An Experimental Study of Recovery From a 2-D Layered Sand Model

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The effect of flow rate on the recovery of oil by waterflooding is studied, using a two-dimensional, layered sand model allowing visual observation. The model consists of three communicating layers of equal thickness of water-wet sand with the permeability ratio of 2:4:1 from top to bottom. Three white mineral oils of viscosity 15, 30, and 150 centipoise have been used for immiscible liquid/liquid displacement under constant pressure drops covering a range of flow rates.The changes in flow regimes in the various layers are observed with respect to the variations in pressure drop across the model. The effects of capillary imbibition, gravity segregation and viscous pressure gradient are observed and an attempt is made to quantify the crossflow. Crossflow of oil from the tight layers to the most permeable layer increases the intermediate recovery of oil for a given volume of water injected. Oil recovery increases with a decrease in flow rate and also with a decrease in oil viscosity. Slow flow rates produce higher recovery but may not be feasible in the field for economic reasons.Most of the crossflow of oil into the permeable layer occurs just behind the flood front and produces a secondary oil bank soon after breakthrough. A sequence of slow flow rate followed by a fast flow rate is shown to improve the recovery of oil for a given volume of water injected, and this occurs within a reasonable experimental time-frame. Slow flow rate is continued to the time of breakthrough to take advantage of the crossflow and then the flow rate is increased and maintained for the remaining life of the waterflood. The slow flow rate is set from a criterion of stable displacement in the most permeable layer based on Peters' stability analysis (1981) and the fast flow rate is based on the maximum pressure the model can take.The effect of variation in interfacial tension on the displacement behavior is also studied. Interfacial tension is reduced from 45.0 to 0.5 dyne/cm by the addition of a surfactant to the injected flood-water. These ranges of interfacial tension are not sufficiently low to increase oil recovery from interfacial effects. The low interfacial tension flood produced less oil than a waterflood for the same volume of injected fluid. This results from the reduced capillary imbibition which is important for oil recovery from a stratified reservoir. Also, the injectivity of the surfactant solution probably decreased due to emulsion forming and plugging of pore channels.


Type of resource text
Date created September 1984


Author Ahmed, Gulfaraz
Primary advisor Castanier, Louis M.
Degree granting institution Stanford University, Department of Petroleum Engineering


Subject School of Earth Energy & Environmental Sciences
Genre Thesis

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Ahmed, Gulfaraz. (1984). An Experimental Study of Recovery From a 2-D Layered Sand Model. Stanford Digital Repository. Available at:


Master's Theses, Doerr School of Sustainability

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