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Document Type

Original Article

Subject Areas

Geology

Keywords

Elastic properties, Kafr El-Sheikh formation, Rock strength, West delta deep marine Egypt

Abstract

Numerous challenges were encountered during the drilling operations conducted at the Sapphire oilfield. Instances of stuck pipe, wellbore instability, breakouts, and washouts have been documented in many wells within this field, resulting in unproductive time and additional expenditures. To mitigate these challenges, it is important to conduct a one-dimensional geomechanical model to get a viable resolution. This entails the creation of three primary in situ stress profiles and the assessment of mechanical characteristics of the geological formations. The primary focus of this investigation was to ascertain the mechanical characteristics of the rock. Therefore, this work offers great input while building a comprehensive one-dimensional mechanical earth model in a set of wells situated in the Sapphire field, which is situated inside the West Delta Deep Marine region. Nevertheless, the understanding of these values is impeded by the lack of extensive rock mechanics testing data, encompassing both mechanical and elastic characteristics. The rock's mechanical properties were calculated using empirical equations due to the lack of core sample data, which required using wireline data instead. The unconfined compressive strength in the present study was calculated based on Young's modulus correlation, initially developed by Dick Plumb, and it showed a good correlation with the well events. Using the rocks' geomechanical properties helps explain the formation's fracability and shows how likely it is to collapse. The occurrence of wellbore instability issues is more probable in shale intervals compared with other geological formations. These results revealed that the shale beds are most likely to fail as Poisson's ratio and Young's modulus of shale are all rather high, but they have a lower friction angle. Hence, to prevent instability issues, the proposed wells must be meticulously engineered.

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