Abstract

South Texas is predominantly known for high pressure and high temperature formations resulting in the primary production of gas. As operating companies produce from shallower sands, deeper sands are the new targets. This is of major concern since the well now has a shallower low frac tolerance with the limitation of a high pore pressure on the deeper pay zone. Consequently, there is an increased probability of lost circulation and gas migration. With focuses on annular cement adhesion along with solutions to lost circulation, oil and gas companies have utilized a new approach toward zonal isolation. This approach includes incorporation of impermeable and fibrous slurries along with an engineered spacer design.

Previously, conventional cement systems were used to provide a means of zonal isolation. With the introduction of depletion and the intensity of gas migration, conventional cement systems were proving to be ineffective. Cement evaluation showed relatively non-isolated zones as well as a significant amount of free pipe. For years, service companies have strived to produce cement systems that would provide effective zonal isolation and combat any types of gas invasion. South Texas sandstone formations proved to be a candidate to test the new fibrous gas impermeable slurries and introduce the market to a high quality cement system that would combat both lost circulation and gas migration.

While drilling through depleted sands, many drilling companies have encountered partial to total losses of relatively expensive oil-based muds. Special case studies will be introduced to represent the value and recognition of the new fibrous cement slurries. In combination with various types of cement and additives, losses were prevented and drilling could be concluded successfully. Cement evaluation was completed and shown to have a dramatic increase in the percentage of pipe isolated and the top of cement achieved. Comparisons will be displayed showing cement evaluation prior to the new technology and the new representation seen today.

With the introduction of new impermeable fibrous slurries along with special mud removal techniques, drilling companies have adopted these slurries as cures and have chosen this as a solo alternative for isolating their producing zones. Drilling companies have seen the benefits of pumping new slurries in order to prevent future remedial work. This method of cementation has proved to be a significant improvement in South Texas; where the adaptation to new technology is limited to null.

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