| Popis: |
After drilling a 3,200-m exploration well, an operator in the United Arab Emirates faced a considerable cementing challenge: 30 producing reservoirs with multiple different pressure properties. For example, several injector wells surround the new well, which created a highpressure zone with an equivalent pore pressure of 11.97 ppg. A nearby zone, however, had an overbalance of 2,448 psi and a high potential for significant losses. The pressure conditions left almost no room between equivalent circulating density and the fracture pressure, so the spacer and lead cement were designed with the same density as the mud. To ensure good hole-cleaning without a clear density hierarchy, engineers analyzed the well conditions using a novel fluid displacement software model to assess effective laminar flow, a functional alternative to turbulent flow when properly implemented. Furthermore, a specialized lost-circulation spacer was designed to mitigate expected losses while cementing. Finally, gastight, lightweight lead cement with high-performance microspheres was designed to cover the upper section of the well, followed by a heavy expandable cement to ensure zonal isolation. The cementing operation was pumped successfully, with cement returns to surface after successful displacement. A successful Shoe Bond Test followed after 96 hours, and drilling resumed. This paper will describe the technical evaluation, risk assessment, and operational execution of the job, with details of the lost-circulation spacer, as well as the lightweight lead and expandable tail slurries. Modeling simulation of the ECD, centralization, and fluid displacement will also be shared. |
