CN108251079A - A kind of drilling fluid suitable for frozen soil gas hydrates storage - Google Patents

Abstract

A kind of drilling fluid suitable for frozen soil gas hydrates storage is related to exploitation of gas hydrates field.Drilling fluid of the present invention includes following components：Sodium metasilicate, sodium chloride, methanol, ethylene glycol, low viscosity carboxymethyl cellulose LV CMC, xanthans, PVP K30, polyvinyl methyl ether and preparation water, it is used available for the storage drilling well of frozen soil layer gas hydrates, there is Solid Free, low temperature resistant, it is compounded in drilling fluid by adding in kinetic inhibitor with synergist, inhibition is generated with stronger hydrate, and components of drilling liquid is small to environmental hazard, has many advantages, such as that efficient, environmental protection, raw material are cheap and easy to get.

Description

A kind of drilling fluid suitable for frozen soil gas hydrates storage

Technical field

The present invention relates to a kind of drilling fluids suitable for frozen soil gas hydrates storage, and in particular to gas hydrates Exploitation field.

Background technology

Gas hydrates in nature are mainly distributed on epeiric ocean deepwater area and land permafrost area.My god Right gas hydrate is one of very promising alternative energy source, and the research to gas hydrates is contemporary geoscience and energy work One big hot spot of industry developmental research.However the most of gas hydrates studied both for ocean deepwater area, about land The research of upper permafrost area gas hydrates is relatively fewer.To be ensconced to assigning the gas hydrates of frozen soil layer certain depths into Row exploration and exploitation, drilling well is essential important means.The phase equilibrium properties of gas hydrates determine such stratum Drilling well is very different with general hydrocarbon formations drilling well, and this kind of strata drilling is also caused to face more complicated well inner question, mesh The technical essential of preceding frozen soil layer gas hydrates drilling well has following two aspects：

1. the drilling feature of frozen soil layer gas hydrates storage

Largely to freeze rock stratum, it is by multi mineral particle, ice cube, not to freeze rock stratum on the frozen soil layer drilling stratum that is related to Multicomponent series of rocks of the compositions such as the water freezed and the air full of vapor, (such as temperature and pressure when external condition changes The fluctuation of power), inevitably cause permafrost haorizon own physical property that the variation of matter occurs；From the viewpoint of drillability, Permafrost haorizon should regard a kind of rock stratum of physical-mechanical properties variation as, and contained liquid phase moisture is fewer in permafrost haorizon, and intensity is got over Height, ice present in blowhole can improve its plasticity, and actual influence of the rock plasticity in drilling is drill bit in drilling Very high resistance can be encountered, and the plasticity of permafrost haorizon is as rock forming mineral granularity becomes smaller, frost property increases and drilling depth Increase and increase.

In drilling process, well temperature changes at any time with the difference of depth, the flushing to flow downward along drill string The scouring media to backflow in medium and annular space be in continuous heat exchanging process with stratum, the scouring media to backflow it is again direct or By being contacted indirectly with surrounding rock, and the friction of bit cutting rock, bottomhole and the borehole wall and rock core can all generate A large amount of thermal energy；The condition that the variation of temperature is stabilized hydrate is destroyed, and causes the decomposition of hydrate, the borehole wall is caused to lose Surely, so as to be adversely affected to drillng operation.

When frozen soil layer gas hydrates are stored and are crept into, it is necessary to consider following factor：1. gas hydrates are in temperature It is easy to decompose in the case of raising, pressure reduction；2. it releases a large amount of gas after decomposing, volume will be expanded to 120- 170 times；3. the equilibrium condition of gas hydrates changes with the difference of gas and the blending constituent of aqueous solution；It is 4. natural Gas hydrate is decomposed into the endothermic reaction；5. the gentle regenerating easily of water of gas hydrate dissociation generation is closed into gas water Object.

Therefore, it is crept on such stratum, on the one hand to consider that the performance of drilling fluid and temperature must assure that natural gas is hydrated The condition on object preservation stratum, inhibits the decomposition of hydrate, on the other hand must also consider that ground environment temperature is extremely low in well In the case of medium cycle.

