Down-hole isolation towards high-temperature reservoir using packing elements with swellable thermo-plastic vulcanizates

Abstract The well completion and fracturing towards deep unconventional high-temperature (HT) petroleum or natural gas reservoirs is considerably strict to the packer especially packing elements. However, existing packing elements including swellable packers usually are made from Hydrogenated Nitrile (HNBR) or Fluorine rubber (FKM) with drawbacks of great expense and difficult tripping into the horizontal wellbore. This paper proposes a compact isolating solution using swellable Thermo-plastic Vulcanizates (TPVs), which is prepared by blending HNBR, low-cost Polyamide66 (PA66) and Porous Super Absorbent Resin (PSAR) with enhanced nanoparticles. The TPVs were characterized by experiments and the system with Plastic/Elastomer Ratio (PER) of 45:55, tensile strength of 18.6 MPa and elongation at break of 635% upon aging (150 °C) was qualified for the packing element material. A novel enhanced packing element is put forward with corrugated-profile structure to address large-size and over-extrusion issues. The numerical study on packer components was conducted based on TPV constitutive model. The prototype with element length of 2.5–2.6 m was validated in the lab and rated as the sealing of more than 70 MPa. An optional disintegrating casing is adopted to avoid the premature damage risk of packers. For the field trial, the multistage fracturing tubular with improved packers was deployed into the horizontal open hole without severe pipe stuck. The fracturing operation was successfully performed and all packers functioned normally with the maximum pressure differential of 73 MPa. It concludes that the new solution exhibited high strength, heat resistance and structure integrity with low cost over the traditional packers towards HT environment.