Abstract
Carbonate rock strengthening using chemical techniques is a strategy to prevent excessive fines migration during oil and gas production. We provide herein a study of the adsorption of three types of hydrolysed polyacrylamide (HPAM) of different molecular weight (F3330S, 11–13 MDa; F3530 S, 15–17 MDa; F3630S, 18–20 MDa) onto calcium carbonate (CaCO3) particles via spectrophotometry using a Shimadzu UV-2600 spectrometer. The results are compared to different adsorption isotherms and kinetic models. The Langmuir isotherm shows the highest correlation coefficient (R2 > 0.97) with equilibrium parameters (RL) ranging between 0 and 1 for all three HPAMs, suggesting a favorable monolayer adsorption of HPAM onto CaCO3. The adsorption follows pseudo-second order kinetics, indicating that the interaction of HPAM with CaCO3 is largely dependent on the adsorbate concentration. An adsorption plot reveals that the amount of HPAM adsorbed onto CaCO3 at equilibrium increases with higher polymer molecular weight; the equilibrium adsorbed values for F3330S, F3530S and F3630S are approximately 0.24 mg/m2, 0.31 mg/m2, and 0.43 mg/m2, respectively. Zeta potential analysis shows that CaCO3 has a zeta potential of +12.32 mV, which transitions into negative values upon introducing HPAM. The point of zero charge (PZC) is observed at HPAM dosage between 10 to 30 ppm, in which the pH here lies between 9–10.
Highlights
Carbonate reservoirs are ubiquitous in the oil and gas industry as they contribute to approximately 60% of the global petroleum reserves and provide lucrative potential for additional gas reserves [1,2]
Hydrolysed polyacrylamides (HPAM) with different molecular weight were adsorbed onto calcium carbonate (CaCO3) samples, and data points from spectrometry are fitted into different adsorption isotherm and kinetic models
The adsorption follows a pseudo-second order kinetics indicating that the hydrolysed polyacrylamide (HPAM) interaction with CaCO3 is largely dependent on the adsorbate concentration
Summary
Carbonate reservoirs are ubiquitous in the oil and gas industry as they contribute to approximately 60% of the global petroleum reserves and provide lucrative potential for additional gas reserves [1,2]. Peng et al [12] studied the effect of cationic polyacrylamide (CPAM) on precipitated calcium carbonate (PCC) flocculation They investigated the kinetics of the CPAM adsorption onto PCC, as well as the effect of CPAM charge density and background ionic strength on the adsorption. The presence of high ionic strength essentially neutralizes the charges of the polymer, the flocculation behavior between polymer adsorbed PCC transitions from an electrostatic attraction to physical bridging interaction. A similar study was conducted by Rasteiro et al [13], whereby they studied the flocculation and adsorption of CPAM on PCC Their results agreed with that from Peng et al [12], where in the absence of salt, an increase in CPAM charge density, adsorption equilibrium is reached at a lower contact time, indicating high charge density favors adsorption. Tahnearnefiornei,ctphoislypmaperertoaipmesrftoorminvaedsstoigrpatteiotnheonatdosoarpotisointivkeilnyetcihcsaragnedd cahdasroarcbtenrits.tTichseoreffoHrPe,AthMis opnatpoerpaoismitsivteolyinvchesatrigeadte CthaeCaOd3sowrphtiiloenakssinesesticnsgahnodwchparoalyctmereisrctoicnscoefnHtraPtAioMn aondtompolseitciuvlealrywcheaigrghetdafCfeacCt Oth3ewadhsiloerapstsioensspinrgocheosws. polymer concentration and molecular weight affect the adsorption process
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