2. the drilling requirement of frozen soil layer gas hydrates storage

The decomposition of mud filtrate invasion and hydrate can cause formation pore pressure to increase to some extent, and pore pressure increases Adding so that drilling fluid density needed for wellbore stability is kept also to increase, this not only seriously affects drilling speed, but also increases borehole wall infiltration, Increase the pore pressure in well week, so as to further reduce the stability of the borehole wall, form vicious circle, therefore drilling fluid needs to have There is good borehole wall stability.

In drilling process, the water that decomposition of hydrate generates into the drilling fluid filtrate on stratum and stratum can cause stratum to contain Water gradually increases, and when stratum water content is excessively high, can aggravate hydrate formation skeleton aquation, cause the borehole wall more unstable； Moreover, decomposition of hydrate can also increase the permeability on stratum, drilling fluid is permeated to the borehole wall generates osmotic pressure, makes collapsing for stratum Pressure of collapsing improves, and fracture pressure reduces, and the borehole wall is made to be more easy to cave in and pressure break, reduces borehole wall stability, therefore drilling fluid needs With good filtration reduction.

Wellbore fluid used in Gas Hydrate Drilling is different from general drilling fluid, is because of gas hydrates Probing is carried out in larger depth, and the drilling fluid of bottom hole works at elevated pressures, and drilling fluid will not only have good cold But drill bit, cleaning hole bottom, suspending excludes landwaste, stablizes hole wall and inhibits the ability of decomposition of hydrate, will also be in high pressure, low temperature There is good rheological property under situation；Relative to 0 DEG C~4 DEG C of ocean gas hydrate storage temperature, frozen soil layer natural gas Hydrate storage temperature is lower, and temperature is up to 0 DEG C~-15 DEG C, therefore it is required that drilling fluid has stronger low temperature resistivity.

Chinese patent literature publication number CN103146364B, patent name are《A kind of high inhibition water-base drilling fluid》, by water 100 parts, 0.2-4 parts of polyamine inhibitor, 0.1-1 parts of inhibitor of coating, 10-25 parts of hydrate inhibitor, 0.1-1 parts of tackifier, 0.5-3 parts of compositions of 0.5-5 parts of fluid loss additive and fluid lubricant.The drilling fluid can inhibit deep water shallow stratum borehole well instability, can It solves the problems, such as the generation of hydrate in deepwater drilling, is applicable in the drillng operation of the 3000m depth of waters.Chinese patent literature discloses Number CN104531106A, patent name are《A kind of efficient hydrate inhibition environmental protection drilling fluid》, by water, bentonite, quaternary amine Type Gemini surface active agent, inorganic salts, sodium carboxymethyl starch, cationic polyacrylamide, solid anti sinking lubricant GFRH compositions, It is exploited available for the petroleum resources of land or ocean, effectively inhibits the generation of hydrate, and components of drilling liquid is to environmental hazard It is small, there is efficient, environmental protection.Chinese patent literature publication number CN105018052A, patent name are《A kind of low solid phase is low Warm polymer drilling fluid》, comprising basal liquid and inorganic agent, wherein basal liquid is answered with sodium bentonite and sodium chloride solution Match；Inorganic agent is compounded for sulfonated bodies cation exchange resin with polysaccharide as flow pattern regulator.The drilling fluid is in low temperature Under the conditions of to decompose strong inhibition capability, good rheological property, fluid loss low.Above-mentioned drilling fluid has one to gas hydrates storage drilling well Fixed effect, but do not consider to use Compositional type hydrate inhibitor.

Ensure that natural gas hydrate stratum drilling safety successfully carries out, must just take measures to well temperature and pressure Power is strictly controlled, and controls and reduce the degree of decomposition of hydrate as far as possible using the drilling fluid with good low temperature properties, To keep wellbore stability and shaft safety, therefore on the basis of the above, the present invention proposes that a kind of frozen soil natural gas that is suitable for is hydrated The drilling fluid of object storage.

