A water-based drilling fluid for stabilizing the borehole wall of shale gas horizontal wells

Abstract

The invention discloses a shale gas horizontal well borehole wall stabilization water-based drilling fluid, which comprises, by mass percentage: 3.0% to 4.0% micro-nano aluminum silicate, 0.5% to 1.0% biomacromolecule thickener, 2.5% to 3.5% modified starch, 1.5% to 2.0% amine ester inhibitor, 4.0% to 6.0% low carbon number organic sodium salt, 1.0% to 1.5% organic and inorganic polymer lubricant, 1.0% to 2.0% liquid lubricant, 1.0% to 1.5% polysilicon fluoride stabilizer, and the balance is water. The shale gas horizontal well borehole wall stabilization water-based drilling fluid solves the problem of easy instability of the borehole wall in view of the special situation of the Tianhuan Depression in the Ordos Basin.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluids, and in particular relates to a shale gas horizontal well wall-stabilizing water-based drilling fluid. Background Art

[0002] Shale gas refers to natural gas that is mainly located in dark mud shale or high-carbon mud shale and is accumulated in an adsorbed or free state. Shale gas exists in nano-micron pores and cracks. Its formation and enrichment have their own unique characteristics. It is often distributed in thick and widely distributed shale source rocks in basins. It is an important unconventional natural gas resource. As a new energy variety, it is not only a potential alternative energy source for conventional natural gas, but also a clean and environmentally friendly energy source. Compared with conventional natural gas, shale gas development has the advantages of long mining life and long production time. Most of the shales that can produce gas are widely distributed, thick, and generally contain shale gas, which enables shale gas wells to produce gas at a stable rate for a long time. Shale gas has become an important alternative energy source and is widely used in gas chemical industry, automobile fuel and other industries.

[0003] The shale gas reserves in Tianhuan Depression of Ordos Basin are rich, but it is difficult to exploit. The data of the wells that have been drilled in Tianhuan Depression of Ordos Basin show that the depth of Uralik Formation is deep, the temperature is high, and the shale is easy to become unstable. Specifically, the characteristics of the rock samples in Tianhuan Depression of Ordos Basin are as follows: the clay mineral composition of the rock samples of Heba Formation is mainly kaolinite, and the rock samples of Klimori Formation and Uralik Formation are mainly illite with high stability, which is a hard and brittle mud shale with weak hydration ability; the rock samples of complex formations have cracks and pores, and clay minerals fill them or are distributed on the surface of particles; the specific surface area and cation exchange capacity are not high, but the specific hydrophilicity is large. The drilling fluid filtrate invades the formation along the micro-cracks of the formation under the action of pressure difference and chemical potential difference, causing local hydration of mud shale, generating strong hydration expansion pressure, and making the well wall unstable.

[0004] Therefore, in view of the complex situation in horizontal well drilling in the new area of ​​Tianhuan Depression in the Ordos Basin, especially the problem of wellbore instability, it is urgent to provide a wellbore stabilizing drilling fluid. Summary of the invention

[0005] The purpose of the present invention is to provide a shale gas horizontal well borehole wall stabilizing water-based drilling fluid, aiming at the special situation of Tianhuan Depression in Ordos Basin, and solving the problem of easy instability of the borehole wall.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well, which comprises, by mass percentage: 3.0% to 4.0% micro-nano aluminosilicate, 0.5% to 1.0% biomacromolecule thickener, 2.5% to 3.5% modified starch, 1.5% to 2.0% amine ester inhibitor, 4.0% to 6.0% low-carbon organic sodium salt, 1.0% to 1.5% organic and inorganic polymer lubricant, 1.0% to 2.0% liquid lubricant, 1.0% to 1.5% polysilicon fluoride stabilizer, and the balance is water.

[0007] As a preferred technical solution of the present invention, the micro-nano aluminum silicate is 3.0%, the biomacromolecule thickener is 0.5%, the modified starch is 3.0%, the amine ester inhibitor is 1.5%, the low-carbon organic sodium salt is 5.0%, the organic and inorganic polymer lubricant is 1.0%, the liquid lubricant is 1.5%, the polysilicone fluoride stabilizer is 1%, and the balance is water.

[0008] As a preferred technical solution of the present invention, the biomacromolecule viscosity enhancer is xanthan gum or modified plant-extracted cellulose.

[0009] As a preferred technical solution of the present invention, the modified starch is lignin starch or cellulose starch.

[0010] As a preferred technical solution of the present invention, the amine ester inhibitor is a primary amine or a secondary amine or a secondary amine of methyl acrylate.

