| Abstract |
Many wellheads had risen due to the increase in the length of casing in the working area of Pertamina Geothermal Energy (PGE) Kamojang and Lahendong. They caused problems related to safety and the decrease of steam production as a source of energy for PLTP Kamojang and Lahendong. Several factors were suspected to affect the extension of the casing namely the fluid temperature, the type of casing / sheath, and poor cement bonding. This research was conducted to find out the effect of fluid temperature on casing related to the rise of wellhead and also to find out whether the tie-back cementing method was effective in minimizing the lengthening of the casing. Besides that, the casing grade related to the length of the casing (congruence elongation) as well as the value of thermal expansion length increase to the casing used was investigated. There were several analyses done in this research that were casing elongation analysis (thermal effect on casing), cement design method analysis and also casing grade result analysis. The data used in this research were well data profile, casing configuration data, cement lab data, cementing SOP used, thermal expansion coefficient and temperature data. The results obtained from the research were the casing length increase of 10-15 cm for two-stage cementing method, while the method of tie-back cementing had not caused the rise of wellheads. Critical temperature (Tc) of casing with an L80 grade ranges from 369 to 375ºF, while that of casing with the C95 grade ranges from 420 to 423.5ºF. Critical depth (Zc) of L3, L4, L5, and L6 wells range from 545 to 806 m with a critical temperature ranges from 369 to 372.5 ºF. If surface steam temperature is higher than the critical temperature then plastic deformation occurs along the production casing. |