New-type Corrosion And Scale Inhibitor And Acidizing Plug-removing System Based On Deep Eutectic Solvents

Corrosion scaling and low permeability oil field recovery difficulties are two major problems facing oil field extraction,which seriously affect crude oil production and restrict the effective development and utilization of oilfields in our country.Nowadays,the corrosion and scale inhibitors used in oilfield extraction have the shortcomings of poor dispersion stability and easy to generate precipitation,while the acidizing plug-removing systems have the disadvantages,such as short penetration distance,too fast reaction rate,and poor corrosion dissolving ability.Therefore,it is urgent to develop neotype corrosion and scale inhibitors and neotype the acidizing plug-removing systems for crude oil extraction to improve oilfield production and ensure our country′s energy security.In this article,the merits of strong solubility effect,fantastic stability,easy availability and well compatibility of deep eutectic solvents are fully utilized to synthesize a neotype corrosion and scale inhibitors with fine capability,and then compound with autogenous acid system to build neotype the acidizing plug-removing systems with controllable reaction rate,long penetration distance and better dissolution effect for plug-removing in low permeability oilfields.The contents of the research in this thesis are as follows:（1）The neotype corrosion and scale inhibitor was synthesized based on deep eutectic solvent,and its corrosion and scale inhibition performance were tested and the mechanism was analyzed.The solvent effect of deep eutectic solvent can effectively increase the co-solubility and dispersion stability of the neotype corrosion and scale inhibitor.The experimental results demonstrated that the neotype corrosion and scale inhibitor has outstanding corrosion and scale inhibition performance,the corrosion inhibition rate of the neotype corrosion and scale inhibitor was measured to be 96.4%,and the scale inhibition rates of Ca SO₄,Ca CO₃,Ba SO₄,and Sr SO₄were 91.7%,88.1%,49.1%,and 19.4%respectively.The active molecules in the neotype corrosion and scale inhibitor can form a dense protective film covering or directly adsorbed on the metal surface through oxidation,which can achieve fine corrosion inhibition effect and protect oilfield pipelines.The neotype corrosion and scale inhibitor includes carboxyl group,hydroxyl group and sulfonic acid group and other active functional groups,which can chelate with Ca²⁺,Sr²⁺and Ba²⁺scale forming ions in the groundwater to achieve scale inhibition purpose.（2）Based on the theory of deep eutectic solvent,two neotype the acidizing plug-removing systems were constructed.Firstly,an autogenous acid system containing deep eutectic solvent,organic/inorganic acid and NH₄F was synthesized,and then compounded with the neotype corrosion and scale inhibitor to form a neotype acidification and declogging system.In this system,part of the acid and choline chloride are bonded with hydrogen to form a deep eutectic solvent,and the rest of the acid and fluorine ions form hydrofluoric acid dissolved in it,which can effectively enhance the stability of the system and reduce the reaction rate of acidification to improve the dissolution performance.The two neotype the acidizing plug-removing systems based on deep eutectic solvents show good dissolution and unblocking effects on clay minerals.The dissolution experiment showed that the dissolution rates of the optimum system 1（DES+HCl+NH₄F+neotype corrosion and scale inhibitor）were 83.0%,50.3%,62.5%,and 10.6%for kaolin,montmorillonite,chlorite and illite,respectively;the dissolution rates of the system 2（DES+NH₄F+neotype corrosion and scale inhibitor）were 80.9%,56.5%,67.3%,and 15.0%for kaolin,montmorillonite,chlorite and illite correspondingly.Further the addition of the neotype corrosion and scale inhibitor retarded the rate of acidification reaction,protected the reservoir skeleton and realized the deep penetration of acidification in low permeability oil fields.