Innovative Strategies for Well Integrity in Offshore Top-Hole Cementing: Laboratory-Validated Success in Shallow Gas Mitigation

Abstract

Abstract This paper primarily aims to address the pressing issue of shallow gas intrusion and gas channeling during offshore top-hole cementing. We seek to introduce and substantiate two novel approaches using the dual gradient drilling system / Riser-less Mud Recovery (RMR) system, emphasizing their practical application in the laboratory and field effectiveness (on jack-up and Semi-submersible, drill Ship, etc.). We applied two different methods of managed pressure cementing (MPC) with RMR in our study. The first method involved confirming the cement at the seabed and then filling the RMR return line with water up to the rig floor. The return line filled with water up to the rig floor including the air gap allowed us to apply extra pressure on the cement during its curing time. The second method involved closing the Suction module (SMO) valve after detecting the cement at the seabed. This trapped the cement in a closed space and prevented any gas from entering during its dehydration time. We tested both methods in laboratory settings to prove the offshore field result. This study has provided important results and valuable insights, leading to strong conclusions. In the offshore drilling context, the innovative RMR-based top-hole cementing methods have proven highly effective in addressing shallow gas challenges. The first method, focusing on pressure management, consistently exhibited efficacy during field applications and laboratory testing. It entailed the identification of cement placement behind the surface casing, followed by water infusion into the RMR return line, effectively preventing gas channeling during cement curing. The second method, employing the permanent SMO valve to confine cement, consistently delivered commendable performance across laboratory and field conditions. It effectively prevented gas infiltration or channeling during the critical cement dehydration phase. In summary, these findings underscore the potential of these techniques to enhance gas mitigation during top-hole cementing in offshore drilling significantly. Both approaches, substantiated through field and laboratory validation, make a substantial contribution to the body of knowledge in offshore drilling and reinforcing well integrity. They also have the potential to reduce environmental impact and drilling costs. This paper introduces innovative solutions to tackle the persistent challenge of shallow gas in offshore drilling. These proposed methods, supported by field data and laboratory validation, provide practical insights and strategies for ensuring cement integrity, thereby contributing significantly to the petroleum industry's knowledge base.