Strong plugging drilling fluid suitable for shale gas wells and preparation method thereof

Patent metadata

Field	Value
Publication number	US-10407608-B2
Application number	US-201815952917-A
Country	US
Kind code	B2
Filing date	Apr 13, 2018
Priority date	Feb 7, 2018
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

The present invention relates to the field of drilling fluids, and discloses a strong plugging drilling fluid suitable for shale gas wells and a preparation method of the drilling fluid. The drilling fluid contains water, bentonite, a tackifier, a flow pattern regulator, a filtrate reducer, a plugging agent, and a weighting agent, wherein, based on 100 parts by weight of water, the content of the bentonite is 1-10 parts by weight, the content of the tackifier is 5-15 parts by weight, the content of the flow pattern regulator is 4-13 parts by weight, the content of the filtrate reducer is 4-13 parts by weight, the content of the plugging agent is 20-55 parts by weight, and the content of the weighting agent is 10-60 parts by weight; the drilling fluid provided in the present invention employs modified nano-silica as a plugging agent to improve dispersity and particle size distribution in the drilling fluid system. Therefore, the drilling fluid is especially suitable for well drilling in shale formations with developed micro-fractures (micro-fissures) and micro-pores, low porosity and low permeability (10−3-10−7 md), and prominent capillary effect.

First claim

The invention claimed is:

1. A strong plugging drilling fluid suitable for shale gas wells, the strong plugging drilling fluid consisting of:
water,
bentonite,
a tackifier,
a flow pattern regulator,
a filtrate reducer,
a plugging agent, and
a weighting agent,
wherein, based on 100 parts by weight of water, the content of the bentonite is 1-10 parts by weight, the content of the tackifier is 5-15 parts by weight, the content of the flow pattern regulator is 4-13 parts by weight, the content of the filtrate reducer is 4-13 parts by weight, the content of the plugging agent is 20-55 parts by weight, and the content of the weighting agent is 10-60 parts by weight;
wherein the plugging agent is modified nano-silica, the modified nano-silica is in a primary mono-dispersed structure and the particle diameter of the modified nano-silica is 25-70 nm; and
wherein the tackifier is hydroxyethyl cellulose; the flow pattern regulator is sodium acrylate; the filtrate reducer is lignite resin; and the weighting agent is iron ore powder.

2. The strong plugging drilling fluid according to claim 1 , wherein, based on 100 parts by weight of water, the content of the bentonite is 5-7 parts by weight, the content of the tackifier is 9-11 parts by weight, the content of the flow pattern regulator is 9-11 parts by weight, the content of the filtrate reducer is 9-11 parts by weight, the content of the plugging agent is 44-46 parts by weight, and the content of the weighting agent is 35-45 parts by weight.

3. The strong plugging chilling fluid according to claim 1 , wherein the pH of the drilling fluid is 8-10.

4. The strong plugging drilling fluid according to claim 1 , wherein the density of the drilling fluid is 1.1-1.8 g/cm 3 .

5. The strong plugging drilling fluid according to claim 4 , wherein the density of the drilling fluid is 1.3-1.5 g/cm 3 .

6. A method for preparing the drilling fluid suitable for shale gas wells according to claim 1 , comprising the following steps:
(1) prehydrating bentonite;
(2) mixing the prehydrated bentonite obtained in the step (1) with modified nano-silica;
(3) mixing the mixture obtained in the step (2) with a tackifier, a flow pattern regulator, a filtrate reducer, and a weighting agent.

Assignees

• Univ Southwest Petroleum

Inventors

• Bai Yang
• Luo Pingya

Classifications

• C09K8/514

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

• C09K8/5045

  containing inorganic compounds · CPC title

• C09K8/426

  for plugging · CPC title

• C09K8/20 Primary

  Natural organic compounds or derivatives thereof, e.g. polysaccharides or lignin derivatives · CPC title

• C04B28/24

  containing alkyl, ammonium or metal silicates; containing silica sols {(reaction mixtures resulting in mineral polymers C04B28/006; polymeric reaction products of alkali metal silicates with isocyanates C08G18/3895)} · CPC title