Ausgeology. Queensland senior lessons

QCE Earth & Environmental Science · Unit 3 Topic 1: Use of non-renewable Earth resources

Coal seam gas.

More than 95% of the gas produced in Queensland is coal seam gas from the Bowen and Surat basins (Business Queensland). This lesson works through the data a coal seam gas field produces, from the coal in a well to the water bores on the farms above it, and uses it to practise the questions in the data test.

The data test

Internal assessment 1 in Units 3 and 4 is a data test, worth 10% of your subject result. The syllabus describes it like this:

“Students respond to items using qualitative data and/or quantitative data derived from practicals, activities or case studies from Unit 3.”

Your teacher gives you between two and four datasets you have not seen before. You have 5 minutes’ perusal and 60 minutes’ working time, and you may use a calculator. Answers can be single words, sentences of up to 150 words, or calculations (QCAA). The questions are of three kinds.

  • About 30% of the marks

    Work out an unknown

    Calculate, determine, identify or use: for example, the thickness of coal in a well, or how much gas a block holds.

  • About 30% of the marks

    Find trends and limits

    Find trends, patterns, relationships, limitations or uncertainty in the data, by comparing, classifying, sequencing or organising it.

  • About 40% of the marks

    Draw conclusions

    Deduce, extrapolate, infer, interpolate, justify or predict from your analysis: for example, when a bore will pass a threshold.

How the lesson works

1 · Watch

Each screen from 2 to 9 has a worked example. Show its steps one at a time, and read why each step is done.

2 · Finish

The next example has its first steps done for you. Do the last step yourself.

3 · Do

Then do one on your own, and answer a check on the science. Screen 10 is a practice data test with three datasets and ten questions.

Why worked examples

People new to a topic who study worked examples do better on later tests than people who solve the same problems themselves. As their expertise grows, worked examples help less, so more of the problems should be done on their own (CESE, 2017).

So each screen starts with every step done for you and ends with you doing them all.

What we are learning

How coal seam gas forms, is found, measured and extracted, how its effects on groundwater are monitored, and how to work with data like this in a data test.

I can

  • 1describe the three kinds of question in the data test and what each asks me to do.
  • 2explain how coal seam gas forms and is held in coal, and how it differs from gas in a stratigraphic trap.
  • 3read a density log to find the coal seams in a well and work out their total thickness.
  • 4calculate gas in place, and explain how uncertainty in the data becomes economic risk.
  • 5describe how coal seam gas is extracted, and describe the trends in a well’s water and gas.
  • 6estimate how long reserves will last from reserves and production data, and say what the estimate assumes.
  • 7calculate how much water coal seam gas wells produce, and describe how the water is treated and used.
  • 8compare monitoring data with a trigger threshold and say what must happen next.
  • 9identify limitations and uncertainty in coal seam gas data, and explain why community concern continues.

QCE Earth & Environmental Science, Unit 3 Topic 1: Use of non-renewable Earth resources. The teacher notes at the end quote the topic’s Science understanding subject matter and show which screen covers each point.

My notebook

In the data test, about 40% of the marks are for what?

Printable activity

Practice data test

Four pages: the three datasets and ten questions from screen 10, with space to write, to do on paper under test conditions. The model answers are under each question on screen 10.

Practice data test (PDF) Editable (Word)

2Formation · identify features

What coal seam gas is.

How does coal seam gas form and stay in the coal, and how is it different from gas in a trap?

Coal seam gas is held in the coal it formed in. Gas in a conventional field has moved out of the rock it formed in and collected in a trap.

This screen · about 25 minutes

  1. Read how coal and its gas form, and how gas is trapped.
  2. Work through the example on section 1.
  3. Finish section 2, then do section 3 on your own.
  4. Answer the check.

From swamp to seam

Coal forms where plant material piles up faster than it can rot and is then covered by sediment. With more time, heat and pressure, the plant material becomes peat, then brown coal, then sub-bituminous coal, bituminous coal and, last of all, anthracite. Water, carbon dioxide and methane are given off along the way (Geoscience Australia).

Gas in coal comes mainly from that change, which happens under high pressure and temperature. Microbes are believed to be a major source as well, particularly at shallow depths (Saghafi, Pinetown and Midgley, 2017).

How the gas is held

Coal seam gas is mostly methane, generally 95 to 97% pure. It is attached to the coal by adsorption, and held there by the pressure of the formation water in the coal’s cleats and fractures. It is typically extracted from seams 300 to 1,000 m below the surface (CSIRO GISERA).

In the Surat area, the gas fields are in the Walloon Coal Measures and the Bandanna Formation (Office of Groundwater Impact Assessment, OGIA).

Gas in a trap

Once oil and gas leave the rock they formed in, they move up and along through porous reservoir rock until a layer they cannot pass through, a seal, stops them, and they collect in a trap. The gas is the lightest, so it collects at the top of the trap, with the oil below it and then the water. Structural traps form where the layers are bent into an arch or broken by a fault. Stratigraphic traps form where the reservoir rock itself changes into another kind of rock or is cut off (Wyoming State Geological Survey; Britannica).

Geoscience Australia counts coal seam gas as an unconventional gas, with shale gas and tight gas. Because coal seam gas is held on the coal by water pressure, the water has to be pumped out before the gas comes off the coal (CSIRO GISERA).

  • Shale (a seal)
  • Sandstone (a reservoir rock)
  • Coal
  • Gas
  • Water
Section 1. Model, not to scale.

Worked example

Section 1. Which well has found gas in a stratigraphic trap, and how is the gas held at the other well?

