The AIM-listed firm said the operating loss for the six-month period to 31 March 2018 was £4.38mln compared to £1.07mln for the same period last year.
The company said the written down was mostly related to intangible assets in Kimmeridge Oil & Gas, specifically the cost associated with drilling the unsuccessful well.
UK Oil & Gas said net cash outflow from operations increased to £1.76mln and investment in both exploration and evaluation assets and oil and gas properties increased to £4.95mln.
The company said: “Over the past year our focus remained upon maximising UKOG's growth potential via a combination of our flagship KL oil exploration play, ably supported by low-risk appraisal and development projects such as the Horse Hill and Arreton Portland discoveries.”
“Our focus will remain firmly on delivering success from this focus over the foreseeable future,” UKOG said.
In morning trading, UKOG’s shares jumped 11.9% to 1.88p.