Utilization of Settled Barite as Permanent Well Barrier Element - Feasibility Study

Abstract

Abstract Settled barite is a flexible material which can be compared with unconsolidated sand slurry barrier materials. It is consisted of different particles with density of 4.2 sg and in combination with additives in drilling fluid (e.g., bentonite, xanthan gum, cuttings) can create a seal barrier. Initially, 402 wells were reviewed, which 307 of them were wells with slot recovery. Among them, 102 wells had cut reported below top of solid, and only 72 of them had circulation pressure data. Acceptance criteria were defined to sort out the final wells to be considered in this study. Finally, 22 wells possessed the requirement for being studied. Our data mining process shows that one can divide the fluid above cement into three zones: light, heavy and consolidated. Engineers are interested to find depth of heavy fluid and conducting cut & pull operation. However, these data shall not be used for studying potential utilization of settled barite as annular barrier. Operational data and experience show barite can be compacted and in combination with other ingredients present in drilling fluid, providing consolidated material. Analysis of 77 field circulation through settled barite shows that settled barite adheres to casing and formation. The initial experimental result, on simple water base fluid, show that settled barite could hold pressure slightly higher than its hydrostatic pressure. One should note that these experiments were conducted in long transparent plastic pipes with least friction. The well data and initial experimental measurements indicate that settled barite may have the potential to act as barrier similar to unconsolidated sand slurries. The objective of this paper is studying prospective utilization of settled barite as annular barrier by reviewing well data from wells drilled in the North Sea and conducting experiments.