Self-Growing Wellbore Casing: A Bioinspired Framework for Sidetracking

Sidetracking is a critical operation for bypassing damaged well sections and accessing bypassed hydrocarbons in mature reservoirs, but conventional small-diameter casing and cementing technologies face severe limitations due to narrow-clearance hydraulics, mechanical drag, and aggressive corrosive downhole environments. To overcome these challenges, this paper proposes a paradigm-shifting biomimetic approach: the in-situ additive manufacturing of a wellbore liner directly behind the drill bit during sidetracking. Inspired by the apical growth of climbing plants, a conceptual bottomhole assembly (BHA) was designed to extrude a continuous carbon-fiber-reinforced polyetheretherketone (CCF/PEEK) composite shell. A coupled multiphysics framework was established to evaluate the technology’s feasibility under representative downhole conditions. Hydrodynamic modeling of the non-Newtonian polymer melt demonstrates that shear-thinning rheology minimizes extrusion pressure requirements, necessitating only a 3.5% pressure increase (46.76 MPa/6782 psi) when doubling the rate of penetration from 5 to 10 m/h. Thermal and crystallization kinetics simulations using the Nakamura framework show that the liner core achieves an optimal crystallinity of 32% within 45 s post-extrusion, ensuring monolithic interlaminar cohesion. Geomechanical analysis using the Tsai–Wong tensor failure criterion confirms that an 8.5 mm thick CCF/PEEK liner provides a collapse resistance of 61.2 MPa/8876 psi, comparable to conventional API K55 steel casings but with a 68.8% reduction in weight and absolute corrosion immunity. Finally, we define the critical operational limitations of the technology, establishing a bottomhole temperature limit of 180 °C/356 °F and a maximum borehole cavern factor of 1.35.