CN108251081A - A kind of marine gas hydrate stores Compositional type drilling fluid - Google Patents

Abstract

A kind of marine gas hydrate stores Compositional type drilling fluid, is related to exploitation of gas hydrates field.Drilling fluid of the present invention includes following components：Sodium formate, sodium chloride, methanol, ethylene glycol, potassium chloride, low viscosity carboxymethyl cellulose LV CMC, potassium humate, xanthans, Vinylcaprolactam homopolymer, propylene glycol phenylate, four just base trimethylammonium bromide and prepare water, it is used available for the storage drilling well of marine gas hydrate, 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 marine gas hydrate stores Compositional type drilling fluid

Technical field

The present invention relates to a kind of marine gas hydrates to store Compositional type drilling fluid, and in particular to gas hydrates are opened Adopt 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, the gas hydrates that the certain depths in underground is ensconced to assigning are explored and are developed, 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 the main problem of more complicated well inner question, at present 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；So as to cause the decomposition of hydrate, borehole well instability is caused, drillng operation is made Into 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, increases the pore pressure in well week, so as to further reduce 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, it can aggravate hydrate formation skeleton aquation, lead to the borehole wall It is more unstable.Also, decomposition of hydrate can also increase the permeability on stratum, and drilling fluid is permeated to the borehole wall generates osmotic pressure, Improve the caving pressure on stratum, fracture pressure reduces, and the borehole wall is made to 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 made to increase rapidly, so as to cause submarine landslide or foundation of sea floor unstability, and then The destruction of the facilities such as drilling, drilling platforms, submarine pipeline may be caused.

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 a kind of marine gas hydrate storage Compositional type drilling fluid.

Invention content

The purpose of the present invention is to provide a kind of marine gas hydrates to store Compositional type drilling fluid, drilling fluid of the present invention Including following components：Sodium formate, sodium chloride, methanol, ethylene glycol, potassium chloride, low viscosity carboxymethyl cellulose LV-CMC, humic acid Potassium, xanthans, Vinylcaprolactam homopolymer, propylene glycol phenylate, four just base trimethylammonium bromide and prepare water, available for sea The storage drilling well of phase gas hydrates uses, and has the function of Solid Free, low temperature resistant, by adding in kinetic inhibition in drilling fluid Agent is compounded with synergist, there is stronger hydrate to generate inhibition, and components of drilling liquid is small to environmental hazard, has height Effect, environmental protection, the advantages that raw material is cheap and easy to get.

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

A kind of marine gas hydrate stores Compositional type drilling fluid, which is characterized in that the drilling fluid is included with the following group Point：Sodium formate mass ratio is 2.8%-3.2%, sodium chloride mass ratio is 4.5%-5.5%, methanol quality ratio is 4.5%- 5.5%th, quality of glycol ratio is 14%-16%, potassium chloride mass ratio is 4.5%-5.5%, low viscosity carboxymethyl cellulose LV- CMC mass ratioes are 1.8%-2.2%, potassium humate mass ratio is 1.8%-2.2%, xanthans mass ratio be 0.4%-0.6%, Vinylcaprolactam homopolymer mass ratio is 0.8%-1.2%, propylene glycol phenylate mass ratio is just base three of 0.8%-1.2%, four Methyl bromide ammonium mass ratio is 0.8%-1.2%, and remaining components is prepare water.

Preferably, the drilling fluid includes following components：Sodium formate mass ratio is 3%, sodium chloride mass ratio is 5%, first Alcohol mass ratio is 5%, quality of glycol ratio is 15%, potassium chloride mass ratio is 5%, low viscosity carboxymethyl cellulose LV-CMC matter Amount ratio is 2%, potassium humate mass ratio is 2%, xanthans mass ratio is 0.5%, Vinylcaprolactam homopolymer mass ratio is 1%th, propylene glycol phenylate mass ratio is that 1%, four just base trimethylammonium bromide mass ratio has been 1%, and remaining components is prepare water.

In above-mentioned drilling fluid, the sodium formate is as drilling fluid host agent, thickener, anti-sloughing agent, easily biological-degradable, and nothing Poison, it is environmentally safe, there is extremely strong shale rejection ability, and the degree of stratum leakage can be mitigated, moderately prevent leakage, it can Ensure the wellbore stability in drilling process, reduce down-hole accident.

