4.  OIL AND NATURAL GAS PROPERTIES AND EQUIPMENT

We review our oil and natural gas producing properties for impairment quarterly or whenever events or changes in circumstances indicate that the carrying amount of such properties may not be recoverable. When an oil and natural gas property’s undiscounted estimated future net cash flows are not sufficient to recover its carrying amount, an impairment charge is recorded to reduce the carrying amount of the asset to its fair value. The fair value of the asset is measured using a discounted cash flow model relying primarily on Level 3 inputs into the undiscounted future net cash flows. The undiscounted estimated future net cash flows used in our impairment evaluations at each quarter end are based upon the most recently prepared independent reserve engineers’ report adjusted to use forecasted prices from the forward strip price curves near each quarter end and adjusted as necessary for drilling and production results.

During the first quarter of 2017, our negative price differential to Brent narrowed and we incurred no significant capital spending.  We considered these and other factors and determined that there were no events or circumstances triggering an impairment evaluation for all of our fields.

Declining forecasted oil prices and other factors caused us to perform impairment reviews of our proved properties in the first quarter of 2016 for all fields in the Etame Marin block offshore Gabon and the Hefley field in North Texas. However, no impairment was required for the quarter ended March 31, 2016.