Method for preparing viscosity depressant for drilling fluid

Abstract

The invention discloses a method for preparing a viscosity depressant for a drilling fluid, comprising the following steps of: mixing lignosulphonate and water in the mass ratio of 1: (1.5-4) to obtain a solution A and adjusting the pH value of the solution A to be 6-7; (2) adding ferrous sulphate into the mixture obtained in the step (1) and reacting for 1-4 hours at 60-80 DEG C; (3) heating themixture obtained in the step (2) to 60-90 DEG C and then adding an organic monomer AMPS and an evocating agent and reacting for 1-4 hours; and (4) drying and crushing the mixture obtained in the step(3) at 80-100 DEG C to obtain the viscosity depressant for the drilling fluid, wherein the mass ratio of the lignosulphonate to the ferrous sulphate to the organic monomer AMPS to the evocating agentis 1:(0.3-0.5):(0.1-0.15):(0.01-0.02). The prepared viscosity depressant is suitable for drilling fluids under the conditions of extraordinarily high temperature and antisaturation saline water.

Description

technical field [0001] The invention relates to a preparation method of a viscosity reducer for drilling fluid, in particular to a preparation method of a viscosity reducer added to drilling fluid used in oil exploration and drilling. Background technique [0002] With the increase of world energy demand and the development of drilling technology, the number of deep wells and ultra-deep wells in my country is also increasing. During drilling, the deeper the wellbore, the higher the temperature inside the wellbore. Due to the automatic dispersion of clay particles in drilling fluid under high temperature conditions, the particle concentration increases and the specific surface area increases. The problem of high temperature thickening of drilling fluid becomes more and more prominent. The viscosity reducer is one of the indispensable drilling fluid treatment agents in the drilling process, and it plays a very important role in adjusting the rheology of the drilling fluid. A...

AI Technical Summary

Problems solved by technology

However, after the 1990s, due to the strengthening of environmental protection awareness in various countries around the world, the application of FCLS, which seriously pollutes the human body and the environment, was restricted. People began to develop chromium-free lignosulfonate and tannin-based viscosity reducers.

Afterwards, research mainly focused on anionic polymer viscosity reducers based on maleic anhydride (MA), sodium allylsulfonate (AS) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) , and zwitterionic polymer viscosity reducers with cationic groups, but there are relatively few studies, especially in recent years, the research work in this area has almost stagnated, and there are even fewer examples of successful field applications, and there is a lack of applicable Viscosity reducer under special conditions (such as ultra-high temperature, anti-saturated brine, etc.)