Water-based drilling fluids for deepwater drilling and use thereof

Patent metadata

Field	Value
Publication number	US-10836947-B2
Application number	US-201916288080-A
Country	US
Kind code	B2
Filing date	Feb 27, 2019
Priority date	Mar 27, 2018
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

A water-based drilling fluid for deepwater drilling includes 0.1%-1.0% by weight of a viscosifier, 0.1%-1.0% by weight of an acidity regulator, 0.5%-3.5% by weight of a filtrate loss reducer, 0.5%-1.5% by weight of a low-temperature yield point enhancer, 1.0%-5.0% by weight of a shale inhibitor, 15%-25% by weight of a hydrate inhibitor, 1.0%-3.0% by weight of a lubricant, 5.0%-10.0% by weight of a temporary plugging agent and seawater.

First claim

What is claimed is:

1. A water-based drilling fluid for deepwater drilling, comprising: 0.1%-1.0% by weight of a viscosifier, 0.1%-1.0% by weight of an acidity regulator, 0.5%-3.5% by weight of a filtrate loss reducer, 0.5%-1.5% by weight of a low-temperature yield point enhancer, 1.0%-5.0% by weight of a shale inhibitor, 15%-25% by weight of a hydrate inhibitor, 1.0%-3.0% by weight of a lubricant, 5.0%-10.0% by weight of a temporary plugging agent and seawater.

2. The drilling fluid of claim 1 , wherein the viscosifier is selected from the group consisting of xanthan gum, welan gum, Gleditisia microphylla gum, sophora bean gum, fenugreek gum, guar gum, konjac gum, sesbania gum, karaya gum, tamarind gum, locust bean gum and a mixture thereof.

3. The drilling fluid of claim 1 , wherein the acidity regulator is selected from the group consisting of sodium hydroxide, sodium carbonate and a mixture thereof.

4. The drilling fluid of claim 1 , wherein the filtrate loss reducer comprises a modified starch.

5. The drilling fluid of claim 4 , wherein the modified starch is produced by:
mixing a raw starch, a base, a haloacetic acid and water for modification to obtain a mixture;
pre-gelatinizing the mixture for modification at 95-105° C. to obtain a pre-gelatinized starch; and
refining the pre-gelatinized starch to obtain the modified starch.

6. The drilling fluid of claim 1 , wherein the low-temperature yield point enhancer is selected from the group consisting of propylene glycol block polyether, polyethylene glycol fatty acid ester, and a mixture thereof.

7. The drilling fluid of claim 1 , wherein the shale inhibitor is selected from the group consisting of a polyamine, potassium chloride, and a mixture thereof.

8. The drilling fluid of claim 1 , wherein the hydrate inhibitor is selected from the group consisting of sodium chloride, ethylene glycol, diethylene glycol, and a mixture thereof.

9. The drilling fluid of claim 1 , wherein the lubricant is selected from the group consisting of polyoxyethylene stearate, fatty alcohol polyoxypropylene ether, pentaerythritol stearate, adipic acid polyester, and a mixture thereof.

10. A method of using the drilling fluid of claim 1 , comprising:
circulating the drilling fluid while oil and gas drilling in deep water or ultra-deep water reservoirs.

Assignees

• Univ Yangtze
• Cnooc China Ltd Zhanjiang Branch Guangdong

Inventors

• Xu Mingbiao
• Li Zhong
• You Fuchang
• Li Yanjun
• Liu Hexing
• Zhou Shanshan

Classifications

• E21B21/001

  specially adapted for underwater drilling (dual gradient drilling E21B21/082) · CPC title

• C09K2208/34

  Lubricant additives · CPC title

• C09K8/12 Primary

  containing synthetic organic macromolecular compounds or their precursors · CPC title

• C09K2208/22

  Hydrates inhibition by using well treatment fluids containing inhibitors of hydrate formers · CPC title

• C09K8/514

  of natural origin, e.g. polysaccharides, cellulose (C09K8/512 takes precedence) · CPC title