[0011] As a preferred technical solution of the present invention, the carbon number of the low-carbon organic sodium salt is ≤4.

[0012] As a preferred technical solution of the present invention, the low-carbon organic sodium salt is sodium formate or sodium acetate.

[0013] As a preferred technical solution of the present invention, the organic-inorganic polymer lubricant is a polymer composed of boric acid and oleic acid ester.

[0014] As a preferred technical solution of the present invention, the liquid lubricant is liquid lubricant RT101.

[0015] As a preferred technical solution of the present invention, the polysilicon fluorine stabilizer is shale inhibitor polysilicon JW-1.

[0016] The beneficial effects of the present invention are as follows: (1) A shale gas horizontal well borehole wall stabilizing water-based drilling fluid of the present invention is configured according to the strategy of enhanced plugging-moderate inhibition-reasonable density-efficient lubrication to obtain a shale gas horizontal well borehole wall stabilizing drilling fluid, wherein micro-nano aluminum silicate, as a basic slurry material, plays a role in viscosity increase and filtration loss reduction; biomacromolecule thickener plays a role in rheology adjustment, increases viscosity, and has a certain filtration loss reduction effect; amine ester inhibitor plays a role in inhibiting hydration and stabilizing the shale formation borehole wall; low carbon number organic sodium salt plays a role in soluble salt weighting and hydration inhibition; organic and inorganic polymer lubricant plays a role in reducing friction, including reducing the viscosity effect between the drill string and the borehole wall, and the drill string in the drilling fluid; liquid lubricant plays a role in improving the lubrication performance of the drilling fluid by changing the interface properties of the friction pair; polysilicon fluoride stabilizer plays a role in improving the anti-dispersion performance of the drilling fluid by increasing the negative charge of the clay particles and the thickness of the hydration film. (2) The water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well of the present invention has a high recovery rate, good rheological properties, filtration loss properties, and temperature resistance, and meets the requirements for drilling in the horizontal section of a shale formation in terms of rock carrying capacity, anti-collapse performance, leak-proof performance, and lubrication and friction reduction. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0018] Example 1

[0019] The invention discloses a water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well. The water-based drilling fluid comprises, by mass percentage, 3.0% of micro-nano aluminum silicate, 0.5% of xanthan gum, 3.0% of cellulose starch, 1.5% of methyl acrylate secondary amine, 5.0% of sodium acetate, 1.0% of a polymer composed of boric acid and oleate, 1.5% of a liquid lubricant RT101, 1% of a shale inhibitor polysilicon JW-1, and the balance is water.

[0020] The following steps are used to prepare the shale gas horizontal well borehole stabilization drilling fluid: first, add micro-nano aluminum silicate to water, stir to fully disperse it, then add the designed amount of xanthan gum, cellulose starch, methyl acrylate secondary amine, sodium acetate, boric acid and oleate polymer, liquid lubricant RT101, shale inhibitor polysilicon JW-1 in sequence, and stir for 5-10 minutes each time each agent is added to fully dissolve or disperse it. The prepared drilling fluid can be tested for its performance after curing for 24 hours. In on-site construction, it can be tested for performance or used for drilling after circulating for 3-5 hours after preparation.

[0021] Example 2

[0022] The invention discloses a water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well. The water-based drilling fluid comprises, by mass percentage, 4.0% micro-nano aluminum silicate, 1% xanthan gum, 2.5% lignin starch, 2.0% methyl acrylate secondary amine, 4.0% sodium formate, 1.5% a polymer composed of boric acid and oleate, 2.0% liquid lubricant RT101, 1.5% shale inhibitor polysilicon JW-1, and the balance is water.

[0023] The following steps are used to prepare the shale gas horizontal well borehole stabilization drilling fluid: first, add micro-nano aluminum silicate to water, stir to fully disperse it, then add the designed amount of xanthan gum, lignin starch, methyl acrylate secondary amine, sodium formate, boric acid and oleate polymer, liquid lubricant RT101, shale inhibitor polysilicon JW-1 in sequence, and stir for 5-10 minutes each time each agent is added to fully dissolve or disperse it. The prepared drilling fluid can be tested for its performance after curing for 24 hours. In on-site construction, it can be tested for performance or used for drilling after circulating for 3-5 hours after preparation.

