Schlumberger has launched the CemFIT Shield* mud-sealing cement system that provides the industry’s first zonal isolation technology specifically designed to improve isolation between hydraulic fracturing stages in long horizontal wells.
Long horizontal wells with multistage completions face drilling fluid removal challenges due to limited centralisation and casing movement that increase the risk of zonal isolation due to drilling fluid channeling. The CemFIT Shield system interacts with residual nonaqueous drilling fluids to limit the detrimental effects of channeling and reduce fluid mobility, which lowers the risk of fracturing fluid migration from zone to zone behind the casing.
Given the increasing trends in longer horizontal well sections with reduced spacing between stages, conventional well integrity methods are reaching their technical limits.
“Measurements taken in horizontal wells indicate that up to 30 per cent of hydraulic fracturing stages communicate with neighboring stages during fracturing treatments, which means that some stages are overstimulated and others may not be stimulated at all,” said James R. McDonald, president, Well Services, Schlumberger. “The CemFIT Shield system delivers more complete zonal isolation, leading to improved well stimulation through better control of the fracture initiation point.”
Extensive laboratory and field testing demonstrated that the CemFIT Shield system is compatible with common oilfield cementing additives, blending processes, equipment, and design considerations, making it easy to use in the field.
In the Permian Basin, the CemFIT Shield system helped an operator improve cement bonding and limit channeling in four long horizontal wells with 10,000-ft laterals. After the cementing operations, cement bond logs for all four wells recorded, on average, a 55 per cent improvement in the bond index, confirming superior zonal isolation compared with offset wells cemented with conventional methods. In addition, preliminary evaluation of microseismic data from subsequent fracture stimulation treatments indicates that fracture lengths in one well cemented with the CemFIT Shield system were as much as 44 per cent longer compared with fracture lengths in a neighboring well cemented with conventional cement.
The CemFIT Shield system improves zonal isolation in long horizontal wells to ensure efficient hydraulic fracturing, avoiding the need for additional investment to mitigate drilling fluid channeling.
*Mark of Schlumberger