science

Tight gas

Tight gas is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tight gas rather than just read about it. In short: Tight gas is commonly used to refer to natural gas produced from reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates. The gas is sealed in very impermeable and hard rocks, making their formation "tight".

Key takeaways

Tight gas belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tight gas to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tight gas from memory before moving on to harder problems.

Reference excerpt

Tight gas is commonly used to refer to natural gas produced from reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates. The gas is sealed in very impermeable and hard rocks, making their formation "tight". These impermeable reservoirs which produce dry natural gas are also called "Tight Sand". In reality the term "tight" refers to reservoirs where wells are unable to be commercially exploited at current economic conditions in the absence of artificial stimulation or changes in well geometry. It is economic criteria (gas price, opex, capex, royalties and fiscal regime) which define this status and in many cases, as gas/oil prices rise then, projects that have been previously shelved become viable; improvements in technology or changes in available infrastructure may also rehabilitate otherwise stranded gas. Tight gas reservoirs historically were generally defined as having less than 0.1 millidarcy (mD) matrix permeability and less than ten percent matrix porosity. Although shales have low permeability and low effective porosity, shale gas is usually considered separate from tight gas, which is contained most commonly in sandstone, but sometimes in limestone. Tight gas is considered an unconventional source of natural gas. Much tight gas was formed 248 million years ago in Paleozoic formations. Cementation and recrystallization changed a conventional gas reserve which reduced the permeability of the rock and natural gas was trapped within these rock formations. Horizontal and directional drilling is used to extract tight gas deposits as they run along the formation which in turn allows more natural gas to enter the well that was dug. Numerous wells can be drilled to access the gas. Hydraulic fracturing is one of the main methods to access the gas which requires breaking apart the rocks in the formation by pumping fracking fluids in to the wells. This increases permeability and allows gas to flow easily, freeing it from the trap. After that deliquifaction is used to help in the extraction. Rock with permeabilities as little as one nanodarcy, reservoir stimulation may be economically productive with optimized spacing and completion of staged fractures to maximize yield concerning cost.

Examples Some examples of tight gas reservoirs are:

Muddy Sandstone/J Sandstone – Wattenberg Gas Field, Denver Basin, Colorado, US Mesaverde Group – Piceance Basin, Colorado, US Rotliegend – Germany and Netherlands Utica – Appalachian Basin, US & Canada

See also Unconventional (oil & gas) reservoir Shale gas Tight oil

References

Illustrations

Worked examples

Example 1 — a first encounter with Tight gas

Start with the simplest possible case. Write down what Tight gas claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tight gas before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tight gas ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tight gas

In research: Tight gas appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tight gas in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tight gas is common in secondary-school and first-year university syllabi. It links to neighbouring topics Petroleum stubs, Unconventional gas, so understanding it makes those chapters shorter.
In everyday life: Look for Tight gas outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tight gas in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tight gas means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tight gas out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tight gas in simple terms?

Why does Tight gas matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tight gas?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tight gas.