While drilling a deep gas well through sensitive shales in the Qawassim formation in the Nile Delta area of Egypt, a major operator encountered severe lost circulation in the 8-1/2-in. intermediate interval, beginning immediately below the 9-5/8-in. casing shoe at approximately 3,100 m. Porous sand stringers are interspersed in the shale sequence, and these stringers were the suspected thief zones.
After performing two cement squeeze jobs over a five-day period (at an approximate total NPT cost of $150,000), the operator was able to drill another 100 m before encountering a drilling break and increasing the mud weight to 14.8 ppg to prevent an influx. As a result of the density increase, the losses recurred at rates up to 150 bbl/hr. Five lost circulation material (LCM) pills were spotted as the operator attempted to reach logging depth.Download