Hole Stability in Nile Delta Area: Abu Madi, Nidoco, and El-Qara Wells

Abstract Hole instability in Nile Delta area, specially in the Middle and East leases is one of the main drilling problems encountered in most of the wells drilled either by Petrobel or Nidoco. Shale swelling, caving, tight holes, and consequently loss of circulation problems were experienced and overcame using several techniques. This paper is focused on the analysis of the main drilling hazards related to shale instability including analysis of pore pressure data obtained from sonic, sigma, and RFT logs and prediction of pore pressure expected in the forecasted wells. It discusses the different mechanisms of Nile Delta shale instability, Field observations and results of X-Ray diffraction analysis of shale samples collected from the area wells led to a significant improvement in shale stability by using potassium polymer mud instead of sodium chloride lignosulphonate mud. Also tight hole and differential pipe sticking possibilities while drilling through low pressure porous sands were reduced by using ultra fine cellulosic materials. Conclusion and recommendations for drilling performance optimization are included in this paper.