Title: Geomechanical model of Ratawi shale reservoir

Authors: Raed H. Allawi

Addresses: Thi-Qar Oil Company, Dhi-Qar, Iraq; Petroleum Engineering College, AL-Ayen University, Dhi-Qar, Iraq

Abstract: Borehole instability problems are considered the majority challenge for several wells in the Ratawi shale reservoir, which increase non-productive time (NPT) and increase well-drilling expenditures. This work aims to construct an integrated mechanical earth model (MEM) to predict the wellbore failure and design optimum mud weight to improve the drilling efficiency of future wells. Several failure criteria were applied in this work, including Modified Lade, Mogi-Coulomb, and Mohr-Coulomb, which were utilised to calculate the proper mud weight and practical drilling paths and orientations. Furthermore, those failure criteria were matched with breakout from the caliper and image log to choose the best one. The results indicated that inadequate mud weight was the leading cause of wellbore instability problems. Therefore, the suitable mud weight for safe drilling in the Ratawi shale formation should be 11.5-13.5 ppg. The results indicate that the inclined wells should not exceed 15° and will be more stable parallel to the maximum horizontal stress direction. [Received: February 16, 2023; Accepted: May 7, 2023]

Keywords: wellbore stability; hole-collapse; horizontal stresses; MEM; mud window.

DOI: 10.1504/IJOGCT.2024.136041

International Journal of Oil, Gas and Coal Technology, 2024 Vol.35 No.1, pp.1 - 16

Received: 15 Feb 2023
Accepted: 07 May 2023
Published online: 12 Jan 2024 *

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