Coiled Tubing Cementing Operation Using MPD Technique in a HP/HT Well

Abstract

In the continual search for Oil and Gas, more and more exploration wells are being drilled in High Pressure-High Temperature (HPHT) environments. Pore and Fracture pressure prediction and understanding the true drilling window in HPHT exploration wells poses significant challenges. Once the pressure profile is ascertained, then the next challenge is to drill and cement the well within those limits to avoid kicks, losses and maintain the integrity of the well.

There are special challenges in cementing HPHT wells. These wells typically have a narrow drilling window which could make it very difficult to manage the bottom hole pressure correctly while cementing the open hole section. In any stage of cementing in this type of wells, hydrostatic, dynamic and circulating effects should be considered. These tight windows in HPHT wells, combined with the effect of temperature and pressure on mud density possess significant risks for cementing operation. Also physical and chemical behavior of cement changes in high pressure and temperature. This paper details the advantages of applying advanced Managed Pressure Drilling (MPD) technology during coiled tubing cementing operations in a case study HPHT well. This advanced technique not only allows for maintaining a Constant Bottom Hole Pressure (CBHP) but also reduces the additional costs associated with cement weight and additives. Furthermore, real time flow monitoring eliminates the down hole fluid losses which in conjunction with CBHP reduce formation damage.

A precise managed pressure coiled tubing cementing program was analyzed and planned inclusive of operational procedures and risks management. The well was displaced to a lighter drilling fluid through coiled tubing, while keeping bottom hole pressure (BHP) constant slightly over the formation pressure by applying surface back pressure (SBP). Four different densities of cement slurries were pumped in the hole through coiled tubing and held bottom hole pressure constant during the entire cementing operation within 30 kg/m3 (0.25 ppg) pore pressure and fracture pressure window. Held annular pressure constant with the help of SBP during the eight hours of cement setting time to ensure that hydrostatic pressure would remain in place.

This document demonstrates the successful application of managed pressure coiled tubing cementing operation. It also elaborates the recommended operational procedures, integrated MPD and Coiled tubing equipment setup, along with real-time graphs and data from the case study well.