CNOOC is operating in YingGehai Basin and QiongSouthEast Basin of South China Sea. Formation testing has been routinely used by this operator in field exploration to confirm hydrocarbon presence, define the hydrocarbon type as well as getting PVT samples. Due to the high cost of DST operation in the offshore environment, formation testing is considered as the main testing method to test the small to medium size sand bodies. And the result is accepted to claim reserve of hydrocarbon.
As the recent offshore exploration has focused more on deeper formation where the sand permeability is between low to ultra-low, the pressure pretest mobility is easily lower than 1md/cp. In some particular formation, the formation mobility is even lower than 0.1md/cp. For this type of permeability of sand, testing becomes very difficult and getting fluid sample to claim reserve becomes a huge challenge. If the formation tester fails to obtain the samples, very often the later DST operation would not achieve a success.
A new probe module of formation tester has been introduced to the industry early 2013 and it has been designed to perform formation testing in low permeability environment. Especially it could apply a much higher drawdown than previous technology to move the tight hydrocarbon.
In this paper, a few cases will be presented to demonstrate how this new probe work in Yinggehai and QiongSouthEast basins fluid sampling operation where we sampled successfully at formation with the mobility is less than 0.1md/cp. With this result, great amount of reserve can be claimed and this new probe has been considered as the unique solution of testing these formation as well as predicting the possible production capability. .