  1. Find the reservoir rock. The dotted layer is sandstone, a reservoir rock. The grey shale around it is a seal.
  2. Follow the sandstone up the slope. To the left, the sandstone gets thinner and ends inside the shale. Gas moving up the sandstone cannot go any further.
  3. Find the gas. The gas has collected at the high end of the sandstone, above the water, with shale above and below it. The reservoir rock is cut off, so this is a stratigraphic trap, and Well A is drilled into it.
  4. Check the other well. Well B is drilled into the coal seam. Its gas is coal seam gas, held on the coal by the pressure of the water in the seam.
  5. Answer. Well A has found gas in a stratigraphic trap. At Well B the gas is held in the coal by water pressure.
Section 2. Model, not to scale.

Finish this one

Section 2. Which well is drilled into a stratigraphic trap?

  1. The left-hand trap. The sandstone is bent into an arch, and gas has collected at its top. The shape of the layers holds the gas, so this is a structural trap.
  2. The right-hand trap. The sandstone is a lens with shale all round it, and gas has collected at its top.
  3. Your step. Decide which trap is stratigraphic.

Which well is drilled into a stratigraphic trap?

Section 3. Model, not to scale.

Your turn

Section 3. Which well will have to pump out a lot of water before any gas flows?

Check the science

What keeps coal seam gas in the coal?

3Exploration · work out an unknown

Reading a bore log.

Where are the coal seams in a well, and how much coal is there?

A density log shows where the coal is, because coal is much less dense than the rocks around it.

This screen · about 25 minutes

  1. Read how a density log picks out coal.
  2. Work through the example on Well 1.
  3. Finish Well 2, then do Well 3 on your own.
  4. Answer the check.

Density logs

After a well is drilled, tools lowered into the hole measure the rocks along its length. A density log records their density. Coal has a low density: coal with little ash is below about 1.75 g/cm³, and coal with a lot of ash below about 2.0 g/cm³. With more ash, such as clay minerals, the density goes up (Lange, 2003). In these model logs the sandstones and mudstones are all above 2.2 g/cm³.

Geologists read each seam’s top and bottom from the log and add up the thicknesses, the net coal thickness. The coal’s area and thickness are usually worked out from well logs (Kelafant, 2015), and they are two of the numbers needed to work out how much gas there is (screen 4).

The logs on this screen are model data. Each reading covers 0.5 m. Tap or hover over a log, or open its table, to read the depths.

Well 1 readings as a table

Worked example

Well 1. What is the net thickness of coal with little ash?

  1. Choose the cut-off. Coal with little ash is below 1.75 g/cm³. Look for where the trace crosses to the left of the dashed line.
  2. Read the first seam’s top and bottom. The density drops below 1.75 at 412.0 m and is back above 2.0 by 414.5 m, so the seam runs from 412.0 to 414.5 m: 2.5 m thick.
  3. List every seam. 412.0 to 414.5 m (2.5 m), 431.0 to 432.5 m (1.5 m) and 468.0 to 471.0 m (3.0 m).
  4. Leave out what does not fit. From 447.5 to 449.0 m the density is about 1.86 g/cm³: below 2.0 but above 1.75, so it is coal with a lot of ash. It is not counted.
  5. Add them up. 2.5 + 1.5 + 3.0 = 7.0 m of coal with little ash.
Well 2 readings as a table

Finish this one

Well 2. What is the net thickness of coal with little ash?

  1. Cut-off. Below 1.75 g/cm³.
  2. Seams so far. 406.0 to 408.0 m (2.0 m) and 425.0 to 428.5 m (3.5 m).
  3. Left out. 452.0 to 453.5 m, about 1.90 g/cm³: coal with a lot of ash.
  4. Your step. Find the last seam, then add up all three.
m
Well 3 readings as a table

Your turn

Well 3. What is the net thickness of coal with little ash?

m

Check the science

Why is coal with a lot of ash denser than coal with little ash?

4Exploration · calculate, then judge the risk

How much gas is there?

How much gas does a block of coal hold, and how sure can a company be?

Gas in place is worked out from four numbers. Each is known from only a few wells or samples, so each is uncertain, and that uncertainty puts the company’s money at risk.

This screen · about 25 minutes

  1. Read how gas in place is worked out, and how reserves are reported.
  2. Work through the example on Block A.
  3. Finish Block B, then do Block C on your own.
  4. Answer the check on economic risk.

Gas in place

The amount of gas held in a block of coal, its gas in place, is four numbers multiplied together (Kelafant, 2015):

Gas in place = gas content × coal thickness × area × coal density

In metric units, the gas content is in m³ of gas per tonne of coal (m³/t), the thickness in m, the area in m² and the density in tonnes per m³. A density of 1.4 g/cm³ is the same as 1.4 t/m³. The answer is in m³ of gas.

The area and thickness come from well logs, with seismic data and maps. The density and gas content come from well logs and from samples of the coal tested in a laboratory (Kelafant, 2015).

Uncertainty and risk

A company drills a few wells and tests a few samples, then estimates the gas in a whole area, so its estimate is a range. Geoscience Australia reports reserves, the part of a resource expected to be recovered commercially, as a range too: a low estimate (1P), a best estimate (2P) and a high estimate (3P). Gas that has been found but is not yet ready for commercial development is a contingent resource, which is less certain than reserves (Geoscience Australia).

Data from exploration, such as the thickness and gas content of the coal, is what a company uses to judge its economic risk: whether there is likely to be enough gas to pay for the wells, pipes and plant.

Model data: Blocks A, B and C, their areas, densities and gas contents, and the 40 million m³ in the check, are made up. The coal thicknesses come from the model wells on screen 3.

Worked example

Block A covers 1 km². Well 1 found 7.0 m of coal with little ash (screen 3). The coal’s density is 1.4 g/cm³ and its gas content 5 m³/t. How much gas is in place?

