Drilling fluid used for active mud shale drilling

Abstract

The invention relates to a drilling fluid used for active mud shale drilling, and the drilling fluid is used in oilfield drilling. The drilling fluid comprises the following components in percentages by weight: 2-6% of bentonite, 0.2-0.5% of coated inhibitor, 0.2-1.0% of flow pattern regulator, 0.2-0.5% of high-temperature-resistant polymer filtrate reducer, 4-7% of potassium chloride, 1-3% of polymeric alcohol, 0.5-1.0% of polyamine inhibitor, 0.5-1.0% of anti-balling fast drilling agent and 45-85% of water. The drilling fluid has the inhibition property and lubricating property approximate to that of an oil-based drilling fluid, solves the problems that the mud making of the mud shale is severe, mud escapes from a vibrating screen, the viscous shearing of the drilling fluid increases and the rheological properties of the drilling fluid deteriorates during strong-mud-making active mud shale drilling, prevents destabilization of the active mud shale, dispersion of drill cuttings, balling of drill bit, and adhesion and coalescence of the mud shale, and increases the drilling speed of the active mud shale.

Description

technical field [0001] The invention relates to the technical field of oil field drilling, in particular to a drilling fluid, which is a drilling fluid used for drilling of strongly water-sensitive active clay formations, easily hydrated and dispersed expansive mud shale formations, natural fractures and easy-to-collapse formations, and horizontal boreholes. drilling fluid. Background technique [0002] When drilling highly water-sensitive active mudstone, soft mudstone, sticky mudstone and expansive bedding-fractured shale, such formations are prone to hydration, expansion and collapse, resulting in wellbore instability and low drilling efficiency. The hydration and dispersion of active shale can easily lead to the increase of clay content in the drilling fluid and the increase of micron and submicron solid phase particles, resulting in unreal thickness of the mud cake, increased viscosity and shear of the drilling fluid, slurry running of the vibrating screen, and deterior...

AI Technical Summary

Problems solved by technology

[0002] When drilling highly water-sensitive active mudstone, soft mudstone, sticky mudstone and expansive bedding-fractured shale, such formations are prone to hydration, swelling and collapse, resulting in wellbore instability and low drilling efficiency

The hydration and dispersion of active shale can easily lead to the increase of clay content in the drilling fluid and the increase of micron and submicron solid phase particles, resulting in unreal thickness of the mud cake, increased viscosity and shear of the drilling fluid, slurry running of the vibrating screen, and deterioration of rheological properties. Viscous mudstone cuttings have strong adhesion to the surface of the drill bit, which enhances the adhesion between the cuttings and the surface of the drill bit to a certain extent, resulting in mud balling of the drill bit, increasing the torque and holding effect, and reducing the cutting depth and rock breaking efficiency of the drill bit.

In short, the hydration and dispersion of clay minerals in active shale will directly lead to downhole complex accidents such as borehole diameter shrinkage, borehole wall collapse, bit balling, poor tripping, and drill sticking.

[0003] Inhibiting the hydration dispersion of shale has always been a highly valued problem in the drilling of water-sensitive formations. At present, domestic and foreign researchers have done a lot of research work to solve the problem of safe and rapid drilling of active shale. In addition to oil-based drilling fluid, water The base strength suppression drilling fluid system is mostly KCL / PHPA (partially hydrolyzed polyacrylamide), polyol (polyethylene glycol, polypropylene alcohol, polyether alcohol, MEG, etc.), cationic polymer, positive gel, silicate, etc. , although the stability of the borehole wall and the drilling speed have been improved, but generally speaking, the drilling cost is too high, and there are still problems such as insufficient inhibition, rheological control and environmental protection

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