INDIRECT PREDICTION OF ROCK ELASTICITY AND COMPRESSIBILITY STRENGTH USING WELL LOGDATA AT SELECTED SITES WITHIN RUMAILA OILFIELD, SOUTHERN IRAQ

Abstract

Wellbore failure is the main reason for about 14% of drilling non-productive time (NPT) for new wells in Rumaila oilfield; these breakouts were observed in Shale and weak shaly Sandstones across the geologic column. The rock mechanical properties which include elasticity (Young’s modulus, Bulk modulus, Shear modulus and Poisson’s ratio) and unconfined compressive strength (UCS) are broadly used in well design and wellbore stability by means of predicting the required drilling parameters that can help to reduce wellbore failure. In this study, an indirect estimation of the rock mechanical properties was carried out using gamma ray, density, sonic (compressional and shear), and Neutron logs. The log data were gathered from four wells (R-518, R-527, Ru-382 and Ru-385) in the Rumaila oilfield, that data cover the geological column from Saadi to Zubair formations. Later, the indirect rock mechanical properties prediction results were compared with the direct measurements that been measured by triaxial mechanical laboratory tests for well R-530 and uniaxial tests on wells R-019, R-062 and R-530 in Rumaila oilfield. The results of indirect estimation of rock mechanical properties showed similarity to direct measurements which make it reliable and can be used for wellbore stability analysis and may contribute effectively in building the geomechanical model.