Ann: Mukuyu-2 Drilling Update, page-217

Background gas levels will never be exactly the same for two wells drilling the same section and with same hydrocarbon scenario because the factors that influence ditch gas levels are not kept constant. Factors that can affect gas readings:

- rate of penetration.
- Mud properties (esp mud weight)
- Design of mud return path from well back to the pits. Long open flow lines will allow gas to get liberated to atmosphere before the mud reaches the mudloggers degasser. Exalo has installed new shakers and mud tanks since M1.
- Different mudlogging company with different gas monitoring equipment.
- Gas equipment calibration procedures between companies will vary. Eg some use a 2 point manual injection of calibration gases while others have 3 or more calibration points and calibration gas is flowed continuously from calibration gas canisters directly into the panel.
- Differences in design and operation of the mud degasser at the shakers. eg gas traps can be non floating which need constant adjustment or floating which maintain a constant level regardless of mud level in possum belly.
- length of sample line between gas trap and mudlogging unit can affect gas readings...especially where ambient outside temps are low. Low temps will cause drop out of heavier gas species.