Mechanisms, Parameters, and Modeling of Naphthenate-Soap-Induced Formation Damage

Abstract

Naphthenate-soap deposition and the related formation damage in petroleum reservoirs are investigated by means of laboratory-scale experimental and theoretical studies. Experiments were carried out in three directions to understand and quantify the naphthenatesoap-deposition problem. Static bottle tests were conducted to determine the precipitation rate for various pH and temperature conditions. Microscopy investigations were carried out to verify the growth of naphthenate-soap particles under different pH conditions. Core-flow tests were conducted to generate naphthenatesoap particles and to determine the permeability impairment caused by subsequent deposition of these particles in porous media under flowing conditions and different pH values. A power-law expression was proposed and verified for the precipitation rate of the naphthenate-soap particles. The parameters of the rate equation were correlated with respect to pH and temperature. This also allowed the determination of the critical pH value for the onset of naphthenate-soap precipitation. The results of the particle-size experiments were described by a particle-growth equation, and the parameters of the equation were correlated with respect to pH. The core-flow experiments proved the occurrence of formation damage caused by naphthenate-soap precipitation and subsequent deposition. The permeability impairment in core-flow experiments was described by a new differential model. The applications presented in this study provide insights for understanding the mechanism and magnitude of naphthenate-soap-induced formation damage and help in taking proper measures to avoid the formation damage caused by naphthenate-soap deposition.

Equilibrium Partitioning of Naphthenic Acid Mixture, Part 1: Commercial Naphthenic Acid Mixture

“…Naphthenic acids are corrosive, although using TAN as an indicator for corrosiveness is unreliable and researchers suspect a smaller subgroup of acids might be culpable . Naphthenic acids affect the stability of water in oil emulsions and oil-in-water emulsions , and cause pipe or formation pore blockage through precipitation. , Some of the cyclic and aromatic naphthenic acids has been shown to be toxic and carcinogenic, which is why dissolved naphthenic acids are considered major contaminants in oil sands process-affected water (OSPW) . Produced water discharge from offshore installations also contains naphthenic acids, which raises some environmental concerns …”

Equilibrium Partitioning of Naphthenic Acid Mixture Part 2: Crude Oil-Extracted Naphthenic Acids

“…Naphthenic acids have been linked to downstream corrosion, emulsion formation, , deposition on processing units, and formation pore blockage . Multiple authors have applied mass spectroscopy to characterize naphthenic acids. ,− ,− Mass spectroscopy has some limitations that need to be accounted for.…”

Adsorption of Carboxylates on Calcite: the Coupled Effect of Calcite–Brine and Brine–Oil Interactions

“…However, since we did not come across any experimental data showing the development of the partitioning with time, we lack the basis for introducing a time-dependent acid transfer within our reactive transport model. A kinetic approach can, however, be adopted for the formation of calcium carboxylate salts/soaps considering the precipitation of calcium myristate experiments reported by Sarac and Civan . The kinetic precipitation of calcium carboxylate salts is addressed hereafter.…”

“…To obtain the kinetic parameters k and p , we fit the oil–brine model to the experimental data from Sarac and Civan. ; in these experiments, the authors mixed CaCl 2 (1 wt % Ca 2+ ) brines of different initial pHs (fixed by NaOH titrations) with an equal volume of model oil (1 wt % myristic acid in toluene) and filtered out and measured the fatty acid calcium precipitates formed at different times throughout the experiment. To limit the number of adjustable parameters, we assumed that the ionization constant of the myristic acid is equivalent to that of oleic acid and that found for naphtenic acids (p K a = 4.9).…”

“…Evolution of calcium myristate precipitation with time. The markers correspond to the experimental data from Sarac and Civan . The solid lines represent the fit of the model considering p K wo = 6.7 and p K Ca = 13.5 and manually adjusting the kinetic parameters ( k = 1e –9 mol·m 3 ·s –1 , p = 0.35), whereas the dashed lines were obtained by fitting the model to the experimental data obtained at pH = 8 with four adjustable parameters (p K wo = 6.5, p K Ca = 13.76, k = 3.82e –9 mol·m 3 ·s –1 , and p = 0.28).…”