Effect of Formation Compaction and Subsidence on Sliding Sleeve Performance

Abstract

Abstract Formation compaction and subsidence forces due to reservoir drawdown have the potential to inhibit the function of sliding sleeves and similar completion systems. The sliding sleeves discussed have the ability to be opened and closed multiple times, allowing for flexible stimulation and production operations. Field data suggested a link between high sliding sleeve function forces and preceding zonal production. The objective was to minimize these effects to give the operator full functionality of the sliding sleeves over the life of the well. This paper will outline how this was achieved, and the results of comparative lab testing. The overall approach was to (1) understand the magnitude and effects of the formation forces, (2) implement product improvements, and (3) validate results through lab testing the proposed solutions. A case study was conducted for 4.5 in. 21.5 lb/ft & 5.5 in. 32.6-35.3 lb/ft casing and sliding sleeves installed in the Valhall field. Wells drilled in the Valhall field had previously suffered production casing collapse failures due to formation compaction and subsidence (Pattillo and Kristiansen 2002). Switching to the current heavy weight casing resolved the issue. The heavy weight casing collapse pressure ratings were used in the early analysis to determine maximum uniform collapse resistance and radial deformation of the sliding sleeve components. Thick-walled cylinder calculations were insufficient for predicting the effect of the non-uniform loading exhibited downhole, as well as predicting metal-to-metal contact within the sliding sleeves due to abrupt changes in geometry. FEA modelling was completed for predicting metal-to-metal contact due to a non-uniform load. Sleeves with improved mechanical collapse resistance were designed and built. Lab testing was conducted by applying a mechanical radial force simulating the formation load to (1) the original sleeves, (2) the newly improved sleeves, and (3) host casing samples. Sliding sleeve performance was assessed through the resultant opening and closing forces. Test results verified the model for radial deformation due to formation forces, and the effect on sliding sleeve performance. The improved sleeves showed no change in performance with a range of applied radial load, whereas the original sleeves showed significant increases in function force. Completion design improvements can enable novel methods of well stimulation and production in areas prone to formation compaction and subsidence forces. These forces can have major effects on the completion and production of a well but are rarely quantified and accounted for in sliding sleeves or similar completion systems designs. At the time of writing, the improved sliding sleeves have been successfully run in a field trial, though did not produce prior to functioning.