Weighted geometric mean model for determining thermal conductivity of reservoir rocks: Current problems with applicability and the model modificationстатья
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Дата последнего поиска статьи во внешних источниках: 1 июня 2022 г.
Аннотация:Thermal conductivity is one of the fundamental physical parameters of rocks used in all fields of Earth science
related to heat transfer in formations. Theoretical modeling of thermal conductivity plays a significant role when
it is impossible to carry out measurements on rock samples or when it is necessary to account for variations in
bulk thermal conductivity caused by natural or technological factors. Among many theoretical models for
determining the thermal conductivity of reservoir rocks, the weighted geometric mean model or so-called
Lichtenecker model is the most popular. We demonstrate that the model systematically underestimates the
predicted thermal conductivity relative to the experimental results obtained from the thermal conductivity
measurements on 20 collections of 1765 samples represented by sandstones, limestone dolomites, limestones,
siltstones, and argillites in various saturation states. The underestimation value depends on lithology, porosity,
and pore fluid and can reach 53% for high porous (27.6% of porosity) gas-saturated rocks: the average value of
the underestimation is 20.5% for dried samples, 14.4% for kerosene-saturated, and 8.6% for water-saturated
collections. It means that the applicability of the weighted geometric mean model for determining the thermal
conductivity of reservoir rocks creates a serious risk of essential errors in the predicted data that requires
revision and improvement of the theoretical model. It is shown that using the correction factor in the weighted
geometric mean model resolves the problem leading to an average absolute relative deviation of less than 0.45%
for dried and kerosene-saturated samples and less than 0.3% for water-saturated samples. We presented the
technique for estimations of the factor for different rock types with corresponding results, and studied its relation
with the pore space geometry of carbonate rocks using Effective Medium Theory. Interrelations were studied
between the correction factor, rock types, pore fluid, and pore space characteristic - aspect ratio. The suggested
improvement technique can be used in numerical calculations after modifying the corresponding option of
thermo-hydrodynamic simulators or in theoretical calculations to decrease the uncertainty in bulk thermal conductivity and increase the reliability of calculation results.