Improved Deepwater Cementing Practices Help Reduce Nonproductive Time

Abstract

Over the course of a fo4ur-year period, during which approximately 42 wells were constructed by this operator, processes were developed to improve cement slurry design and reduce nonproductive time (NPT) during cementing operations on deepwater wells. Cementing best practices have been followed for many years; however, not all of these practices are applicable to deepwater operations, especially for the riserless sections. Results of developing (1) slurry design practices, (2) temperature prediction and mud removal modeling, and (3) the use of SSR® subsurface release plugs will be reviewed. The choice of cement blend used can have a profound impact on cost, not only in terms of failure in the event of the wrong design, but also in terms of supply logistics. As deepwater operations move farther away from shore bases, the need for a systems approach to cover all cement design needs from conductor to plugging should be considered. The challenges across this breadth of application range from dealing with shallow water flow potentials to relatively high temperature and pressure. Both conventional and foamed cement slurries can be successfully used in this endeavor when properly designed and placed. Placement design should include a thorough understanding of the static gel development behavior of the drilling fluid. Although it is generally accepted that conventional circulating temperature estimates are not appropriate for use in deep water, the use of alternatives is not always practiced. Over the course of this project, this operator realized better cement slurry performance and lower slurry costs following the correct use of wellbore thermal simulators. Attention to detail in applying the correct data to computer simulations resulted in lower slurry costs while at the same time achieved improved performance as measured by improved casing shoe integrity. Real-time monitoring and detailed pressure analysis were used to manage cementing operations and the correct application of SSR plugs. Feedback of these processes from operators and service tool personnel has resulted in improved job performance as measured through reduced NPT and well construction costs. These new processes have resulted in a 100% success rate as compared to the previous 74% success rate. Introduction In deepwater operations there is always the desire to improve logistics to reduce waste and cost associated with materials and equipment transport.[1] Distances from a shore base increase the importance of this as related to job planning. Current cement shortages in some regions of the world also require that the design take into account materials unique to a given area. Recent R&D efforts have aided in improving logistics associated with cementing the riserless casings.[2] However, this Gulf of Mexico (GOM) deepwater operator has further improved its use of bulk cement to allow flexible slurry designs during the entire drilling operation. Wells currently being drilled in deep water are being designed to put more emphasis on achieving long-term zonal isolation.3 While drilling and completion temperatures may not be as critical as they once were, the deeper wells being drilled have flowing wellhead temperatures that require strength retrogression consideration in the cement design. While this aspect adds to planning considerations, this operator was still able to maximize logistical benefits while minimizing costs.