| Popis: |
In the last years the quest for hydrocarbons findings moved into extreme drilling condition, such as ultra-deep waters, ultra-high temperatures and drilling fluids densities. Adding to these the very narrow density windows (reservoirs with very low differential fracture pressure - pore pressure), both operators and drilling fluids service companies faces increased challenges to deliver the well for production. It is common that for such applications the bottom-hole static temperature is over 180°C/356°F, even reaching temperatures in excess of 250°C/482°F in some fields, acid gases (CO2, H2S) are also present, so the list of challenges is formidable. In this paper, the authors details the common challenges for such extreme conditions wells and best practices, present a new generation synthetic-based fluid capable to withstand temperatures in excess of 500°F/260°C, as well as a unique hydraulics engineering calculations software which enable real time equivalent-circulation density (ECD) calculations. The design and development of the mew ultra-high temperature mud system is presented and its components. At the core of the system it is a new amine-free emulsifier, which is stable to temperature above 300°C/572°F. In addition, the authors will present the extensive lab work required to optimize the formulation for high densities and extreme high temperatures, detailing also the critical fluids engineering guidelines for drilling in such harsh conditions. Using laboratory, field, and computer data, the authors will demonstrate the effectiveness of the new fluid in delivering optimum drilling in extreme HTHP conditions. Also, it is illustrated how the rheology is maintained at minimum level with a micron-size weighting material, and the engineering software used for pre-planning and while drilling to accurately calculate the ECD and maintain it within the required range. |
