Alkali/Cosolvent/Polymer Flooding of High-TAN Oil: Using Phase Experiments, Micromodels, and Corefloods for Injection-Agent Selection

Abstract

Summary Chemical enhanced oil recovery (EOR) leads to substantial incremental costs over waterflooding of oil reservoirs. Reservoirs containing oil with a high total acid number (TAN) could be produced by the injection of alkali. Alkali might lead to the generation of soaps and emulsify the oil. However, the generated emulsions are not always stable. Phase experiments are used to determine the initial amount of emulsions generated and their stability if measured over time. On the basis of the phase experiments, the minimum concentration of alkali can be determined and the concentration of alkali above which no significant increase in the formation of initial emulsions is observed. Micromodel experiments are performed to investigate the effects on the pore scale. For the injection of alkali into high-TAN oils, the mobilization of residual oil after waterflooding is seen. The oil mobilization results from the breaking up of oil ganglia or the movement of elongated ganglia through the porous medium. As the oil is depleting in surface-active components, residual oil saturation is left behind either as isolated ganglia or in the down gradient side of grains. Simultaneous injection of alkali and polymers leads to a higher incremental oil production in the micromodels owing to larger pressure drops over the oil ganglia and more-effective mobilization accordingly. Coreflood tests confirm the micromodel experiments, and additional data are derived from these tests. Alkali/cosolvent/polymer (ACP) injection leads to the highest incremental oil recovery of the chemical agents, which is difficult to differentiate in micromodel experiments. The polymer adsorption is substantially reduced if alkali is injected with polymers compared with polymer injection only. The reason is the effect of the pH on the polymers. As in the micromodels, the incremental oil recovery is also higher for alkali/polymer (AP) injection than with alkali injection only. To evaluate the incremental operating costs of the chemical agents, equivalent utility factors (EqUFs) are calculated. The EqUF takes the costs of the various chemicals into account. The lowest EqUF and, hence, the lowest chemical incremental operating expenditures are incurred by the injection of Na2CO3; however, the highest incremental recovery factor is seen with ACP injection. It should be noted that the incremental oil recovery owing to macroscopic-sweep-efficiency improvement by the polymer needs to be accounted for to assess the efficiency of the chemical agents.

Coupling Microfluidics Data with Core Flooding Experiments to Understand Sulfonated/Polymer Water Injection

“…The commercial price of Na 2 SO 4 is USD 80–120/Ton. The average price of this salt is around 0.1 USD/kg, which is much lower than the average price of polymer, alkaline, and co-solvent (3 USD/kg, 0.25 USD/kg, and 3 USD/kg, respectively [ 42 ]). The spiked amount of sulfate to design sulfate-modified water for this study is 8–16 g/L (two times and four times the sulfates in SSW).…”

“…The micromodel is an artificial structure micromodel or homogeneous micromodel, due to its random distribution of circular grains. Such micromodels have been previously used for several EOR investigations [ 39 , 40 , 41 , 42 ]. Figure 2 shows pore structure images and dimensional measurements of the model, and Table 2 provides porosity and permeability values.…”

“…This is a compact experimental setup that includes injection pumps, a micromodel holder, a DSLR camera for imaging, pressure sensors (connected to the inlet and outlet of the micromodel holder), and fluid and waste reservoirs. An upgraded version of the experimental setup and components, as described by Schumi et al [ 42 ], was used for the flooding experiments. The flooding process was performed at an injection flux of 1.0 ft/day, with corresponding injection rates included in Table 2 .…”

On the Role of Polymer Viscoelasticity in Enhanced Oil Recovery: Extensive Laboratory Data and Review

“…Furthermore, the micromodel is placed under a microscope equipped with a high-speed camera (qualitative evaluation). There is a broad range of micromodel types that can be used for flooding experiments such as GSG micromodels based on Bentheimer CT images [ 15 , 88 , 89 ], completely transparent real porous-media-resembling plastic micromodels (Hogeweg et al 2018) and symmetric micromodels as presented in the work of Galindo-Rosales [ 61 ] and Scholz et al [ 59 ]. An overview image of a GSG micromodel as used by Wegner et al [ 15 ], Rock et al [ 30 ], Gaol et al [ 89 , 90 ] and Hincapie et al [ 29 ] as an example is shown by Figure 13 .…”

A characterization of different alkali chemical agents for alkaline flooding enhanced oil recovery operations: an experimental investigation

“…Alkaline injection has also been coupled with other enhanced oil recovery methods including surfactant injection [20], polymer injection [21,22], polymer and surfactant flooding [23][24][25][26], smart water injection [27], and even steam-assisted gravity drainage [28]. Potts and Kuehne [29] underwent experiments using fired Berea sandstone cores and reservoir cores to compare the difference between both when undergoing polymer/alkaline injection.…”