Deepwater region has been an area of intense interest in recent years, due to the hydrocarbon resources in deepwater areas are very captivating for oil companies. Unfortunately, in deepwater environment, where the water depth is greater than 500 m, faced with some new problems such as low temperature, weak formations, shallow water/gas flow, environmental protection issues and high rig rates of deepwater rigs.

Compared with conventional cementing, deepwater cementing is required to have short thickening time, a fast transition from liquid to solid, rapid development of compressive sthrenth and environmental friendly. Conventional cement slurries and low density cement slurries are usually taking a long time to set and can't allow significant compressive strength development at such low temperature. In addition, conventional cement additives are often environmentally unacceptable subject to more stringent environmental regulations. Therefore, it is stringent to design environmental friendly low density cement slurry to overcoming these challenges during deepwater cementing.

As these deepwater cementing problems are concerned, a new deepwater cement DWC, mainly combining the sulfoaluminate cement and class G oil well cement, was designed for the first time. And, various environmental friendly additives, including cement dispersant, fluid loss control agent and accelerator, were developed. Finally, a unique low density deepwater cement slurry was developed.

Laboratory tests show that the low density slurries has exhibited no free fluid, excellent fluid loss control, right-angle-set, short time of wait-on-time at low temperature, and a shortened transition time of static gel strength. The slurries can be simply prepared, conveniently implemented in field and be composed of environmentally friendly additives. Results presented in this paper should help resolving problems in deepwater cementing.

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