Geomechanical Earth modelling to investigate the wellbore instability analysis for Eridu oil field.

Wellbore instability is the main problems that faced through drilling operations such as kick or blowout, stuck pipe and lost circulation which takes extra time to treatment, also increase time of nonproductive and expenditure of well drilling. The purpos of study is constructed one dimensional geomechanical model for Eridu oilfield by using open hole log measurements such as(Density, Sonic compression and Shear wave velocities, Gammaray, Caliper, and Bit size). These logs are incorporated into the software for computing componts of 1D-MEM (Rock mechanical characteristics, pore pressure, in-situ stress magnitudes and orientations). these parameters calibrate with field measurements tests such as repeated formation pressure,hydraulic fracturing and labatory core testing. Then validate the model by coupling with several failure criteria such as (Mogi Coulomb, Modified Lade and Mohr Coulomb) to detected best failurea criteria. The results showed the most suitable failure criterian for Eridu oilfield is Mogi Coulomb. The results of sensitivity stability analyses appeared the value of safe mud weight window was 10.5 ppg and become narrow with deviation higher than 35 degree, while breakout mud weight didn't had affected by wellbore azimuth becouse contrast of low-stress. Furthermore, to prevent shear failure should be drilling with inclination less than 35 degree and to prevent breakdown should be drilling with inclination between (25-65) degree both, in direction of mini-horizontal stress. These outcomes could be used to prevent wellbore instability occur and determine appropriate mud weight window when planning to drill nearby wells in future. Also, to achieve better drill effectiveness and use as cost-effective tools. [ABSTRACT FROM AUTHOR]