CN108441193A - A kind of ocean hydrate storage polyvinyl alcohol composite type drilling fluid - Google Patents

Abstract

A kind of ocean hydrate storage polyvinyl alcohol composite type drilling fluid, is related to exploitation of gas hydrates field.Drilling fluid of the present invention includes following components：Polyvinyl alcohol, sodium chloride, potassium chloride, ethylene glycol, potassium humate, polyacrylic acid potassium, xanthans, Vinylcaprolactam homopolymer, ethylene glycol diethyl ether, tetra-n-butyl ammonium phosphate and preparation water, it can be used for sea bed gas hydrate storage drilling well to use, has the function of Solid Free, low temperature resistant, it is compounded with synergist in drilling fluid by the way that kinetic inhibitor is added, 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 ocean hydrate storage polyvinyl alcohol composite type drilling fluid

Technical field

The present invention relates to a kind of ocean hydrates to store polyvinyl alcohol composite type drilling fluid, 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, preceding Person accounts for oneself and finds the overwhelming majority of quantity.Gas hydrates are one of very promising alternative energy sources, to gas hydrates Research be contemporary geoscience and energy industry developmental research a big hot spot.Submarine sedimentary strata, which is contained, a large amount of natural gas Hydrate will be explored and be developed to the gas hydrates for assigning the plant certain depths in underground, and drilling well is essential heavy Want means.The phase equilibrium properties of gas hydrates determine that such strata drilling and general hydrocarbon formations drilling well have very very much not Together, this kind of strata drilling is also caused to face more complicated well inner question, at present the main problem of gas hydrates drilling fluid There is the following：

(1) when being crept into natural gas hydrate stratum, since reservoir stress can discharge near the reservoir borehole wall and shaft bottom, stratum Pressure reduction；And the friction of bit cutting rock, bottomhole and the borehole wall and rock core can all generate a large amount of thermal energy, make hydration The temperature, pressure condition that object is stabilized is destroyed；To cause the decomposition of hydrate, borehole well instability is caused, drillng operation is made At adverse effect.

(2) decomposition of mud filtrate invasion and hydrate can cause formation pore pressure to increase in various degree, pore pressure Increase so that drilling fluid density needed for wellbore stability is kept also accordingly to increase, this not only seriously affects drilling speed, but also increases the borehole wall Infiltration, makes the pore pressure in well week increase, and to further decrease the stability of the borehole wall, forms vicious circle.

(3) due to entering the water that decomposition of hydrate generates in drilling fluid filtrate and stratum in stratum in drilling process, Stratum water content is caused gradually to increase.When stratum water content is excessively high, hydrate formation skeleton aquation can be made to aggravate, lead to the borehole wall It is more unstable.Also, decomposition of hydrate can also be such that the permeability on stratum increases, and drilling fluid is permeated to the borehole wall generates osmotic pressure, The caving pressure on stratum is set to improve, fracture pressure reduces, and makes the borehole wall be more easy to cave in and pressure break, reduces borehole wall stability.

(4) sea bed gas hydrate is stored, gas hydrates are stored in drilling process, the decomposition of hydrate The super quiet pore pressure in the storage soil body is set to increase rapidly, so as to cause submarine landslide or foundation of sea floor unstability, in turn It may cause the destruction of the facilities such as drilling, drilling platforms, submarine pipeline.

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 The generation for solving the problems, such as 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, The petroleum resources exploitation that can be used for land or ocean, effectively inhibits the generation of hydrate, and components of drilling liquid is to environmental hazard It is small, have many advantages, such as efficient, environmental protection.Chinese patent literature publication number CN105018052A, patent name are《A kind of low solid phase is low Warm polymer drilling fluid》, including basal liquid and inorganic agent, wherein basal liquid are answered with sodium bentonite and sodium chloride solution Match；Inorganic agent is that sulfonated bodies cation exchange resin is compounded 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 ocean hydrate stores polyethylene Alcohol Compositional type drilling fluid.

