science

Stock tank oil

Stock tank oil 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 Stock tank oil rather than just read about it. In short: Stock tank oil is the volume of oil after flashing to nominal atmospheric (or other stated) storage pressure and temperature (as opposed to reservoir conditions). Background Crude oil is a complex mixture of many individual compounds which influence the physical properties of the oil, such as its density (API gravity), viscosity, Permeability, Dew point, Formation Volume, etc..

Key takeaways

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

Reference excerpt

Stock tank oil is the volume of oil after flashing to nominal atmospheric (or other stated) storage pressure and temperature (as opposed to reservoir conditions).

Background Crude oil is a complex mixture of many individual compounds which influence the physical properties of the oil, such as its density (API gravity), viscosity, Permeability, Dew point, Formation Volume, etc.. The properties also influence how the oil is classified and its value. The quantity of oil originally in place in a reservoir is usually expressed as Stock Tank Oil Originally In Place (STOOIP), this is usually given in millions of stock tank barrels (MMstb).

Processing Crude oil from subterranean reservoirs is usually produced with associated gas, produced water and solids such as sand. The crude oil must be stabilised to prevent excessive gassing during storage and to remove water and solids. Stabilisation involves passing the wellhead fluids through one, two, or three stages of separation operating at successively lower pressure to flash off lighter hydrocarbons and to remove water and solids. For a three stage train the operating pressures of the high, intermediate and low pressure separators might typically be:

HP separator: 1200 psig IP separator: 200 psig LP separator: 50 psig Stock tank: 2 psig The vapor pressure and relative volatility of constituent compounds is:

Alternatively, plant may be arranged with each stage operating at successively higher temperature. The product is dead crude which is stored in stock tanks operating at just above atmospheric pressure. Offshore production also produces a dead crude but is often spiked with natural gas liquids (NGL) as a convenient transport route for these liquids. This is known as live crude. The NGL is flashed off and recovered in the onshore separation plant. The operating pressure and temperature of the separation plant may be specified such that the oil meets a required vapor pressure, such as Reid Vapor Pressure.

Properties Density and viscosity are important property inputs into correlations for pipe-flow calculations. Stack Tank Oil (STO) density (or API) may also be used by regulatory bodies to classify oil and oil products. Other properties such as Molecular Weight, saturated aromatic resin and asphaltene (SARA), refractive index, wax appearance temperature, asphaltene precipitation, and acid number, are also specified at Stock Tank conditions. Typically stock tank conditions are 14.7 psia and 60 °F (101,325 Pa and 16 °C).Flowrates of oil are commonly specified at Stock Tank conditions, e.g: Stock Tank barrels of oil per day STBOPD.

Worked examples

Example 1 — a first encounter with Stock tank oil

Start with the simplest possible case. Write down what Stock tank oil 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 Stock tank oil 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 Stock tank oil 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 Stock tank oil

In research: Stock tank oil 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 Stock tank oil 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: Stock tank oil is common in secondary-school and first-year university syllabi. It links to neighbouring topics Petroleum industry, Petroleum production, Petroleum stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Stock tank oil 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 Stock tank oil in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Stock tank oil 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 Stock tank oil out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Stock tank oil in simple terms?

Stock tank oil is the volume of oil after flashing to nominal atmospheric (or other stated) storage pressure and temperature (as opposed to reservoir conditions). Background Crude oil is a complex mixture of many individual compounds which influence the physical properties of the oil, such as its d…

Why does Stock tank oil 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 Stock tank oil?

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 Stock tank oil.