Invention content

The purpose of the present invention is to provide a kind of drilling fluid suitable for frozen soil gas hydrates storage, drilling wells of the present invention Liquid includes following components：Sodium metasilicate, sodium chloride, methanol, ethylene glycol, low viscosity carboxymethyl cellulose LV-CMC, xanthans, poly- second Alkene pyrrolidone K30, polyvinyl methyl ether and preparation water are used available for the storage drilling well of frozen soil layer gas hydrates, There is Solid Free, low temperature resistant, compounded in drilling fluid by adding in kinetic inhibitor with synergist, there is stronger water Object generation inhibition is closed, and components of drilling liquid is small to environmental hazard, have many advantages, such as that efficient, environmental protection, raw material are cheap and easy to get.

In order to achieve the above object, the present invention adopts the following technical scheme that.

A kind of drilling fluid suitable for frozen soil gas hydrates storage, which is characterized in that the drilling fluid includes following Component：Sodium metasilicate mass ratio is 1.8%-2.2%, sodium chloride mass ratio is 4.5%-5.5%, methanol quality ratio is 4.5%- 5.5%th, quality of glycol ratio is 19%-21%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 1.8%-2.2%, Huang Virgin rubber mass ratio is 0.4%-0.6%, PVP K30 mass ratio is 0.8%-1.2%, polyvinyl methyl ether matter Amount is than being 0.4%-0.6%, and remaining components is prepare water.

Preferably, the drilling fluid includes following components：Sodium metasilicate mass ratio is 2%, sodium chloride mass ratio is 5%, first Alcohol mass ratio is 5%, quality of glycol ratio is 20%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 2%, xanthan colloid Amount ratio is 0.5%, PVP K30 mass ratio is 1%, polyvinyl methyl ether mass ratio is 0.5%, remaining components To prepare water.

In above-mentioned drilling fluid, the sodium metasilicate increases as drilling fluid host agent, thickener, anti-sloughing agent in drilling process Shale stability, and can mitigate stratum leakage degree, moderately prevent leakage, in the present invention inorganic salts sodium chloride and silicic acid Sodium can generate synergistic effect, improve the rejection ability of drilling fluid, since sodium metasilicate barrier can form high efficiency permeable membrane, chlorine The activity of water in drilling fluid can be reduced by changing sodium, induced the fluid in shale gap and oozed out from shale into drilling fluid, so as to Achieve the purpose that shale goes aquation and improves shale stability.

In above-mentioned drilling fluid, the sodium chloride is used as low-temperature resistance agent as thermodynamic inhibitor, reduces the solidifying of drilling fluid Solid temperature degree.

In above-mentioned drilling fluid, the methanol is as thermodynamic inhibitor, kinetic inhibitor synergist；Methanol can be changed The thermodynamic condition of hydrate generation, it is suppressed that the nucleation of hydrate.

In above-mentioned drilling fluid, the ethylene glycol is as low-temperature resistance agent, kinetic inhibitor synergist；Ethylene glycol is one kind two First alcohol has stronger hydrogen bond Forming ability, after being mixed with water, firm hydrogen bond can be formed with water, can be greatly lowered The freezing point of solution.

In above-mentioned drilling fluid, the low viscosity carboxymethyl cellulose LV-CMC is used as thickener, anti-sloughing agent.

In above-mentioned drilling fluid, the xanthans is used as creeping agent, the flow pattern of adjusting drilling well liquid.

In above-mentioned drilling fluid, the PVP K30 is used as kinetic inhibitor, and polyvinyl first As kinetic inhibitor synergist, dynamics suppression is relatively used alone in the inhibition for compounding kinetic inhibitor for base ether, methanol It is significantly improved during preparation.

In above-mentioned drilling fluid, the water of preparing is conventional source water water, such as river water, well water and filtered seawater etc.；It bores Well liquid preparation method is conventional drilling liquid making method.

The drilling fluid is in use, corresponding drilling fluid cooling equipment can be equipped in drilling platforms, for controlling drilling fluid Low temperature；Corresponding solid control equipment can be equipped in drilling platforms, the clay particle for that will be distributed in drilling fluid removes, and reaches drop Low-soild effect.

