High-Pressure High-Temperature (HPHT) reservoirs offer deep-sea drilling operations that pose great operational challenges due to tight mud weight margins and high in-situ operating stress levels that are likely to cause wellbore collapses and fracturing. The conventional geomechanic model employed is an idealized elastic model and has not undergone calibration with rock strength parameters based on laboratory measurements or in real time with field data to prevent non-productive time. The proposed research is based on a hybrid geomechanical modeling framework which integrates systematically the true triaxial lab test data such as unconfined compressive strength (UCS), cohesion, friction angle, and elastic moduli along with field logs such as density, sonic velocity, resistivity and caliper measurements of HPHT wells. The design of core plugs with confiningpressure up to 70 Mpa was regarded to be under realistic conditions such as the real reservoir environment, whereas Eatons method of field-derived stress profiles and breakout analyses were used to estimate the horizontal stress of the core plugs. The hybrid model involved failure criterion according to the Mogi-Coulomb model, and the time dependent behavior like creep was considered by introducing viscoplastic modeling. The findings proved to be more accurate in predicting zones of collapse pressure and time-varying stability windows than in the traditional log-based geomechanical methodology. It has been validated with caliper log breakouts, stuck-pipe events and mud loss intervals to verify the effectiveness of the workflow with an accuracy of 79.58% of wellbore stability classification. The approach to integration developed under this approach enhances the design of safer drilling and enhanced risk management of HPHT wells by effective calibration of rock strength and realistic stress analysis.
Marvellous Amos2 John Lander Ichenwo*1 (Wed,) studied this question.