Overcoming Challenges and Optimizing Liner Deployment in Long Laterals
A North Sea field development included installation of long 4½-in. completion liners in the horizontal reservoir sections of each well. To minimize overall risk, the operator planned to use managed-pressure drilling (MPD).
A North Sea field development included installation of long 4½-in. completion liners in the horizontal reservoir sections of each well. To minimize overall risk, the operator planned to use managed-pressure drilling (MPD). Despite the expected positive effects of MPD, a strong understanding of the downhole dynamics during deployment of the lower-completion liner was needed. To address this challenge, the operator installed a newly developed work-string-dynamics logging tool directly above the liner-hanger-running tools.
Logging-Tool Technology Overview
The logging tool is a compact and robust memory-based surveillance tool made for drillpipe-conveyed well operations. It is designed, manufactured, and maintained to be used without being a weak point in the string. The tool is equipped with an electronics package consisting of sensors, batteries, and memory.
The logging tool records
- Axial loads (tension and compression)
- Torque (left/right)
- Pressures (absolute internal pressure, absolute external pressure, and differential pressure)
The logging tool is typically shipped to the rigsite ready to be run in the well. The rig crew treats the tool as though it is a standard drillpipe pup joint, eliminating the need for dedicated field personnel and increased personnel on board. After starting logging, the tool can log for 36 days continuously, enabling multiple installations on a single battery package.
Logging Tool Description
The tool consists of three major components—a main body, housing, and a tool joint. The main body (inner mandrel) contains the electrical package with sensors. The housing protects the electrical package and is installed on the outside of the main body. The tool joint is mounted on the lower section on the main body. Axial loads on the tool are transferred through the main body and the tool joint; the housing is not exposed to axial loads. Torque is transferred through a robust spline system.
The logging tool was placed directly above the liner-hanger-running tool in the installation string on seven liner deployments in this campaign. For all installations, both the primary logging tool and the backup were started at the base before shipment to the rigsite. This allowed for testing and field verification of the tool’s memory and battery lifetime. After completion-liner installation, the operator recovered the deployment string to surface with the logging-tool memory sub, which was then shipped back to the workshop onshore. The vendor then downloaded the data for analysis.
In total, the logging tool had more than 27 days of operational time in the well for this project. On several of the jobs, the tool returned with full memory after having logged data for 36 days.
Over the course of the project, the logging tool recorded
- Downhole data of up to 10,486-psi absolute pressure
- Differential pressures of up to 3,814 psi
- Axial loads of up to 82 tons of compression
- Tension of up to 63 tons
- Torque values of up to 15,000 lbf-ft
- Temperatures as high as 116°C
Key Log Data
The key log data recorded during the campaign were torque, axial loads, and pressure.
Torque modeling is performed to understand effective torque transfer from surface to downhole and to ensure that operations do not jeopardize the integrity and functionality of any downhole connections or tools in the well.
Accurate and detailed axial-load data near the liner-top tools confirmed the successful and unsuccessful setting of liner-top packers.
Pressure is often used to manipulate and operate downhole tools in various ways. Often, operators are reliant on surface pressure readings and manipulation of rig pump rates to achieve the desired pressure to operate these tools. However, other pressure variations occur downhole without a means of monitoring at the surface. Closed-end displacement, piston effects from pipe movement, and varying fluids with differing specific gravities result in pressure variations at depth. These variations can influence liner installations in unexpected ways. In the operator’s project, this phenomenon was observed when differential pressure downhole resulted in lost seal rings on the lower-completion liner-hanger-running tool.
Rotating the Liner. In this project, downhole data were applied to evaluate actual liner-top torque when the liner needed to be rotated and worked to its final depth. Liner connections and downhole completion tools have limited robustness, and the operator performed modeling to determine maximum allowable surface torque so as not to jeopardize liner integrity. The downhole data at the liner top provided valuable input to refine this modeling when it became necessary to rotate the liner and work it to bottom.
Packer-Setting Signature. In this project, downhole data acquisition provided detailed axial-load data, which helped identify how much compression is set down on the packer during the operational sequence to set the liner-top packer. Setting a liner-top packer results in a distinct and repeatable load and pressure signature. This signature can be useful in providing confirmation that the packer has been set properly.
Lost Packoff Seals. The ability to analyze downhole pressure variations was helpful in troubleshooting why seal rings were lost from the packoff-seal stack on the liner-running tool. The cause was differential pressure across the seals when the liner-hanger-running tool was released from the lower completion.
Overall Campaign Results. Downhole data captured by the logging tool helped quantify and refine torque-transfer modeling, allowing for a more aggressive rotation of the completion liner while remaining within the design limitations of the equipment. This was an important use of these data because one-third of the wells in this campaign required rotation of the completion liner during deployment.
The logging-tool data were also valuable in troubleshooting unexpected results, determining root causes quickly, and developing rapid mitigations in subsequent wells.
Downhole data helped the operator improve operations continuously and prevent failures and nonproductive time through
- Renewing a focus on prevention of premature liner-running-tool release
- Optimizing the packer-setting operational sequence to prevent failures
- Managing differential pressure to prevent running-tool seal damage and potential fishing operations
Conventional vs. Floated Liner Deployment. Load data provided additional input for friction-factor tuning and refinement of torque-and-drag modeling efforts. The initial wells in the campaign all deployed the liner conventionally, filling the deployment string as the liner was run in hole. This worked reasonably well for the first six wells in the campaign, although half of them required rotation and working down of the completion liner.
After a particularly challenging liner deployment halfway through the campaign, the project team realized it would be necessary to implement the contingency option of floating the lower-completion liner.
Conventional and floated liner deployment resulted in very different axial loads and pressure responses. Having a logging tool in the deployment string allowed for a comparison of these approaches.
After the initial floated liner deployment was proved successful, floating the liner was adopted as a best practice on all subsequent wells of the campaign. In total, five wells used floated liner deployment and achieved greater operational efficiency and a 1% improvement in actual liner depth relative to planned liner depth. Only one of the floated completion liners required rotation to achieve planned total depth.
A work-string-dynamics logging tool can provide greater insights than common surface parameters into the forces actually experienced by tools at depth in wells during deployment of the lower completion and liner-hanger system. Additionally, the use of a downhole logging tool in multiple wells allows operators to compare loads and pressures experienced during these operations across several wells. This incremental detail is helpful for optimizing operations and troubleshooting challenges. Because downhole data help in quickly understanding operational challenges and identifying root causes, failure investigations are streamlined and the time to develop countermeasures to mitigate against repeat failures in upcoming wells is shortened.
In combination with drilling-and-completion design improvements on the front end of the project, the improved understanding of the downhole dynamics related to liner deployment played an important role in the success of the recent 11-well field-development campaign in the North Sea. On average, this program achieved 98.9% of the planned completion-liner total depth, a substantial improvement from the previous campaigns, as shown in Fig. 1.
This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 181288, “Overcoming Challenges, Improving Understanding, and Optimizing Liner Deployment in Long Laterals,” by Kim Daniel Mathisen, SPE, Tore Sørheim, SPE, and Tom Rune Koløy, SPE, Trican, and Neil Decker, SPE, Hess, prepared for the 2016 SPE Annual Technical Conference and Exhibition, Dubai, 26–28 September. The paper has not been peer reviewed.