The drilling fluid in use, make a trip, more bit change and well logging when, can as needed into drilling fluid add in weight Spar improves drilling fluid density, for inhibiting decomposition of hydrate, prevents blowout, and drilling fluid density is adjusted to 1.2-2.0g/ cm³, when subsequent well taken out barite by ground recycle unit, and drilling fluid is made to restore initial density.

The drilling fluid can add in chlorination in use, in case of saline bed, mud shale easily collapse stratum into drilling fluid system Calcium solution.

The drilling fluid in use, can be needed according to practical storage add in alkalinity control agent adjust pH value 9-10 it Between.

The present invention the advantage is that relative to the prior art：

1st, the present invention uses sodium metasilicate as drilling fluid host agent, and is clay-free drilling fluid, has good rheological characteristic, and Can increase to the shale stability in drilling process, and more can fully carry and hang gang drill bits, can effectively reduce and It prevents the repetition of drilling cuttings from crushing, and the degree of stratum leakage can be mitigated, moderately prevent leakage.

2nd, drilling fluid of the present invention can solve the problems, such as that hydrate generates in gas hydrates storage drilling process, can prevent The safety accidents such as bit freezing and catheter blockage caused by forming hydrate in drilling process.

3rd, drilling fluid of the present invention has good low-temperature stability, by the way that drilling fluid is controlled to keep low-temperature condition, can prevent A large amount of decomposition of foot of hole position hydrate in gas hydrates storage drilling process, initiation aperture can be avoided seriously to expand, The accidents such as blowout, well slough, casing deformation and surface subsidence.

4th, drilling fluid of the present invention damages small caused by reservoir, is conducive to that gas water is found and protected in drilling process Close produce layer.The drilling fluid has the characteristics that Solid Free, low-density, therefore, nearly balance can be achieved in drilling process even Underbalance pressure drilling can effectively reduce intrusion of the solid phase to stratum, so as to advantageously reduce to gas hydrates reservoir Damage.

5th, drilling fluid of the present invention uses Compositional type hydrate inhibitor, is compounded by kinetic inhibitor and synergist, Hydrate generation inhibition is relatively used alone kinetic inhibitor and is obviously improved, and frozen soil layer gas hydrates are stored up It hides, the decomposition of hydrate can be reduced, so as to reduce the probability that decomposition of hydrate causes drilling failure.

Specific embodiment

Experimental method used in following embodiments is conventional method unless otherwise specified.

The sodium metasilicate used in following embodiments is produced for Tianjin Zhi Yuan chemical reagent Co., Ltd, and analysis is pure；Chlorination Sodium is the prosperous prosperous Chemical Co., Ltd.'s production in Tianjin, and analysis is pure；Methanol is produced for Guangdong Weng rivers chemical reagent Co., Ltd, point It analyses pure；Ethylene glycol is produced for Tianjin Zhi Yuan chemical reagent Co., Ltd, and analysis is pure；Low viscosity carboxymethyl cellulose LV-CMC is The sincere hundred million Chemical Co., Ltd.s production of Renqiu City；Xanthans is the sincere hundred million Chemical Co., Ltd.s production of Renqiu City；Polyvinylpyrrolidone K30 is produced for Tianjin great Mao chemical reagent factories, and analysis is pure；Polyvinyl methyl ether is given birth to for Hubei Xin Mingtai Chemical Co., Ltd.s Production, purity 98%；Methane gas comes from Wuhan Huaxing Ind ＆ Tech Co., Ltd., purity 99.9%.

In the following embodiments, each noun dummy suffix notation, unit correspondence are as follows：Temperature, is abbreviated as T, and unit is Celsius Degree；Apparent viscosity writes a Chinese character in simplified form AV, unit mPa.s；Plastic viscosity is abbreviated as PV, unit mPa.s；Yield value is abbreviated as YP, unit Pa；Filter loss is abbreviated as FL, unit ml.

