Geologically Constrained Optimization of Horizontal Well and Fracture Design in Tight Sandstone Reservoirs: Insights from the Chang 7 Member, Ordos Basin

Efficient development of tight reservoirs in shallow-water delta-front environments is often constrained by misaligned horizontal well design and the underlying geological architecture. To address this, a quantitative optimization workflow is proposed, integrating 3D architectural characterization of single sandbodies with reservoir simulation. Using the Chang 7 Member of the Ordos Basin as a case study, three dominant sandbody types—isolated channels, vertically stacked channels, and mouth bars—were characterized in terms of geometry, stacking pattern, and internal permeability anisotropy. High-resolution geological models incorporating stratigraphic cyclicity and heterogeneity were constructed. Local grid refinement around wellbores and fracture networks was implemented to improve simulation fidelity. Sensitivity analyses identified optimal values for horizontal section length, fracture stage, and fracture half-length for each sandbody architecture. The results indicate that production response is highly sensitive to sandbody geometry and heterogeneity, with diminishing returns observed beyond critical design thresholds. Field validation with three horizontal wells confirmed that optimized parameter sets aligned with geological architecture resulted in significantly improved and more stable oil production. To support application in similar reservoirs, a dimensionless design chart was developed using ratios of horizontal well length to sandbody length (Lh/Ls) and fracture length to sandbody width (Lf/Ws). This empirical tool enables rapid pre-drill assessments and informs well planning strategies aligned with sandbody architecture. By emphasizing the integration of geological and engineering disciplines, the approach offers a scalable framework for optimizing horizontal well design in geologically complex tight formations.