What it means
For a company that extracts natural resources, reserves are like inventory in the ground. The reserves-to-production ratio, often called the R/P ratio, shows how long that inventory would last if the company kept extracting at the same pace.
The numerator is proven reserves, which are the quantities that engineers believe can be recovered with reasonable certainty under current economic and technical conditions. The denominator is production over the latest year, in the same units, such as barrels of oil, cubic metres of gas or tonnes of ore.
A higher ratio suggests a longer life for the business, which supports a long-term valuation and can help the company secure lending. A low ratio signals that the company must find, buy or develop new reserves soon, and the cost of that effort should be reflected in its spending plans.
The ratio is a snapshot, not a forecast. Production from a field normally declines as it matures, and reserve estimates can be revised up or down when prices, technology or geology change, so the actual life can differ widely from the simple figure.
Analysts compare the ratio over time and between peers. A company whose ratio is steady while it produces heavily is replacing the resources it extracts, whereas one whose ratio falls year after year is depleting its base.
The ratio also appears in national statistics, where it is applied to a country's total reserves of oil or gas. The same cautions apply, and people should avoid reading the number as a date by which a resource will run out.
In practice
Real-world examples.
Example
A natural gas company reports reserves of 90 billion cubic metres and annual production of 6 billion cubic metres. Its ratio is 15 years, and the finance team uses it when discussing a $400,000,000 loan with lenders.
Example
A gold mining firm finds that its ratio has fallen from 12 years to 7 years over three years because it has produced steadily without adding new reserves. The board approves a larger exploration budget to restore a longer mine life.
Example
An investment fund compares three oil companies. One has a ratio of 8 years, one 14 years and one 22 years, and the analyst asks why the lowest is producing heavily while the highest has a large share of undeveloped reserves.
Formula
Calculation
Reserves-to-production ratio = proven reserves at year end / production during the year.
Suppose an oil producer has proven reserves of 150 million barrels and produced 10 million barrels during the year. The ratio = 150,000,000 / 10,000,000 = 15 years. If the company sold the oil at $70 a barrel, its annual revenue would be 10,000,000 x 70 = $700,000,000, and at the current rate of extraction the reserves are worth around 150,000,000 x 70 = $10,500,000,000 in gross revenue over 15 years, before costs and taxes.Case study
Seen in the real world.
Redstone Petroleum is an illustrative, fictional oil company with proven reserves of 120 million barrels and annual production of 8 million barrels. Its reserves-to-production ratio was therefore 15 years.
Lenders were comfortable, but the finance director noticed that the field's output was declining by about 7% a year, so the real life of the reserves would be longer than 15 years at a lower average rate. She also noticed that the oil price used in the reserve estimate was higher than the current market price, which put some of the reserves at risk of being reclassified.
She presented a range of cases to the board, showing outcomes at different prices and decline rates, and recommended a modest exploration programme to protect the ratio. The illustrative lesson is that the ratio is a useful start for discussion, but it should not be read as a precise countdown.
Watch out
Common mistakes.
- Reading the ratio as the number of years until the resource is exhausted, when production declines, new discoveries are made and estimates are revised.
- Mixing units, such as comparing reserves in barrels with production in barrels of oil equivalent, which distorts the result.
- Comparing ratios across companies without checking how each defines and audits its reserves, since standards and conservatism differ.
Questions
People also ask.
What is a good reserves-to-production ratio?
It depends on the sector and stage of development, but a ratio of ten years or more is often seen as comfortable, with shorter ratios requiring active replacement of reserves.
Does a higher ratio always mean a better company?
No, a high ratio can reflect reserves that are costly or slow to develop, so profitability and cost of extraction should be reviewed alongside it.
How do falling commodity prices affect the ratio?
Lower prices can make some reserves uneconomic to extract, which reduces the proven reserves figure and shortens the ratio.
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