* Investment focuses on offshore exploration wells
* Trinidad and Tobago wants to increase oil, natgas output
PORT OF SPAIN, April 13 (Reuters) - Canada's Niko Resources (NKO.TO) and Britain's Centrica (CNA.L) will invest $70 million in three offshore exploration wells this year in Trinidad and Tobago, the Caribbean's leading oil and natural gas producer, officials said on Wednesday.
The two companies, along with Trinidad and Tobago's state-owned integrated energy company Petrotrin, are joint venture partners in an offshore region known as Block 2ab.
Ajith Muralidharan, a manager at Niko Resources, said drilling is scheduled to begin in September and that surveying so far had "shown prospects with substantial potential."
The investment comes as Trinidad and Tobago seeks to lure investment and increase oil and natural gas output in its vital energy sector, which accounts for 45 percent of the country's gross domestic product and 60 percent of its foreign exchange earnings.
Government statistics show oil production has fallen steadily over the last decade from 145,000 barrels a day to 100,000 bpd over the last 10 years.
Natural gas reserves declined from 22 trillion cubic feet (TCF) to just over 14.5 TCF during the same period.
Trinidad and Tobago's Energy Minister Carolyn Seepersad- Bachan welcomed the drilling plan as a sign exploration may be poised to pick up again after falling over the past two years largely because of high drilling costs and the onset of the global recession. (Editing by Kevin Gray and Jim Marshall)