Casing design (temperature-base) of the K well in ‘NPY’ geothermal field-Indonesia

This study explains the casing design for the K well in geothermal field, that involve high temperature of wellbore about 200 °C – 300 °C. In the wellbore, elevated temperature generates stress that occurs in the casing material, cause casing installed in the wellbore to expand and shrink, and ultimately failure at a certain temperature conditions point. This failure will change the production casing in length, as well as the well integrity. The casing design for geothermal well must consider high temperature first, because the thermal effect on the casing strength, resistance and burst, that cause the maximum joint strength of the casing decreases, and leads to the collapse of the well. This study concludes that the design of geothermal well casing configuration which is suitable for the K well are casing grade L80 for surface section, casing grade S95 for production section, and grade S95 for slotted liner section. which agreed with the design factors for the temperature maximum of plastic deformation i.e. 599.26 F, 667.6 F, and 852.36 F for respectively sections: surface, production, and liner depths. This study also gives a benefit, i.e. recommendation for the field similar characteristics with the K well – Indonesia. Pore and fracture or overburden pressure gradients, is a determinant in casing shoe depth selection, the depth where temperature variation, play role in decreasing the strength of casing material. It must be a major concern. Author suggest a reservoir geomechanics studies on pore and fracture pressures gradient on the reference geothermal well, may provide a comparison in casing depth selection based on resistivity logs analysis besides BPCD.