Invention content

The purpose of the present invention is to provide a kind of ocean hydrates to store polyvinyl alcohol composite type drilling fluid, drilling well of the present invention Liquid includes following components：Polyvinyl alcohol, sodium chloride, potassium chloride, ethylene glycol, potassium humate, polyacrylic acid potassium, xanthans, poly- second Alkenyl caprolactam, ethylene glycol diethyl ether, tetra-n-butyl ammonium phosphate and preparation water, can be used for sea bed gas hydrate storage Drilling well uses, and has the function of Solid Free, low temperature resistant, passes through in drilling fluid and kinetic inhibitor is added is compounded with synergist, has There is stronger hydrate to generate inhibition, and components of drilling liquid is small to environmental hazard, has efficient, environmental protection, raw material cheap The advantages that being easy to get.

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

A kind of ocean hydrate storage polyvinyl alcohol composite type drilling fluid, which is characterized in that the drilling fluid includes following Component：Polyvinyl alcohol mass ratio is 1.8%-2.2%, sodium chloride mass ratio is 4.5%-5.5%, potassium chloride mass ratio is 4.5%-5.5%, quality of glycol ratio are 9%-11%, potassium humate mass ratio is 1.8%-2.2%, polyacrylic acid potassium quality Than for 1.8%-2.2%, xanthans mass ratio be 0.4%-0.6%, Vinylcaprolactam homopolymer mass ratio is 0.8%- 1.2%, ethylene glycol diethyl ether mass ratio is 0.8%-1.2%, tetra-n-butyl ammonium phosphate mass ratio is 0.8%-1.2%, remaining Group is divided into preparation water.

Preferably, the drilling fluid includes following components：Polyvinyl alcohol mass ratio is 2%, sodium chloride mass ratio is 5%, Potassium chloride mass ratio is 5%, quality of glycol ratio is 10%, potassium humate mass ratio is 2%, polyacrylic acid potassium mass ratio is 2%, xanthans mass ratio is 0.5%, Vinylcaprolactam homopolymer mass ratio is 1%, ethylene glycol diethyl ether mass ratio is 1%, Tetra-n-butyl ammonium phosphate mass ratio is 1%, and remaining components are to prepare water.

In above-mentioned drilling fluid, host agent of the polyvinyl alcohol as drilling fluid, anti-sloughing agent can increase drilling fluid density, increase Add drilling fluid low temperature resistivity；And polyvinyl alcohol property is stablized, and is not influenced by external environment pH value, temperature etc., can be with big portion The high polymer divided is compatible；Polyvinyl alcohol is biodegradable, can meet the requirement of environmental protection；It can increase steady to the shale in drilling process It is qualitative, and the degree of stratum leakage can be mitigated, moderately prevent leakage；The lubricity of drilling fluid can be improved, reduce frictional resistance.

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

In above-mentioned drilling fluid, the potassium chloride as thermodynamic inhibitor, the polyacrylic acid potassium as fluid loss additive, and Potassium chloride and polyacrylic acid potassium compounding are used in mixed way, potassium ion in drilling fluid can play coating and flocculation, by part It is removed using solid control equipment after the clay particle flocculation coalescence being distributed in drilling fluid, reaches inhibition and the low-soild dual work of drop With.

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, can form firm hydrogen bond with water, can be greatly lowered The freezing point of solution.

In above-mentioned drilling fluid, the potassium humate is used as fluid loss additive.

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 Vinylcaprolactam homopolymer is used as kinetic inhibitor, and ethylene glycol diethyl As kinetic inhibitor synergist, the inhibition for compounding kinetic inhibitor is relatively used alone for ether, tetra-n-butyl ammonium phosphate It is significantly improved when kinetic inhibitor；The Vinylcaprolactam homopolymer with N- caprolactams (VCL) for monomer, it is even Nitrogen bis-isobutyronitrile is initiator, is synthesized by solution polymerization process, and synthetic method is known technology, and not this patent protects content, Wherein, N- caprolactams (VCL) produce for BASF AG, purity 100%；Azodiisobutyronitrile is day Zhi Yuan chemical reagent Co., Ltd of Jinshi City produces, and analysis is pure.