[0024] The following steps are used to prepare the shale gas horizontal well borehole stabilization drilling fluid: first, add micro-nano aluminum silicate to water, stir to fully disperse it, then add the designed amount of xanthan gum, cellulose starch, methyl acrylate secondary amine, sodium acetate, boric acid and oleate polymer, liquid lubricant, shale inhibitor polysilicon JW-1 in sequence, and stir for 5-10 minutes each time each agent is added to fully dissolve or disperse it. The prepared drilling fluid can be tested for its performance after curing for 24 hours. In on-site construction, it can be tested for performance or used for drilling after being prepared and circulated for 3-5 hours.

[0025] Example 3

[0026] The invention discloses a water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well. The water-based drilling fluid comprises, by mass percentage, 3.0% of micro-nano aluminum silicate, 0.5% of xanthan gum, 2.5% of cellulose starch, 1.5% of methyl acrylate secondary amine, 4.0% of sodium acetate, 1.0% of a polymer composed of boric acid and oleate, 1.0% of a liquid lubricant RT101, 1.0% of a shale inhibitor polysilicon JW-1, and the balance is water.

[0027] The following steps are used to prepare the shale gas horizontal well borehole stabilization drilling fluid: first, add micro-nano aluminum silicate to water, stir to fully disperse it, then add the designed amount of xanthan gum, cellulose starch, methyl acrylate secondary amine, sodium acetate, boric acid and oleate polymer, liquid lubricant RT101, shale inhibitor polysilicon JW-1 in sequence, and stir for 5-10 minutes each time each agent is added to fully dissolve or disperse it. The prepared drilling fluid can be tested for its performance after curing for 24 hours. In on-site construction, it can be tested for performance or used for drilling after circulating for 3-5 hours after preparation.

[0028] Example 4

[0029] The invention discloses a water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well. The water-based drilling fluid comprises, by mass percentage, 3.5% of micro-nano aluminum silicate, 0.8% of xanthan gum, 3.0% of cellulose starch, 1.8% of methyl acrylate secondary amine, 5.0% of sodium acetate, 1.3% of a polymer composed of boric acid and oleate, 1.5% of a liquid lubricant RT101, 1.3% of a shale inhibitor polysilicon JW-1, and the balance is water.

[0030] The following steps are used to prepare the shale gas horizontal well borehole stabilization drilling fluid: first, add micro-nano aluminum silicate to water, stir to fully disperse it, then add the designed amount of xanthan gum, cellulose starch, methyl acrylate secondary amine, sodium acetate, boric acid and oleate polymer, liquid lubricant RT101, shale inhibitor polysilicon JW-1 in sequence, and stir for 5-10 minutes each time each agent is added to fully dissolve or disperse it. The prepared drilling fluid can be tested for its performance after curing for 24 hours. In on-site construction, it can be tested for performance or used for drilling after circulating for 3-5 hours after preparation.

[0031] Example 5

[0032] The invention discloses a water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well. The water-based drilling fluid comprises, by mass percentage, 4.0% of micro-nano aluminum silicate, 1.0% of xanthan gum, 3.5% of cellulose starch, 2.0% of methyl acrylate secondary amine, 6.0% of sodium acetate, 1.5% of a polymer composed of boric acid and oleate, 2.0% of a liquid lubricant RT101, 1.5% of a shale inhibitor polysilicon JW-1, and the balance is water.

[0033] The following steps are used to prepare the shale gas horizontal well borehole stabilization drilling fluid: first, add micro-nano aluminum silicate to water, stir to fully disperse it, then add the designed amount of xanthan gum, cellulose starch, methyl acrylate secondary amine, sodium acetate, boric acid and oleate polymer, liquid lubricant RT101, shale inhibitor polysilicon JW-1 in sequence, and stir for 5-10 minutes each time each agent is added to fully dissolve or disperse it. The prepared drilling fluid can be tested for its performance after curing for 24 hours. In on-site construction, it can be tested for performance or used for drilling after circulating for 3-5 hours after preparation.

[0034] Comparative Example 1

[0035] Compared with Example 1, the liquid lubricant RT101 and the shale inhibitor polysilicon JW-1 were replaced with water of equal mass, and other conditions were the same as those in Example 1.

[0036] Comparative Example 2

[0037] Compared with Example 1, the liquid lubricant RT101 was replaced by the solid lubricant GR-1, and the other conditions were the same as those of Example 1.

[0038] Comparative Example 3

[0039] Compared with Example 1, the liquid lubricant RT101 was replaced by a solid lubricant (Yan'an Shengyuan Chemical), and other conditions were the same as those in Example 1.

[0040] Comparative Example 4

[0041] Compared with Example 1, the liquid lubricant RT101 is replaced by a liquid rare earth lubricant, and other conditions are the same as those of Example 1.

