In this thesis a full well design and detailed tubing design has been developed for the HPHT well K-14. Wellcat™ casing design software has been used for tubing string analysis. K-14 has been designed using the same conditions as for wells in the Morvin HPHT field. The main issues related to this specific well design are the completion of the reservoir section, the tubing design with all relevant loads, and a HPHT well design with flexibility for intervention and stimulation by hydraulic fracturing. The reservoir drainage plan is based on wells with horizontal reservoir sections for optimal and cost effective recovery. The tubing has been designed and engineered for all the loads that the well may be exposed to during its lifetime. It is very important that all possible loads have been investigated, so the well complies with the HPHT requirements. The loads seen by the well can be divided in two groups: the loads induced by production and the loads during installation (qualification/pressure testing) and intervention.The focus of the well design has been to achieve optimal drainage with a simple and flexible solution to meet the requirements for intervention. Extreme loads may occur for wells in HPHT fields. There are additional aspects to consider when engineering these wells, such as steel and material degradation when exposed to high temperatures, and large temperature variations from production to bullheading with cold fluids. The effect of extreme temperature changes are seen by the liquids in the closed annuli, they will expand/contract resulting in an increase/decrease in pressure seen by the tubulars. The temperature variations will also affect sealing elastomers that are under high pressures, making them brittle and reduce/loose the sealing capacity. The aspects of well design and tubing design are discussed in detail through the development and engineering of the HPHT well K-14