Ann: Preliminary Wireline results shows Multiple Potential Zones, page-428

Drilling breaks are an important piece of information. Before the advent of MWD...the only real time source of information on lithology being drilled and presence of hydrocarbons was a mudlog.....a depth based log of drilling rate, logged cutting samples and mud gas data. Mudlogs usually include other useful data as well. With the switch from tricone insert/milltooth to PDC (polycrystalline diamond) drill bits there is often an industry mindset that rate of penetration data isn't as useful but even with a PDC bit in the hole ROP data can be used to delineate significant changes in lithology and reservoir quality. Even today when a significant drilling break is encountered a driller will take measures to evaluate the break in case it is the top of a reservoir or potentially a zone of overpressured formation.

Re CO2 and H2S. These are two of a number of contaminants that can affect the economics of a field. H2S in significant quantities will increase the cost of completing a well as H2S rated casing and tubing must be run. The gases have to be separated out from the production stream which also adds to processing costs. In the old days such gases were simply vented to the atmosphere but this is generally no longer an option. Mercury is another contaminant in gas that can add to processing costs.