Abstract: Methods are provided for increasing overall fluid mobility in a near-wellbore region in an oil sands reservoir, for example in a reservoir having an inter-well region between a first well and a second well of a well pair in which at least a portion of the near-wellbore region is within the inter-well region. The methods may involve inoculating the near-wellbore region with a microorganism, wherein the near-wellbore region comprises a hydrocarbon phase and an aqueous phase, the viscosity of the hydrocarbon phase being greater than the viscosity of the aqueous phase. Conditions may be maintained in the near-wellbore region so that the microorganism metabolizes at least a portion of the hydrocarbon phase so that saturation of the near-wellbore region by the hydrocarbon phase decreases and saturation of the near-wellbore region by the aqueous phase increases.