Development Strategies for Horizontal Wells in Low-Permeability Tight Fractured Oil Reservoirs: A Case Study of the Chang 6 Reservoir in the Ordos Basin

Waterflooding of low-permeability tight fractured oil reservoirs is commonly associated with early water breakthrough, a high risk of severe waterflooding, and low displacement efficiency. Taking the Chang 6 low-permeability reservoir in the Jihuang 32–Xiaojianzi Block, Dingbian area of the Ordos Basin, as a case study, this paper systematically investigates the applicability and optimization of development strategies for horizontal wells in this type of reservoir. After characterizing the reservoir petrophysical properties and fracture development characteristics, an integrated field-scale workflow combining production-response analysis, reservoir engineering calculations, three-dimensional numerical simulation, and field production statistics was applied to evaluate primary depletion and water-injection pressure maintenance. Under the adopted reservoir and operating assumptions, the reservoir engineering calculation and scenario-based numerical simulation yielded ultimate primary-depletion recovery estimates of 19.1% and 21.70%, respectively. By July 2024, the 26 primary-depletion horizontal wells in the study area had reached an average recovery degree of 12.4%, representing their observed development status rather than the ultimate recovery estimate. In addition to its considerable development potential, this strategy can mitigate the high water cut and severe waterflooding problems associated with water injection and can avoid several water-injection-related cost items, including injection-system operation, produced-water handling, and post-waterflood remediation. The field performance of primary depletion was further evaluated using production statistics from 26 horizontal wells developed under primary depletion in the study area. To address the principal development constraints, including high water cut, low fluid production rates, and wellbore restrictions, an integrated suite of technical measures is proposed, comprising refined well placement, staged reservoir-energy supplementation, wellbore blockage remediation, and refracturing. The results provide a field-based reference for development strategy evaluation in tight fractured reservoirs with geological and dynamic characteristics comparable to those of the investigated Chang 6 reservoir.