Primary porosity is associated with the matrix, and secondary porosity is Kayar, Ajmer district, and gold-pyrite exploration at Bhukia-Jagpura, Rajasthan, India. . real flow conductivity of the reservoir (such as permeability) from the relation of. The basis for these relations is a direct or inverse relation between porosity and permeability and, as matrix conduction effects are not taken into account. Correlation between Rock Permeability and Formation Resistivity Factor-A Rigorous Rock properties related to exploration and production consist of porosity.
Currently, most permeability values are determined from ex situ samples taken from boreholes.
Permeability determination -
This method is very expensive and extremely slow, requiring up to several days or weeks to process. In addition, samples are often unavailable due to disturbance during drilling or contaminant considerations. So the permeability should be determined directly using geophysical logging tools Sturrock ; Tong et al.
One of the used logging methods for determining permeability is nuclear magnetism resonance NMR logging tool Balzarini et al. While the technique is available, it does have several disadvantages, such as the small depth of investigation, the high cost, the low signal-to-noise ratio Tong et al. When rock was submitted to an alternating electrical field at different frequencies, its resistivity and permittivity are complex quantities characterized by a dispersive behaviour, that is, the resistive and reactive components of the complex resistivity vary over the frequency spectrum.
The complex resistivity is a non-invasive technique and can work in downhole. It depends on microstructure of shaly sand cores and can be used to estimate the permeability, which is a determining factor for making production decision in petroleum industry and need to be measured in downhole. Compared with the nuclear magnetism resonance logging tools, the complex resistivity has several advantages, such as deep investigation depth and high signal-to-noise ratio.
Since the internal structure of the pore space affects the electrolytic charge transport and fluid flow in a similar way, the induced polarization IP can be used as an in situ permeability estimation method. It has several advantages compared to the NMR logging tools, such as high investigation depth and high signal-to-noise ratio Tong et al. The time-domain IP for estimation of hydraulic properties has received much attention Titov et al.
In most literatures, chargeability was used as the time-domain IP parameter. It is demonstrated that chargeability can be related smoothly and definitively to excess conductivity or intergranular permeability.
On the other hand, the chargeability also relates to the formation water resistivity which changes greatly and it is very difficult to be obtained for the water-flooding oil field, such as Daqing Oil Field. In the frequency domain both real and imaginary parts of complex resistivity of earth are measured by using different frequencies.
These are then used to estimate the hydraulic conductivity and cation exchange capacity of clays. Denicol and Jing had shown that the frequency dependence behaviour in the frequency range 10— kHzas characterized by the slope of impedance versus log fshows a correlation with permeability.
In most of these studies, frequency spectra of the complex electrical parameters were measured and frequency dependency of these parameters was used, but the porosity of the rocks had received little attention.
On the other hand, most of the used frequencies in these studies are too high and the corresponding frequency spectra are very difficult to be measured in the logging tools. In this paper, we use the frequency dependency of the imaginary part of the complex resistivity combined with the porosity data to estimate the permeability of shaly sand reservoir.
The frequency region is Hz—1. These two physical characteristics complex quantity and dispersion or frequency dependence can be used as a means to estimate rock petrophysical properties, such as specific surface area and permeability Cerepi The complex electrical behaviour of a rock results from both its conductive and idelectric response in the presence of a varying AC electrical field; the former is related to the transport of free charges and the latter is associated with polarization phenomena at pore—grain interface.
The interface region between matrix and the fluid filling the pore space is of particular interest due to the existence of the ionic double layer.
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The concept of electrical double layer, which is always present whenever there is an interface, forms the theoretical basis for understanding the electrical properties of rocks, especially shaly sands.
This permeability must be used with some caution. First, the pressure measurements are made on the borehole wall that has suffered possible drilling damage and pore throat plugging from mud solids. Second, one must take note if the measurement is in an invaded zone with two phases and, hence, the permeability determined is an effective permeability, not an absolute permeability.
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Depending on rock type and fluid saturations, the effective permeability may be an order of magnitude too small. The chapter on fluid sampling in the General Engineering section of this Handbook presents examples of wireline formation tester responses and derived permeability and the use of these pressure measurements to determine fluid gradients.
Drillstem tests See discussions in Acquiring bottomhole pressure and temperature data and Formation testing while drilling FTWD Determining permeability Point-by-point permeability values are needed over the reservoir interval at the wellbores for several purposes.
First, the distribution and variation of the permeabilities are needed by the engineers to develop completion strategies. Second, this same information is needed as input to the geocellular model and dynamic-flow calculations e.
For both of these, the first consideration is the location of shales and other low-permeability layers that can act as barriers or baffles to vertical flow. A second consideration is the nature of the permeability variation i. When good-quality core data are not available, estimates of permeability can be made from empirical equations. Permeability is controlled by such factors as pore size and pore-throat geometry, as well as porosity. To take some account of these factors, the widely used Timur equation  relates permeability to irreducible Sw and porosity, and therefore can be applied only in hydrocarbon-bearing zones.
This form of his equation applies to a medium-gravity oil zone: Estimates that are based only on porosity are likely to have large prediction errors, especially in carbonate reservoirs. Equations of the following form, or a logarithmic-linear form, are useful particularly in sandstones: They should be adjusted according to local knowledge. In field evaluation, the starting point for calculations of permeability is the routine-core-analysis data.
These data, and the associated SCAL measurements of permeability and porosity as a function of overburden stress, are input to calculations to develop permeability values at reservoir conditions and the permeability vs. This ratio is much smaller for low-permeability values and approaches a value of 1. The permeability correction is larger at low permeabilities.Resistivity
In developing the permeability vs. This will naturally account for major differences in grain size, sorting, and key mineralogical factors. Alternatively, a sufficiently thick reservoir interval can be subdivided into layers of 50 to ft each. A superior petrophysical methodology will be developed if a thick reservoir is appropriately subdivided, compared with treating the full reservoir interval with a single permeability vs.
A single permeability vs.