If an oil reservoir has significant height and is bounded laterally by sealing boundaries, optimizing oil production using a horizontal well requires varying the well location along the open vertical axis, especially in highly anisotropic reservoirs. This work analyzes early, transitional, and late-time dimensionless pressure and its derivative responses for a horizontal well in an anisotropic reservoir that is vertically unbounded but laterally sealed. The main objective is to investigate reservoir conditions and well design that prolong oil production despite anisotropy and sealing boundaries. The dimensionless pressure model was developed using source and Green’s functions. Late-time responses were quantified, dominant parameters identified, and the onset of transitional and latetime flow was estimated using Odeh and Babu strategies. Wellbore skin and storage effects were not considered. Results show that longer horizontal wells hasten boundary effects, while shorter wells prolong production. Larger reservoir length delays late-time flow due to distant lateral boundaries. Smaller well widths offer larger and longer productivity. Higher anisotropic ratios increase productivity across all flow periods. Dimensionless pressure and its derivative characterize late-time flow, increasing with well length, reservoir dimensions, and permeability. Pressure gradients vary with flow time during the early period, remain constant during the early transient, and increase in late time due to the sealing of boundaries. The onset of boundary effects depends on reservoir anisotropy, well width, and well length. These findings provide guidance for well design and placement to optimize oil production.