Canadian Superior Energy Inc., a financially troubled Calgary-based oil and natural gas explorer and producer, says it has filed an application for protection from creditors.

The company said it has filed the application under the federal Companies' Creditors Arrangement Act with the Court of Queen's Bench of Alberta, which was to consider the measure Thursday.

Company shares fell Thursday after the bankruptcy protection application was announced, and the Toronto Stock Exchange began an expedited review to delist the company's stock from Canada's key stock market.

The bankruptcy filing by Canadian Superior, which has faced trouble with a major Caribbean natural gas development and pressure from shareholders, came after the company was given a second extension to repay a $37.5-million credit line from its major bank.

Earlier this week, the company said it now has until March 12 to repay the amount to Canadian Western Bank. The credit line was originally to have been paid back last week, but the bank extended the deadline to Friday and then again to March 12.

The debt has been reduced by $9 million garnered from recent asset sales.

Canadian Superior explores for and produces oil, natural gas and liquefied natural gas, with operations in Western Canada, the United States and North Africa. It also has operations offshore of Trinidad and Tobago and Nova Scotia.