In above-mentioned drilling fluid, the preparation water 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 cools down equipment in use, corresponding drilling fluid can be equipped in drilling platforms, for controlling drilling fluid Low temperature；It can be equipped with corresponding solid control equipment 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 be added weight Spar improves drilling fluid density, for inhibiting decomposition of hydrate, prevents blowout, 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.

Chlorination can be added in use, in case of saline bed, mud shale easily collapse stratum in the drilling fluid into drilling fluid system Calcium solution.

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

The present invention the advantage is that compared with the existing technology：

1, the present invention uses polyvinyl alcohol as host agent, and polyvinyl alcohol is biodegradable, can meet the requirement of environmental protection；And Polyvinyl alcohol property is stablized, and is not influenced by external environment pH value, temperature etc., can be compatible with most high polymer；And this hair Bright drilling fluid is clay-free drilling fluid, has good rheological characteristic, lubricity, and more can fully carry and hang gang drill Bits can effectively reduce and prevent the repetition of drilling cuttings broken, and can mitigate the degree of stratum leakage, moderately prevent leakage.

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

3, drilling fluid of the present invention has good low-temperature stability, keeps low-temperature condition by controlling drilling fluid, can prevent Gas hydrates store drilling process in foot of hole position hydrate a large amount of decomposition, can avoid cause aperture seriously expand, The accidents such as blowout, well slough, casing deformation and surface subsidence.

4, 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, to advantageously reduce to gas hydrates reservoir Damage.

5, drilling fluid of the present invention uses Compositional type hydrate inhibitor, is compounded by kinetic inhibitor and synergist, Hydrate generates inhibition relatively exclusive use kinetic inhibitor and is obviously improved, and sea bed gas hydrate is stored up It hides, the decomposition of hydrate can be reduced, to reduce the probability for causing submarine landslide or foundation of sea floor unstability.

Specific implementation mode

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

The polyvinyl alcohol used in following embodiments produces for Xilong Chemical Co., Ltd, and analysis is pure；Sodium chloride is The prosperous prosperous Chemical Co., Ltd.'s production in Tianjin, analysis are pure；Potassium chloride produces for Shanghai traditional Chinese medicines reagent group, and analysis is pure；Second two Alcohol produces for Tianjin Zhi Yuan chemical reagent Co., Ltd, and analysis is pure；Potassium humate is the limited public affairs of Renqiu City high-tech chemical industry goods and materials Department's production；Polyacrylic acid potassium produces for Hebei Yan Xing Chemical Co., Ltd.s；Xanthans is the sincere hundred million Chemical Co., Ltd.s life of Renqiu City Production；Ethylene glycol diethyl ether produces for lark prestige Science and Technology Ltd., purity 99%；Tetra-n-butyl ammonium phosphate is the Henan Longhua of Zhengzhou section Chemical product Co., Ltd produces, content 97%；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：Polyvinyl alcohol mass ratio is 1.8%, sodium chloride mass ratio is 4.5%, potassium chloride mass ratio is 4.5%, quality of glycol ratio is 9%, potassium humate mass ratio is 1.8%, polyacrylic acid potassium Mass ratio is 1.8%, xanthans mass ratio is 0.4%, Vinylcaprolactam homopolymer mass ratio is 0.8%, ethylene glycol diethyl ether Mass ratio is 0.8%, tetra-n-butyl ammonium phosphate mass ratio is 0.8%, and remaining components are to prepare water.