Embodiment one, each component content is in drilling fluid：Sodium metasilicate mass ratio is 1.8%, sodium chloride mass ratio is 4.5%th, methanol quality ratio is 4.5%, quality of glycol ratio is 19%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 1.8%th, xanthans mass ratio is 0.4%, PVP K30 mass ratio is 0.8%, polyvinyl methyl ether mass ratio It is 0.4%, remaining components is prepare water.

Embodiment two, each component content is in drilling fluid：Sodium metasilicate mass ratio is 2%, sodium chloride mass ratio is 5%, first Alcohol mass ratio is 5%, quality of glycol ratio is 20%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 2%, xanthan colloid Amount ratio is 0.5%, PVP K30 mass ratio is 1%, polyvinyl methyl ether mass ratio is 0.5%, remaining components To prepare water.

Embodiment three, each component content is in drilling fluid：Sodium metasilicate mass ratio is 2.2%, sodium chloride mass ratio is 5.5%th, methanol quality ratio is 5.5%, quality of glycol ratio is 21%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 2.2%th, xanthans mass ratio is 0.6%, PVP K30 mass ratio is 1.2%, polyvinyl methyl ether mass ratio It is 0.6%, remaining components is prepare water.

One, two, three drilling fluid allocation method of above-described embodiment is conventional drilling liquid configuration method, passes through following experimental method It is evaluated：

1 drilling fluid Shale Hydration inhibition is evaluated

When carrying out the Lab-evaluation of correlated performance to drilling fluid, inhibition evaluation experimental is one of important composition portion Point, the present invention is tested using mud shale expansion Inhibition test, and specific experiment data are as shown in table 1.

1 aquation inhibition of table evaluates data

As can be seen from Table 1, under the same conditions, one, two, three drilling fluid system of embodiment is to the inhibition energy of shale expansion Power is clearly.Wherein, initial 2 hour line percent expansion is only 3.5%, 3.4%, 3.2%, and at the end of testing, 16 is small When line percent expansion be only 7.8%, 7.6%, 7.3%, and the clear water to compare mutually be 40.3%；In experimentation, clearly Shale expansion percentage in water is over time in the trend to increase substantially, and shale is swollen in embodiment drilling fluid The variation of swollen percentage is but relatively steady, and when experiment proceeds to 16h, the expansion rate variation of shale is smaller, expansion rate variation by Gradually tend towards stability.It can be seen that the drilling fluid system can significantly reduce the hydration swelling amount of mud shale, it can be effectively prevented ground Layer hole instability caused by due to aquation.

2 drilling fluid low temperature rheological behaviours are evaluated

Frozen soil layer gas hydrates storage temperature is usually 0 DEG C~-15 DEG C, with decomposing inhibition method drilling hydrate Layer, often inhibits the decomposition of hydrate by reducing the temperature of drilling fluid, it requires drilling fluid temperature less than formation temperature, and With good cryogenic property.

In the experiment of drilling fluid low temperature rheological behaviour, drilling fluid is cooled down first in high-low temperature test chamber to a certain constant Temperature.When the temperature of drilling fluid, which is reduced to, tests required a certain steady temperature, continue at this temperature 1 hour Cooling.Period at the uniform velocity stirs drilling fluid with glass bar two minutes in every 15 minutes, and the temperature inside drilling fluid is made to keep uniformly dividing Then cloth tests the rheological characteristic parameter of drilling fluid by six fast electronic rotation viscosimeters at this temperature.Treat that rheological characteristic is tested After finishing, rapidly with the density of densimeter test drilling fluid, the filter loss of drilling fluid is tested immediately later.Final measure includes The situation of change of drilling fluid rheology under the conditions of 0 DEG C, -5 DEG C, -10 DEG C, -15 DEG C, -20 DEG C.

Experiment test property of the drilling fluid in 5 different temperatures, experimental result such as following table.