  1. Write the formula. Gas in place = gas content × thickness × area × density.
  2. Put every number in metric units. 1 km² = 1,000 m × 1,000 m = 1,000,000 m². 1.4 g/cm³ = 1.4 t/m³.
  3. Work out the mass of coal first. Thickness × area × density = 7.0 × 1,000,000 × 1.4 = 9,800,000 t of coal.
  4. Multiply by the gas content. 9,800,000 t × 5 m³/t = 49,000,000 m³.
  5. Answer with units. About 49 million m³ of gas is in place in Block A.

Finish this one

Block B covers 2 km². Well 2 found 8.5 m of coal with little ash (screen 3). The coal’s density is 1.4 g/cm³ and its gas content 4 m³/t. How much gas is in place?

  1. Formula. Gas in place = gas content × thickness × area × density.
  2. Metric units. 2 km² = 2,000,000 m². 1.4 g/cm³ = 1.4 t/m³.
  3. Mass of coal. 8.5 × 2,000,000 × 1.4 = 23,800,000 t.
  4. Your step. Multiply by the gas content, and give the answer in millions of m³.
million m³

Your turn

Block C covers 1 km². Well 3 found 6.0 m of coal with little ash (screen 3), with a density of 1.5 g/cm³. Three samples of the coal gave gas contents of 3, 5 and 7 m³/t. Work out the low and the high estimates of the gas in place.

million m³
million m³

Check the science

Block C will only make money if it holds at least 40 million m³ of gas. The low, best and high estimates are 27, 45 and 63 million m³. What should the company do?

5Extraction · describe trends

Getting it out.

How is the gas got out of the coal, and what does a well produce over its life?

A coal seam gas well pumps out water first. As the water pressure falls, gas comes off the coal and flows up the well.

This screen · about 20 minutes

  1. Read how the gas is extracted.
  2. Work through the example on the well’s water.
  3. Finish the gas, then work out a percentage on your own.
  4. Answer the check.

Dewatering

A coal seam gas well releases the gas by pumping out groundwater, which lowers the pressure in the seam (Independent Expert Scientific Committee, IESC). This dewatering usually comes first: the first stage of production takes formation water out of the seam. At the surface, the water is separated from the gas and piped away to be used or treated (CSIRO GISERA). Over the life of a well, the amount of water it pumps peaks early (OGIA).

Typically, a well is lined with steel casing from top to bottom (CSIRO GISERA).

Fracking

Some wells are fracked. Hydraulic fracturing injects a fluid of water, sand and chemicals: 84 to 96% water, 3 to 15% proppant such as sand, and about 1% chemicals. In Australia it is used in about 20 to 40% of coal seam gas wells (CSIRO GISERA).

Well W1 as a table

Model data: one made-up well, W1, showing its average output in each year. Water coming first follows GISERA and OGIA; the numbers are not from a real well.

Worked example

Describe the trend in Well W1’s water.

  1. Read the start and the end. Water fell from 120 kL a day in year 1 to 16 kL a day in year 8.
  2. Describe the shape. It fell fastest at first, by 65 kL a day from year 1 to year 3 (120 to 55), then levelled off: it fell only 4 kL a day from year 6 to year 8.
  3. Link it to the science, if the question asks. This matches what OGIA reports: over the life of a well, the water it pumps peaks early.
  4. Write the answer with numbers. The water fell steeply from year 1 to year 3, from 120 to 55 kL a day, then levelled off at about 16 to 20 kL a day in years 6 to 8.

Finish this one

Describe the trend in Well W1’s gas.

  1. Start and end. 2 thousand m³ a day in year 1, 12 thousand m³ a day in year 8.
  2. Shape, so far. The gas rose quickly at first, while the water was falling.
  3. Your step. Find when the gas peaked.
year

Your turn

By what percentage did Well W1’s water fall from year 1 to year 4?

%

Check the science

Why does a coal seam gas well pump out water before much gas flows?

6Resources · calculate and state assumptions

The industry in numbers.

How big is Australia’s coal seam gas industry, and how long would its reserves last?

These are real figures, from Geoscience Australia, Business Queensland and OGIA.

This screen · about 20 minutes

  1. Read the figures.
  2. Work through the example on reserve life.
  3. Finish the second reserve life, then work out the number of new wells on your own.
  4. Answer the check on what the estimate assumes.
Coal seam gas in figures
FigureValueSource
Coal seam gas produced in Australia in 20241,665 PJGeoscience Australia
2P reserves, the best estimate, 202428,955 PJGeoscience Australia
2C contingent resources, the best estimate, 202424,857 PJGeoscience Australia
Coal seam gas wells drilled in Queensland since 2010over 12,000Business Queensland
Coal seam gas wells in the Surat Cumulative Management Area, end of 2024a little over 11,000OGIA, 2025 draft
Wells expected there by 206021,000OGIA, 2025 draft
Liquefied natural gas exported from Queensland each year, average since 2016over 22 million tBusiness Queensland

Almost all of Australia’s coal seam gas reserves and contingent resources are in Queensland (Geoscience Australia). A petajoule (PJ) is a million billion joules. The Surat Cumulative Management Area is on screen 8.

Worked example

At the 2024 rate of production, about how long would the 2P reserves last?

  1. Choose the data. 2P reserves: 28,955 PJ. Production in 2024: 1,665 PJ a year.
  2. Divide. 28,955 ÷ 1,665 = 17.4 years.
  3. Round sensibly. About 17 years, the same as Geoscience Australia’s estimate.
  4. Say what it assumes. Production stays at the 2024 rate, and no reserves are added or taken away.

Finish this one

If all the 2C contingent resources became reserves too, about how long would the gas last at the 2024 rate?

