Abstract
The primary cause of nonproductive time (NPT) incurred by Saudi Aramco in the deep gas drilling environment is stuck-pipe incidents. These incidents are mostly caused by hole cleaning, differential sticking, and wellbore stability issues.
To address the stuck-pipe incidents, the Saudi Aramco drilling engineering division and a service company together developed new procedures and techniques that proved to be efficient in stuck-pipe reduction.
Poor hole cleaning was identified as the main reason for stuck-pipe incidents. Procedures with compilation of best practices having reference to planning, drilling, tripping, and working tight spots were introduced. Torque & drag (T&D) simulation, along with equivalent circulating density (ECD) monitoring, was introduced as a road map to give a bigger picture and to give warning signs along the way.
In addition, past experiences showed that mud weight could significantly be reduced without gas flow occurring. This highlighted that, due to the complex nature of the reservoir, uncertainty existed in reservoir pressure estimation. Hence, it was recommended to run a formation-pressure-while-drilling service to better understand the formation pressure distribution. The idea was to measure, while drilling, the formation pressure of different layers, which would allow an optimal overbalance adjustment to mitigate the differential sticking risk.
Even though drilling in the direction of minimum horizontal stress leads to maximizing the propagation of fractures during the stimulation phase hence increasing production rates, it has also been observed that it leads to wellbore instability, which in turn causes stuck-pipe incidents. To address the stuck pipes in such situations, a technique was developed based on creation of mechanical earth models (MEM). This practice has helped to interpret the response of the wellbore by identifying hazards and to raise awareness of wellbore stability.
The services have been an innovative approach to mitigation of stuck-pipe incidents in deep gas drilling. The techniques are a way forward to reduce stuck-pipe incidents and hence lost-in-hole situations.
