The following research note from RBC dated 19 September 2012 notes the CO2 issues at p5:-
"In the Upstream newswire (15-Aug) it was reported that Exxon was believed to have made a significant discovery offshore Vietnam, in Block 118 (Ca Voi Xanh-3X). This well is located some 100km north of the Neon Block 120 and was Exxon’s third well in its drilling programme, having made an earlier discovery suggested to be up to 10Tcf (with 30% CO2). Additionally, Premier in Block 104 (28-Oct-2011), immediately to the north of Neon in Block 105 announced an unsuccessful well (104-QMX-1X) which was tested at a depth of 3832m in fractured basement but flowed gas with 99% CO2.
Although we suggest the Exxon wells have some look through for Neon Block 120 being look-a-like plays, we don’t believe the Premier result to be directly applicable to Neon (Block 105) as we understand the company is not chasing the fractured basement play. However, the key risk in this more northern area is CO2 volumes."