  1. Add them. 28,955 + 24,857 = 53,812 PJ.
  2. Your step. Divide by the production in 2024.
years

Your turn

OGIA expects the number of coal seam gas wells in the Surat Cumulative Management Area to grow from a little over 11,000 at the end of 2024 to 21,000 by 2060. On average, about how many new wells a year is that?

wells a year

Check the science

Geoscience Australia says the reserves would last about 17 years at 2024 production rates. Which is a limitation of that estimate?

7Impacts · calculate

The water.

How much water do the wells pump out, and what happens to it?

Pumping water out of the coal is how the gas is released, so the wells produce a lot of water.

This screen · about 20 minutes

  1. Read the figures and what happens to the water.
  2. Work through the example on water per well.
  3. Finish the fall since 2016, then work out the Surat Basin’s share on your own.
  4. Answer the check.

OGIA’s 2025 report, released as a consultation draft, says that coal seam gas extraction of groundwater in the Surat Cumulative Management Area has stabilised at around 52,000 megalitres (ML) a year. It has been falling since a peak of around 67,000 ML a year in 2016. Of the 52,000 ML, about 43,000 ML a year comes from the Surat Basin and about 9,000 ML from the Bowen Basin (OGIA).

Water from coal seam gas wells in the Surat Cumulative Management Area
FigureValue
Peak extraction, 2016around 67,000 ML a year
Extraction over the last three yearsaround 52,000 ML a year
from the Surat Basin43,000 ML a year
from the Bowen Basinaround 9,000 ML a year
Coal seam gas wells, end of 2024a little over 11,000

Source: OGIA, Underground water impact report 2025 for the Surat Cumulative Management Area, consultation draft.

What happens to the water

The water is generally brackish, with a salinity of about 300 to 10,000 mg/L. Reverse osmosis has been widely used to treat it, and leaves behind a very salty brine. In Queensland, the options for managing the water include irrigation, water for livestock, use in towns and industry, dust suppression, reinjection into aquifers and release to the environment. Most uses need the salt taken out first. When the IESC wrote its fact sheet in 2014, the brine was being stored in containment ponds while options for using or disposing of it were explored, and commercial salt harvesting and reinjection were being trialled (IESC).

Worked example

On average, how much water does each well pump out a day?

  1. Choose the data. About 52,000 ML a year from a little over 11,000 wells.
  2. Convert to litres. 1 ML = 1,000,000 L, so 52,000 ML = 52,000,000,000 L a year.
  3. Share it between the wells. 52,000,000,000 ÷ 11,000 = about 4,700,000 L per well per year.
  4. Turn it into a day. 4,700,000 ÷ 365 = about 13,000 L per well per day.
  5. Say what the average hides. The amount of water can vary greatly between wells and between coal seams (IESC), and a well pumps the most water early in its life (OGIA), so few wells pump exactly the average.

Finish this one

By what percentage has the water extracted fallen since the 2016 peak?

  1. The fall. 67,000 − 52,000 = 15,000 ML a year.
  2. Your step. Give the fall as a percentage of the peak.
%

Your turn

What percentage of the 52,000 ML a year comes from the Surat Basin?

%

Check the science

Treating the water by reverse osmosis leaves brine. What did the IESC’s fact sheet say was being done with it?

8Monitoring · extrapolate and decide

Bores and drawdown.

How do we know whether the gas wells are lowering the water in farm bores, and what happens if they are?

Taking water out of the coal lowers the water pressure in and around it, and many farms and towns draw their water from bores into the same layers of rock.

This screen · about 25 minutes

  1. Read how bores are monitored and what the trigger thresholds are.
  2. Work through the example on Bore M1.
  3. Finish Bore M2, then sort four bores on your own.
  4. Answer the check.

The Surat Cumulative Management Area (CMA), set up in 2011, is the only one in Queensland. There, the independent Office of Groundwater Impact Assessment assesses the combined effect of coal seam gas, conventional oil and gas, and coal mining on groundwater, and publishes an underground water impact report every three years (OGIA).

The layers that coal seam gas and coal mining target lie among some important aquifers of the Great Artesian Basin. The Springbok Sandstone lies above the Walloon Coal Measures, and the Hutton Sandstone below them (OGIA).

Trigger thresholds

A bore is counted as affected when its water level is predicted to fall by more than a bore trigger threshold: 5 m in a consolidated aquifer, or 2 m in an unconsolidated aquifer. Bores predicted to pass it within the next three years are in the immediately affected area (IAA); bores predicted to pass it at any time in the future are in the long-term affected area (LAA). IAA bores “must undergo a bore assessment and proceed through the make good process” (Gasfields Commission Queensland).

OGIA’s 2025 draft identifies 76 IAA bores and 747 LAA bores. Of the IAA bores identified in earlier reports, make good has been completed for 212, and the rest are at various stages. The dedicated monitoring network has about 807 water level and water chemistry monitoring points, and the draft plans to extend it to 888 (OGIA).

Bores M1 and M2 as a table

Model data: two made-up monitoring bores, read once a year. The thresholds are the real ones for each kind of aquifer.

Worked example

Bore M1 draws water from a sandstone aquifer. If the trend continues, when will its drawdown pass the trigger threshold?

  1. Find the threshold. Sandstone is a consolidated aquifer, so the threshold is 5 m.
  2. Find the rate. The drawdown went from 0.0 m in 2019 to 3.0 m in 2025: 3.0 ÷ 6 years = 0.5 m a year.
  3. Find what is left. 5.0 − 3.0 = 2.0 m to go.
  4. Extrapolate. 2.0 ÷ 0.5 = 4 years after 2025, so about 2029.
  5. State the assumption. This assumes the drawdown keeps growing at the same rate. If more wells start nearby, it could come sooner.

