Lost circulation is the partial or complete loss of drilling fluid and/or cement slurry to the formation during drilling or cementing operations or both. This can be brought on by natural or induced causes. Natural causes include situations such as naturally fractured formations or unconsolidated zones. Induced losses occur when the hydrostatic fluid column pressure exceeds the fracture gradient of the formation and the formation pores break down enough to receive rather than resist the fluid. When lost circulation occurs, it can provoke new requirements of time and mud or cement - and add substantially to the overall cost of a well.
Typical ways to address lost circulation during cementing operations is with bridging or plugging material, the use of rapid-set or thixotropic cement, or with lightweight cement systems.
- Reduce the slurry density (lightweight cement)
- Add a bridging or plugging material
FracSeal™ cement is a low-density cement that can be designed to handle low-fracture-gradient wells while maintaining sufficient hydrostatic pressure to manage pore pressures effectively. It has high-viscosity and expansive forces to help with hole cleaning and displacement and superior bridging by combining lost circulation materials with inherent diverting capabilities of foam cement. FracSeal cement should be considered in situations where loss of whole fluid to the formation is anticipated. FracCem™ cement should be considered in areas where foam cement is not available.
Tuned® Light cement comprises a family of low-density conventional cements designed to increase the probability that cement will circulate up the annulus and not out to the formation. Tuned Light cement provides superior bridging by combining lost circulation material with the inherent diverting properties of microspheres. Tuned Light cements can be designed to low slurry densities enabling a reduction in the equivalent circulating density.
Additional Halliburton solutions to address lost circulation include: