Synthetic cores containing various percentages of different clay minerals were flooded with water which contained different types of salts in varied amounts, and the flow rate·was measured during the application of direct electrical current at varying current density. Kerosene also was used as the flowing fluid, and some chemical additives, such as sodiwn acid pyrophosphate, were tested in conjunction with the application of electrical current.The experimental results indicated that the increase in the flow rate of liquids was due not only to the electroosmotic effect but also to some changes in the pore structure. These changes in the pore configuration took place during the electrochemical treatment and generally resulted in higher final hydrodynamic permeability. As a result of the physicochemical changes in the clay properties, the tendency of the clay to swell and absorb water was markedly decreased. In these systems, the electrical or electrochemical treatment appeared to be an irreversible process. The extent to which these electrochemical changes were produced depended in general on the amount of current passed, the magnitude of potential gradient imposed, the amount and type of clay minerals present, and the type and concentration of electrolytic solution used.

FOR many years the permeability of reservoir sands has been measured by flowing air through a cleaned and dried core sample. This differs from the true reservoir permeability in one important respect: the rock particles in the reservoir are surrounded by interstitial water, not air, and their physical shape and condition of hydration are greatly dependent thereon. Permeability as defined must be measured with a single-phase fluid. Since no means exist for removing the oil and gas from a core sample by simply flowing water through it, the sample must be cleaned and then resaturated with water before testing. The present discussion attempts to show that after the cleaning process a considerably different permeability is determined with salt or fresh water than is obtained with air. The postulate is made that the salt-water permeability is probably closer to the true reservoir permeability than is the measurement with air. This is discussed in relation to both physically possible and economically feasible measure-men~. Data on more than 1200 core samples are given to show the nature of the effects observed, and a plea is made for others to consider water permeability measurements as a routine necessity, eventually replacing air permeability in regions where the differences are great. Q 27rk SPI = h(P. -P",) = p.log. r./r w [4] or in terms of practical units, and allowing for shrinkage:[ 1 p.FVF loglo r./r;. 5

Part II of their paper already published in the Journal of Canadian Petroleum Technology, Vol. 3, No. 1, pages 9–14, Spring, 1964: "Use of Direct Electrical Current for Increasing the Flow Rate of Reservoir Fluids During Petroleum Recovery." Abstract The possible use of direct electrical current for increasing the flow rate of reservoir fluids during petroleum recovery was recently investigated by Ambah et al. [1964] (29). As pointed out by the writers, however, thestudy of the application of electrokinetic phenomena in oil production was notcomplete, and many other problems remain to be solved. The possibility of using electric current for enhancing the injectivity ofwater in waterflood systems or simply increasing the rate of production intight formations was further investigated in the present study. In all cases, the volumetric rate of flow increased on increasing the electrical potential imposed. Additional theoretical analysis is also presented here. Theoretical Analysis Reuss [1808] (2) was the first to notice that if two electrodes were placedin a liquid on opposite sides of a porous diaphragm, on application of an electromotive force the liquid would flow from one compartment to the other. An equilibrium will be reached when the hydraulic head, due to the difference influid level, is balanced by the driving force caused by the imposed e.m.f. Wiedemann's [1852] (3) first and second laws stated that: When an electrical field is applied to a liquid in capillaries, the flowis proportional to the electric current or the applied potential. If, instead, this flow is prevented, the electroosmotic pressure is likewise proportional tothe current. Quincke [1860] (4) recognized electroosmosis and streaming potential as inverse phenomena and explained them by assuming the existence ofan electric double layer at the boundary surface between the liquid and thesolid wall. It can be assumed that the solid surface is negatively charged andthe positively charged part of the double layer is present in the liquid phase.Thus, upon the application of an external electrical field, the positivelycharged liquid layer will move toward the cathode, drawing with it watermolecules in the free liquid stream because of the viscous drag. Conversely, ifa liquid is forced through capillaries, a streaming potential or a streamingcurrent, depending on which is measured, is produced which is proportional tothe pressure differential applied.

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