Finish this one

Bore M2 draws water from river alluvium. If the trend continues, when will its drawdown pass the trigger threshold?

  1. Threshold. River alluvium is an unconsolidated aquifer, so the threshold is 2 m.
  2. Rate. 0.9 ÷ 6 years = 0.15 m a year.
  3. Your step. Work out what is left, and extrapolate to a year.

Your turn

Predictions for four bores, made in 2025 (model data)
BoreAquiferPredicted drawdown by 2028Largest predicted drawdown
PSandstone6.2 m9.0 m
QRiver alluvium1.5 m1.8 m
RRiver alluvium2.4 m3.1 m
SSandstone3.9 m7.5 m

Which bores are in the immediately affected area, and so need a bore assessment now?

Check the science

OGIA predicts that a farmer’s bore will pass its trigger threshold within three years. What must happen?

9Limits · limitations and uncertainty

Limits and uncertainty.

What can the data not tell us, and why are people still concerned?

Every dataset has limits. Some groundwater predictions run for centuries, so nobody can check them against measurements yet.

This screen · about 25 minutes

  1. Read about the survey and the groundwater model.
  2. Work through the example on the survey’s limitations.
  3. Finish a change in percentage points, then pick a conclusion on your own.
  4. Answer the check.

What people think

CSIRO’s GISERA has surveyed residents of the Western Downs about coal seam gas since 2014, and added eastern Maranoa in 2016. In 2024 it phoned 601 residents, 401 of them in the Western Downs. It reports that in 2024 acceptance of coal seam gas reached its highest level since the surveys began, and that over 40% of people in both regions said they never or seldom think or talk about it (CSIRO GISERA).

The survey as a table

What the groundwater model cannot yet tell us

OGIA predicts the effects on groundwater with a computer model. It calibrated 3,000 sets of model settings against the measurements, used the best 500 to make predictions, and identifies IAA bores from the P50 prediction (OGIA).

The areas predicted to be affected in the Walloon Coal Measures and the Springbok Sandstone may vary by about 10 to 15%, possibly more for other formations, and there is greater uncertainty in the Bowen Basin, where there is less data to calibrate the model against (OGIA).

Some effects are slow. In the Hutton Sandstone, below the coal, the impact is likely to be less than 10 m and to occur decades from now. Inside the gas fields, groundwater levels are predicted to take hundreds of years to recover fully; another part of the same draft says more than 1,000 years (OGIA).

The syllabus asks you to appreciate that community concern over the industry also reflects the limited information available on its long-term effects (QCAA).

Worked example

What are the limitations of the GISERA survey as evidence of how people in the Western Downs feel about coal seam gas?

  1. Who was asked. The fact sheet does not label the chart by region, but its 2024 figures match the fact sheet’s figures for the Western Downs, so it appears to show the Western Downs only. People in eastern Maranoa answered differently: in 2024, 23% of them approved, against 12% in the Western Downs (CSIRO GISERA).
  2. How many. 401 Western Downs residents in 2024, by phone. The fact sheet does not give the numbers for earlier years, so we cannot judge how precise those years are.
  3. What was asked. Each person chose one of five words, from reject to embrace. The five words on their own do not say why people feel as they do.
  4. What it cannot show. Attitudes are not measurements. The survey cannot tell us whether bores, roads or anything else were actually affected.
  5. Answer. The survey shows the attitudes of one region’s residents in four years. It gives no sample sizes before 2024, no reasons, and no measure of actual impacts.

Finish this one

By how many percentage points did the share who reject coal seam gas fall from 2016 to 2024?

  1. Read the values. 2016: 13.4%. 2024: 7.9%.
  2. Your step. Subtract.
percentage points

Your turn

Which conclusion does the survey support?

Check the science

Why is it hard to settle concerns about the long-term effects of coal seam gas on groundwater?

10Practice data test

Practice data test.

Ten questions on three datasets you have not seen before.

Put together everything you have practised. Datasets A and C are model data; dataset B is real, from OGIA’s 2025 draft report.

This screen · about 30 minutes

  1. Read the three datasets during perusal. Do not write yet.
  2. Answer the ten questions in your notebook boxes or on the printable test.
  3. Open each model answer, and tick the answers that make its points.

The real test gives 5 minutes’ perusal and 60 minutes’ working time. This one has fewer questions, so allow 2 minutes’ perusal and 25 minutes’ working time. Three of the questions ask you to work out an unknown, three to find trends and limits, and four to draw conclusions, the same mix of marks as the real test.

Perusal

2:00

Dataset A Well 4 and Block D Model data

Well 4 readings as a table

Well 4 is in Block D, which covers 1.5 km². The coal in Block D has a density of 1.45 g/cm³. Three samples of the coal from Well 4 were tested for their gas content.

Gas content of the coal samples
SampleGas content (m³/t)
13.8
24.6
35.4

Coal with little ash is below 1.75 g/cm³ (Lange, 2003).

Dataset B Water bores predicted to be affected Real data

Long-term affected area: water bores predicted to pass the trigger threshold at any time
Formation, in the order OGIA lists themBores
Alluvium (Main Range Volcanics)1
Westbourne Formation9
Gubberamunda Sandstone2
Springbok Sandstone103
Walloon Coal Measures321
Hutton Sandstone8
Bandanna Formation1
Existing bores445
Bores with make good agreements, decommissioned, or of uncertain status302
All long-term affected bores747
Immediately affected area: water bores predicted to pass the trigger threshold in 2026 to 2028
FormationBores
Springbok Sandstone20
Walloon Coal Measures56
All immediately affected bores76

Most of the gas comes from the Walloon Coal Measures. The Springbok Sandstone lies above them, and the Hutton Sandstone below.