The rheological characteristic of 2 embodiment of table, one drilling fluid at different temperatures

T(℃)	ρ(g/cm3)	Gel(Pa/Pa)	PV(mPa.s)	YP(Pa)	Fl(ml)
						0	1.13	1.5/2	17.3	7.3	6.5
-5	1.15	1.5/2	19.5	7.7	6.3
						-10	1.16	2/2.5	21.6	8.2	6.2
-15	1.16	2/2.5	24.8	8.5	5.8
						-20	1.16	2/2.5	26.2	8.9	5.5

The rheological characteristic of 3 embodiment of table, two drilling fluid at different temperatures

T(℃)	ρ(g/cm3)	Gel(Pa/Pa)	PV(mPa.s)	YP(Pa)	Fl(ml)
						0	1.15	1.5/2	18.5	7.5	6.3
-5	1.16	1.5/2	20.4	7.7	6.1
						-10	1.17	2/2.5	22.2	8.3	5.8
-15	1.17	2/2.5	25.3	8.6	5.7
						-20	1.17	2/2.5	27.5	9.0	5.3

The rheological characteristic of 4 embodiment of table, three drilling fluid at different temperatures

From table 2-4 it is found that as temperature reduces, the plastic viscosity and shear force of drilling fluid increase, but change it is little, all can In the range of receiving.In addition, drilling fluid ratio of dynamic shear force/yield value to plastic viscosity is higher, be conducive to cutting carring, clean wellbore, filter loss reduce with temperature and It reduces.Rheological characteristic and stability are preferable under cryogenic for the drilling fluid being configured.

The generation of 3 methane hydrates inhibits evaluation

In terms of the hydrate generation rejection evaluation of drilling fluid, the present invention is tested in autoclave by acquiring The variation of temperature, pressure and other parameters in the process, and the directly observation for combining visualization window carries out；Experimental test procedures are：It is first First the drilling fluid of prepared certain volume is put into reaction kettle, methane gas is passed through, sets high pressure low temperature experimental enviroment, Air source is cut off, opens data acquisition software, collected temperature, pressure data are protected in the temperature and pressure variation in observing response kettle It deposits, during the experiment, in order to simulate drill string rotation, control mixing speed is 200r/min, is surveyed under conditions of it there is disturbance The hydrate inhibition effect of examination drilling fluid of the present invention.

In drilling process, drilling fluid is about 2-4h from shaft bottom to drilling platforms cycle period, according to API standard and is led to Experimentally, under the conditions of the temperature and pressure on simulation certain depth stratum, the drilling fluid containing hydrate inhibitor is in 16h Interior no hydrate generation illustrates that the drilling fluid can meet requirement of the drilling well to hydrate inhibition, experimental temperature selection -5 DEG C, -10 DEG C, -20 DEG C, pressure selection 5mPa, 10mPa, 15mPa, mixing speed 200r/min, experimental period selection 16h.

Comparative example 1

Deionized water is fitted into the reaction kettle of gas hydrates inhibition evaluation experimental device, simulation 500m depth is bored Well environment, i.e. experimental pressure are 5mPa, and experimental temperature is 2 DEG C, mixing speed 200r/min, the generation of hydrate in reaction kettle Time is 1.7h.

Comparative example 2

Sodium chloride is configured to the aqueous solution that mass percent is 10%, is packed into gas hydrates inhibition evaluation experimental In the reaction kettle of device, 1500m depth drilling environments are simulated, i.e. experimental pressure is 15MPa, and experimental temperature is 2 DEG C, mixing speed 200r/min, the generated time of hydrate is 3.2h in reaction kettle.

The generation of 5 hydrate of table inhibits tables of data

The result shows that：In one, two, three drilling fluid system experimentation of embodiment, reacting kettle inner pressure and temperature are 16 That apparent variation does not occur in the reaction time of hour, pressure curve more steadily, is dissolved in interior gas always after uncapping Body is released in seconds, does not observe the generation of hydrate, accordingly it is found that drilling fluid system of the present invention can be in dynamic environment very Inhibit the generation of hydrate well.

4 contamination resistances are evaluated

Test drilling fluid contamination resistance：It is surveyed after a certain amount of bentonite (4%, 8%) maintenance 72h is added in drilling fluid Its performance is tried, evaluates contamination resistance, test temperature is -5 DEG C, as a result be see the table below.