[0042] Comparative Example 5

[0043] Compared with Example 1, the liquid lubricant RT101 was replaced by the liquid lubricant SD-505, and the other conditions were the same as those of Example 1.

[0044] Comparative Example 6

[0045] Compared with Example 1, the shale inhibitor polysilicon JW-1 was replaced with KCl solution, and other conditions were the same as those in Example 1.

[0046] Comparative Example 7

[0047] Compared with Example 1, the shale inhibitor polysilicon JW-1 was replaced by the bionic inhibitor FS-Y2J, and the other conditions were the same as those in Example 1.

[0048] Comparative Example 8

[0049] Compared with Example 1, the shale inhibitor polysilicon JW-1 was replaced by the amino polymer inhibitor G319, and the other conditions were the same as those in Example 1.

[0050] Comparative Example 9

[0051] Compared with Example 1, the shale inhibitor polysilicon JW-1 was replaced by the inhibitory lubricant solid polyol PGCS-1, and the other conditions were the same as those in Example 1.

[0052] Test Example 1

[0053] The performance of the shale gas horizontal well borehole stabilization drilling fluid prepared in Example 1 and Comparative Examples 1-5 before and after aging (aging condition is 140°C / 16h), as well as the lubrication coefficient and adhesion coefficient after aging were measured. The measurement results are shown in Table 1.

[0054] Table 1

[0055]

[0056] It can be seen from Table 1 that the shale gas horizontal well wall stabilization drilling fluid prepared according to the formula of the present invention has good lubrication performance, which can reach 0.1163.

[0057] Test Example 2

[0058] The shale of Zhongping 1 well was taken as a rock sample, and the anti-dispersion performance of the shale gas horizontal well wall stabilization drilling fluid prepared in Example 1, Comparative Example 1 and Comparative Examples 6-9 was determined by rolling dispersion experiment with rolling dispersion recovery rate as the assessment index. The measurement results are shown in Table 2.

[0059] Table 2

[0060] <![CDATA[ ]]> <![CDATA[ Example 1 ]]> <![CDATA[ Comparative Example 1 ]]> <![CDATA[ Comparative Example 2 ]]> <![CDATA[ Comparative Example 3 ]]> <![CDATA[ Comparative Example 4 ]]> <![CDATA[ Comparative Example 5 ]]> <![CDATA[ Recovery rate (%) ]]> <![CDATA[ 99.53 ]]> <![CDATA[ 98.29 ]]> <![CDATA[ 98.67 ]]> <![CDATA[ 99.13 ]]> <![CDATA[ 98.98 ]]> <![CDATA[ 99.07 ]]>

[0061] It can be seen from Table 2 that the shale gas horizontal well borehole stabilization drilling fluid prepared according to the formula of the present invention has good anti-dispersion performance.

[0062] Test Example 3

[0063] The core of Zhongping 1 Well was taken as a sample, and the core was immersed in the shale gas horizontal well borehole stabilization drilling fluid prepared in Example 1 and Comparative Example 1 to simulate the effect of the drilling fluid on the reservoir core after drilling the formation. The strength of the core was then tested to reflect the influence of the drilling fluid on the lithology strength. The measurement results are shown in Table 3.

[0064] Table 3

[0065] <![CDATA[ ]]> <![CDATA[ Soaking time / d ]]> <![CDATA[ Diameter / mm ]]> <![CDATA[ Length / mm ]]> <![CDATA[ Compressive strength / MPa ]]> <![CDATA[ Example 1 ]]> <![CDATA[ 1 ]]> <![CDATA[ 25.4 ]]> <![CDATA[ 36.3 ]]> <![CDATA[ 93.42 ]]> <![CDATA[ Comparative Example 1 ]]> <![CDATA[ 1 ]]> <![CDATA[ 25.4 ]]> <![CDATA[ 36.3 ]]> <![CDATA[ 75.38 ]]>

[0066] It can be seen from Table 3 that after adding liquid lubricant and polysilicon fluoride stabilizer, the compressive strength of the core after immersion can be effectively improved, indicating that the shale gas horizontal well borehole stabilization drilling fluid prepared by the present invention can effectively improve the problem of borehole wall instability.

[0067] Test Example 4

[0068] The core of Well Zhongping 1 was taken as a sample, and the hydration expansion properties of the core were tested using a shale expansion instrument with the shale gas horizontal well borehole stabilization drilling fluid prepared in Example 1 and water as test fluids. The test results are shown in Table 4.