Source: OGIA, Underground water impact report 2025 for the Surat Cumulative Management Area, consultation draft, Tables 11-1 and 11-4. The parts of the Springbok Sandstone and the Walloon Coal Measures are added together.

Dataset C Two monitoring bores Model data

Bores X and Y as a table

Bore X draws water from sandstone, a consolidated aquifer (trigger threshold 5 m). Bore Y draws water from river alluvium, an unconsolidated aquifer (trigger threshold 2 m).

Questions

  1. Work outDataset A What is the net thickness of coal with little ash in Well 4?

    Show the model answer

    8.0 m. The seams below 1.75 g/cm³ are 509.0 to 511.5 m (2.5 m), 538.0 to 542.0 m (4.0 m) and 560.0 to 561.5 m (1.5 m). The layer from 524.0 to 525.0 m, at about 1.87 g/cm³, is coal with a lot of ash, so it is not counted.

  2. Work outDataset A Using the middle gas content, calculate the gas in place in Block D. Show your working.

    Show the model answer

    Area: 1.5 km² = 1,500,000 m². Density: 1.45 g/cm³ = 1.45 t/m³. Mass of coal = 8.0 × 1,500,000 × 1.45 = 17,400,000 t. Gas in place = 17,400,000 t × 4.6 m³/t = 80,040,000 m³, about 80 million m³.

  3. Work outDataset C Calculate the average rate of drawdown in Bore X from 2019 to 2025.

    Show the model answer

    3.6 m ÷ 6 years = 0.6 m a year.

  4. Trends and limitsDataset B Identify the pattern in which formations hold the existing long-term affected bores.

    Show the model answer

    Most are in the Walloon Coal Measures, the formation most of the gas comes from: 321 of the 445 existing bores, about 72%. The next largest group is the Springbok Sandstone, directly above the coal measures, with 103. Only 21 are in all the other formations together.

  5. Trends and limitsDataset C Compare the trends in Bores X and Y.

    Show the model answer

    Both show drawdown growing steadily from 2019 to 2025, with no sign of slowing. Bore X’s grew much faster: 3.6 m against 0.3 m, about 12 times as much. Bore X is already more than two-thirds of the way to its 5 m threshold; Bore Y has reached 0.3 m of its 2 m.

  6. Trends and limitsDataset A Identify two sources of uncertainty in your answer to question 2.

    Show the model answer

    Any two of these. The gas content varies between the samples, from 3.8 to 5.4 m³/t, so the gas in place could be anywhere from about 66 to 94 million m³. There are only three samples. The thickness comes from one well, but the coal may be thicker or thinner elsewhere in the block.

  7. ConcludeDataset C Predict when Bore X will pass its trigger threshold, and state the assumption you made.

    Show the model answer

    The threshold is 5 m, because sandstone is a consolidated aquifer. 5.0 − 3.6 = 1.4 m to go, and 1.4 ÷ 0.6 = about 2.3 years after 2025, so about 2027. This assumes the drawdown keeps growing at 0.6 m a year.

  8. ConcludeDataset C In 2025, should Bore Y have a bore assessment? Justify your answer.

    Show the model answer

    Not yet. Bore Y draws from alluvium, so its threshold is 2 m. Its drawdown grew by 0.3 m in 6 years, 0.05 m a year, and it has 1.7 m to go, which would take about 34 years. It is not predicted to pass the threshold within three years, so it is not in the immediately affected area. It should go on being monitored, because the rate could change.

  9. ConcludeDataset B Infer why most of the affected bores draw water from the Walloon Coal Measures.

    Show the model answer

    The gas wells pump water out of the Walloon Coal Measures to lower the pressure in the coal, so the water pressure falls most in those rocks, and bores that draw water from them are affected most. The Springbok Sandstone, directly above, has the next largest number. The Hutton Sandstone, the next aquifer below, has only 8. OGIA says a layer between it and the coal measures, the Durabilla Formation, greatly limits the flow of water between them, so how well an aquifer is connected to the coal matters, as well as how many bores draw from it.

  10. ConcludeDataset A Block D will only make a profit if it holds at least 70 million m³ of gas. Using your answers to questions 2 and 6, justify whether the company should develop Block D now. Use up to 150 words.

    Show the model answer

    Not yet. The best estimate, about 80 million m³, is above 70 million m³, so the block could make a profit. But the low estimate, about 66 million m³, is below it, so there is a real chance of a loss. The estimate also rests on one well and three samples. The company should drill more wells and test more of the coal to narrow the range. If the low estimate is then above 70 million m³, it could go ahead with much less economic risk.

Printable activity

Practice data test

Four pages: the three datasets and ten questions from screen 10, with space to write, to do on paper under test conditions. The model answers are under each question on screen 10.

Practice data test (PDF) Editable (Word)
For teachers

Curriculum

Queensland Curriculum and Assessment Authority (QCAA), Earth & Environmental Science 2025 v1.0 General senior syllabus (January 2024), Unit 3: Living on Earth, Topic 1: Use of non-renewable Earth resources (22 hours). The syllabus is © State of Queensland (QCAA) 2024, licensed under CC BY 4.0. Its Science understanding subject matter for the topic, which can be assessed in the external examination, is:

Formation and location of non-renewable mineral and energy resources

  • Explain the differences between metallic, non-metallic and energy resources.
  • Describe non-renewable resources as those that are typically replenished at timescales of centuries to millennia, including
    • metallic resources (gold and iron ore)
    • non-metallic (mineral sands)
    • fossil fuels (coal, coal seam gas, crude oil and natural gas).
  • Interpret information relating to
    • metallic formation including banded iron formations and hydrothermal and alluvial gold formations
    • non-metallic formation (mineral sands) including alluvial and placer deposits
    • fossil fuel formation (coal seams and stratigraphic traps).

