Overcoming Tight Annulus Cementing Design Challenges: Gulf of Mexico Case Study

Dooply, Mohammed (Schlumberger) | Sianipar, Sakti (Schlumberger) | Rodriguez, Faiber (Schlumberger) | Poole, David (Chevron) | Fuenmayor, Cesar (Chevron) | Carrasquilla, Juan (Schlumberger) | Rosero, Ivan (Schlumberger)


Achieving successful cement placement in tieback casings and liners on deepwater wells is very critical. One of the design challenges is to displace compressible drilling fluid in the tight annulus within the mechanical limitations of downhole tubulars. Accounting for the compressible nature of drilling fluids with changing pressure and temperature, combined with fluid contamination level, will provide better understanding of cementing dynamic pressure during placement.

Cementing tight annulus normally requires managing high placement pressures within the tubulars mechanical limits. Field measurements from case studies in Gulf of Mexico, were analyzed comparing with simulated cementing dynamic pressure accounting for effect of synthetic based mud compressibility as it is displaced by viscous spacer and cement slurry. The rheology of contaminated mixture also provided an input for better interpretation of cementing surface pressure response. These analyses, including estimating hook load variations while cementing, allow selection of appropriate fluid placement rate without exceeding the mechanical limits while also achieving effective fluid displacement.

Comparison analysis of measured and simulated data shows that use of complete fluid rheology profile at various temperature and pressure provides a more accurate prediction of cementing dynamic pressure in tight annulus cementing with synthetic based mud. This approach also allows a better estimation of the minimum rate required for efficient mud displacement enabling an optimal design of the cement slurry thickening time, when coupled with a representative mud circulation schedule.

Precise annular clearance of tieback strings provides better understanding of fluid positions inside the tieback strings and annulus, which ensures achieving planned top of cement to mitigate annular pressure buildup. This is critical to protect the outer casing against any potential collapse loading in a blowout scenario in deepwater drilling environment.