Role of Monovalent and Divalent Ions in Low-Salinity Water Flood in Carbonate Reservoirs: An Integrated Analysis through Zeta Potentiometric and Simulation Studies

Abstract

The presence of principal ions in the water injected is essential for enhanced oil recovery by formation of water-wet state in carbonates. This study reaffirms this and presents an evaluation of the positive influence of both divalent as wells as monovalent ions on wettability alteration mechanisms during low salinity waterflooding using brines of varying ionic composition, referred to as “smart brines”. Zeta potentiometric analysis and reservoir simulation studies were conducted with diluted and smart brines that were prepared by varying the composition of principal ions. Surface charge of oil-saturated whole core samples of rock in the presence of various diluted and smart brines was estimated by zeta potential measurements. A comprehensive analysis of zeta potentiometric and reservoir simulation studies was done to establish and investigate the linkage between the recovery mechanism and the incremental recovery achieved. It is noted that zeta potential increases with the increasing level of dilution and it can be attributed to electric double-layer mechanism. On the contrary, simulation studies implied a different mechanism where an increase in effluent’s pH and Ca2+ mole fraction along with decrease in moles of minerals and saturation index implied rock dissolution was dominant mechanism. Moreover, the effect of mineral dissolution beyond the injection block is highly doubtful. This study demonstrates that an integrated approach from both zeta potentiometric and simulation studies can be used to provide insights into the underlying science of interactions at pore scale during a low salinity waterflood using smart brines. With the aid of an adequately designed upscaling procedure and protocol, the laboratory results can be further used towards developing field-scale models to obtain with realistic recovery factors with optimized brine composition and salinity.

Interplay Between Ca2+, Mg2+, and SO42– Ions and Their Influence on the Zeta-Potential of Limestone during Controlled-Salinity Waterflooding

“…Figure shows consistent results for zeta-potential of limestone with the measurements reported in the literature for the impact of Ca 2+ , Mg 2+ , and SO 4 2– ions when they coexist in the same brine. The results shown in Figure are in agreement with other studies that reported negative zeta-potential for carbonate rocks in seawater, diluted seawater, and diluted seawater brines with increased concentration of SO 4 2– ions while showing positive zeta-potential for seawater brines with increased concentrations of Ca 2+ or Mg 2+ ions. ,,,,,,, The reported oil recoveries during injection of diluted seawater and low-salinity brines is commonly explained by the expansion of the electric double layer and establishment of stable water films. ,,, In a more detailed explanation, Alroudhan et al attributed the incremental recoveries in oil-wet carbonates during low-salinity waterflooding to the generated repulsion forces in the rock/oil/brine interfaces. They discussed that the key requirement for the injected water is to generate a negative zeta-potential at the mineral–brine interface when the oil–brine interface is negatively charged.…”

A calibrated surface complexation model for carbonate-oil-brine interactions coupled with reservoir simulation - Application to controlled salinity water flooding

“…Surface complexation models have been used to characterize crude oil-rock-brine (CORB) interactions in the reservoir 5,10,17,18,23,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] . They have the capability to describe surface adsorption/desorption phenomena of CORB using chemical reactions, mass balance, charge balance and equilibrium constants 49 .…”

Investigasi Sifat ION Na+ & NH4 + Pada Hybrid-Alkali ASP Flooding Menggunakan Simulator CMG GEM 2020

“…Permeabilitas yang digunakan pada model konseptual ini adalah pada layer satu 100 mD, layer dua 150 mD, layer tiga 200 mD, layer empat 250 mD, dan layer lima 300 mD. Berbagai parameter seperti perubahan pH, variasi mineral mol kalsit, perubahan konsentrasi ion dalam fase air telah dianalisis secara kritis untuk menilai setiap mekanisme yang mendasari, (Gopani et al, 2021). Komponen minyak yang sudah diikat, NH 4 Ao, NaAo, serta HAo akan mudah tersapu oleh fl uida pendorong, yang mana fl uida pendorong tersebut adalah polimer mengalir ke sumur minyak.…”