Exploration of mineral and energy resources

  • Explain how mineral and energy resources are discovered using a variety of techniques to identify the location, spatial extent of the deposit and quality of the resource, including
    • literature and historic records
    • remote sensing techniques, including satellite and aerial imaging, hyperspectral imaging, and geophysical datasets for magnetic and gravitational
    • direct sampling geochemical techniques, including soil, rock sampling, auguring, drilling and core sampling.
  • Interpret geophysical and geochemical data to predict the presence of a resource, e.g.
    • remote sensing (magnetic imaging to detect iron ore)
    • density (bore hole logging).

Extraction, separation and processing of mineral and energy resources

  • Explain how a feasibility study is conducted to determine whether the resource can be extracted effectively and profitably, which includes analysis of the
    • size and value (market value and associated economic factors) of the resource
    • suitable extraction methods
    • refining processes of the commodity
    • environmental impacts
    • rehabilitation plan
    • other key parameters such as availability of
      • support facilities and infrastructure
      • site access
      • social impacts (land rights, employment, health).
  • Analyse how the type, volume and location of mineral and energy resources influences the methods of extraction, including
    • for coal, gold and iron ore
      • open-cut mining
      • underground mining (stoping, room and pillar, also known as bord and pillar)
    • for mineral sands
      • dredging
      • open-cut mining
    • for coal seam gas, oil and natural gas
      • onshore and offshore drilling
      • fracking.
  • Determine the appropriate method of extraction (e.g. sluicing, froth flotation, gravitational separation, smelting) by analysing the physical and chemical properties of
    • metallic resources: gold and iron ore
    • non-metallic resources: mineral sands.
  • Explain how the method of extraction, processing and separation is determined by the physical and chemical properties of these metallic and non-metallic resources.

Environmental monitoring and management

  • Describe how resource extraction can affect the atmosphere, hydrosphere and biosphere.
  • Explain how common environmental factors are monitored to minimise environmental impacts on
    • air quality, e.g. ozone, SO2, CO, visibility, fine particles PM10
    • water quality, e.g. pH, dissolved oxygen, turbidity, BOD
    • soil quality, e.g. pH, erosion, changes in soil structure
    • distribution and abundance of organisms, e.g. line transects, Lincoln index
    • noise pollution, e.g. sound level meters, sleep patterns.
  • Interpret data from environmental monitoring, including distribution and abundance surveys, air quality, water quality.
  • Interpret data relating to the effectiveness of environmental monitoring strategies.
  • Interpret data about the effectiveness of turbidity management strategies, using settling ponds.

The syllabus prints three of these points with a dash, shown here as a comma or a colon.

The lesson follows one energy resource, coal seam gas, from formation to monitoring, and uses its data to practise the data test. Where it covers the subject matter:

  • Non-renewable resources: coal seam gas as a fossil fuel (screens 1, 2 and 6). The lesson does not set out metallic, non-metallic and energy resources side by side.
  • Formation of coal seams and stratigraphic traps: screen 2 (coal from peat to anthracite, how coal seam gas forms and is held, and structural and stratigraphic traps in three model cross-sections), q-sec3, q-held.
  • Exploration, density (bore hole logging): screen 3 (three model density logs, net coal thickness), n-log3, q-ash. Screen 4 uses the results to estimate the resource.
  • Feasibility, the size and value of the resource: screen 4 (gas in place, reserves and contingent resources) and screen 6 (production, reserves and reserve life).
  • Extraction of coal seam gas by onshore drilling and fracking: screen 5 (dewatering, casing, fracking and its fluid, a well’s water and gas), n-wpct, q-water-first.
  • How extraction affects the hydrosphere, monitoring, and interpreting monitoring data: screens 7 and 8 (the water pumped out and how it is treated and used; monitoring bores, trigger thresholds, the immediately and long-term affected areas, make good), n-surat, q-brine, q-iaa, q-next.

The lesson does not cover metallic and non-metallic resources, oil, conventional gas beyond the traps on screen 2, literature and historic records, remote sensing, soil, rock and auger sampling, open-cut and underground mining, separation and processing, air, soil and noise monitoring, line transects and the Lincoln index, or settling ponds. The other lessons on the Queensland page cover these: Should it be mined? for metallic and non-metallic resources, mining, processing and monitoring, and the Ore deposits and Coal, oil and gas lessons for formation.

Of the Science as a human endeavour points, screen 4 covers using scientific knowledge from coal seam gas exploration to assess economic risk; screen 9 covers community concern and the limited information on long-term effects; screens 7 to 9 use quantitative monitoring data to judge the risk to the environment; and screen 8 applies trigger thresholds and the actions that must follow them. The lesson does not cover licensing and permissions, carbon pricing, EIAs, or validating models with seismic surveys. Of the Science inquiry points, screens 3 and 4 and the practice test use geophysical exploration data to predict the presence of a resource.

The data test

Internal assessment 1 is a data test worth 10%, set in Unit 3. The syllabus describes it as: “Students respond to items using qualitative data and/or quantitative data derived from practicals, activities or case studies from Unit 3.” Its question specifications set the mark allocation (± 2%):

  • “Unknown scientific quantities or features of datasets”, “~ 30%”, objective 2: “calculate using algorithms, determine, identify, use”
  • “Trends, patterns, relationships, limitations or uncertainty in datasets”, “~ 30%”, objective 3: “categorise, classify, compare, contrast, identify, organise, sequence”
  • “Conclusions based on analysis of datasets”, “~ 40%”, objective 4: “deduce, determine, draw (a conclusion), extrapolate, infer, interpolate, justify, predict”

The teacher provides unseen stimulus that “contains between two and four datasets.” Responses can be single words, “sentences (up to 150 words per question)” or calculations. Conditions: “Perusal time: 5 minutes”, “Working time: 60 minutes”, an individual supervised task, with a QCAA-approved graphics or scientific calculator.