[0069] Table 4

[0070]

[0071] It can be seen from Table 4 that the drilling fluid system prepared by the present invention has a strong ability to inhibit hydration expansion.

[0072] Test Example 5

[0073] The leakage prevention performance of the stable permeability leakage of the shale gas horizontal well wall drilling fluid prepared in Example 1 was measured by a sand bed filter loss meter. The results are shown in Table 5.

[0074] Table 5

[0075] <![CDATA[ ]]> <![CDATA[ Average penetration depth (mm) ]]> <![CDATA[ Filtrate loss (mL) ]]> <![CDATA[ Example 1 ]]> <![CDATA[ 10 ]]> <![CDATA[ 0 ]]>

[0076] It can be seen from Table 5 that the average invasion depth of the shale gas horizontal well wall stabilization drilling fluid prepared in Example 1 is 10 mm, the invasion is shallow, and it has good permeability and plugging performance.

[0077] Test Example 6

[0078] A high temperature and high pressure (HTHP) plugging simulation experimental device was used to measure the plugging pressure bearing capacity of the shale gas horizontal well wall stabilization drilling fluid prepared in Example 1 for 200 μm micro-cracks. The measurement results are shown in Table 6.

[0079] Table 6

[0080]

[0081] It can be seen from Table 6 that the shale gas horizontal well borehole stabilization drilling fluid prepared in Example 1 plugged 200 μm cracks without leakage during the experiment, and had good plugging effect and pressure bearing capacity.

[0082] Test Example 7

[0083] 5% NaCl, 10% NaCl, 0.5% CaCl2, 1% CaCl2, 6% reservoir inferior soil (passing through a 100-mesh sieve), and 10% reservoir inferior soil (passing through a 100-mesh sieve) were added to the shale gas horizontal well borehole stabilization drilling fluid prepared in Example 1, and the anti-pollution performance of the shale gas horizontal well borehole stabilization drilling fluid prepared in Example 1 before and after aging (aging conditions were 140°C / 16h). The results are shown in Table 7.

[0084] Table 7

[0085]

[0086] As can be seen from Table 6, after the shale gas horizontal well borehole stabilization drilling fluid prepared in Example 1 was contaminated with 5% NaCl, the viscosity and filtration loss remained basically unchanged. With the increase of NaCl addition, the viscosity decreased slightly and the filtration loss increased slightly, but the range of change was not large. Overall, its performance was less affected by NaCl, indicating that it had good salt resistance. After hot rolling with 6% reservoir inferior soil contamination, the viscosity remained basically unchanged and the filtration loss increased slightly. After being contaminated with 10% reservoir inferior soil, the viscosity decreased and the filtration loss remained basically unchanged, indicating that it had good resistance to inferior soil. After being contaminated with 0.5% CaCl2, the viscosity decreased and the filtration loss remained unchanged. After being contaminated with 1% CaCl2, the viscosity decreased slightly and the filtration loss increased slightly, indicating that the calcium resistance was good.

[0087] The above description shows and describes several preferred embodiments of the invention, but as mentioned above, it should be understood that the invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein through the above teachings or the technology or knowledge of the relevant field. Changes and modifications made by those skilled in the art should be within the scope of protection of the claims attached to the invention without departing from the spirit and scope of the invention.

Claims

1. A water-based drilling fluid for stabilizing the borehole wall of a shale gas horizontal well, characterized in that: The composition comprises, by mass percentage, 3.0% micro-nano aluminum silicate, 0.5% biomacromolecule thickener, 3.0% modified starch, 1.5% amine ester inhibitor, 5.0% low-carbon organic sodium salt, 1.0% organic and inorganic polymer lubricant, 1.5% liquid lubricant, 1% polysilicon fluoride stabilizer, and the balance is water; the biomacromolecule thickener is xanthan gum or modified plant-extracted cellulose; the modified starch is lignin starch or cellulose starch; the amine ester inhibitor is a primary amine or a secondary amine or a secondary amine of methyl acrylate; the carbon number of the low-carbon organic sodium salt is ≤4; the low-carbon organic sodium salt is sodium formate or sodium acetate.

2. The water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well according to claim 1, characterized in that: The organic-inorganic polymer lubricant is a polymer composed of boric acid and oleic acid ester.

3. The water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well according to claim 2, characterized in that: The liquid lubricant is liquid lubricant RT101.

4. The water-based drilling fluid for stabilizing the wellbore of a shale gas horizontal well according to claim 3, characterized in that: The polysilicon fluorine stabilizer is shale inhibitor polysilicon JW-1.

Images