Abstract
A hyperbranched polyamine was synthesized by self‐condensing vinyl polymerization with divinyl sulfone, N‐phenyl‐p‐phenylenediamine, by A2 + approach. The hyperbranched polyamine was characterized by FT‐IR, TGA, and phase analysis light scanning. Average grain diameter of hyperbranched polyamine was 36.7 nm. Hyperbranched polyamine has good thermal stability. Hyperbranched polyamine (HBPA) was employed successfully as nanoplugging agent in oil‐based drilling fluid system, which could plug nanopore formation in shale formation. HBPA has a little effect on rheological properties of oil‐based drilling fluid and the FLAPI and FLHTHP decreased dramatically with an increase of hyperbranched polyamine. Emulsion‐breaking voltage has a slight increase, which is beneficial to maintain stability of oil‐based drilling fluid. When the HBPA concentration is greater than 1 wt%, plugging rate of oil‐based drilling fluid for artificial core is close to 100% and the permeability recovery value can reach 99.7% after adding 1 wt% HBPA, which prove that HBPA has an excellent plugging performance.
Highlights
Drilling is linked to drilling fluid that can often cause borehole instability
Hyperbranched polyamine (HBPA) as nanoplugging agent was synthesized by using an A2 + BB2 method (Figure 2)
The hyperbranched polyamine was synthesized by selfcondensing vinyl polymerization with divinyl sulfone, Nphenyl-p-phenylenediamine, by an A2 + BB2 method
Summary
Drilling is linked to drilling fluid that can often cause borehole instability. Borehole instability often leads to various kinds of problems such as hole collapse, tight hole, stuck pipe, bit balling, high torque, and drag, which can increase drilling time and costs [1]. Whether water-based drilling fluid or oil-based drilling fluid strengthen the blocking that prevent filtrate into the formation of micro-cracks and reduce the formation collapse pressure is the key of drilling shale gas horizontal well, which can improve the pressure-bearing capability of borehole wall and expand the safe density window of drilling fluid. The deformable polymer could seal nanosized microfractures and pore throats in shale formation, decrease the permeability of filtrate penetrate into the formations, lower pressure transmission, and block borehole collapse [17]. A variety of sealing mechanism can be utilized to block microcracks and make the drilling fluid form a layer of isolation film near borehole wall, enhancing the plugging effect of oil-based drilling fluid and maintaining borehole wall stability, which is expected to solve borehole wall instability problem that use oil-based drilling fluid to drill shale gas horizontal well. The synthesis and properties of hyperbranched polyamine and its nanoplugging properties are described in detail
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