Net pay is normally determined by a porosity cut off and water saturation e.g. in a sandstone reservoir you may have 100m gross section and using a cut off of POR 12% you would look at the whole section - any rock exhibiting > 12% and meeting the water satuartion cut off (higher than) will be deemed net pay.

Based on the NR it would appear that there is very little net pay in the approximately 800m gross fractured rock section. The porosity in the matrix appears to be very low (this is why they are not quoting a net pay figure). The moveable oil and wet gas appear to be in the fracture matrix (secondary porosity). Tullow will test this first as you usually test bottom up. It is possible there may be some fracture reservoir flow however it is probable that this will deplete quickly unless there is an extensive connected fracture network with good permeability (unlikely but not impossible). Stimulating by fracking might improve productivity but the equipment will not be in Kenya.

My experience indicates that the upper 30m is good but the the lower section of 800m will not be commercial - in this well at least.

Wet gas is not much good in Kenya. The liquids can be stripped and the gas used for gas lift of the upper reservoir (low GOR) as an alternative to pumps but you don't need much gas for this. Local power generation is another possible use but again this will require limited volumes of gas.