* Sees Q4 $1.8 billion charge

* Ended year with $1.75 billion cash

* Plans to issue $500 mln in debt

* Shares down 2.5 percent (Recasts first paragraph, adds debt offering, byline, analyst comment)

By Anna Driver

HOUSTON, Jan 27 (Reuters) - Chesapeake Energy Corp (CHK.N: Quote, Profile, Research) said on Tuesday it plans to offer $500 million in debt, although the U.S. natural gas producer told investors last month it had no plans to tap capital markets.

The Oklahoma City, Oklahoma company also expects to take impairment charges totaling $1.8 billion in the fourth quarter and ended the year with $1.75 billion in cash, less than the $2.5 billion it projected in December.

"It just shows me that management is losing its credibility," Phil Weiss, energy analyst Argus Research said. "They keep telling us they are slowing down, but they are still acting like a growth company. I don't get it anymore."

Chesapeake shares fell 2.5 percent in after-hours trading.