California heavy-oil sands are very similar in alteration patterns during thermal recovery processes. Hot-water and steam reactions (up to 200°C) result in additional smectite and zeolite growth. These reactions alone do not predict the permeability decrease. As in sedimentary diagenesis, grain size allows a better understanding of permeability decreases and fines migration patterns. Finer-grained sediments have a greater order-of-magnitude permeability decrease to injected fluids as compared to coarser sediments. In-situ combustion reactions are much higher temperatures {500+ °C), but inter-well sediment alteration is limited to the matrix. This contrasts with samples from a combustion air injector, where both metamorphic fabrics and minerals were present.

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