What is it about?
Oil and gas reservoirs contain thin productive layers separated by stronger rock barriers. These barriers can stop hydraulic fractures or divert them along layer boundaries, leaving some productive layers poorly connected. This study investigates how branch wellbores, called radial boreholes, can guide fractures across these barriers and help fractures initiation in several productive layers. We developed a coupled fluid-rock model using the discrete lattice method, which allows complex fractures to grow without prescribing their paths in advance. The model was validated against analytical solutions and CT images from previous laboratory experiments. By tracking changes in stress, rock displacement and fracture growth, we explain how borehole reach and geological conditions work together to control connections between layers.
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Why is it important?
The study provides a mechanical explanation for how radial boreholes can improve connections between stacked reservoir layers. Boreholes that cross layer boundaries reshape local stresses and help transmit rock movement across interfaces, supporting fracture growth through barriers. When they reach several productive layers, they can also supply fluid to separate fracture initiation sites, allowing multiple layers to be stimulated without requiring a single fracture to grow continuously through every intervening barrier. A key methodological contribution is the combination of discrete lattice simulation, analytical and experimental validations, stress and displacement analysis, and statistical sensitivity assessment. This approach makes it possible to examine geological effects systematically, despite the variability that complicates comparisons between laboratory rock samples. The study also translates simulation results into fracture propagation maps that distinguish arrested, cross-layer, skip-layer and hybrid fracture patterns. Within the investigated conditions, these maps provide a basis for selecting borehole reach according to layer properties, interface strength and natural fractures, supporting more targeted stimulation design.
Perspectives
For me, the most valuable insight is that the reach of a radial borehole can change both where fractures begin and how they connect different rock layers. This opens a way to design stimulation around the arrangement of productive layers and barriers. I hope this work helps connect observations of fracture geometry with the underlying stress and rock movement mechanisms. The next step is to test how these findings translate to field conditions, including curved boreholes, fluid leak-off and interactions between multiple boreholes. These developments could help turn the proposed propagation maps into practical tools for designing stimulation in complex layered reservoirs.
Tengda Long
China University of Petroleum Beijing
Read the Original
This page is a summary of: The effect of geological features on hydraulic fracture propagation guided by radial boreholes in the thin interbedded reservoirs, Petroleum Science, July 2026, Tsinghua University Press,
DOI: 10.1016/j.petsci.2026.03.016.
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