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 potassium chloride is as thermodynamic inhibitor, and potassium ion in drilling fluid, can play flocculation Effect will be removed using solid control equipment after the clay particle being partly distributed in drilling fluid flocculation coalescence, reach inhibition and reduction The double action of solid phase.

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 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 propylene glycol phenylate, Four just base trimethylammonium bromide, methanol as kinetic inhibitor synergist, compound the inhibition of kinetic inhibitor compared with It is significantly improved when kinetic inhibitor is used alone；The Vinylcaprolactam homopolymer is with N- caprolactams (VCL) For monomer, azodiisobutyronitrile is initiator, is synthesized by solution polymerization process, and synthetic method is known technology, not this patent Content is protected, wherein, N- caprolactams (VCL) are produced for BASF AG, purity 100%；Azo two Isobutyronitrile is produced for Tianjin Zhi Yuan chemical reagent Co., Ltd, and analysis is pure.

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 use sodium formate as drilling fluid host agent, and be clay-free drilling fluid, with good rheological characteristic with And stronger shale rejection ability, the degree of stratum leakage can be mitigated, and more can fully carry and hang gang drill bits, can had Effect reduces and prevents the repetition of drilling cuttings from crushing.

2nd, 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.

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 marine gas hydrate is stored up It hides, the decomposition of hydrate can be reduced, so as to reduce the probability for causing submarine landslide or foundation of sea floor unstability.

Specific embodiment

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

The sodium formate used in following embodiments is produced for Dezhou Run Xin laboratory apparatus Co., Ltd, and analysis is pure；Sodium chloride For the prosperous prosperous Chemical Co., Ltd.'s production in Tianjin, analyze pure；Methanol is produced for Guangdong Weng rivers chemical reagent Co., Ltd, analysis It is pure；Ethylene glycol is produced for Tianjin Zhi Yuan chemical reagent Co., Ltd, and analysis is pure；Potassium chloride is given birth to for Shanghai traditional Chinese medicines reagent group Production, analysis are pure；Low viscosity carboxymethyl cellulose LV-CMC is the sincere hundred million Chemical Co., Ltd.s production of Renqiu City；Potassium humate is Renqiu High-tech chemical industry goods and materials Co., Ltd of city produces；Xanthans is the sincere hundred million Chemical Co., Ltd.s production of Renqiu City；Propylene glycol phenylate is U.S. Dow Chemical of state produces, and analysis is pure；Four just base trimethylammonium bromide be Shandong West Asia chemical industry Co., Ltd 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 formate mass ratio is 2.8%, sodium chloride mass ratio is 4.5%th, methanol quality ratio is 4.5%, quality of glycol ratio is 14%, potassium chloride mass ratio is 4.5%, low-viscosity carboxymethyl is fine Tie up element LV-CMC mass ratioes be 1.8%, potassium humate mass ratio is 1.8%, xanthans mass ratio is 0.4%, polyvinyl oneself Lactams mass ratio is 0.8%, propylene glycol phenylate mass ratio is that 0.8%, four just base trimethylammonium bromide mass ratio has been 0.8%, remaining components is prepare water.

Embodiment two, each component content is in drilling fluid：Sodium formate mass ratio is 3%, sodium chloride mass ratio is 5%, first Alcohol mass ratio is 5%, quality of glycol ratio is 15%, potassium chloride mass ratio is 5%, low viscosity carboxymethyl cellulose LV-CMC matter Amount ratio is 2%, potassium humate mass ratio is 2%, xanthans mass ratio is 0.5%, Vinylcaprolactam homopolymer mass ratio is 1%th, propylene glycol phenylate mass ratio is that 1%, four just base trimethylammonium bromide mass ratio has been 1%, and remaining components is prepare water.

Embodiment three, each component content is in drilling fluid：Sodium formate mass ratio is 3.2%, sodium chloride mass ratio is 5.5%th, methanol quality ratio is 5.5%, quality of glycol ratio is 16%, potassium chloride mass ratio is 5.5%, low-viscosity carboxymethyl is fine Tie up element LV-CMC mass ratioes be 2.2%, potassium humate mass ratio is 2.2%, xanthans mass ratio is 0.6%, polyvinyl oneself Lactams mass ratio is 1.2%, propylene glycol phenylate mass ratio is that 1.2%, four just base trimethylammonium bromide mass ratio has been 1.2%, 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%, 3.3%, and at the end of testing, 16 is small When line percent expansion be only 7.9%, 7.7%, 7.4%, 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

