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Degradable drilling fluid used for drilling in soft coal seam

A technology for soft coal seam and drilling fluid, applied in the field of drilling fluid, can solve the problem of insignificant effect, achieve the effect of complete gel breaking, meet environmental protection requirements, and remove damage

Inactive Publication Date: 2012-06-27
CHINA UNIV OF GEOSCIENCES (WUHAN)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, tests have shown that the use of acid or oxidizing agents (such as ammonium persulfate) alone is not effective in removing filter cakes in horizontal well sections

Method used

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  • Degradable drilling fluid used for drilling in soft coal seam
  • Degradable drilling fluid used for drilling in soft coal seam
  • Degradable drilling fluid used for drilling in soft coal seam

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] This example 1 mainly reflects: (1) The basic performance parameters (density, apparent viscosity, filtration loss, pH and filter cake thickness) of the degradable drilling fluid used for drilling soft coal seams; (2) Used for drilling soft coal seams The changes in apparent viscosity of the degradable drilling fluid over time, filter cake removal test results, and coal gas permeability test results.

[0027] 1. Experimental formula

[0028] The degradable drilling fluid used for drilling soft coal seams of this embodiment is composed of water, degradable polymer (medium viscous carboxymethyl cellulose), fluid loss agent (modified starch), bridging agent (ultrafine carbonic acid). Calcium), pH adjuster (ammonium chloride) and biological enzyme breaker; calculated by the amount added per 100 ml of water: 0.6 g of medium-viscosity carboxymethyl cellulose, 1 g of modified starch, superfine calcium carbonate (400 Mesh) 1.2 grams, a little ammonium chloride (adjust the pH to 7) ...

Embodiment 2

[0064] This example 2 mainly reflects: (1) The basic performance parameters (density, apparent viscosity, filtration loss, pH and filter cake thickness) of the degradable drilling fluid used for drilling soft coal seams; (2) Used for drilling soft coal seams The apparent viscosity of the degradable drilling fluid changes over time.

[0065] 1. Experimental formula

[0066] The degradable drilling fluid used for drilling in soft coal seams, calculated by the amount added per 100 ml of water: degradable polymer (medium viscous carboxymethyl cellulose) 0.6 g, bentonite 2 g, fluid loss agent (modified starch) 0.75 g , Bridging agent (ultra-fine calcium carbonate, particle size of 400 mesh, can be adjusted according to the radius of the pore throat of the coal) 1.0 g, JBR breaker 0.1 g, pH adjuster (ammonium chloride) is added to adjust the drilling fluid pH to 7.

[0067] The breaker JBR is white powder, produced by Hubei Jingzhou Jiahua Technology Co., Ltd.

[0068] The preparation met...

Embodiment 3

[0081] This example 3 mainly reflects: (1) The basic performance parameters (density, apparent viscosity, filtration loss, pH and filter cake thickness) of the degradable drilling fluid used for drilling soft coal seams; (2) Used for drilling soft coal seams The apparent viscosity of the degradable drilling fluid changes over time.

[0082] 1. Experimental formula

[0083] The degradable drilling fluid used for drilling in soft coal seams, calculated by the amount added per 100 ml of water: degradable polymer (medium viscous carboxymethyl cellulose) 0.6 g, bentonite 2 g, fluid loss agent (modified starch) 0.75 g , Crosslinking agent (ultra-fine calcium carbonate, particle size of 400 mesh, can be adjusted according to the radius of the pore throat of the coal) 1.0 g, biological enzyme breaker SE-40.01 g, pH regulator (ammonium chloride) is added in Adjust the pH of the drilling fluid to 7.

[0084] Biological enzyme breaker SE-4 is brown liquid, produced by Jiangsu Kunshan Jingkun ...

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Abstract

The present invention relates to a drilling fluid used for ground coalbed methane drill or underground gas drainage, especially is suitable for drilling in the soft coal seam. The degradable drilling fluid used for the soft coal seam is characterized in that the fluid is composed by mixing water, a biodegradable polymer, slurry clay, a filtrate loss reducer, a bridging agent, a pH modifier and a gel breaker; by referring the amount of computation per 100 ml of water 0.5-0.75 g of degradable polymers, 0-2 g of slurry clay, 0.5-2 g of the loss reducer, 1-2 g of the bridging agent and 0.01-0.1 g of the gel breaker, the addition amount of the pH regulator satisfies the drilling fluid pH value to 7. The fluid of the invention has the advantages of good rheology and filtrate loss performance, the drilling fluid can meet the requirements of cuttin carrying of the soft coal seam drilling rock debris and wellbore stability; the gel breaker degradation and dilute hydrochloric acid double acidification can effectively remove the damage of degradable drilling fluid onto coalbed methane reservoir, and restore or even improve the gas permeability of coal petrography.

Description

Technical field [0001] The invention relates to a drilling fluid suitable for surface coalbed methane drilling or underground gas drainage, and is particularly suitable for drilling soft coal seams. Background technique [0002] Due to the complex geological structure conditions in our country, many coal-forming ages, wide distribution of coal mine areas, and large differences in coal reservoir characteristics. For simplicity, it can be divided into two typical types: hard coal seams with normal coal structure and soft coal seams with developed structures. For soft coal seams, due to coal and gas outbursts, soft coal seams, low mechanical strength, etc., problems such as collapsed holes, stuck holes or jet holes are likely to occur when conventional powder discharge drilling methods such as clean water or air are used, and it is difficult to drill holes. The efficiency of gas drainage is low. The development of coalbed methane in soft coal seams is one of the most severe challe...

Claims

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Application Information

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IPC IPC(8): C09K8/20
Inventor 蔡记华乌效鸣刘浩谷穗肖长波
Owner CHINA UNIV OF GEOSCIENCES (WUHAN)
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