Synthesis Of Modified Lignin As Drilling Fluids Thinner And Study Of Its Interaction With Montmorillonite

With the increase in the number of special wells, super-deep wells and complicated wells, the stratum formation is more and more complicated. The viscosity and yield point of drilling fluid increase due to high temperature, increase of solid contamination, calcium contamination or failure of the treatment agent, which can cause strong flow resistance, high energy consumption, drill sticking and other problems. Therefore, the thinner for drilling fluid is a kind of very important treatment agent during the oil exploration. Alkali lignin is a by-product of the pulp and paper industry, which is cheap and a renewable resource derived from the abundant plant. The production of alkali lignin in China is very large, but only a small portion of it has been technologically utilized as low-value products. Most of it has been discarded or incinerated, which not only causes the waste of large quantity of renewable resource, but also leads to environmental pollution. Because there is a variety of functional groups in the molecule structure, alkali lignin can be modified by chemical reactions to improve its performance, which has great significance for the utilization of waste and environmental protection.This dissertation is mainly focused on the modification of industrial alkali lignin, interaction between modified product and montmorillonite and the evaluation of viscosity reduction properties, with the characterization methods of colloid chemistry. Finally, at the last part of the dissertation, we try to propose the viscosity reduction mechanism of the modified product.The main content of the dissertation includes the following parts:1. Preparation and characterization of sulfomethyled lignin amine (LSN)In this dissertation, LSN was prepared by Mannich reaction and sulfomethylation, with the modified reagents of diethylenetriamine, formaldehyde and Na2SO3. The solubility changes, Fourier transform infrared spectroscopy (FTIR) and Element analysis demonstrate the existence of amino group and sulfonic group. The basic physicochemical properties of LSN were characterized by surface tension and foaming performance. The approximate molecular weight of LSN was calculated by Ubbelohde Viscometer, about8.72×104.2. Study on the interactions between LSN and montmorilloniteThe effects of LSN on clay suspensions were investigated systematically by adsorption, zeta potential and rheology analysis. The adsorption of LSN on the montmorillonite follows the Langmuir type. The adsorption capacity and zeta potential increase with the increasing of LSN concentrations until a plateau approached. The molecules adsorb on montmorillonite surfaces mainly through hydrogen bonding, which forms between the amide group and surface hydroxyl of montmorillonite. The adsorption kinetics of LSN on the montmorillonite surfaces shows that the adsorption can reach equilibrium within30min. Temperature has little effect on adsorption capacity, but pH has great effect on adsorption capacity. With the increase of pH value, absorption amount of LSN reduces. The addition of NaCl and CaCl2can both increase the absorption amount significantly.3. Evaluation of viscosity reduction property of LSN in various mudThe viscosity reduction property of LSN was evaluated by rheological experiments. Results showed that LSN can significantly reduce the viscosity and yield point in both fresh water mud and salt water mud under the condition of high temperature. Meanwhile, the adsorption of LSN on montmorillonite particles can inhibit the dispersion of non-prehydrated montmorillonite, which can also reduce the viscosity of drilling fluids.