Study on Wellbore Reconstruction Technology for Re-fracturing in Horizontal Wells of Conglomerate Reservoirs

The tight conglomerate reservoirs in the Mahu area of Xinjiang exhibit strong heterogeneity. Following years of production after initial horizontal well fracturing, accelerated production decline has been observed, while inter-cluster residual oil retains exploitable potential. Precision re-fracturing technology can effectively enhance the recovery efficiency of remaining oil, with expandable tubular wellbore reconstruction technology providing favorable downhole conditions for re-fracturing operations. Finite element numerical simulations of expandable tubulars were performed to analyze the evolution of Mises stress, strain, and contact stress during the expansion process. Results indicate that radial plastic deformation of the tubular occurs under the force of an expansion cone, with stable expansion pressure maintained at 40–42 MPa. A series of full-scale physical simulations, including compression resistance and annular sealing pressure-bearing capacity tests, verified that the expandable tubular meets the requirements for high-pressure re-fracturing operations. By coupling factors such as tubing flexibility, running friction, and buckling, the maximum achievable length for tubular insertion was analyzed to optimize single-operation reconstruction length. Field trials of expandable tubular wellbore reconstruction were implemented in the Mahu block, achieving a reconstructed length of 1,041 m. This process successfully blocked 34 initial fracturing perforation clusters, with the re-fracturing operation sustaining a peak pressure of 83 MPa. Post-fracturing logging confirmed the integrity of the expandable tubular. Both laboratory research and field trials validate the feasibility of expandable tubular wellbore reconstruction for re-fracturing in horizontal wells, providing technical insights for enhancing production in low-yield unconventional hydrocarbon reservoirs.