Synthesis and Characterization of Salt Tolerant Ternary Polyampholyte as Rheology Enhancer and Fluid Loss Additive for Water-Based Drilling Fluids

Nurbatyr Mukhametgazy, Iskander Sh. Gussenov, Alexey V. Shakhvorostov, Heikki J. Tenhu, Munziya Abutalip, Sarkyt E. Kudaibergenov

2023

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DOI 10.30919/es965
Data confidence 70 medium
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Abstract

A novel ternary polyampholyte (TPA) was synthesized via free radical copolymerization in deionized water using ammonium persulfate as an initiator.The TPA composition included 80 mol.% acrylamide (AAm), 10 mol.% 2-acrylamido-2-methyl-1propanesulfonic acid sodium salt (AMPS), and 10 mol.% (3-acrylamidopropyl) trimethylammonium chloride (APTAC).TPA was used as an alternative to low viscosity polyanionic cellulose (PAC-LV) to prepare bentonite based drilling fluids with different concentrations of NaCl (1-35 wt.%).Gel strength (GS) measurements demonstrated that, at a 6:1 [initiator]:[catalyst] ratio, even in high salinity brines (25-35 wt.%), the GS values exceeded industry standards, highlighting the superior performance of bentonite/ternary polyampholyte (BT/TPA) in high salinity media.Notably, TPA addition significantly reduced the filter cake thickness to 0.09 cm, outperforming BT/PAC-LV (0.18 cm) and bentonite alone (0.41 cm).Furthermore, the BT/TPA drilling fluid exhibited the lowest permeability/thickness ratio at 13 mD/cm, indicating its potential as a rheology enhancer and fluid loss additive for salt-resistant Water-Based Drilling Fluids (WBDF) applications.The filtration performance of bentonite and bentonite/polymer dispersions showed a clear trend in fluid loss values: BT/TPA < BT/PAC-LV < Base fluid.The high-salinity BT/TPA drilling fluid had remarkably low fluid loss, measuring just 3.5 ml, well below the API standard limit of 12 ml.