Oil production from Southeastern Mexico mainly comes from highly fracturated carbonate reservoirs. The appropriate management of oil production, natural depletion of the reservoirs with time, and continuous upper movement of oil- water contact represent the biggest challenge to isolate properly the production zone in development wells drilled within the area.

Drilling these wells through pay zone typically requires special pressure managed drilling techniques that considers the use of Nitrogen; either as foaming agent of the base polymer drilling fluid or as two-phase component. It can allow achieving the low equivalent circulating densities needed to penetrate the depleted reservoirs. The geological complexity of the area, mainly represented by compartmentalized reservoirs delimited by multiple fractures tied to vertical heterogeneity of the production zone, comprised by limestone and dolomite separated by shaly cap rocks shows the complete picture of the final conditions of the well to be isolated.

In this paper a systematic approach is presented, not only to highlight the use of ultra-light cement slurries1 , but to remark pre-planning, well preparation, downhole tools, equipment and techniques used for cement placement to achieve zonal isolation within target intervals and/or oil-water contact. The main challenge remains the ability to properly isolate intervals that present washouts of more than three times the nominal external diameter of the bit. Also, the omnipresence of very low pore pressures, as low a 0.30 g/cm3 (2.5 lb/gal) of equivalent circulating density.

Therefore, here are presented the different slurry types used to perform these special cementing jobs, and also the operating procedures used by the cement placement techniques. Several examples have been selected to support the effectiveness of the applied methodology. Even though examples are related to a particular location and circumstances within Southeastern Mexico, the designed slurries and placement techniques can be customized to be applied successfully in similar areas.

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