Oil accumulations in the Khaur field, west Pakistan, occur in folded late Tertiary freshwater sandstones, as well as in Eocene limestones, which are the principal reservoir rocks in other oil fields of the region. Migration of the oil from source beds in the Eocene section into the overlying fresh-water beds is apparently not related to the presence of faults. It is suggested that extremely high reservoir pressures may have facilitated the opening of temporaryfissures during folding which permitted intermittent upward movement of fluids.

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