Cementing Technologies of Balanced Off-Bottom Cement Plugs in Eastern Ecuador

Because the setting cement plugs applied in Ecuador oil field have a low success rate, this study explored the factors that influence the stability and quality of cement plugs during operation. It also took targeted measures to develop the cementing technologies of balanced off-bottom cement plugs in Eastern Ecuador. Specifically, low-density and high-strength cement slurry and viscous reactive pills were prepared to solve the problem of the unstable interface between a cement plug and the lower drilling fluid. A drill pipe with a inserted pipe was designed to address unqualified cement plugs due to the excessively narrow annular gap between the drill pipe and the wellbore. A flow diverter was developed to deal with the severe mixture of slurry and drilling fluid caused by the downward slurry spraying due to the lower open end of the drill pipe. Then, sponge balls were prepared to tackle the shortcomings such as no isolation plug in the drill pipe, as well as high costs and complex operations of existing tools. Laboratory tests show that the high-strength cement slurry with a low density of 1.74 kg/L and a compressive strength of 22.5 MPa for 24 h could satisfy the requirements of operations. The viscous reactive pills, with a density of 1.44 kg/L, a yield stress of 48 Pa, and a gel strength of 49 Pa, could effectively support the upper cement slurry. All of the above-mentioned tools can solve quality problems in the cement plug placement. The field application in Eastern Ecuador shows that the developed cementing technologies perform well and can greatly raise the success rate of operations, and thus, it can be widely popularized and applied.