High connection gases during drilling but low pore pressures from wireine(post drilling).

06 November 2014 Hi, We just completed an exploration / appraisal well, where we experienced high connection gases while drilling, which resulted in increasing the mud weight till we saw no more connection gases. Results of the post drilling pore pressure measurement taken on wireline showed that the reservoirs were hydrostatic (8.2 - 8.5ppg). Now the well design was high pressured (prognosed high case formation pressures was 11 - 12.95ppg). We started drilling with 12.5ppg and had to raise the MW to 13.5ppg before the connection gases stopped. The drilling assembly was designed with minimal sensors (gamma and resistivity only) due to a long history of losing the entire string when we drilled HP wells and took kicks. This meant we couldn't really determine the pore pressure while drilling as we had no sensors. Although pore pressure monitoring during the drilling (resistivity and gases), was indicative of high pore pressures. My question is has anyone experienced this before and what could be the reason for this.

Thanks
SC

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