You guys need to stop listening only to yourselves. Read the whole piece below and please try and understand it. Takeaways are South China Sea and also where C02>20%, the mean is 50%. So what this means - is where CO2 content is high - it is usually very high! Premier Oils well to the north is rumored to be 90%+ CO2. Where is is low (e.g. Dong Fang), it is usually an overall low %.
CO2 can be depth related but "in gases with very high (>50%) CO2 contents, the CO2 is typically derived from thermal destruction of marine carbonates", which is exactly the risk on this prospect as there are carbonates in the Basin. Obviously the JV has tried to drill in an area they feel there is the lowest risk - but at the end of the day - it is an exploration well!
http://work.geobiology.cn/ebook/Journal%20of%20GEOLOGY%20NO%205-6/095%20Geological%20slructure%20and%20hydrocarbon%20potential%20of%20Song%20Hong%20basin%EF%BC%88NGO%20VAN%20DINH%20&%20LE%20VAN%20TRUONG%EF%BC%89.pdf
I am not saying CO2 will eventuate and certainly to test, there must be some indication of low methane on the gas chromatograph - but for goodness sakes - understand the risk is still there!!
"Carbon Dioxide (CO2):
On average, the global risk of encountering >1% concentrations of CO2 in a gas accumulation is < 1 in 10, and the risk of encountering >20% concentrations of CO2 is < 1 in 100 (Thrasher and Fleet, 1995). However, here is the issue: the mean CO2 content of reservoirs with >20% CO2 is 50% CO2. In other words, when CO2 is abundant, it is frequently so abundant that it can kill the prospect economics. Furthermore, high CO2 concentrations are encountered in diverse areas (Thrasher and Fleet, 1995), including:
South China sea
Gulf of Thailand
Central European Pannonian basin
Australian Cooper-Eromanga basin
Colombian Putumayo basin
Ibleo platform, Sicily
Taranaki basin, New Zealand
North Sea South Viking Graben
CO2 sources include:
Organic sources (i.e., kerogen cracking, and bacterial degradation of petroleum).
Thermal decarbonation of carbonate minerals.
Exsolution from magmas.
Thermochemical sulfate reduction (TSR) of hydrocarbons.
Various geochemical characteristics can be used to distinguish CO2 from each of these sources (e.g., Jenden et al., 1992; Ballentine et al., 1999; Brown, 1999; Cathles and Schoell, 1999; Battani et al., 1999; Imbus et al., 1998; Thrasher and Fleet, 1995). These techniques have revealed that, in gases with very high (>50%) CO2 contents, the CO2 is typically derived from thermal destruction of marine carbonates and/or exsolution from magmas (Jenden et al., 1992; Thrasher and Fleet, 1995). TSR, a process described in the H2S section below, does not yield gases with very high (>50%) CO2 contents. Similarly, CO2 derived from organic sources (kerogen cracking and bacterial degradation of petroleum) rarely exceeds 20% of an accumulation and is only important in special cases, such as certain heavily biodegraded oil fields. Regardless of the source of the CO2 in an accumulation, its abundance is controlled not only by its origin, but also by in-reservoir reaction of the CO2 with silicate minerals, a temperature-dependent process (Smith and Ehrenberg, 1989).
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