HPHT wells present many economic, technical, operational and HSE challenges. Casing Drilling is introduced as a potential alternative method for drilling HPHT wells. The benefits and limitations of Casing Drilling are investigated in this study in correlation with the current HPHT challenges.
The operational mud weight window can be widened beyond the traditional trip margin through the well-known Plastering/Smear Effect of Casing Drilling. Moreover, many mud challenges in HPHT wells can be eliminated including static and dynamic barite sag, drilling mud deterioration under static conditions, heavy solids content and wellbore cleaning inefficiency. The wells drilled with casing are more gauged and the quality of the cement sheath is better. Casing drilling can provide better protection for logging tools and allow many conventional tools to be used without any modification.
Casing Drilling can significantly reduce the cost of drilling through harsh environments. Additionally, drilling hazards of HPHT wells will be minimized because Casing Drilling can eliminate drilling problems such as stuck pipes, well control incidents, surge and swab effects, wellbore instability, and lost circulation. However, to ensure that this technology can present the previously argued benefits, there are some challenges that need more studies. Most of these issues are related to the manufacturing features of the materials (e.g., dope channels and substantial thermal expansion) and excessive loads (e.g., wear, torque and drag). The recommendations suggested in the study can help in limiting and overcoming these challenges.
The proposed methodology can potentially take drilling HPHT wells to a new level and also pave the way for xHPHT environment. Casing Drilling opens a new window to the current technologies and tools in HPHT wells without significant modification. Also it is a potential option to eliminate economic, operational and HSE challenges in drilling HPHT wells.