Effect of Variable Saturation Exponent on the Evaluation of Hydrocarbon Saturation

Worthington, Paul F.; Pallatt, Nadia

doi:10.2118/20538-pa

Cited by 46 publications

(31 citation statements)

References 4 publications

(4 reference statements)

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“…The experiments of Worthington and Pallatt [1992] on sandstones with multimodal pore size distributions show a dependence of the saturation exponent on water saturation that includes exponents between n=l.5 and n=2.4. If this variation is unrecognized, errors of more than 10 saturation units in the petrophysical evaluation of water saturation can result [Worthington and Pallatt, 1992]. Another important factor that influences the value of the saturation exponent is wettability.…”

Section: •Rn O'w •Tn Ftmentioning

confidence: 96%

“…Experimental investigations [Worthington and Pallatt, 1992] and theoretical calculations based on effective medium theory [Sen, 1997] show that this phenomenon seems to be related to variations of microporosity, multimodal pore size distribution, and surface roughness. The experiments of Worthington and Pallatt [1992] on sandstones with multimodal pore size distributions show a dependence of the saturation exponent on water saturation that includes exponents between n=l.5 and n=2.4. If this variation is unrecognized, errors of more than 10 saturation units in the petrophysical evaluation of water saturation can result [Worthington and Pallatt, 1992].…”

Section: •Rn O'w •Tn Ftmentioning

confidence: 98%

“…If this modeling proves true, the main difference that might account for this dependence is that gas hydrates form in the reservoir and stay there as a nonmobile solid phase, whereas oil or gas migrate into and accumulate in the reservoir and may form different saturation patterns. The use of a value close to 2 for the saturation exponent in waterwet, oil-or gas-bearing formations is justified by numerous laboratory experiments [see, e.g., Wei and Lile, 1991;Worthington and Pallatt, 1992;Saner et al, 1996;Garrrouch, 1996] and the fact that practical application of this value generally proved successful over many years in hydrocarbon exploration.…”

Section: Implications For Hydrate Content Estimates From Resistivity mentioning

confidence: 99%

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Modeling of the influence of gas hydrate content on the electrical properties of porous sediments

Spangenberg¹

2001

J. Geophys. Res.

191

123

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Abstract. The geophysical investigation of gas hydrate accumulations within marine sediments and the sediments of permafrost regions suffer from a lack of information on the influence of the hydrate content on the physical sediment properties. The estimation of the hydrate content using downhole electrical measurements based on Archie's law requires the knowledge of the saturation exponent. The saturation exponent is an empirical parameter that includes influences from the internal rock structure such as pore shape, connectivity and constrictivity of the pore network, and the distribution of the conducting phase. Based on different models that account for the different morphological forms of gas hydrates found during gas hydrate sampling in various research wells, the influence of gas hydrate content on the electrical properties of the hydrate bearing sediment was investigated. For all studied forms of hydrate occurrence, disseminated in the pore space, nodular, and layered, the saturation exponent depends on the sediment properties and on saturation itself. The growth of gas hydrate nodules, lenses, and layers is a process that is assumed to result in the displacement and compaction of the surrounding sediment. Because of this change of sediment properties during hydrate generation, the saturation exponent for these forms of hydrate occurrence depends strongly on the relationship between porosity and formation resistivity factor, expressed in the form of Archie's cementation exponent. For the case that hydrate occurs disseminated in the pore space and the assumption that capillary effects are important for hydrate generation, the saturation exponent depends on grain size and grain size sorting. For the parameters chosen for these model calculations, the saturation exponent aries between 0.5 and 4. The use of a constant mean value for the saturation exponent of approximately 2 can result in both underestimation and overestimation of the hydrate content.

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Section: •Rn O'w •Tn Ftmentioning

confidence: 96%

Section: •Rn O'w •Tn Ftmentioning

confidence: 98%

Section: Implications For Hydrate Content Estimates From Resistivity mentioning

confidence: 99%

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Modeling of the influence of gas hydrate content on the electrical properties of porous sediments

Spangenberg¹

2001

J. Geophys. Res.

191

123

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“…The saturation exponent is around 1.6 for the "equilibrium" displacement, but we see that the resistivity index tends to curve toward the saturation axis. This kind of "non-Archie" behavior is experimentally observed (Worthington and Pallatt 1992;Moss et al 1999), and can be explained by the increasing amount of electric current in the water layers as S w decreases. If water is only residing in water layers, and the connectivity of the layers is preserved, the resistivity index yields I R = 1/S w .…”

Section: Fig 10mentioning

confidence: 74%

A Dynamic Network Model for Two-Phase Flow in Porous Media

Tørå

Øren²,

Hansen

2011

Transp Porous Med

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We present a dynamic model of immiscible two-phase flow in a network representation of a porous medium. The model is based on the governing equations describing two-phase flow in porous media, and can handle both drainage, imbibition, and steady-state displacement. Dynamic wetting layers in corners of the pore space are incorporated, with focus on modeling resistivity measurements on saturated rocks at different capillary numbers. The flow simulations are performed on a realistic network of a sandpack which is perfectly water-wet. Our numerical results show saturation profiles for imbibition in agreement with experiments. For free spontaneous imbibition we find that the imbibition rate follows the Washburn relation, i.e., the water saturation increases proportionally to the square root of time. We also reproduce rate effects in the resistivity index for drainage and imbibition.

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“…Many of these models have been reviewed by Worthington [47]; Glover et al [14]; and Friedman [13]. Early measurements of the electrical properties of rocks were primarily conducted by Wenner [43]; Smith-Rose [36] [47]; de Lima and Sharma [7]; de Lima and Niwas [9]; Toumelin and Torres-Verdin [39].…”

Section: Models Of Bulk Electrical Conductivitymentioning

confidence: 99%

Estimating a new approach for describing electrical conductivity parameters in partially saturated sediments

Swaid¹

2009

WIT Transactions on Ecology and the Environment

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Electrical resistivity imaging has the capacity to map changes in soil water content and quality in the vadose zone. However, interpretation of the images is difficult because of the numerous variables that influence the measured resistivity. The dominant variables include porosity, degree of saturation, pore water salinity, clay content and clay type.There have been numerous models published that combine these variables in order to predict the bulk electrical conductivity of any mixture. All these equations need to be calibrated against controlled samples in order to determine parameters that account for geometrical effects and grain surface conduction.Recently, Glover et al. (Earth and Planetary Science Letters 2000) published an extension to Archie's equation to account for the nonlinear behavior seen in the relationship between pore water salinity and soil/rock bulk conductivity. In this paper the Glover et al. model is extended to partial saturation conditions.The application of the new model in the evaluation of salinity and changes of soil moisture is possible wherever the required criteria are met. Furthermore, more, this relation can also be taken to estimate the changes in soil moisture caused by root uptake.

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Effect of Variable Saturation Exponent on the Evaluation of Hydrocarbon Saturation

Cited by 46 publications

References 4 publications

Modeling of the influence of gas hydrate content on the electrical properties of porous sediments

Modeling of the influence of gas hydrate content on the electrical properties of porous sediments

A Dynamic Network Model for Two-Phase Flow in Porous Media

Estimating a new approach for describing electrical conductivity parameters in partially saturated sediments

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