Abstract
In this paper, a series of poly ammonium shale inhibitors were prepared from diethylamine, epichlorohydrin, and melamine (DEM) and their inhibition to shale were evaluated by bentonite linear expansion test, anti-swelling experiments, and mud ball experiments. Additionally, other properties of drilling fluid treated by poly ammonium were evaluated. Anti-swelling results showed that anti-swelling rate of DEM-8 reaches up to 97.8% when its concentration reaches to 0.8%. Mud ball experiment and drilling fluid evaluation showed DEM-8 has strong inhibitive capability to bentonite hydration swelling and controlling the particle size of bentonite in a large scale. The inhibition mechanism of DEM-8 was studied by thermogravimetric analysis and scanning electron microscope. The results demonstrate that DEM-8 can be adsorbed on clay surface through electrostatic interaction and hydrogen bonds by an anchoring effect and a hydrophobic effect.
Highlights
Shale oil/gas has been one of the technologies highlighted in the world in recent years
The results show that the product synthesized under 90 °C, DEM-8, displays most potent inhibition with the lowest clay-swelling rate of 53.75% within 90 min
The possible reason may attribute to the proper ratio of crosslinking agent helping to form a cross-linked net work, and the low ratio and low temperature is not efficient to cross link the polyammonium while the high ratio and high temperature may lead the polyammonium to cross link and assemble into a tight agglomeration
Summary
Shale oil/gas has been one of the technologies highlighted in the world in recent years. Borehole stability problems such as bit balling, disintegration of cuttings, borehole wash-out and stuck pipe mostly occur in shale formations due to hydration and swelling of water-sensitive shales [1–3]. When water-sensitive shales (high montmorillonite content) are exposed to water-based drilling fluids, depending on the chemical characteristics of the shale or drilling fluid, this can result in a rapid swelling or dispersion of the shale [4]. A high level of shale inhibitor has been utilized widely in drilling operations [4, 5], but same additives may be unfavorable due to the environmental protection requirements, which limits their usage or restricts their discharge [6]. Organic amine compounds with high performance as shale inhibitor have drawn much attention of the researchers.
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