Byron Energy says it now ranks as the twelfth biggest oil producer in the Gulf of Mexico — out of 119 companies.

Chief Maynard Smith says he’s transitioned Byron from a small-scale explorer to “a significant producer” in the shallow waters of the Gulf of Mexico.

Investors were pretty happy with that assessment — pushing the shares up 20 per cent to 33.5c today.

“The company’s ranking is based solely on Byron’s 50 per cent working interest share of the oil production from the SM71 F Platform,” Byron told investors.

“This is an outstanding result given that one year ago, the company went to the equity market to raise the necessary funds to finish the construction of the platform and subsequently initiate production from all three wells on the platform.”

The company began production at its South Marsh Island 71 project in the June quarter.

It produced 330,239 barrels of oil and 287,876 mmBTU (million British Thermal Units) of gas.

Byron (ASX:BYE) made $US9.1m ($12.6m) for its 41 per cent stake.

From July to September 19 the well produced 311,498 barrels of oil.

Mr Smith says the extra cash from the South Marsh project has allowed them to keep more equity in another block in the area and speed up drilling in two others.

Byron has leases over five separate properties in the Gulf, with some at early exploration stage and some achieving farm-outs, or stake sales, to Metgasco (ASX:MEL) and Otto Energy (ASX:OEL).

The South Marsh Island block 71 is the only one producing so far and Byron is the operator, meaning it is the company doing the work to produce oil and gas.

Bryon has sold stakes, or is in the process of selling, in all of the blocks it hold leases over.

Byron also updated its total reserves estimate, with 3P reserves of 41.4 MMboe (million barrels of oil equivalent, which includes both oil and gas), up from 2.9 MMboe last year.

Typically “reserves” refer to oil or gas discoveries that are commercially recoverable using existing technology.

A 2P means it’s proven and probable, while a 3P includes “possible”.

Byron shares over the last 12 months.