Damage ratio, permeability

Another interesting result reported by Sarkar and Sharma (55) was that after saturating the core initially with a polar crude oil, the damage ratio was only 1/1.5 and the permeability decline was very slow. Thus, allowing the rock surfaces to come in direct contact with the polar oil did make the rock less susceptible to damage. This effect is apparently related to adsorption of polar components on the rock surfaces and altered wettability of the fines. 

The formation brine used to establish the core s initial permeability contained 2.7% total dissolved solids, TDS, with a monovalent-divalent (calcium) ratio of 30. Once a core is equilibrated with this brine, any increase in the ratio or drastic decrease in TDS has the potential for decreasing permeability. Obviously fresh water represents a significant decrease in TDS and, hence, the 54% permeability damage. Adding KC1 helps overcome the decreased salinity but, in so doing, increases the ionic ratio resulting in still measureable but usually reduced permeability damage. 

Even very small amounts of calcium provide a desirable decrease in the Na/Ca ratio. Prior studies indicating potassium chloride totally negates permeability reduction may have utilized water that contained some small amount of calcium ion to measure KC1 solution permeability. A second factor, which might explain the lack of KC1 damage reported in prior studies is a low ionic concentration, especially calcium, in the water used to equilibrate the cores prior to the KC1 tests. 

Two variables are fundamental to assessing the flow across complex fault zones. The first variable is the cumulative fault-rock thickness across the fault zone, i.e., the total thickness of fault-rock from all faults along the flow path. This depends upon the fault frequency along the flow path and is not equivalent to the fault damage zone thickness (cf. Knott, 1993) unless the fault zone is invaded by cements. The second variable is the connectivity of the faults or deformation features with low permeabilities in the fault zone. In the case of a completely connected array with no windows of undeformed material along possible flow paths, the flow is controlled by the permeability of the fault rocks. Where a more open network of faults is present then the flow will depend upon the tortuosity associated with flow around the low permeability zones and the ratio of matrix to fault-rock permeability. The interaction of these two factors will control the effective transmissivity of the zone. We have constructed a database on... 

Eiectromagnetic (eddy currant) Complex electrical conductivity, complex magnetic permeability Density, reinforcement ratio, porosity, damage accumulation, geometry, structure, flaw size... 

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