Geological studies consistently demonstrate that subsurface oil and gas reservoirs are overlain and sealed by specific, lower-permeability sedimentary rock layers such as shales and siltstones.
The retrieved literature consistently confirms that petroleum and natural gas accumulations are sealed and contained by overlying fine-grained sedimentary layers (such as shales, mudstones, or tight siltstones) that act as caprocks or seals. Multiple basin analyses across different regions (Egypt, China, etc.) support this structural and stratigraphic relationship. No papers refute the claim.