Jonathan Roger has not done badly for a man who thinks he was the source of some disappointment to his parents in his youth.

As head of the exploration and production arm of Centrica, the utility that owns Scottish Gas, Mr Roger, 42, has one of the biggest jobs in the North Sea.

But things could have turned out very differently for the Aberdeenshire-born executive had he not experienced a sudden change of heart as a teenager.

Mr Roger was set to proceed with a boyhood plan to train as a doctor when he had to admit that niggling doubts about whether medicine was for him got too loud to ignore.

"As I was going through my later teenage years I began to wonder, is that really for me? And two weeks from starting medical school I decided it wasn't," explains Mr Roger.

Faced with the need to make a quick call about an alternative course, he plumped for engineering, which seemed likely to open lots of doors.

The son of a man who ran a firm that supplied food to oil rigs, the decision set the young Mr Roger on a road he has travelled with distinction.

Before joining Centrica, Mr Roger held a succession of increasingly big jobs in the oil and gas industry off Scotland and in Indonesia. His employers ranged from ConocoPhillips, the US major, to Aberdeen-based Venture Production, which found value in North Sea assets that the big fish disdained.

Now managing director of Centrica Energy Upstream, Mr Roger took charge of the E&P unit after the utility completed a hostile takeover of Aberdeen-based Venture late in 2009.

Centrica wanted to increase its control over the supply of commodities for which prices were expected to rise on the back of growing global demand.

The deal put a £1.3 billion valuation on a company that Mr Roger had seen grow from 10 to 200 employees. As chief operating officer, he played a key part in that process.

Centrica only succeeded after Mr Roger and other board members had spent months opposing the bid.

"It was a very passionate organisation, I was very proud to be part of what Venture was, part of that growing UK independent," he says. "The organisation didn't want to be acquired, the management team and the board didn't want the deal to go through and obviously fought quite hard for it not to go through and thought the potential of the business was more than what was on offer."

After Centrica triumphed, Mr Roger stayed on, chiefly out of concern for what might become of the company and its people.

"I agreed originally to stay for six months only and the reason for that was - there was a risk if all four directors left, who's looking after the organisation in the short-term while the new organisation gets developed and who's looking after the people?"

Another change of heart followed. "Over the next few months I guess I really enjoyed the business. Some of the concerns I had around how it would operate, the level of empowerment it would have, kind of fell away," he explains.

"Centrica really were keen. They designed the business very much taking the best out of both businesses, the best people, the best location, so I felt the business had a real chance of being successful. The company did want to invest in it, grow it, look after the people and take it forward, that's why I agreed to stay on."

Speaking in his spacious office in the smart new headquarters of the Centrica Energy upstream business which offer commanding views of Aberdeen, Mr Roger looks like someone who is thoroughly enjoying himself.

He believes that the FTSE-100 giant has managed to retain the kind of entrepreneurialism and pioneering spirit that is normally associated with independents.

For example, Mr Roger notes Centrica has used innovative technology to develop assets that could otherwise have been left idle. He says the F3FA platform, which came onstream last year is the largest self-installing platform in the North Sea. Using a platform that could be redeployed on other fields helped transform the economics of a find made in the early 1970s.

Centrica Energy Upstream grew operating profits by 36% last year, to £769 million from £566m in 2010. It is one of the top three gas producers on the United Kingdom Continental Shelf.

Mr Roger highlights achievements in three key areas. He is pleased with the extent to which Centrica has retained key people and got them aligned behind new objectives. Centrica employs 350 people in Aberdeen, 50 of whom have been recruited in recent months.

Mr Roger is proud of his unit's record with the drill bit and says: "We have brought onstream eight new fields or field extensions and had a very successful exploration track record of 50%, well above the typical industry level."

He is also pleased to have won approval from the main Centrica board to grow the business significantly through acquisitions. In November Centrica bought £1bn of Norwegian assets from Statoil. Two months later it paid £142m for ConocoPhillips' share of the Stratfjord gas field in UK and Norwegian waters.

The father of two claims the company has become one of the fastest growing new entrants ever seen in Norway. It also has operations in Trinidad.

In February Centrica stoked controversy by agreeing to buy a portfolio of oil and gas assets in the UK North Sea from Total for $388m (£246m).

Months earlier the firm had threatened to leave the giant South Morecambe Bay gas field idle following the tax hike in the 2011 Budget.

Asked by The Herald if Centrica had cried wolf, Mr Roger insists the tax increase has had an impact on the company's investment plans. He notes that around 80% of the £1.5bn Centrica has spent on upstream acquisitions lately has been used to buy Norwegian assets.

But the UK looks set to remain a key focus for Centrica. Mr Roger says the company would like to participate in the development of the basin west of the Shetlands, where majors like BP and Shell are investing billions developing huge new fields.

Centrica also hopes to establish positions in one or two other new basins in coming years, including the Barents Sea.

Given his fond memories of the time he spent at Venture, Mr Roger says he will want to give another small company a go at some point.

But mindful of the fact that not many companies can hope to achieve the kind of growth that Centrica is targeting he will be happy to swim with the big fish for a while yet.