6 embodiment of table, one drilling fluid system contamination resistance is evaluated

Formula	ρ(g/cm3)	Gel(Pa/Pa)	PV(mPa.s)	YP(Pa)	Fl(ml)
						Embodiment one	1.15	1.5/2	19.5	7.7	6.3
One+4% bentonite of embodiment	1.18	2/2.5	21.3	8.4	5.6
						One+8% bentonite of embodiment	1.21	2.5/3	23.5	9.6	4.9

7 embodiment of table, two drilling fluid system contamination resistance is evaluated

Formula	ρ(g/cm3)	Gel(Pa/Pa)	PV(mPa.s)	YP(Pa)	Fl(ml)
						Embodiment two	1.16	1.5/2	20.4	7.7	6.1
Two+4% bentonite of embodiment	1.19	2/2.5	21.8	8.5	5.5
						Two+8% bentonite of embodiment	1.22	2.5/3	24.7	9.7	4.8

8 embodiment of table, three drilling fluid system contamination resistance is evaluated

Formula	ρ(g/cm3)	Gel(Pa/Pa)	PV(mPa.s)	YP(Pa)	Fl(ml)
						Embodiment three	1.17	1.5/2	21.3	7.9	6.0
Three+4% bentonite of embodiment	1.21	2/2.5	23.3	8.6	5.4
						Three+8% bentonite of embodiment	1.23	2.5/3	25.8	9.8	4.7

After adding in 4% and 8% bentonite in drilling fluid it can be seen from table 6-8, the viscosity and shear force of drilling fluid on It rises, but amplitude of variation is little, shows that the drilling fluid contamination resistance is stronger.

5 rate of recovery are evaluated

The rate of recovery of drilling fluid is tested by rolling dispersion experiment, using certain block frozen soil layer landwaste as test object, Heat rolling 16h at 80 DEG C, the sieve for being 0.45mm with aperture recycle, and the experimental data are shown in the following table.

The different system rolling rate of recovery comparisons of table 9

As can be seen from Table 9, the rate of recovery of drilling fluid system is higher, and the primary and secondary rate of recovery reaches 90% or so, Landwaste primary recovery reaction drilling fluid chemistry inhibition is strong and weak, and landwaste of the secondary returning yield reaction after mud soak exists Dispersibility in clear water, dispersibility it is smaller illustrate landwaste be suppressed effect it is stronger, the borehole wall more they tends to stablize.

6 lubricities are tested

Using drilling fluid extreme boundary lubrication instrument, the extreme boundary lubrication coefficient of drilling fluid of the present invention is tested, the results showed that three realities The extreme boundary lubrication coefficient for applying example is respectively 0.0897,0.0903,0.0912, within 0.1, shows that drilling fluid of the present invention has Good lubricity.

Claims (2)

1. a kind of drilling fluid suitable for frozen soil gas hydrates storage, which is characterized in that the drilling fluid is included with the following group Point：Sodium metasilicate mass ratio is 1.8%-2.2%, sodium chloride mass ratio is 4.5%-5.5%, methanol quality ratio is 4.5%- 5.5%th, quality of glycol ratio is 19%-21%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 1.8%-2.2%, Huang Virgin rubber mass ratio is 0.4%-0.6%, PVP K30 mass ratio is 0.8%-1.2%, polyvinyl methyl ether matter Amount is than being 0.4%-0.6%, and remaining components is prepare water.

2. a kind of drilling fluid suitable for frozen soil gas hydrates storage as described in claim 1, which is characterized in that described Drilling fluid includes following components：Sodium metasilicate mass ratio is 2%, sodium chloride mass ratio is 5%, methanol quality ratio is 5%, ethylene glycol Mass ratio is 20%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 2%, xanthans mass ratio is 0.5%, polyethylene pyrrole Pyrrolidone K30 mass ratioes are 1%, polyvinyl methyl ether mass ratio is 0.5%, and remaining components is prepare water.