Afren Plc, the U.K. oil and gas producer operating in West Africa, fell the most in three weeks in London trading after abandoning a well off Ghana.

Afren dropped 10 percent to 26 pence at 11:09 a.m. local time, the most since Dec. 5, valuing the London-based company at 116 million pounds ($170.3 million).

The explorer drilled the Cuda-1x well in the Eastern Basin to 12,425 feet (3,787 meters), Afren said today in a statement. The well found “an unexpectedly severe high pressure zone in the top of the Upper Cretaceous which ultimately required Cuda-1x to be plugged and abandoned,” it said.