Working fluid system applicable to water-base drilling fluid filter cake removal before well cementing

Abstract

The invention discloses a working fluid system applicable to water-base drilling fluid filter cake removal before well cementing. The working fluid system is composed of the following components in percentage by mass: 0.5-1.5% of solid-phase denudation main agent, 0.1-1% of solid-phase denudation aid, 0.15-0.5% of viscosity breaker, 0.5-1.5% of surfactant, 1-3% of clay stabilizer and the balance of water. The pH value of the solution is regulated to 12-14 by NaOH or KOH. The solid-phase denudation main agent is composed of any one or mixture of ethylenediamine tetraacetic acid, disodium edetate, diethyltriamine pentaacetic acid and pentasodium amino trimethylene phosphonate; and the solid-phase denudation aid is composed of any one or mixture of sodium gluconate, oxalic acid and potassium sodium tartrate. By combining the characteristics of well cementing operation, the working fluid system can shorten the construction time, has higher reaction speed, achieves the goals of removing the filter cake and enhancing the cementing strength of the well-cementing interface, and thus, has broad market prospects.

Description

technical field [0001] The invention relates to a working fluid system suitable for removing water-based drilling fluid filter cake before cementing in the process of oil and gas exploration and development. Background technique [0002] During the drilling of oil and gas wells, the drilling fluid is filtered off under the action of differential pressure, and solid particles accumulate on the well wall to form a filter cake. Drilling fluid filter cake is an important factor to reduce the damage of drilling fluid to the reservoir, maintain the stability of the wellbore wall and the quality of the wellbore. However, since the drilling fluid filter cake itself has no consolidation ability and low strength, after cementing and cementing, the filter cake becomes a weak layer between the cement sheath and the well wall, which may form channeling channels in the later stage, resulting in formation fluids (oil, gas, water) channeling occurs. Therefore, in the process of circulatin...

AI Technical Summary

Problems solved by technology

[0007] (3) The most commonly used weighting agent for water-based drilling fluid is BaSO 4 Mainly, some CaCO is added during reservoir drilling 3 , the acidic scavenging solution system can still effectively dissolve CaCO 3 , but under alkaline conditions, it has not been found that it can effectively remove BaSO 4 , CaCO 3 Scavenging liquid system for weighting agent filter cake;

[0008] (4) Although corrosion inhibitors are added to the existing acidic cleaning liquid system, the corrosion degree and corrosion rate of the casing (screen) under the condition of acidic treatment liquid are higher than those under the condition of alkaline