Construction of a Mechanical Earth Model to Determine a Safe Mud Window in one of the Southwestern Oilfields of Iran

Document Type : Research Paper

Authors

1 Department of Chemical and Petroleum Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran

2 Department of Mining Engineering, Faculty of Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran

Abstract

In contemporary oil and gas industry projects, there is a notable prevalence of technical and economic obstacles. As a result, mitigating non-productive time (NPT) is imperative in preventing loss, kicks, and instability. The precision of pore pressure and fracture pressure forecasts is pivotal in ascertaining the normal compaction trend. This research has introduced a mud window model based on the geomechanical attributes of a prominent oilfield in the southwestern region of Iran at a depth of 4000 to 4309 meters (Fahliyan Formation). The Earth model was formulated utilizing Geolog v.19 software. In addition, the initial phase encompassed the determination of the Normal Compaction Trend, followed by a comparative evaluation and selection of the optimal function. Moreover, pore pressure values were established using the Eaton method and correlated with data collected from the oilfield and its vicinity. Furthermore, establishing the optimal correlation among sonic velocity, density, and resistivity logs is essential to initiate the mud window. Also, the fracture pressure prediction was conducted using the Breckels-van Eekelen and Hubbert-Willis methods. In addition, the results aligned with the drilling report, but the Hubbert-Willis method aligned more closely with the LOT and FIT test results. Moreover, a comparison of in-situ stress between the oilfield and the well indicated that, despite the prevalent slip-strike fault stress map, the stress regime of this well was normal. Ultimately, the in-situ stress was determined by overlaying the stress polygon obtained from the sonic log with the one derived from the Mogi-Coulomb analysis. Analysis of the optimal mud window using various failure criteria indicated that the Mogi-Coulomb criterion takes precedence over other failure criteria. The optimal mud window ranges from 13.5 to 13.95 at a depth between 4002 and 4309. The Mohr-Coulomb failure criteria resulted in underestimating the optimal mud window compared to other criteria.

Keywords

Main Subjects

References

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Journal of Petroleum Research
Volume 35, 1404-4 - Serial Number 143
November and December 2025
Pages 125-149

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