Increasing Drilling Operational Margins of an Onshore Mature Field in Pakistan by Including a Dynamic Drilling Modeling Approach

Abstract

Access to new reserves and subsequent production is becoming a challenging scenario for oil and gas companies all over the world. In this particular context, a major operator planned an onshore well in Pakistan (located 350km north of Karachi) as part of a revamped drilling campaign in this mature field. However, in previously drilled wells in the vicinity several drilling issues were encountered including, but not limited to, a challenging drilling window with kicks and losses. These are mainly due to formation structural conditions that require very strick control of the equivalent circulating density (ECD) and the equivalent static density (ESD) for new wells drilled in the area. If successful operationally and if reserves prove economically exploitable, this well will be used as potential reference for future infill drilling in this reservoir. To overcome the issues and ensure the greatest potential to successfully drill this well, it was decided to use managed pressure drilling (MPD) equipment for the last two challenging well sections. Because of this, a full dynamic drilling modelling solution was selected to support the planning phase and subsequently, the decision process during the operations. The dynamic models applied include consideration of temperature, pressure, mud compressibility and rheology as well as gel breaking effects in a transient simulation. For well control considerations a two-phase model considers both influx of the reservoir fluid and modelling of the fluid properties by equation of state as well as distribution and migration of the influx in a drilling kick scenario. As direct result of this study, it was decided to revise and slightly adjust the optimized drilling fluid weight to better manage the ECD/ESD, thereby avoiding compromising the integrity of the well during the operations. Some of the specific parameters were re-defined based on the modelling results, providing enhanced best practices for the MPD utilization. The implemented approach required the drilling practices to be tailored for this particular well and opened the opportunity to implement the lessons learned into the company well design process and drilling practices. For this, a multi-domain collaboration is key to minimize the uncertainty associated with the behavior of the drilling dynamics with respect to the drilling window and the overall operational system. In addition it requires the inclusion of dynamic modelling to provide a more realistic planning approach makes it possible to consider different drilling opportunities in mature fields with challenging profiles. This paper will describe the analysis done using this dynamic drilling modelling approach, with focus on the primary and secondary well control.