This paper is a review of two recent open hole gravel packed, water injection wells drilled from an offshore drilling rig, with particular focus on the loss of fluids and subsequent control of those losses, and makes recommendations for future wells based on the lessons learned. The techniques and fluids used to drill the deviated interval, place the gravel and remove filter cake prior to flowing back lost fluids and testing injectivity are discussed. The causes of loss of returns at various points during completion operations are identified and the remedial actions taken at the rig site are documented. Suggestions for future operations that should eliminate these losses are also outlined.
The drill-in and completion fluids chosen for these operations had to meet several criteria. In particular the bridging particles selected had to be a size range specifically chosen to effectively seal the formation of interest, and quickly form an impermeable filter cake on the surface of the formation, which prevented further invasion by the well bore fluids and subsequent reductions in formation permeability. Once the zone of interest had been drilled, the filter cake had to provide continued fluid loss control during displacements, placement of completion equipment and gravel pumping operations. However, at times potentially damaging losses were experienced. Once the gravel packing operation was complete, it had to be possible to remove the filter cake and bridging particles so that injectivity could be obtained, without plugging or bridging of the gravel pack or completion equipment. The techniques used to control losses also had to meet the same goals of preventing formation damage and avoid plugging of gravel and completion equipment.
The experience gained on these two wells shows that careful planning of fluids formulation, drilling practices and completion techniques are necessary to ensure the required fluid loss control while drilling and completing the well, especially while placing gravel. The filter cake formed can then be removed at the desired time to ensure maximum injectivity.