Kinetics and Equilibria of Calcium Lignosulfonate Adsorption and Desorption onto Limestone

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractEquilibria and kinetics are two basic ingredients for the proper understanding of adsorption and desorption processes between surfactants and rocks. The adsorption and desorption of calcium lignosulfonate (CLS), commonly used as a sacrificial agent in surfactant-based EOR processes, has been studied.Kinetic results showed that adsorption and desorption are both time-dependent, not instant. Both adsorption and desorption were characterized by a biphasic pattern: a fast step followed by a slow step. Apparent adsorption and desorption rate coefficients were determined by a second-order kinetic model. Desorption is a much slower process than adsorption. Desorption is an un-equilibrium process under normal reservoir flow rate conditions. Equilibrium results show that CLS adsorption and desorption onto limestone can be described well by the Langmuir isotherm over the tested CLS concentration range, and that increasing concentration increases adsorption density. There is significant hysteresis between CLS adsorption and desorption isotherms. Increasing flow rate slightly decreased CLS equilibrium adsorption. Increasing both NaCl and CaCl 2 concentrations increased adsorption density; however, CaCl 2 had a much greater impact on the adsorption. Increasing pH decreased CLS adsorption onto limestone. The reasons for the effects of the different factors are elucidated in this paper.

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“…The calculated equilibrium adsorption densities listed in Table 8 are 0.387 and 0.456 and 0.348 mg/g, respectively, which are higher (20-25%) than the adsorption densities (0.307, 0.365 and 0.263 mg/g) determined after 48 hours, which indicated CLS adsorption onto dolomite takes a longer time to reach equilibrium than it does onto limestone. 24 The rate constants of D01-E and D01-F are 0.193 and 0.212 at 23°C and 45°C, respectively, which indicates an increasing reaction rate between CLS and dolomite with increasing temperature. Thus, the required time to reach adsorption equilibrium should be shorter at the higher temperature.…”

“…Limestone 24 Equilibria and kinetics are two basic properties needed to adequately understand the adsorption and desorption processes between surfactants and rocks. The adsorption and desorption of calcium lignosulfonate (CLS), commonly used as a sacrificial agent in surfactant-based EOR processes, was examined in a series of dynamic depletion experiments.…”

“…24 The plot of Table 9. The calculated equilibrium adsorption densities shown in Table 9 are much higher than those calculated from the pseudo-second-order equation; however, these are not reasonable.…”

“…This report summaries results of this project taken from Annual Reports, 7-9 published work from refereed journals and conference presentations, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and yet unpublished work. Areas of interests are: 1) mobility control, 2) understanding and mitigation of reduced injectivity, and 3) modeling process mechanisms.…”

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“…3,6 To aid in predicting utilization of surfactant adsorption on pure minerals (silica, calcite, dolomite, kaolinite, and bentonite) that are common reservoir rock components, studies were performed to determine surfactant adsorption and desorption quantities, rates, mechanisms, and effects of physical parameters such as temperature, pressure, brine and surfactant composition and concentration, and pH on various rock components. [7][8][9][10][11] Work in this area will continue, particularly in determining adsorption values versus specific surface areas of the mineral to determine sweep efficiency in a homogeneous system. These results are required to develop models to be used in numerical simulation to predict usage in a reservoir.…”