Abstract
Estimation of pore pressure and fracture gradient is very important in achieving a successful drilling operation. With proper estimation of pore pressure and fracture gradient, the drilling engineers can design accurate mud density that can-balance and stabilize the formation pressure without fracturing the formation. Proper estimation will minimize washouts, kicks, lost circulation and stuck pipe. This paper is on a Model developed using Visual Basic and Microsoft excel applications to compute the mud hydrostatic pressure, pore pressure, overburden gradient, fracture pressure and the overbalance pressure from a real field drilling data in order to predict the possible depths were stuck pipes could occur. The results from the analyses showed that at the depths where the pressure difference between the mud hydrostatic pressure and the formation pore pressure was greater than 500 psi, the pipe would most likely get stuck while a negative overbalance showed a kick. Also, from the analyses, between 8,100ft to 12,300ft depth, the pipe was freed from sticking and there was no kick because the hydrostatic presssure between these depths balanced accurately with the pore pressure.(overbalance less than 500psi). But from 12,300ft to 12,700ft, there was a kick because the formation pore pressure was quite higher than the hydrostatic pressure due to the abnormal pressure zone encountered. This situation could be managed by increasing the mud weight while maintaining a pressure overbalance less than 500 psi and mud hydrostaic pressure less than the fracture pressure at the same time. However, from 14,800ft and above, there was pipe sticking because the pressure overbalance was higher than 500 psi as a result of high mud weight. This model provides a platform for Well Engineers to detect the zones where kicks are likely to occur and the zones where the pipe could get stuck thereby effectively reducing losses resulting from down time caused by stuck pipes and fishing operations.
