Texirish, thank you for your excellent post. If I may, I would add one more point of comparison between XOM, CVX and OXY, and that is price. I would suggest that a simple and meaningful price metric for comparison is enterprise value to proven reserves. Notwithstanding significant assets in production facilities, pipelines, ships, etc., the bulk of the value for these asset-rich companies lies in proven reserves. As of today the enterprise value (EV) to proven reserves of these three companies are:

CVX, $27/barrel of oil equivalent (boe)
XOM, #28/boe
OXY, $20/boe

The EV/proven reserves for major oil and gas producers varies quite a lot, given differences in extraction cost (deep water, tar sands, etc), geopolitical risk and other factors, so the above ratios need to be put into that context. Nevertheless, EV/proven reserves is a good starting point for comparison of similar companies.