North Sea Cementing Enables Waterflood Success | SLB

North Sea Operator Improves Cement Bonding to Achieve High Waterflood Injection Rates Near a Weak Shale Zone

Published: 10/09/2020

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Protect weak shale to enable waterflood

For a new injector well, a deviated 300-m [984-ft] well segment was drilled through the unconsolidated sandstone formation and the shale caprock formation using oil-based mud.

Achieving competent cement isolation across the weak shale was critical to enable high-pressure water injection into the sandstone and achieve target production rates from the heavy oil reservoir.

Overcome mud removal challenges

The 9 5/8-in liner for the section was run with only one centralizer per joint to minimize torque and drag force to ensure the liner would reach TD. Previous experience with placing conventional Class G cement across the interval under similar constraints showed that challenges related to removing oil-based mud inhibit optimal cement bonding, often leaving permeable mud channels even after following industry best practices.

Ultrasonic log showing high cement bonding in a 300-m segment of a North Sea water injector well.
Ultrasonic log shows CemFIT Shield system eliminated mud channeling across the full cemented interval. Competent isolation enabled high-pressure injection into the sandstone formation to optimize the waterflood.

Interact with leftover drilling fluid

CemFIT Shield mud-sealing cement system improves bonding by interacting with nonaqueous drilling fluid left on downhole wellbore surfaces after hole cleaning to limit channeling—without detrimental effects on slurry or set cement properties.

Deliver cement, log the well, test injection

A volume of 11 m3 [69 bbl] of CemFIT Shield system was mixed and continuously pumped into place without operational issues. A wireline ultrasonic imaging tool (USIT) log result showed highly competent, well-bonded cement across the 288-m [945-ft] cemented interval, including 63 m [207 ft] of highly bonded cement across the unconsolidated sandstone. The log showed no mud channels.

After the operator perforated the sandstone, an injectivity test verified water injection at the desired high pressure to optimize the waterflood.

North Sea, Europe, Offshore

To achieve waterflood isolation requirements in a well with mud removal constraints, a North Sea operator turned to an innovative technology that delivered competent, highly bonded cement.

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