Seabed formation temperature containing hydrate is generally 0 DEG C -4 DEG C, to decompose inhibition method drilling hydrate formation, often passes through drop The temperature of low drilling fluid inhibits the decomposition of hydrate, 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 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	1.13	1.5/2	16.1	6.6	6.9
5	1.14	1.5/2	18.3	7.1	6.6
						0	1.15	2/2.5	19.4	7.5	6.3
-5	1.15	2/2.5	22.7	7.7	5.9
						-10	1.15	2/2.5	23.2	8.1	5.7

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	1.15	1.5/2	17.3	6.7	6.8
5	1.16	1.5/2	19.2	6.9	6.5
						0	1.17	2/2.5	21.3	7.2	6.1
-5	1.17	2/2.5	23.1	7.8	5.8
						-10	1.17	2/2.5	25.6	8.3	5.5

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	1.16	1.5/2	18.3	6.9	6.7
5	1.17	1.5/2	20.1	7.2	6.3
						0	1.18	2/2.5	21.2	7.5	5.9
-5	1.18	2/2.5	23.5	7.9	5.7
						-10	1.18	2/2.5	26.6	8.5	5.4

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.

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 certain bathybic temperature and pressure of water is simulated, the drilling fluid containing hydrate inhibitor It is generated in 16h without hydrate, 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.

The generation of 5 hydrate of table inhibits tables of data

Number	Initial pressure (MPa)	Final pressure (MPa)	Pressure drop (MPa)	Temperature (DEG C)
					Embodiment one	5	4.84	0.16	2
Embodiment one	10	9.73	0.27	-5
					Embodiment one	15	14.63	0.37	-10
Embodiment two	5	4.85	0.15	2
					Embodiment two	10	9.74	0.26	-5
Embodiment two	15	14.64	0.36	-10
					Embodiment three	5	4.87	0.13	2
Embodiment three	10	9.75	0.25	-5
					Embodiment three	15	14.65	0.35	-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, 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	1.14	1.5/2	18.3	7.1	6.6
One+4% bentonite of embodiment	1.18	2/2.5	20.2	7.6	6.3
						One+8% bentonite of embodiment	1.21	2.5/3	22.5	8.8	5.4

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	19.2	6.9	6.5
Two+4% bentonite of embodiment	1.19	2/2.5	21.7	7.7	6.2
						Two+8% bentonite of embodiment	1.22	2.5/3	23.4	8.9	5.3

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	20.1	7.2	6.3
Three+4% bentonite of embodiment	1.21	2/2.5	22.3	7.8	5.9
						Three+8% bentonite of embodiment	1.23	2.5/3	24.7	8.0	5.0

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 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	91.8	89.1
Embodiment two	92.0	89.3
			Embodiment three	92.2	89.5

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 0.0917,0.0924,0.0931, within 0.1, shows that drilling fluid of the present invention has Good lubricity.

Claims (2)

1. a kind of marine gas hydrate stores Compositional type drilling fluid, which is characterized in that the drilling fluid includes following components： Sodium formate mass ratio is 2.8%-3.2%, sodium chloride mass ratio is 4.5%-5.5%, methanol quality ratio be 4.5%-5.5%, Quality of glycol ratio is 14%-16%, potassium chloride mass ratio is 4.5%-5.5%, low viscosity carboxymethyl cellulose LV-CMC matter Amount than for 1.8%-2.2%, potassium humate mass ratio be 1.8%-2.2%, xanthans mass ratio is 0.4%-0.6%, poly- second Alkenyl quality of caprolactam ratio is 0.8%-1.2%, propylene glycol phenylate mass ratio is the just base trimethyl of 0.8%-1.2%, four Ammonium bromide mass ratio is 0.8%-1.2%, and remaining components is prepare water.

A kind of 2. marine gas hydrate storage Compositional type drilling fluid as described in claim 1, which is characterized in that the brill Well liquid includes following components：Sodium formate mass ratio is 3%, sodium chloride mass ratio is 5%, methanol quality ratio is 5%, ethylene glycol matter Amount ratio is 15%, potassium chloride mass ratio is 5%, low viscosity carboxymethyl cellulose LV-CMC mass ratioes are 2%, potassium humate quality Than be 0.5% for 2%, xanthans mass ratio, Vinylcaprolactam homopolymer mass ratio is 1%, propylene glycol phenylate mass ratio is 1%th, four just base trimethylammonium bromide mass ratio be 1%, remaining components for prepare water.