This study was undertaken to investigate the transient behavior of particulate plugging of porous media. The objectives of the experiments were to study in detail a well-characterized system and to check the validity of theoretical predictions. Experiments included injection of clay suspensions under different conditions into sandpacks, measurement of pore-size distribution, and monitoring of permeability and effluent particle concentrations.

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This study was undertaken to investigate the transient behavior of particulate plugging of porous media. The objective of the experiments was to study in detail a well-characterized system and check the validity of theoretical predictions. Kaolin and bentonite suspensions were injected into 40 to 170 mesh Ottawa sandpacks. The pore size distribution of the pack was measured. The permeability and effluent particle concentrations were monitored continuously. Experiments were conducted at different flow rates, pH values, ionic strengths, and particle concentrations with each clay mineral. The effect of each of these parameters on the permeability reduction and effluent particle concentration profile was evaluated. The particle size distribution of the influent stream was also measured at different pH and ionic strengths. It was observed that high ionic strengths, low pH, low flow rates and high particle concentrations cause more rapid permeability reduction. The particle and pore size distributions together with the surface charges on the particles and pores can be used to ·estimate theoretically the rates of permeability decline. A comparison of theoretical predictions with experimental observations shows a semi-quantitative agreement. All trends in the permeability reduction profile obtained by varying parameters (such as flow rate, pH, …) are consistently predicted. The usefulness of studying well-characterized systems is demonstrated. The results provide a better insight into the mechanisms responsible for particulate plugging. The findings will be useful for estimating and minimizing damage due to drilling mud infiltration, waterflooding and fines migration in unconsolidated sands. Electrochemical conditions under which particle deposition occurs can be qualitatively predicted. Coagulation effects due to changes in pH and ionic strength may affect interpretation of the results.

The hypothesis that the recovery of oil by a steam drive could be duplicated by a combination hot water and non-condensible gas drive has been confirmed in bench scale, non physically scaled experiments. Despite the inherent limitations of such laboratory experiments, it is believed that the results point to the potential of a new powerful enhanced oil recovery process for both viscous and high gravity crudes. Introduction Steam drive operations in the Kern River and San Ardo fields have been reported to recover upwards of 600 barrels of oil per acre foot, or more than 50% of the oil in place at the time of beginning steaming operations.1,2 The viscosity-temperature relationship of the Kern River crude is such as to promote the attainment of economically high oil steam ratios3. This factor combined with the fact that adequate steam rates can be achieved at relatively low pressures (resulting from the unique combination of oil saturation and specific reservoir permeability) make it easy to explain why Kern River reservoirs are such ideal candidates for steam drive operations. There is insufficient documentation of the results of steam drive operations in other reservoirs to make a judgement on the universality of the steam drive in attaining high recovery efficiencies. Theoretical and laboratory results do point rather strongly to the possibility that an unassisted steam will be just as spectacularly efficient in reservoirs of high gravity crudes4,5 but not in those containing viscous crudes3. The principal factor that appears to limit the efficiency of the steam drive is, as in any enhanced oil recovery scheme, the existence of a very poor permeability distribution. In fact, the economics of the steam drive is less sensitive to this factor than are other enhanced oil recovery processes because of the low cost of a unit reservoir volume of the recovery agent, i.e., steam vapor. As a result, large reservoir volumes of steam can be circulated through a reservoir at relatively little cost. But, if there are large lens or intervals of low oil saturation, or significant intervals which are depleted preferentially, then a large amount of steam (energy) will be wasted in heating and circulating fluid through those intervals. The overall efficiency suffers. In reservoirs of viscous oil, the most damaging effect of a channel of low oil saturation, other than the energy that is wasted in generating steam to circulate through and raise the temperature of barren sands, is that the steam pressure within the depleted sand will effectively prevent any significant drainage of oil into the steam zone. Oil production becomes limited to the oil that is entrained at the steam oil interface3,5. One way of countering this phenomenon is of course to cycle the injection of steam (lowering and raising the pressure of the steam within the channel) as suggested by experimental results with models of dipping reservoirs and diurnal injection6,7, and by field pilots in tar sands8.

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