A. Sahin* and S. Saner*
*Center for Petroleum and Minerals, Research Institute, King Fahd University of Petroleum and Minerals,Dhahran, Saudi Arabia.
email: email@example.com; firstname.lastname@example.org
The Upper Jurassic Arab-D is a complex carbonate reservoir present in the Eastern Province of Saudi Arabia. It has been subdivided into five zones on the basis of porosity. A statistical analysis of the extensive dataset from the three productive zones in the reservoir unit (Zones 1, 2 and 3) has shown that patterns of well-log porosity and core porosity distributions are strikingly similar in each zone, but that the means are not. Consistently higher mean values observed in core distributions can be explained by a possible bias in core selection and/or differences in the measurement conditions. The results also show that each zone has a distinctive pattern of porosity distribution, reflecting its general lithological character.
The corresponding distributions of vertical and horizontal core permeability are similar, but the means of horizontal permeability in Zones 1 and 2 are higher than the corresponding means of vertical permeability. The reverse is true for Zone 3, in which mean vertical permeability is slightly higher than horizontal permeability. This is probably due to the presence of vertical hairline fractures, which were frequently observed in mud-dominated facies in Zone 3.
permeability distribution for each zone is generally consistent with the corresponding
porosity distribution, reflecting a degree of correlation between porosity and
permeability. However, semi-log plots of core porosity versus core permeability
indicate a relatively poor correlation between these variables, with the correlation
coefficient being less than 0.7 for all zones. Separate correlation plots for
each lithology within Zone 1 indicate that the lithological control on porosity
is not very significant in this zone.