(Bloomberg) – Thierry Desmarest, who transformed the French company now known as TotalEnergies SE into one of the world’s largest energy companies, has died. He was 78.

He died on Wednesday after suffering from Alzheimer’s disease for 10 years, Le Monde newspaper reported, without further details. The company confirmed his death.

Desmarest was Chief Executive Officer of what was then called Total SA from 1995 to 2010, and again for a short period in 2014. Under his supervision, Total bought other companies to become one of the world’s biggest publicly traded oil companies.

Over the course of less than a year, in 1998-1999, he engineered the takeover of Belgium’s Petrofina SA to create France’s biggest oil company, then the purchase of its French rival, Elf Aquitaine SA, in what was the country’s largest takeover battle. That further consolidated the oil industry, following British Petroleum Plc’s purchase of Amoco Corp. and Exxon Corp.’s acquisition of Mobil Corp.

Mineral resources. Thierry Desmarest was born in Paris on Dec. 18, 1945, the son of an administrative judge. He graduated from the Ecole Polytechnique and the National Mining School, France’s top technical universities. His first job was with the Direction des Mines, the government body that oversees France’s mineral resources.

At 37, he went off for two years to oversee mining operations in the mineral-rich Pacific territory of New Caledonia. That was followed by five years as a technical adviser to various French government ministries.

He joined Total in 1981 to run its Algerian units, and went on to lead its Latin American, French, East Asian and West African operations. In 1989, he became director general of its worldwide exploration and production activities, promoted by new CEO Serge Tchuruk.

Under Tchuruk and Desmarest, it made major discoveries in Nigeria, Indonesia and Colombia. Profit in the first two years they were in charge was three times the previous two years.

When Tchuruk left to take over engineering company Alcatel Alsthom in 1995, Desmarest became Total’s CEO.

He decorated his office with geological curiosities from his travels and kept on pushing for new finds and lower costs, Bloomberg reported in 1999.