The contribution investigates the relationship between in situ stress regimes, natural fracture systems and the propagation of induced hydraulic fractures in APLNG's (Australia Pacific Liquid Natural Gas) acreage within the Jurassic to Cretaceous Surat Basin in southeast Queensland. On a regional scale the data suggest that large basement fault systems have significant influence on the lateral and vertical interplay between geomechanical components which ultimately control permeability distribution in the area. At a local scale we show several case studies of significant in-situ stress variations (changes in tectonic regime from reverse to strike-slip, changes in horizontal stress orientation as well as changes in differential horizontal stress magnitude) which are identified from wireline image log interpretations and geomechanical models constructed from wireline sonic and density data. These variations are reflected in hydraulic fracture propagation, which is monitored through microseismic monitoring, tiltmeter monitoring. Reverse stress regimes result in the propagation of horizontal fractures; in areas of higher differential stress linear hydraulic fracture orientations are common, whereas in regions of lower differential stress the orientation of hydraulic fractures appears influenced by both stress and pre-existing fractures. The paper is relevant for fracture simulation in areas with complex in-situ stress regimes. The major technical contribution of the study is the use of geomechanical modelling for predicting hydraulic fracture propagation styles.

We present regional in situ stress analyses based on publicly available log and pressure data from coal seam gas developments in the Permian Bowen basin, Australia. Together with earlier data from the eastern part of the Jurassic Surat basin, our results show a broad, but systematic, rotation of SHmax azimuths in this part of eastern Australia as well as systematic changes in stress state with depth. Overall, the geomechanical state of the region appears to reflect the interplay between basin-controlling structures and a complex far-field stress regime. At the reservoir level, within and between Permian coal seams, this stress complexity is reflected in highly variable stress states both vertically and laterally. Stress data, including direct pressure measurements and observations of borehole failure in image logs, have been used to calibrate sonic-derived one-dimensional wellbore stress models that consistently exhibit a change in tectonic stress regime with depth. Shallow depths (<600 m) are characterized by a reverse-thrust stress regime and deeper levels are characterized by a strike-slip regime. Changes in the stress state with depth influence the mechanical stratigraphy of rocks with widely contrasting mechanical attributes (coals and clastic sediments). Our results highlight the interdependency between regional tectonic, local structural and detailed rheological influences on the well scale geomechanical conditions that have to be taken into consideration in drilling and completion designs.Supplementary material: Database of additional wells with image log data are available at https://doi.org/10.6084/m9.figshare.c.3785849

&lt;p&gt;The Upper Triassic evaporites of Western Europe, also known as the &amp;#8216;Keuper&amp;#8217;, are well-known and have been mostly considered as an efficient d&amp;#233;collement level for the thrusts of the external fold-and-thrust belts. Numerous recent studies aimed to reappraise their role, and especially the role of salt tectonics, in the formation of several mountain belts such as the Pyrenees, the Betics, Provence, and the Alps.&lt;/p&gt;&lt;p&gt;The Western Alps represent a good laboratory to study the role of salt in shaping a mountain belt because it contains areas with (1) no evaporites, (2) evaporites involved as an efficient d&amp;#233;collement level during orogeny and (3) evaporites mobilised in salt tectonics since the Lias rifting. We propose here, based on literature and our recent works regarding salt tectonics in the SW Alps, to present and discuss the different salt-related structural styles observed along-strike the Western Alps. A focus will be done on the SW Alps where evaporites influence their structure during the whole Alpine history from rifting until collision. They were mobilised by the Lias rifting through reactive diapirism. Salt tectonics carried on during the post-rift period by passive diapirism, controlled by sediment loading. A few structures were reactivated during the Oligocene and in places evaporites influenced the structure of the subalpine chains until the Mio-Pliocene.&lt;/p&gt;&lt;p&gt;Our study shows that evaporites strongly influence the structure of a mountain belt at different scales and that along-strike variations of structural style are observed along the strike of the Western Alps depending on the presence, the amount or the absence of evaporites.&lt;/p&gt;