Strong-inhibition drilling fluid system

Abstract

The invention relates to a strong-inhibition drilling fluid system, comprising the following components by mass percent of 2.5-4.5% of bentonite slurry, 0.1-0.3% of alkaline regulator, 0.3-2.0% of shale inhibitor, 0.2-0.4% of metal ion polymer, 2.0-5.0% of walchowite, 2.0-5.0% of sulfomethal phenolaldehy resin, 1.0-3.0% of cation emulsified asphalt, 0.5-3.0% of lubricating agent, 0.2-0.8% of emulsifier, 2.0-8.0% of crude oil, and 1.0-3.0% of calcium carbonate superfine powder according to 100% of water. The compound in a general formula (I) is also provided; R1 is H or CH3; R2 is H, CH3 or C2H5; and X is an integer between 2 and 20 and applied to the shale inhibitor. The compound and the cation emulsified asphalt are applied to the drilling liquid system; the drilling liquid system is strong in shale inhibition; the shale recovery rate can be up to 90.33% and is improved by over 35.02% in comparison with that of water shale; the high temperature resistance can be up to 150 DEG C; the lubricating friction coefficients before and after aging respectively are smaller than 0.1; the strong-inhibition drilling fluid system is strong in capacity of resisting poor soil, salt and calcium contamination, strong in rejection capability, and good in blocking effect; the API (American petroleum institute) water loss of the drilling fluid is smaller than 4.5mL, and the HTHP (high temperature and high pressure) water loss is smaller than 12mL.

Description

technical field [0001] The invention relates to a drilling fluid system, in particular to a drilling fluid system for ultra-deep sidetracking mudstone with strong inhibition. Background technique [0002] As the oilfield development enters the middle and late stage, the bottom water of old wells is coning, and most of the wells are flooded. In order to improve the recovery rate and the production degree of reserves, the sidetracking method is adopted to connect the fractured-vuggy reservoirs around the wellbore. At present, sidetracking has become one of the effective ways to improve the oil recovery of Ordovician reservoirs. [0003] Drilling in mudstone formations often leads to complex wellbore instability, because mudstone is prone to hydration, dispersion and expansion when it meets water, which reduces the strength of the rock and causes the wellbore to collapse. Therefore, the requirements for the inhibition of drilling fluid are very high, and sidetracking in deep w...

AI Technical Summary

Problems solved by technology

In order to meet the requirement of avoiding water, when sidetracking old wells, it is necessary to raise the kickoff point to the mudstone formation of Carboniferous Bachu Formation or Ordovician Sangtamu Formation, so that the trajectory forms a certain displacement before entering the Ordovician reservoir. Avoiding the original wellbore water body, the sidetracking wellbore will travel about 100m in the mudstone section of the Bachu Formation or Sangtamu Formation. The clay mineral content of the mudstone in the Bachu Formation and Sangtamu Formation is more than 20%, of which the I-Monite mixed layer is as high as 40% , the hydration expansion and dispersion characteristics are extremely strong, and mudstone collapses and blocks are prone to occur during drilling, and the original drilling fluid system is difficult to meet the requirements

It is mainly manifested in the lack of inhibition and lubricity of the existing drilling fluid system. When the burial depth is greater than 5000m and above, sidetracking wells are prone to complex downhole accidents such as excessive torque and friction of the drilling tool, and pipe sticking.

[0005] When drilling mudstone abroad, the oil-based drilling fluid system is mainly used to solve the problem of mudstone collapse. This system has the characteristics of good temperature resistance and strong ability to inhibit mudstone hydration, but the cost is high, and there are environmental pollution and safety hazards.

The strong inhibitory drilling fluid systems developed in China include methyl glucoside MEG drilling fluid, positive gel drilling fluid, polyalcohol drilling fluid, formate drilling fluid, etc., all of which have strong inhibitory properties, but these drilling fluid systems Large amount of inhibitor added, high cost, poor salt resistance, not suitable for the promotion and application of sidetracking wells

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