Engineered Design of Drilling Fluids using Compressible Particulates to Mitigate Annular Pressure Build-up in Subsea Deepwater and HP/HT wells

Annular Pressure Build-up (APB) is caused by heating of trapped drilling fluids (during production), which may lead to burst/collapse of the casing or axial-ballooning, especially in subsea HP/HT wells. APB may also lead to zonal isolation issues, well control issues, and production losses. Accordingly, economical techniques for fluid selection, casing design and/or production tubing isolation must be selected to mitigate the APB issue. Compressible particles that may collapse when subjected to pressure; could make additional space for drilling fluid to expand and are therefore useful to mitigate the APB issue. The present work focuses on the modeling of the effects of compressible particles (type/concentration) on APB when added to drilling fluids inside the casing/tubing annuli. The response of fluids (without compressible particulates) in the trapped annuli to the increasing temperature has been studied in literature using theoretical and computational modeling; the approach accommodates two separate physical effects in the annuli i.e. volumetric expansion (PVT response) of the trapped drilling fluid and circumferential expansion of the well casings. The present work incorporates the impact of compressible particles in the above modelling framework. Accordingly, the model workflow was developed for the simulation of compressible particles effects on APB in deepwater HP/HT wells. As the fluid pressure builds up due to the wellbore heatup, the particle collapse would initiate that would provide space for the fluid expansion reducing APB. The effect has been studied quantitatively using the modeling approach for two types of particulates: one with pressure resistance up to 5000 psi and another with pressure resistance up to 10,000 psi. The chosen concentrations of particulates were 5% and 10%. The modeling results have demonstrated that almost 50% reduction in APB is plausible by using an appropriate type and concentration of the compressible particles. The modeling approach could be used to design engineered combinations of the compressible particulates to mitigate the APB in an economical manner. The work may provide a critical solution to the APB challenge in subsea HP/HT wells