Deepwater fields present challenges to the pre-commissioning of the pipelines responsible for transporting oil and gas. Hydrostatic pressure exerted by long water columns to the downline system must be addressed and overcome because it can collapse the downhole equipment that had previously been used only in shallow waters. With the development of deepwater fields, coiled tubing (CT) provides several advantages over regular downlines. Considering that the pipelines are longer than 200 km and larger than 20 in. diameter, months of continuous work are necessary during their pre-commissioning; consequently, higher flow rates are required to reduce time and costs. Large-bore CT as downline has proven to be a cost-effective and reliable means to access deepwater pipeline pre-commissioning. With reduced layout and costs, as compared to regular downline systems, CT can provide the only economically feasible solution for some scenarios. To extend CT life without compromising its integrity and the operation, on-site pipe management and high cycle fatigue studies were conducted. A multi-skilled crew also helped to reduce personnel on board for a small vessel application without reducing health, safety, and environment (HSE)/service quality (SQ) levels. Customized and reduced equipment layout was implemented to address deck load and space restrictions. The use of a regular downline dramatically affects costs because several external layers must be added to provide suitable collapse pressure resistance, increasing its diameter and requiring a larger storage reel in accordance with minimum bending radius (MBR) to avoid damage to the downline, compromising deck layout. Complex manufacturing increases procurement costs and timing, and makes on-site repair capabilities impossible. However, 3.5 in. CT considerably reduced the final operational time, reducing friction pressure losses while maintaining a feasible layout. Improvements made on rig-up and operational procedures, as compared to previous similar project experience, enhanced technology advantages and reduced the deployment and recovery time needed. Because of vessel limitations with rough weather conditions on this project, the CT eventually had to be recovered to the surface. Consequently, these improvements reduced rigging time and safely extended the operational window, enabling multiple deployments, even within shorter intervals of fair weather. An optimized deck layout for CT and monoethylene glycol (MEG) collection spreads was necessary for small vessel use; it reduced customer costs, considering that a much larger vessel was simultaneously operating on the other pipeline end for the largest high-pressure dewatering spread ever installed on a vessel for a pre-commissioning operation. The CT control cabin was placed perpendicularly to the reel; consequently, a closed-circuit TV system was mounted behind the reel to allow pipe spooling. Brazil's largest and deepest pre-commissioning operation was performed safely with service quality excellence, increasing efficiency levels of the industry within this scope of work. Several lessons learned have been assessed for further improvements.
The demand for well plug and abandonment (P&A) operations in Brazil has increased significantly during the last 3 years, resulting in a steep learning curve that can lead to development of state-of-the-art methodologies that save time, reduce operational risks, and provide reliable cost-effective solutions. This paper presents a comprehensive analysis of recent well abandonment operations in a mature field in Brazil, which included wells that were depleted or no longer economically viable. A methodology is discussed and highlights the use of a casing collar locator (CCL) to perform depth correlation before setting packers and placing cement plugs, real-time pressure signals to monitor packer setting, and coiled tubing (CT) internal and external pressure management to help ensure that all cement is pumped out of the CT.
The systematic approach adopted by a service company and a Brazilian National Oil Company (NOC) to achieve the goal of safely abandoning wells with different completion types using light workover vessels is discussed. Having determined the abandonment methodology, the service company personnel developed processes and procedures to reach the objective. These include advances in coiled tubing (CT) rigup procedures and using a real-time telemetry system. This approach facilitated the timely and cost effective abandonment of more than 15 wells since 2017 in a safe and environmentally acceptable manner.
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