Published: 06/18/2019
Published: 06/18/2019
An operator was completing the initial development phase in the North Sea with six horizontal oil wells and eight water injection wells. While drilling and cementing the injector wells, the operator encountered severe lost circulation issues. Only one out of seven cementing jobs in the 12 ¼-in section was executed with full returns.
Adding to the challenge, the operator needed to set the casing of an upcoming injector well into depleted sandstone to provide adequate pressure support to the target area. This reduced the fracture gradient considerably. The operator needed to control fluid losses and ensure successful cement placement around the shoe to avoid water injection into the undesired formation.
Reviewing the data from previous operations in the field revealed that losses were present while running casing, prior to cementing operations. To optimize mud removal and ECD management in the narrow window between the fracture gradient and pore-pressure gradient, Schlumberger ran simulations of different fluids and lost circulation material (LCM) using CEMENTICS zonal isolation software. The team recommended adding Losseal Microfracture lost circulation control treatment into the spacer and CemNET advanced loss-control fiber technology into the cement slurry. In collaboration with M-I SWACO, a Schlumberger company, the cementing team also proposed pumping WARP advanced fluids technology with treated micronized weighting agents to help deliver lower ECD values.
Schlumberger executed the cementing operation as planned with no losses once the spacer exited the casing shoe, confirming that Losseal Microfracture treatment and CemNET loss-control fiber technology combined to minimize losses. The casing was successfully pressure tested to 26.1 MPa and the operator confirmed a 45-m circumferential cement barrier above the reservoir—50% higher than the 30-m acceptance criteria. In addition, the engineered LCM treatments helped the operator exceed the formation integrity test objective by 13%, avoiding costly, time-consuming remedial operations compared with offset wells. As a result of this successful application, the operator plans to deploy Losseal Microfracture treatment and CemNET technology to stop lost circulation in future field operations.
Challenge: Control lost circulation while cementing water injection wells in a troublesome formation with depleted zones and a narrow operating window between pore and fracture pressure.
Solution: Combine Losseal Microfracture lost circulation control treatment with CemNET advanced loss-control fiber technology to mitigate fluid losses and ensure cement integrity.
Results:
