Managing Wellbore Instability in Horizontal Wells through Integrated Geomechanics Solutions: A Case Study from a Carbonate Reservoir

Abstract

Abstract Saudi Aramco is one of the pioneers in optimizing hydrocarbon production and reducing development cost using latest technologies aimed to increase gas production and enhance gas recovery. The case study discussed here shows results from an integrated approach used to drill wells in the minimum horizontal stress direction to create multiple transverse fractures during stimulation that helps enhancing production. The real challenge involved in drilling such horizontal wells is to maintain wellbore stability (especially in a transition zone from high porosity to low porosity and vice versa) mainly due to wellbore breakouts and differential sticking. Due to variably depleted reservoir pressures together with geological and structural complexities, pre-drill geomechanical models need to be updated in real-time, which require extra vigilance, in terms of optimizing mud weight while drilling, to address both formation breakouts and risk of differential sticking. If these problems are not addressed in a timely manner, initial signs of wellbore instability can aggravate with time leading to stuck pipe and loss of tool downhole. To address above issues, an integrated approach was applied during well planning and execution phases using prior drilling experience in conjunction with a geomechanical analysis to make recommendations for the planned well. While drilling, potential uncertainties in the geomechanical model due to formation heterogeneity and varying in-situ stresses, were further addressed by updating the model using real-time logging while drilling (LWD) data along with real-time drilling geomechanics (RTDG) support and advanced mud logging technology. In addition, advanced cutting return-monitoring technology was implemented which helped monitor proper hole cleaning and minimize the risk of stuck pipe due to compressional formation failure at the wellbore. Based on this analysis, revised drilling practices and recommendations were made to address the wellbore instability issues. The case study presents results from a challenging well using this integrated approach showing significant improvement in well safe delivery within planned drilling time and achieved the planned target gas rate.