Have got some basic doubts about Oil & Gas Research. Pls assist.

I am a fresher in equity research & valuation; want to have a career in this field. Kindly take time & answer the below.

1. While doing oil & gas research, not every company posts its 3Ps in its annual reports. then how do we go forward in projecting the sales numbers; where do we get related info & how do we make sense of them?
2. (a)While forecasting FY09 Income statement of Oil & Gas comp, I have Q1, Q2 of '09, so is it okay if I forecast Q3, Q4 and add them all to get Annual numbers? Is there any other better method?
   (b) Also since we dont have any quarter numbers for FY10, how do we go forward... shall we use Annual numbers and go on forecasting?
3. Do the last 5 year Annual numbers suffice in doing Valuation of Oil & Gas company. If not, please let me know alternate methods?

These questiones might sound basic for most of you guys but hoping for responses.
Thanks in advance.