Permeability is a measure of the ability of a reservoir rock to transmit fluids, and is arguably the most important parameter within a simulation model. For the Mangala field, permeability has been measured extensively from core analyses, wireline logging and well test analyses. Implicit in each of these measurement techniques is a specific scale and measurement direction. It is thus not surprising that differences still remain even after correcting the measured permeabilities from various sources to an absolute permeability.
This paper presents the detailed methodology that was used for the calculation of permeability from the various sources and discusses possible explanations for the differences in the numbers.
In some of the lower reservoir units, Mangala core permeabilities are significantly higher than the permeabilities measured from well tests, and it is proposed that permeability "baffles" on a multi-meter scale may be causing this decrease in well test permeabilities. These "baffles" are related to depositional features (e.g. current bedding and channel pinch-outs) and are likely to be strongly directional, leading to a horizontal permeability anisotropy which has important implications for reservoir development.
The Mangala field was discovered in January 2004 (Yashwant, et al, 2006) by targeting a simple, tilted fault-block trap formed within the rifted, Tertiary Barmer Basin (Figure-1 and Figure-2).