The present-day stress state of the Abadan Plain in Southwest Iran is a critical factor in the management of drilling operations and reservoir development. This research integrates multiple data sources, including borehole image logs, leak-off test (LOT) data and petrophysical logs from 11 wells, to characterize the regional stress field. Borehole breakouts and drilling induced fractures were analyzed to identify the orientation of the maximum horizontal stress (S_Hmax), which was found to consistently align in a northeast-southwest direction across the region. Using a stress polygon method, results showed that the S_Hmax values ranged from 50.78 MPa to 62.1 MPa in the Gurpi Formation, from 92.91 MPa to 116.82 MPa in the Gadvan Formation and between 114.48 MPa and 127.23 MPa in the Fahliyan Formation. The results also revealed that the region exhibits a consistent strike-slip stress regime, with S_Hmax > vertical stress (S_V) > minimum horizontal stress (S_hmin) in multiple wells, which has important implications for fault reactivation and drilling operations. These insights are crucial for improving drilling practices, understanding fault reactivation, and making informed decisions for future exploration and development in the area.

In-situ stresses are highly important for wellbore stability studies during drilling, completion and production. Different methods are available to estimate the horizontal stresses especially maximum horizontal stress. Typically, Circumferential Borehole Image Logs can be run to determine the direction and width of breakouts and then stresses at different depths based on the equation developed by Barton et al. (1988). This research focuses on image logs from Harvey-1 well located in the Southern Perth basin to compare the maximum horizontal stresses obtained by various methods. The magnitudes of stresses from the breakout width approach (Barton's method) exhibit a considerable offset in comparison with elastic methods. Further investigations show that the likely reason for the offset relates to the fundamental assumption of the breakout width approach in which shear failures are considered to be constrained to horizontal planes. Failures within the wellbore are not necessarily horizontal and can be developed in different non-planar trajectories with various angles to the horizontal plane. Furthermore, the possible in-situ stresses from regional studies are constrained by means of stress polygons against which the reliability of results from breakout methods can be checked. Results indicate that due diligence and special care must be exercised for determination of maximum stresses from breakouts and more reliable methods are required than those currently used.