Development of unconventional hydrocarbon resources as a result of horizontal drilling and multistage fracturing has raised several environmental concerns. Long-term zonal isolation provided by cement is one of the major challenges in the completion of horizontal wells since the implementation of casing centralization in the wellbore is a difficult task. This situation can create eccentricity in the wellbore, thus affecting the mud displacement process in the narrow region of the casing. During the mud displacement process, cement has the tendency to flow in the upper wide part of the annulus, thus bypassing mud in the narrow part of the annulus. This causes channeling of the cement in the wide side, leaving slow moving or immobile mud in the narrow region behind. In such cases, the poor cementing can have consequences such as gas migration to surface or water zone and stimulation failure.
Current best cementing practices have deficiencies in providing excellent cementing efficiency especially in long horizontal section of the wellbore. Therefore, a novel technique, using Magneto-Rheological fluid, is proposed to improve the mud displacement efficiency in the narrow side. Magneto-Rheological fluid can act as a smart spacer by a moving magnetic field to balance the fluid flow in the annulus. Consequently, more flow will be directed to the narrower annular region that could not be cemented or swept otherwise. The simulation results on the impact of magneto-rheological fluids as a smart spacer on velocity distribution and volumetric movement of fluids are presented.
Horizontal drilling is a common technique used in unconventional shale gas and oil reservoirs. Horizontal shale wells are often completed with multi-stage fracturing jobs and it is imperative to have high quality cement job to insure zonal isolation, otherwise communication between zones can occur which can result in a lower quality fracturing job and well completion. A poor completion can result in lost production and leaks can lead to ground water contamination and safety concerns. Nelson et al. 2009, Darbe and Ravi 2010, Williams et al. 2011a, Williams et al. 2011b, and Gottschling 2009 discussed the challenges of cementing unconventional reservoirs. Luke and Soucy (2008) reported that 25% of cemented horizontal wells in unconventional plays experienced fracture initiation problems compared to 4% for uncemented wells.