the region

for those familiar with the area,

Melbourne is situated at the top of the port Phillip Bay

[00:03:18.330] right above the eye

in this image,

the eye of Philip

and to the south.

so there I’ve drawn two cross sections that are West east

across section one goes across um.. the rip,

which is that small opening of the port Phillip bay,

and onto the S nippy and peninsula where the Mo the bath are


and the port Phillip basin in this area is bounded by two

major faults.

And we can see down cross section one on the right,

the Bella rainfall and the cell windfall,

and those faults bound like

a sink line with a thickness of

sediments of allying in nonconformity of,

in excess of a kilometer on the point APN.

The target

reservoir for the hot Springs facility is,

um… is sandstone high,

high energy sense stones at the base of the sink line of the

Eastern view group.

and these are located in the Eastern side of the Sinclair

of this cross section.

There is also a second cross section across

section two, which is offshore,

and we’ll see that it shows sensibly the same structures.

so this has been interpreted from seismic, and we can see,

again, the,

the basal high energy sense stones at the base of a sink

line, like structure,

which is bounded by the Selwyn fault to the east of note is

recent volcanics,

which are present in inside the sequence and partially

responsible for the elevated heat flow in the region.

To illustrate this,

we have created a video using the leapfrog suite of


So you can see starting from the top,

the digital elevation with a vertical exaggeration,

which highlights the dunes recent quaternary during the

deposits, along the coast.

We have a series of offset Wells coming up to the south of

the Alba hot Springs, there’s peninsula hot spring,

which is a large hot Springs development.

Then further south there’s St. Andrews,

which is a proposed one.

and to the west,

we have two offset Wells from the government drilled in,

in the sixties and seventies

using that data set and seismic

data available for the south.

We can generate the structure of the sink line,

and you can see here coming through to the via surfaces that

define the top and bottom of the Eastern view group and,

and the Beriberi formation,

which is the target reservoir for this project.

All the lying, this sense stone unit

is um…

is primarily a thick succession of model,

which forms a good insulator and helps the heat to be

contained within this, this target reservoir.

We can now see restructure of the reservoir itself,

and you can see there’s a lot more data in the vicinity of

the project with the several offset Wells from the

operations to the cells.

And now if we removed the vertical exaggeration,

zoom out specifically on the project of Alba thermal


you can see the existing vertical production borders drilled

before I involvement.

And two new deviated injection Wells that have been recently

drilled with the gamma Ray trace highlighting the key

formation contacts.

So as I said,

we have now drilled two new injection Wells for the purpose

of this project.

The function of those Wells is to return the water after

circulated through the hot Springs pools back to the

reservoir and,

and that water tends to be cooler in winter and marginally

warmer in, in summer.

But because of the heat gain,

the specifics of this drilling program was that it was

conducted in the middle of the COVID pandemic.

We managed to drill those two worlds in between two COVID

lockdowns in Victoria,


with a team that was primarily based outside of that state.

So to the site geologists,

which we provided at Rock water were primarily based in WA

while the, the drillers is we’re based out of Queensland

and that that was not a small feat,

but a very successful project.

The, the success of that drilling men,

that we have another set of data,

which we have been able to analyze as part of the,

the reporting necessary for the,

the licensing of this project,

starting the temperature data and

in this case,

the bottom hole temperature for the new Wells,

which is compared to that of observation Wells from the

government further to the west. So nippy and 38 here,

for example,

and those temperature data sets are matched by a one D heat

conductive model,

which gave a heat fluff 83 million,

one per square meter,

which is consistent with regional estimates by others.

and while it might be small,

when you compare that to some conventional surface heat

flow, this is a relatively high heat flow for the Australian

context in, in a sedimentary environment.

The water quality of hot Springs water is important because

it, it, it characterized it,

the experience people will have in, in, in the facility.

So to the left, you can see a video.

When we,

when we started,

you’ll see a lot of small bubbles rising to the surface.

This is essentially the H two S and CO2 within the water.

That’s the gassing.

And that,

that causes the PH to increase when the water is flows for

the, when exposed to, to air,

the water is primarily sodium chloride with some

bicarbonate, the well that is further to the west,

furthest to the west nippy and 37 has a lower concentration

by cabinet when compared to the one that is closer to the


and this is understood to be a feature,

the recharged float paths for, for this reservoir.

