Iron oxide/hydroxide cementation took place during telogenesis and led to reduction of primary porosity
. Thin sections stained with blue epoxy were used to estimate the visual porosity of sandstone using point counting and SEM images.
A plot of IGV versus cement volume indicates that compaction contributed to the major primary porosity
loss of Chang 7 sandstones (Figure 15).
We explore the role of initial host rock permeability, primary porosity
, and intrusion depth on the dynamics of silica transport and permeability changes induced by the dissolution of silica from the host rock and precipitation of secondary quartz.
The presence of paleo-structures growing during deposition may have been responsible for the excellent primary porosity
seen in many of the Fms.
The concept of "double porosity" recognizes both primary porosity
(flow through the glacial till matrix of silt and/or clay) and secondary porosity (flow through fractures, worm holes, root holes, and along preferential pathways such as varves or other depositional features).
Such correlation is characteristic of all types of carbonate rocks in Estonia (Shogenova 1998; Shogenova & Puura 1997, 1998) and can be interpreted as primary porosity
(Schon 1996, p.
Step 1: facies analysis (including establishing the primary porosity
and permeability distributions, and the "primary aquastratigraphy"--a term newly defined in this article); Step 2: petrographic analyses (paragenetic sequence, mapping amounts and spatial distribution of diagenetic phases); Step 3: geochemical analyses (isotopes, trace elements, fluid inclusions, etc.); Step 4: burial history and paleohydrology; Step 5: integration with extant data (especially petrophysical data), if available, and Step 6:modeling (not necessary, but desirable in at least some cases).
structures growing during deposition, may have been responsible for the excellent primary porosity
seen in many of the reservoirs.
The primary porosity
is severely destroyed by diagenetic events, hence producing secondary porosity, making them good reservoirs across Potwar sub-basin.
If the carbonate cements formed during early diagenetic stage, it could provide a framework that resists burial compaction and retains primary porosity
until decarbonatization at greater burial depth [1-3].
Water in fine-grained glacial and alluvial materials travels down from the surface to underlying ground water aquifers principally through fractures (termed secondary porosity) and not by flow between the grains (termed primary porosity
The deep burial diagenesis and associated pressure dissolution and cementation has almost eliminated the primary porosity
. The porosity in the studied sandstones is secondary in origin and is attributed to dolomitization and fracturing.