Brazilian energy firm Eneva has revealed plans to fast track the development of onshore natural gas fields to meet soaring thermoelectric fuel demand.

The announcement came amid reports the company is facing a gas shortfall for four power plants in the northeastern state of Maranhão.

In a statement on Monday, Eneva said it was working with sister firm Parnaíba Gás Natural (PGN) to guarantee supply to the Parnaíba I (676 MW), Parnaíba III (176 MW) and Parnaíba IV (56 MW) facilities.

"Eneva and PGN are working to optimize current and future production within the life cycle of the gas fields," Eneva said in the statement.

"This involves, among other measures, managing existing wells, drilling additional ones and accelerating production at other discovered fields which are approved for commercial operation."

PGN says its Parnaíba basin gas reserves hold about 311Bm3. Gavião Real remains the only field in production, with Gavião Azul and Gavião Branco under development.

Meanwhile, PGN said it was no closer to announcing the startup of its troubled Parnaíba II plant.

The 518MW project had been earmarked to begin operating in March but has been beset by construction delays and fears of a fuel scarcity.

Eneva said it was still discussing a request to alter the plant's supply terms with power regulator Aneel.

"[We] will disclose the final terms and conditions of the Parnaíba II negotiation as soon as it is finalized with Aneel, given that the process is confidential until conclusion," the company said.

Parnaíba Gás Natural, a former subsidiary of Eike Batista's debt-mired OGX, is a joint venture between Cambuhy (73%), Eneva (18%) and E.ON (8%). The company has a majority stake in the concession of eight onshore blocks.