Lightweight or, alternatively, foamed cement slurries for surface casing operations are often necessary during special situations (i.e., low fracture gradients) for the required zone to be isolated. The foamed cement technique reduces the heat of hydration (HoH) of the slurries, reducing potential risk of shallow hydrate flow and losses because of its reduced hydrostatic pressure. This alternative for lightweight slurries has been used globally with successful results. The foamed cement operation was designed and executed considering specific aspects and details, including a combination of factors, such as expected low fracture gradient, mechanical property requirements, logistic constraints in terms of the difficulty managing two types of cement (large tonnage of Blend and G cement vs. rig capacity and safety volume requirements), long sections to be cemented, and the uncertainty of the cement volume excess necessary to achieve return in the seabed. Because this was the first cement operation for the operator at this remote deepwater field, the planning phase required extensive discussions. Rig silo capacities and deck space on the rig were limited, which constrained the possibility of considering backup for all bulks, chemicals, and equipment. Execution of the cement operation was as per the approved program without deviation. The cement volume returned at seabed indicated an openhole diameter with ±100% washout. A tracer additive (fluorescent dye) mixed with the spacer was successfully used to indicate fluid return at seabed (2120-m water depth). As part of the best practices to execute this operation, a liquid additive system was used to provide pump volume flexibility. Foamed cement laboratory tests were performed, considering field samples and the foaming agent (surfactant) were injected straight at the suction of the pump. As expected, the foamed cement operation is an extremely efficient and effective technique to achieve zonal isolation in a surface casing string of a deepwater well. Currently, this procedure is frequently used in fields globally. A case study of the first foamed cement application for surface casing in French Guiana is discussed.

End-of-well operations can improve drilling performance through selection of the proper tools to optimize rig time and tailoring solutions. For deepwater projects, it is necessary to optimize costs without compromising safety and quality while delivering maximum efficiency. An innovative technique is presented for placing a long cementing plug using sacrificial tubing and a special tool. This method also allowed checking the top of cement (TOC) after a short waiting on cement (WOC) period. Plugging and abandonment operations were performed in deepwater wells in the Caribbean Sea, saving up to two days of rig time by using a single intervention to isolate the openhole length from 600 to 1500 m and allowing continued, timely operations. A case study of this operation is presented that discusses the experience and lessons acquired, which should be beneficial for the industry. Conventional balanced plugs are not efficient in openhole lengths greater than 500 ft because of operational limitations and design considerations. In such scenarios, fit-for-purpose downhole tools can provide reliable solutions, such as using a release mechanism to safely place a cement plug of the necessary length with proper thickening time distributed along the volume pumped. This technique avoids the long WOC times necessary to achieve adequate compressive strength. The release tool enables running sacrificial pipe; placing cement through the sacrificial pipe; displacing cement slurry with a dart, which provides an indication of its latching at the surface; and disconnecting to retrieve the landing string. In the laboratory, a 500-psi slurry compressive strength was obtained after 6 hours and 15 minutes. This allowed the TOC to be tagged after 6 hours of WOC. Because this procedure does not require the 3 1/2-in. stinger to be pulled out of the plug, the risk of spacer contamination in the slurry was reduced. Based on laboratory results, three operations using the release tool and discussed design considerations were performed successfully for the first time in the Caribbean Sea, with no nonproductive time (NPT) or quality issues experienced, saving up to USD 500,000 for the operator. Laboratory tests, such as compressive strength, provided a good indication of the time necessary to tag the TOC, which met the operation objectives. The tool capabilities and operational and design considerations can be used as a reference for projects in similar environments that require alternatives with proven solutions. The main benefit was reduced operator costs for rig daily charges resulting from placing one plug rather than several balanced plugs. This was also beneficial for the mud company because a large spacer volume was not incorporated into the mud. Another benefit was allowing tagging of the plug in the same operation because of the short WOC.

Exploration deepwater wells demand proper planning to mitigate any potential risks during well construction where uncertainty can play an important role. For this reason, designing dependable barriers under such a scenario requires innovative techniques, such as Managed Pressure Cementing (MPC). Using Managed Pressure Drilling (MPD), the operator can control the wellbore pressure while drilling each section. This unconventional solution for a short operational window has been successfully applied in some fields around the world, with additional advantages when cementing jobs are designed and executed. The tight operational window expected for a 9-5/8-in. liner and the presence of gas were the main drivers to analyze the most likely scenarios for the cement job. The analysis describes that by managing the hydrostatic pressure of the fluids by applying pressure in the backside makes it possible to maintain control of the wellbore—without influxes or losses—before, during, and after the cement job. Nevertheless, to achieve the most reliable hydraulic modeling, critical parameters were identified for use as part of the input for a state-of-art cement simulator. The scope of the cementing job for this case study was designed using a state-of-the-art simulation software to determine expected hydraulics outcomes. The main target was to maintain the bottomhole Equivalent Circulating Density (ECD) between 12.2 and 12.4 ppg during the entire cementing job operation. This 0.2-ppg margin was achieved by applying designed Surface Back Pressure (SBP) by using an MPC operational technique and finishing in a statically overbalanced condition. Dynamic pore-pressure and leak-off tests performed before the cement job confirmed the operating window. The information obtained was analyzed using appropriate software. This previous data was important to define appropriate fluids volumes and design to calculate the minimum SBP necessary for the safe execution of the job, always aiming to reduce chances of kicks and mitigate losses. The cementing operation was performed according to the planned procedure, with no deviations, and the cementing job was performed in accord with the pumping schedule and SBP. Displacement was completed with zero mud losses, and lift pressure was observed as expected. MPC is a recommended method for zonal isolation in such cases as a small operational window, even more so when challenging deepwater scenarios are encountered. A case study of this cementing job is presented in this paper to discuss the planning process, details of the execution, and lessons learned.