And the water has got,

is characterized as brackish.

It has some,

some salts about three grand Polit or 3000 mg/L.

Those new Wells were also flow tested..

and the result gave an estimation of permanently thickness

for each, each of those Wells.

And that that can be correlated to the permeability

of um..

net thickness of the reservoir,

and we get a permeability thickness of NXS 200 square meter,

200 Darcy meters for this reservoir,

which is a very adequate for directories project.

Now turning all this new data into a model that can be used

to predict impacts in terms of the movement of the injection

water into the reservoir.

And the pressure changes relies on a sound conceptual model.

The approach which has been taken this project is to rely on

conceptual models that have been developed in Europe,

in particularly in Paris for areas that have been targeting

a direct use reservoir at similar temperatures for many


And in, in Paris, this complex reservoir,

which is made up of reservoir layers,

intubated with confining layers that are not producing water

as been simplified in a conceptual model that’s referred to

as the sandwich model.

So that’s what you can see at the bottom left.

And the concept in this sandwich model is to sum all the

reservoir layers in our case,

the high permeability sense stone producing layers,

and divide them into two half reservoir layers.

And to some older non-producing layers

in our case,

it’s the intubated lignite,

the lower poor low porosity sand stones and seal stones.


and those are combined into a single layer at the middle in

the middle of the sandwich .

Above and below that you have the

cap rock and the bedrock,

which you now catered represent the underlying and overlying


The benefit of this conceptual model is that it allows for

the heat we supply from the impervious confining layer

as the plume of injected water moves through the reservoir,

and what it does is it gives a more realistic movement and,

and tends to slow the movement of the model plume.

So that’s what we can see at the bottom, right?

Which is a figure that shows the temperature at a production

well of the time as a result of injection from,

from another injection, well located in the same reservoir.

And you can see that the,

the bottom curve is the homogenous.

Single layer reservoir tends to predict a very fast

breakthrough or drop in temperature of the production. Well,

while the dark blue,

which is the sandwich model predicts a much slower break

through and slower drop in temperature.

And that,

that is found to be more realistic and more similar to the

monitoring data for,

for this particular reservoir in Paris and unexplained,

why this approach was taken to put this into perspective,

the florets you can see on this curve slightly higher than

what this project is requiring.

So this predicts 125 cubic meters per hour, while the,

the transmissivity in our case is higher at 200 Darcy

meters for when a low injection temperature,

but also lower production temperature.

Now I’m showing the slide that illustrates how this

conceptual model is,

is constructed with a total of nine layers,

each of the bedrock,

and capric have three layers of refinement

while the

layer four, five, and six represent a sandwich model,

which we’ve discussed.

And you can see how that grid follows the geology core model

that was constructed and leapfrog.

Now is the next slide,

I will show the result of the modeling process and how those

layers are constructed in three dimensions.

So we start zooming in onto

the three Wells of the project,

to production we’ll that is vertical and the two injection


So you can see the two half reservoir layers in red,

and then the lower permeability

confining layers,

either the,

at the middle of the sandwich or the bed rocking capric


And now all the layers of the model based on their relative


we are now showing the initial temperature within those


And you can see the natural do similar gradient and some of

the horizontal temperature variation within the reservoir

layer, the top reservoir layer,

in this case,

we bringing in some of the offset Wells to the cells,

which are the injection Wells from the nearby Hot springs


And then the model starts.


we can see injection happening in the south where the nearby

operation is with

low injection temperatures.

And now we’re zooming in onto the Alba injection balls.

You can see that a feature of those injection boards is the

injection temperatures alternates between cold in winter and

hotter in summer, because winter dominates,

you have an overall cooling effect, as you can see.

And after 30 years,

the zone of impact of injection is characterized with the

relative contribution of injected water in the reservoir

between the zero and a hundred percent here in the color


And finally, we can see the,

the head calculation for the reservoir,

which illustrate current of depression,

pressure drop around the production. Well,

well there’s pressure buildup around the injection Wells,

but regionally the,

the gradient within the reservoir is maintained with a

relatively small impact.


this modeling was used to support the application for the

project and which, which has now been,

been submitted for this project.

I hope you enjoyed this talk,

and I’ll be glad to take any questions in the Q and A.

Thank you very much.

(up beat music)