def vshale_to_vclay(vshale, multiplier):
    """
    Converts a shale volume to clay volume using a multiplier.

    Parameters
    ----------
    vshale : float
        Shale volume
    multiplier : float
        Shale to clay multiplier (decimal)

    Returns
    -------
    float
        Returns a clay volume.

     References
    ----------
    Bhuyan, K. and Passey, Q. R. (1994) ‘Clay estimation from GR and neutron-density porosity logs’, SPWLA 35th Annual Logging Symposium, pp. 1–15.
    """
    return vshale * multiplier