Embodiment two, each component content is in drilling fluid：Polyvinyl alcohol mass ratio is 2%, sodium chloride mass ratio is 5%, Potassium chloride mass ratio is 5%, quality of glycol ratio is 10%, potassium humate mass ratio is 2%, polyacrylic acid potassium mass ratio is 2%, xanthans mass ratio is 0.5%, Vinylcaprolactam homopolymer mass ratio is 1%, ethylene glycol diethyl ether mass ratio is 1%, Tetra-n-butyl ammonium phosphate mass ratio is 1%, and remaining components are to prepare water.

Embodiment three, each component content is in drilling fluid：Polyvinyl alcohol mass ratio is 2.2%, sodium chloride mass ratio is 5.5%, potassium chloride mass ratio is 5.5%, quality of glycol ratio is 11%, potassium humate mass ratio is 2.2%, polyacrylic acid potassium Mass ratio is 2.2%, xanthans mass ratio is 0.6%, Vinylcaprolactam homopolymer mass ratio is 1.2%, ethylene glycol diethyl ether Mass ratio is 1.2%, tetra-n-butyl ammonium phosphate mass ratio is 1.2%, and remaining components are to 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, inhibition energy of one, two, three drilling fluid system of embodiment to shale expansion Power is clearly.Wherein, initial 2 hour line percent expansion is only 3.4%, 3.2%, 3.0%, and at the end of testing, 16 is small When line percent expansion be only 7.5%, 7.3%, 6.8%, and the clear water to compare mutually be 40.3%；In experimentation, clearly Shale expansion percentage in water is in over time 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

Seabed formation temperature containing hydrate is generally 0 DEG C -4 DEG C, creeps into hydrate formation to decompose inhibition method, often passes through drop The temperature of low drilling fluid inhibits the decomposition of hydrate, it requires that drilling fluid temperature is less than formation temperature, and with good Cryogenic property.

In the experiment of drilling fluid low temperature rheological behaviour, cooling drilling fluid is to a certain constant first in high-low temperature test chamber Temperature.When the temperature of drilling fluid, which is reduced to, tests required a certain steady temperature, continue at this temperature 1 hour It is 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 parameter of drilling fluid by six fast electronic rotation viscosimeters at this temperature.Wait for that rheological characteristic is tested After finishing, the density of drilling fluid is tested with densimeter rapidly, tests the filter loss of drilling fluid immediately later.It finally measures and includes The situation of change of drilling fluid rheology under the conditions of 10 DEG C, 5 DEG C, 0 DEG C, -5 DEG C, -10 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)
						10	1.11	1.5/2	16.5	7.2	6.5
5	1.13	1.5/2	17.6	7.5	6.3
						0	1.14	2/2.5	19.8	7.9	6.2
-5	1.14	2/2.5	22.7	8.1	5.9
						-10	1.14	2/2.5	24.3	8.6	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)
						10	1.13	1.5/2	17.8	7.3	6.3
5	1.14	1.5/2	18.6	7.6	6.1
						0	1.16	2/2.5	20.4	8.0	5.9
-5	1.16	2/2.5	22.5	8.2	5.7
						-10	1.16	2/2.5	25.7	8.7	5.3

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

T(℃)	ρ(g/cm3)	Gel(Pa/Pa)	PV(mPa.s)	YP(Pa)	Fl(ml)
						10	1.15	1.5/2	18.8	7.4	6.2
5	1.16	1.5/2	19.5	7.8	6.0
						0	1.17	2/2.5	20.6	8.2	5.7
-5	1.17	2/2.5	22.7	8.5	5.6
						-10	1.17	2/2.5	26.1	9.0	5.1

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 configured.

3 methane hydrates, which generate, inhibits evaluation

In terms of the hydrate of drilling fluid generates rejection evaluation, the present invention is tested in autoclave by acquiring The variation of temperature, pressure and other parameters in the process, and the directly observation of visualization window is combined to carry 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, data acquisition software is opened, 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 there is disturbance The hydrate inhibition effect of examination drilling fluid of the present invention.

