Design and Performance Evaluation of a Unique Deepwater Cement Slurry

Abstract

The exploration and development of deepwater hydrocarbon resources necessitate the fast evolution of drilling and completion technologies for deepwater wells. To drill and complete deepwater wells successfully, sophisticated technologies need to be developed to solve various problems arising from low temperature, weak formations, shallow water/gas flow, environmental protection, and high deepwater rig rate.It is a challenge to develop a good cement slurry that can be used successfully for deepwater wells under low-temperature environment. Such cement slurry should have several distinct properties, such as a short thickening time, a fast transition from liquid to solid, a rapid development of compressive strength, and environmental friendliness. It usually takes a long time for conventional cement slurry to set and only limited compressive strength can be achieved at low temperatures. In addition, most additives used for the conventional cement have adverse effects on the environment. Therefore, it is of upmost importance to design an environmentally friendly and low-density cement slurry that is appropriate for deepwater wells.In this paper, a new deepwater cement [sulfur polymer cement (SP-C)] was designed and tested for the first time. This new deepwater cement combines the advantages of the sulfoaluminate cement and Class G oilwell cement. Green cement additives including cement dispersant, fluid-loss-control agent, and accelerator were also developed. Consequently, a unique low-density cement slurry was obtained for deepwater-well applications. Laboratory tests showed that the low-density slurry exhibited favorable properties including the nonexistence of free fluid, an excellent fluid-loss-control capability, a short waiting-on-cement time at low temperatures, and a shortened transition time of critical gel strength. This new cement slurry can be easily prepared and applied in deepwater wells without adverse impacts on the marine environment.

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“…For example, China's Bohai Oilfield, East China Sea Oilfield, South China Sea Oilfield, etc. have already become important energy reserve areas in China (Wang et al 2011, Wang et al 2009, Luo et al 2017, Bu et al 2020. However, the complexity of the deepwater environment, especially the brittle failure of the cement sheath and the sinking of the wellhead (Ravi et al 2009), has brought huge challenges to the exploration and production of deepwater resources (Lv et al 2021, Tian et al 2022, Zheng (2023).…”