Drilling fluid plugging agent while drilling

Abstract

The invention relates to a drilling fluid plugging agent while drilling, comprising 60-100 parts of plant fibers, 5-20 parts of asphalt, 5-15 parts of graphite and 5-20 parts of weak water absorbent gel by weight. The weak water absorbent gel is a polymer which has mean grain size of 200-20 meshes and water absorbent multiple of 10-100g.g-1 and is prepared by reacting 20-60 parts of monomer, 0.05-1.0 part of potassium peroxydisulfate, 0.05-1.0 part of sodium bisulfite, 0.005-0.5 part of methylene-bis-acrylamide and 2-10 parts of inorganic fillers by weight under constant temperature of 20-60 DEG C for 8-12h by way of aqueous solution polymerization, drying and pelleting, wherein the polymeric monomer is one or more of acrylamide, acrylic acid, dimethyl diallyl ammonium chloride and 2-acrylamide-2-methyl propanesulfonic acid. The plugging agent has little effect on the rheological property of the drilling fluid, can reduce the API filtration and the coefficient of friction resistance of the drilling fluid in an auxiliary manner and is suitable for controlling leakage of and plugging the windows with high density and narrow pressure.

Description

Technical field: [0001] The invention relates to a drilling fluid plugging agent while drilling. In particular, it relates to a plugging agent for drilling while drilling under the conditions of high temperature, high density and narrow pressure window. It has dual effects of leak prevention and plugging. Background technique: [0002] Lost circulation is a problem often encountered in the drilling process. Lost circulation not only consumes drilling time and loses drilling fluid, but also can cause a series of complicated situations such as pipe sticking, blowout, and well collapse. It even leads to the scrapping of the wellbore and great economic losses. [0003] Lost circulation is the result of the combined action of subjective and objective factors. The existence of formation voids and fractures is the objective condition for lost circulation. However, in some deep wells and complex well sections, the excessively high drilling fluid density will induce and aggravat...

AI Technical Summary

Problems solved by technology

Most of its additives are inert particles. This kind of treatment agent is cheap, but the amount of addition is large. Some additive components such as peach shell, sawdust, cottonseed shell, bagasse, asbestos, fiber, etc., are added to high-density drilling fluid , although it also has the function of plugging while drilling, but because of the large amount of product added, the viscosity of the drilling fluid system is significantly increased, and the friction coefficient of the drilling fluid is also increased, and the vibrating screen cannot be used during use, otherwise it will The phenomenon of mud running increases the drilling cost, reduces the drilling speed, and increases the probability of downhole accidents. Therefore, the existing physical lost circulation agents are not suitable for application under high-density conditions.

[0009] Chemical plugging technology mainly achieves the purpose of plugging through the chemical reaction of polymers. This method covers a wide range of methods and involves polymer cross-linking reactions, resin curing, etc. The relatively intense chemical reaction occurs, the construction and configuration are complex, and the controllability of the reaction is affected by various underground factors, which has high risks and high construction costs. From the perspective of its mechanism of action, it basically does not belong to the technical category of plugging while drilling. It is necessary to stop drilling before entering the leaky layer and use the prepared plugging fluid to stop the leak, which prolongs the drilling time and interferes with the discovery of the pay zone

[0010] Therefore, judging from the application status of lost circulation agents, the existing physical and chemical lost circulation materials are not suitable for high density and narrow pressure window conditions.

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