During deepwater drilling, drilling fluid is about 2-4h from shaft bottom to drilling platforms cycle period, according to API standard with And General Experimental Procedures, under the conditions of the certain water of simulation bathybic temperature and pressure, the drilling fluid containing hydrate inhibitor It is generated without hydrate in 16h, that is, illustrates that the drilling fluid can meet requirement of the deepwater drilling to hydrate inhibition, experimental temperature 2 DEG C, -5 DEG C, -10 DEG C of selection, pressure select 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.

5 hydrate of table, which generates, inhibits tables of data

Number	Initial pressure (MPa)	Final pressure (MPa)	Pressure drop (MPa)	Temperature (DEG C)
					Embodiment one	5	4.81	0.19	2
Embodiment one	10	9.72	0.28	-5
					Embodiment one	15	14.64	0.36	-10
Embodiment two	5	4.83	0.17	2
					Embodiment two	10	9.73	0.27	-5
Embodiment two	15	14.65	0.35	-10
					Embodiment three	5	4.84	0.16	2
Embodiment three	10	9.74	0.26	-5
					Embodiment three	15	14.68	0.32	-10

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, contamination resistance is evaluated, 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

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	1.14	1.5/2	18.6	7.6	6.1
Two+4% bentonite of embodiment	1.18	2/2.5	20.9	8.2	5.3
						Two+8% bentonite of embodiment	1.21	2.5/3	22.6	9.4	4.6

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	1.16	1.5/2	19.5	7.8	6.0
Three+4% bentonite of embodiment	1.2	2/2.5	21.7	8.4	5.2
						Three+8% bentonite of embodiment	1.22	2.5/3	23.7	9.5	4.5

After 4% and 8% bentonite is added 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 that drilling fluid is tested by rolling dispersion experiment, using certain block seabed landwaste as test object, 80 Heat rolling 16h at 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

System	Primary recovery (%)	Secondary returning yield (%)
			Embodiment one	90.6	89.4
Embodiment two	90.8	89.7
			Embodiment three	91.2	90.3

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 reacts drilling fluid chemistry inhibition power, and landwaste of the secondary returning yield reaction after mud soak exists Dispersibility in clear water, dispersibility is smaller to illustrate that the suppressed effect of landwaste is stronger, and 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 0.0893,0.0906,0.0927, within 0.1, shows that drilling fluid of the present invention has Good lubricity.

Claims (2)

1. a kind of ocean hydrate stores polyvinyl alcohol composite type drilling fluid, which is characterized in that the drilling fluid includes with the following group Point：Polyvinyl alcohol mass ratio is 1.8%-2.2%, sodium chloride mass ratio is 4.5%-5.5%, potassium chloride mass ratio is 4.5%- 5.5%, quality of glycol ratio is 9%-11%, potassium humate mass ratio is 1.8%-2.2%, polyacrylic acid potassium mass ratio is 1.8%-2.2%, xanthans mass ratio are 0.4%-0.6%, Vinylcaprolactam homopolymer mass ratio is 0.8%-1.2%, second Glycol diethyl ether mass ratio is 0.8%-1.2%, tetra-n-butyl ammonium phosphate mass ratio is 0.8%-1.2%, remaining components be with Water processed.

2. a kind of ocean hydrate as described in claim 1 stores polyvinyl alcohol composite type drilling fluid, which is characterized in that described Drilling fluid includes following components：Polyvinyl alcohol mass ratio is 2%, sodium chloride mass ratio is 5%, potassium chloride mass ratio is 5%, second Glycol mass ratio is 10%, potassium humate mass ratio is 2%, polyacrylic acid potassium mass ratio is 2%, xanthans mass ratio is 0.5%, Vinylcaprolactam homopolymer mass ratio is 1%, ethylene glycol diethyl ether mass ratio is 1%, tetra-n-butyl ammonium phosphate quality Than being 1%, remaining components are to prepare water.