Double-modified starch fluid loss additive used for oil and gas field drilling fluid and preparation method thereof

Abstract

The invention discloses a double-modified starch fluid loss additive used for oil and gas field drilling, comprising silicified carboxymethyl starch or silicified carboxymethyl starch and carboxymethylated sodium alginate. The preparation method is that: the starch, inorganic silicate and alcohol-based dispersant are added to a reaction container, the starch and the inorganic silicate are evenly dispersed in the alcohol-based dispersant after being stirred; the alkali liquor is prepared with alkali, then, the alkali liquor with volume fraction of 40 percent is dripped into the reaction container; after the dripping of the alkali liquor, and a first-stage reaction is conducted under normal pressure, 30-50 degrees C. for at least 50 minutes; after the first-stage reaction is completed, the chloroacetic acid solution or the sodium alginate and the chloroacetic acid solution are added to the reaction container, and then the alkali liquor with volume fraction of 60 percent is dripped into the reaction container under stirring; after the dripping of the alkali liquor, a second-stage reaction is conducted under normal pressure,40-60 degrees C. for at least 90 minutes; the solid-liquid separation of the reaction product is conducted, and the dried solid is the double-modified starch fluid loss additive.

Description

technical field [0001] The invention belongs to additives used in oil and gas field drilling fluids, in particular to a starch fluid loss reducer used in oil and gas field drilling fluids and a preparation method thereof. Background technique [0002] During the drilling process of oil and gas fields, the invasion of drilling fluid filtrate into the well wall will cause shale hydration and expansion, resulting in instability of the well wall and various downhole complex situations, and damage to the oil and gas layers when drilling into production layers. Fluid loss reducer (or called fluid loss control agent, fluid loss reducer) is often added to reduce the fluid loss of drilling fluid as much as possible by forming a low-permeability, flexible, thin and dense filter cake on the well wall . [0003] Modified starch products - sodium carboxymethyl starch is a kind of modified starch products. As a fluid loss reducer for drilling fluid, it is considered to have a promising ...

AI Technical Summary

Problems solved by technology

As a fluid loss reducer for drilling fluid, it is considered to have a promising future because of its biodegradability, no environmental pollution, abundant raw material sources, low price, and strong anti-calcium and salt resistance. Environmentally friendly fluid loss reducer, but because of its poor temperature resistance, it is easy to degrade at high temperature when the bottom hole temperature increases, which reduces the molecular weight and eventually fails fermentation, so its popularization and application are severely limited

In addition, its fluid loss reduction performance is not ideal enough and needs to be improved

[0004] At present, most studies on the modification of starch fluid loss reducers to improve temperature resistance have problems such as complex process, harsh modification conditions, and most of the modifiers used are non-environmental-friendly substances, which lead to high modification costs. , little practical value

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