Applied Wellbore Stability Analysis to Pyrenees Development Area: A Field Case Available to Purchase

Nine infill horizontal production wells were drilled in the Crosby, Ravensworth and Stickle oil and gas fields offshore Western Australia as part of the 2015 Pyrenees development plan. Prior to the drilling campaign, major concerns existed after encountering tight holes when drilling previous vertical and horizontal wells through the siltstones of Windalia Formation and shales of Muderong Formation, which are present above the reservoir section. As the kick-off point for the lateral wells would require high inclination angles (80° and above) that would cut through both Windalia and/or Muderong formations, borehole stability was a priority to be addressed. On top of that, lost circulation events in the Pyrenees reservoir sands in previous wells pointed out that the drilling window could become extremely narrow or nonexistent, as increasing the mud weight to keep the overlying Windalia and Muderong formations stable would potentially create lost circulation in the Pyrenees sands. Therefore, a comprehensive review of a legacy geomechanical model from the appraisal phase was carried out, and by incorporating laboratory rock measurements and drilling experience from the first horizontal wells, a fit-for-purpose model was calibrated and used as a planning tool, and eventually in the real time monitoring while drilling.