Vertical and horizontal permeability variation within a sandstone reservoir based on minipermeameter measurements

Abstract

The drilling and coring through the entire reservoir interval in two wells separated by 570 m presented the opportunity to carry out mini (probe) permeametry measurements on comparable reservoir zones. The reservoir sandstones were deposited in a shallow marine, tidally influenced environment and consist of alternating fine grained micaceous wackes to coarser grained high permeable subarkosic arenites. Statistical analysis of the data had three main objectives: (1) correlation between lithofacies and permeability; (2) characterization of vertical and horizontal permeability variation at the reservoir and reservoir zone scale; and (3) to study relationships between core plug and minipermeameter measurements. Nine lithofacies types are recognized in the cores, ranging from massive homogeneous sandstones through to fine grained, micaceous sandstones with varying degrees of bioturbation. A good correlation is found between minipermeameter measurements and lithofacies. Variograms at the reservoir and reservoir zone scales show similar trends vertically and horizontally (between wells). Variance in core plug data is greater than that for minipermeametry data. Permeability as measured by minipermeametry is significantly higher than core plug measurements, although overall trends are similar in the two data sets. There is generally better agreement between plug and minipermeameter measurements for the highly permeable homogeneous sandstones than for the fine grained micaceous sandstones with relatively low permeability.