We expect to remove approximately half of the undeveloped drilling locations from our year-end reserves estimates, the majority of which are shallow gas. This relates in part to our plans to direct less capital to these assets in the future as we now have better opportunities elsewhere in our portfolio as well as the decline in gas prices which has made a number of drilling locations uneconomic. Reservoir performance issues associated with our shallow natural gas properties have also reduced the number of drilling locations and associated reserve volumes although we expect to continue drilling approximately 200 shallow gas wells per year subject to gas prices and portfolio changes. We expect to have in the order of six years of drilling inventory after adjustments at year-end 2009.
The performance shortfall is related primarily to shallow gas performance associated with increased interference and poorer infill well performance. This poorer performance has steepened the decline of our shallow gas properties yet it has not had a material impact on our current year production and we continue to see overall corporate production performance that remains in line with our expectations. We have also incorporated this decline in performance into our 2010 production guidance.
We expect our overall 2009 corporate finding & development ("F&D") costs, finding, development & acquisition ("FD&A") costs and recycle ratios to be negatively impacted by the revisions noted above. While this will also impact our net asset value, we believe that the impact may be less on a proportional basis given the declines are largely attributable to natural gas properties and the later life impact of some of the reserve changes.