Filtrate reducer zwitterionic polymer for drilling fluid

Abstract

The invention discloses a filtrate reducer zwitterionic polymer for a drilling fluid. The filtrate reducer zwitterionic polymer is prepared from the following raw materials: polyacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, dimethyl propyl ammonium chloride, sodium p-styrenesulfonate, an initiator, deionized water, a sodium hydroxide solution with the mass fraction of 40%, modified cassava starch, modified shellfish shell powder and ethylene glycol. A hydration group and an adsorption group are arranged on a molecular chain of the acrylamide copolymer, so that the adsorption capacityis high; 2-acrylamide-2-methylpropanesulfonic acid contains sulfonate radicals of ionizable groups, the hydration effect with clay particles is improved, and the tolerance to salt and calcium can be improved, so that the drilling fluid is stabilized; a cationic group is introduced into a molecular chain of dimethyl propyl ammonium chloride, so that the improvement of the blocking inhibition effectwith clay particles is facilitated. The filtrate reducer provided by the invention has good temperature resistance and salt resistance, is suitable for fresh water and saline water drilling fluid systems with various concentrations, is biodegradable, and has no pollution to the environment.

Description

technical field [0001] The invention belongs to the technical field of additives for drilling fluids, and in particular relates to a fluid loss control amphoteric ion polymer for drilling fluids. Background technique [0002] Drilling fluid is the circulating medium used in the drilling process. During the drilling process, the drilling fluid mainly completes the tasks of suspension, pressure control, rock formation stability, buoyancy, lubrication and cooling. During the drilling process, due to the pressure difference, the water in the drilling fluid will inevitably leak into the formation through the wellbore wall, causing the drilling fluid to lose water. [0003] In the prior art, fluid loss control is mostly realized by adding a fluid loss reducer to the drilling fluid. At present, there are many kinds of fluid loss control agents used in drilling sites, such as minerals, natural organic substances and their modified substances, and synthetic organic substances. Howe...

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Problems solved by technology

However, the existing fluid loss control agents for drilling fluids generally have the following deficiencies: 1. The temperature resistance is poor, and the fluid loss agents are prone to decompose at higher temperatures, resulting in weakening of the fluid loss control effect. In order to increase its fluid loss control effect, It is necessary to increase the dosage of fluid loss additives, resulting in increased production costs and a great change in the rheological properties of the drilling fluid; 2. The ability to resist salt and calcium is poor, although some fluid loss additives meet the temperature resistance requirements , but in the saturated NaC1 solution, the water loss of the mud exceeds 40ml, which affects its use effect; 3. Some fluid loss reducers with better performance are expensive and costly, and are not suitable for large-scale use on site

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