Water-based drilling fluid system and preparation method and application thereof

Abstract

A water-based drilling fluid system is prepared from water-based liquid, sodium carbonate, a polyamine inhibitor, modified starch, xanthan gum, a low-molecular-weight encapsulating inhibitor, a density reducing agent, a bit balling prevention lubricant, a pressure-bearing plugging agent, sodium chloride and ethylene glycol, wherein with respect to 100 parts by weight of the water-based liquid, the sodium carbonate accounts for 0.2-0.3 part by weight, the polyamine inhibitor accounts for 3-4 parts by weight, the modified starch accounts for 1-2 parts by weight, the xanthan gum accounts for 0.2-0.3 part by weight, the low-molecular-weight encapsulating inhibitor accounts for 0.3-0.7 part by weight, the density reducing agent accounts for 1-3 parts by weight, the bit balling prevention lubricant accounts for 2-3 parts by weight, the pressure-bearing plugging agent accounts for 1-2 parts by weight, the sodium chloride accounts for 10-20 parts by weight, and the ethylene glycol accounts for 10-20 parts by weight. The invention also provides a preparation method and application of the water-based drilling fluid system. The water-based drilling fluid system can be effectively applicable to deep-water narrow-density window operation.

Description

technical field [0001] The present application relates to but is not limited to a water-based drilling fluid system and its preparation method and use, especially to but not limited to a water-based drilling fluid system suitable for deepwater narrow density window operations and its preparation method and use. Background technique [0002] Affected by the upper seawater in deep water wells, formation compaction is often insufficient, the difference between pore pressure and fracture pressure is small, and the safe density window of drilling fluid is small. During the operation of water-based drilling fluids in deep water wells, in order to prevent the formation of hydrates, a certain amount of thermodynamic inhibitors (such as NaCl, KCl, ethylene glycol, etc.) are mainly added to the system. Although the addition of these inhibitors achieves the purpose of inhibiting the formation of hydrates, it causes the density of the entire system to increase, which cannot meet the req...

AI Technical Summary

Problems solved by technology

Although the addition of these inhibitors achieves the purpose of inhibiting the formation of hydrates, it causes the density of the entire system to increase, which cannot meet the requirements of deep-water well operations with a narrow density window.

At the same time, part of the overlying strata was replaced by seawater during the deep-water deposition process, resulting in under-compaction of the stratum, high pore pressure, poor cementation, and easy expansion and dispersion of seabed mud shale.

There are usually hundreds of meters of siliceous ooze in the shallow formation of the seabed, which has low shear strength and poor bearing capacity, and is prone to wellbore instability, and cannot successfully drill to the designed well depth

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