Thermal Behavior of Multifluid-Saturated Formations Part 1: Effect of Wettability, Saturation, and Grain Structure

Abstract

Abstract A conceptual model is developed for prediction of thermal conductivity of multi-fluid saturated formations. The model incorporates the physical properties as well as wettability and solid-fluid affinity concepts. The fluid saturation distribution, the Biot number related to the surface of contact between the solid matrix and fluids, and a grain contact parameter successfully explained the thermal behavior of given rock fluid systems. Experimental measurements on actual rock-fluid systems confirmed the validity of the proposed method. Both the model and experimental results indicated the thermal conductivity of formations to be a function of the square root of wetting phase saturation. The degree of compaction and cementation between solid grains of the rock is also an effective factor in determining the thermal conductivity. Being expressed in terms of a dimensionless grain contact parameter, the compaction cementation was correlated with the formation resistivity factor. Introduction Analyses of thermal recovery processes and geothermal steam and hot water formations require knowledge about thermal behavior and properties of multi-fluid saturated porous media. The validity of such analyses and the applicability of their results are sensitive to the reliability of these data. In particular, it is important to use the proper values of the system's thermal properties and to have a good notion about their modes of change with the existing variables. A porous sandstone consists of a framework of solid grains, whether cemented together or not, within which pores and openings are present. Such openings are filled with different combinations of fluids. Thermal properties of these rock-fluid systems will be, of course, a certain combination of the individual properties of their constituents and a function of the existing environmental conditions. In addition these properties are functions of the modes of behavior and interactions between fluids and solid matrix. The literature contains a considerable amount of work on different methods and techniques for measurements and prediction of some of these properties. However, such methods and data are limited to porous media saturated with a single fluid. Very little has been done on the mixed fluid saturation problem and the above effects were not quantitatively evaluated.