Each screen’s examples practise one main kind of question: unknowns on screens 2, 3, 4 and 7, trends and limits on screens 5 and 9, and conclusions on screens 6 and 8. The practice test on screen 10 has three questions of the first kind, three of the second and four of the third, close to the syllabus’s mix. It is shorter than a real test: allow about 25 minutes, or set the printable under test conditions. Its datasets A and C are model data and dataset B is real. It is not marked with the instrument-specific marking guide; the model answers show the points a good answer makes.

How the lesson is taught

Worked examples, then practice. On each of screens 2 to 9, students study a worked example a step at a time, finish an example whose first steps are done for them, then do a similar problem on their own, and answer a check on the science. The approach draws on the worked example effect, first shown by Sweller and Cooper (1985) and summarised for teachers by the Centre for Education Statistics and Evaluation (CESE, 2017), and on the fading Renkl and Atkinson (2003) describe, in which problem-solving steps are added to example study one at a time until learners solve problems on their own. As students gain expertise, worked examples help less (CESE, 2017), so the help fades within each screen and the practice test gives none.

Students can work alone or in pairs. In pairs, have one student explain each step before the other reveals the next. Screens 2 to 9 take about 20 to 25 minutes each: plan three or four lessons, with the practice test as a lesson of its own.

The results box on screen 10 shows which I can statements a student got right first time, from the Your turn and Check the science questions on screens 1 to 9. The Finish this one questions are practice and do not count.

Handle with care

  • Some students’ families may work in the gas industry, have gas wells or bores on their land, or oppose the industry. The lesson is about reading the data, not about whether the industry is good or bad.
  • The gas fields are on Aboriginal Country. To include Traditional Owner perspectives, invite local Traditional Owners, following your school’s protocols.

About the data and the models

  • Cross-sections (screen 2): made up to show the traps, and not to scale.
  • Density logs (screens 3 and 10): made up. Each layer has one density, and each 0.5 m reading adds a little random noise (up to 0.025 g/cm³ either way). The cut-offs, 1.75 g/cm³ for coal with little ash and 2.0 g/cm³ for coal with a lot of ash, are from Lange (2003), a Kansas Geological Survey report on coals in Kansas; companies set their own. The sandstone and mudstone densities, 2.35 to 2.55 g/cm³, are chosen to look realistic. Net coal thickness: Well 1, 7.0 m; Well 2, 8.5 m; Well 3, 6.0 m; Well 4, 8.0 m.
  • Gas in place (screen 4 and the practice test): the formula is from Kelafant (2015), written here in metric units. The areas, densities and gas contents are made up.
  • Well W1 (screen 5): made up. Its shape, water first and then gas, follows GISERA and OGIA.
  • Monitoring bores M1, M2, X and Y and the predictions for bores P to S: made up. The thresholds are the real ones.
  • The figures on screens 6 and 7, the bore numbers on screens 8 and 10, and the survey on screen 9 are real.

Where sources disagree, and what to check

  • OGIA’s 2025 report was a consultation draft when this lesson was written, and its publications page said the 2021 report stays in force until the 2025 report is approved. Check the lesson’s figures from it against the final report: the water, the wells, the IAA and LAA bores (Tables 11-1 and 11-4), the model uncertainty and the recovery times.
  • The draft gives two recovery times for groundwater in the gas fields: more than 1,000 years (p. 134) and hundreds of years (p. 152). Screen 9 gives both.
  • Geoscience Australia’s reserve life sentence uses 2024 production of 1,593 PJ, while its production figures give 1,665 PJ. 28,955 ÷ 1,665 = 17.4 years, which matches its 17 years. The lesson uses only the 2024 figures.
  • Depth: GISERA gives 300 to 1,000 m for coal seam gas extraction, and OGIA’s draft gives coal seam gas well depths of 80 to 800 m below ground in the Surat Basin (Table 3-2). Screen 2 gives GISERA’s figure.
  • The IESC fact sheet on the water is from 2014, so what is done with the brine may have changed.
  • GISERA’s chart of attitudes is not labelled by region, but its 2024 values match the fact sheet’s Western Downs figures, so the lesson treats it as the Western Downs.

Answers at a glance

  • Screen 1: x-test, drawing conclusions.
  • Screen 2: q-sec2 Well D; q-sec3 Well F; q-held the pressure of the water in the cleats and fractures.
  • Screen 3: n-log2 8.5 m; n-log3 6.0 m; q-ash more mineral matter.
  • Screen 4: n-gip-b 95.2 million m³; n-gip-lo 27 and n-gip-hi 63 million m³; q-risk test more of the coal first.
  • Screen 5: n-gas-peak year 4; n-wpct 71%; q-water-first pumping lowers the pressure.
  • Screen 6: n-life2c about 32 years; n-wells about 280 a year; q-life it assumes production and reserves stay the same.
  • Screen 7: n-wfall about 22%; n-surat about 83%; q-brine containment ponds.
  • Screen 8: n-m2 about 2032; q-iaa P and R; q-next a bore assessment, then make good.
  • Screen 9: n-reject 5.5 percentage points; q-survey a larger share embraced coal seam gas in 2024 than in any earlier survey; q-long some effects take decades or centuries.
  • Number answers are accepted within a small margin: for example, 270 to 290 new wells a year, and 2031 to 2033 for Bore M2.
  • Practice test: the model answers are under each question on screen 10. The printable has none, so print this page or copy them out for marking.

Saved progress

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References

Word list