NovelN,N‐dimethylacrylamidecopolymer containing multiple rigid comonomers as a filtrate reducer inwater‐baseddrilling fluids and mechanism study

Abstract

Ultra‐high temperature dramatically deteriorates rheological properties and filtration performance of water‐based drilling fluids (WBDFs), especially for a salt‐gypsum formation that greatly restricts the application of WBDFs in ultra‐deep well drilling operations. Hence, the research in this article used an anionic copolymer (DANS) prepared by N, N‐dimethylacrylamide, 2‐acrylamide‐2‐methylpropanesulfonic acid, N‐vinylpyrrolidone, and sodium 4‐styrenesulfonate as an anti‐ultra‐high temperature and anti‐salt contamination filtrate reducer. Due to its multiple bulky cyclic structures in the side chain, DANS exhibits excellent thermal stability in the thermal gravimetric, rheological, and filtration tests. By adding 1.0 wt% DANS, the American Petroleum Institute (API) filtration volume of sodium bentonite‐based fluids (SBT‐BFs) decreased from 56.0 to 9.2 ml after aging at 240°C. Even under both 20 wt% NaCl contamination and 240°C aging, SBT‐BFs with 2.0 wt% DANS could maintain a filtration volume of 9.4 ml, whereas SBT‐BFs without DANS reached a filtration volume of 203.0 ml. The possible filtration control mechanism of DANS was further investigated via the Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), ζ potential, particle size distribution, filter cake micro‐morphology, and transmission electron microscopy (TEM). Confirmed by FTIR and AFM results, the effective adsorption was formed between DANS and bentonite even under a high‐salinity environment. Thus, a firm “dot net” structure formed by bentonite/DANS was observed by TEM, significantly improving the colloidal stability, dispersibility, and filter cake compactness of SBT‐BFs. Finally, by utilizing DANS as the core treatment agent, a high‐density WBDFs system with a temperature resistance of 240°C and a salt‐tolerance of 20 wt% has been successfully prepared.

Synthesis of a network‐structured polymer with low viscosity effect and its use as filtrate reducer for water‐based drilling fluids

“…During the drilling process, the larger bentonite particles are used as bridge particles, while the smaller bentonite particles are used as filler particles to fill the gaps between the larger particles, resulting in a thin and dense mud cake. 8,50 SWBDF and SWBDF with 3.5% DSD-β-CD were hot rolling at 220 C for 16 h and the particle size distribution of bentonite before and after hot rolling was measured. The experimental results are shown in Figure 10.…”

“…The main drilling fluids in common use are water-based drilling fluids and oil-based drilling fluids. 8 However, oil-based drilling fluids are not only costly, but also seriously pollute the environment, which greatly limit the application of oil-based drilling fluid technology. [9][10][11] On the contrary, water-based drilling fluids have the advantages of low cost and environmental friendliness, [12][13][14] and gradually becomes the preferred drilling fluid.…”

A molecular dynamics study on adsorption mechanisms of polar, cationic, and anionic polymers on montmorillonite

“…16–19 On the other hand, polymers can also be physically adsorbed on clay via van der Waal, electrostatic, and hydrogen-bonding interactions. 20–23 Our aim in this study is to investigate the general principles behind polymer/clay interactions, but the strength of chemisorption depends on the number and distributions of chemical bonds, which are determined by the specific preparation method and cannot be discussed unless the details of preparation method are provided. Therefore, we focus only on physical adsorption in this paper.…”

Synthesis of novel zwitterionic polymers and their properties as filtrate reducer for water‐based drilling fluid

“…At present, the commonly used method is to use acrylamide‐based polymers as the main monomer and introduce monomers with high‐temperature and salt‐resistant groups. Wang et al 29 synthesized a high‐temperature and salt‐resistant filtration reduction agent (DANS) using N,N‐dimethylacrylamide (DMAM), AMPS, NVP and SSS as monomers through free radical polymerization. DANS and bentonite had effective adsorption and formed a solid network structure.…”