CN1978584A - Harm-free core-drilling fluid, and its preparing method and use - Google Patents

Abstract

This invention discloses a kind of no damage fetching core borehole liquid and its preparation method. It is made up of the water 100000- 160000, NaCl 15000-19000, Na2CO3 200-400, NaOH 50-150, PAC-SL 150-550, FLOWZAN 200-600, Starch 1200-1800, the modified SOLTEX 1200-1800, Baracarb(5) CaCO3 a 2000-4000, Baracarb(50) CaCO3 b 2000-4000, Baracarb(600) CaCO3 c 2000-4000. The character of the no damage fetching core borehole liduid is in that: it has no damage to the core and the stratum; it has the good lubricating ability and has the good capability in cleaning well and inhibiting the drill chip disperses; the additive such as the FLOWZAN, the starch and the PAC-SL are all degraded by the organism. The Baracarb crushed by the marble is the inorganic additive and has no pollution to the environment; also it can not change the wetting property of the petrosal.

Description

A kind of harm-free core-drilling fluid and preparation method thereof and application

Technical field

The present invention relates to a kind of core drilling liquid and preparation method thereof and application, specifically a kind of invasion depth is shallow, environment is not had harm-free core-drilling fluid and the preparation method and the application of influence.

Technical background

Drilling fluid system is a kind of mixture system of complexity, and its composition contains alkali, inorganic salts, polymer organic polymer, and the pollution of environment is mainly shown high COD, high BOD, high suspended matter and pH value, oils and heavy metallic salt etc.The rejected well drilling liquid discharging is the principal pollutant of drilling operation, does not add the enrichment that control is easy to cause environmental pollutant, works the mischief to environment.

External core drilling liquid is divided into two classes: a class is a water-base drilling fluid; Another kind of is oil base drilling fluid, wherein water-base drilling fluid respectively from different perspectives to core sampler sfgd., but they exist some defectives again separately; Oil base drilling fluid is comparatively perfect to rock core protection in theory, but all unavoidably is subjected to the intrusion of the local water and the surface water in the practical application and loses oil-base mud to the due provide protection of rock core.

Domestic core drilling liquid has experienced from the modification wellbore fluid and has been tied to systems such as low bentonite and solid free brine drilling fluid, that is to say domestic also in all its bearings to protecting rock core to do various effort.

Drilling fluid mainly shows in the drilling fluid solid phase to core hole and fissured obstruction to the infringement of rock core, thereby reduces the rate of permeation of core, particularly has the compressibility bentonite clay particle, and it can invade the rock core deep layer, and rock core is caused damage; Be the filtrate of drilling fluid on the other hand, it can cause a series of injuries such as water-sensitive, salt is quick, alkali is quick.

Following table is the prescription and the commentary of three tame foreign oil companies core drill well liquid commonly used.

Major company of external a few family core drill well liquid system

Sequence number	Babcock and Wilcox	Type	Prescription	Advantage	Shortcoming
						1	Halli burton	Water base	Water+sea salt+potassium acetate (provides K +)+sepiolite clay+terpolymer (improving rheological, tackifier)+NaOH+ weighting agent	(1) salt solution being invaded insensitive (2) can stop or alleviate and cave in	(1) it is big to contain clay (2) filter loss

		Oil base	Emulsifying agent+oxidized bitumen+lime carbonate+the CaO of kerosene+organic clay+methyl alcohol+on the spot	(1) not moisture, salinity, rock permeability and water saturation degree (2) wettability of having exempted emulsification obstruction and change interstitial water change minimum	(1) contains that there is environmental issue (3) in clay (2) if when formation water flows into, may form weak soap with CaO in the system and emulsifying agent reaction
						2	Mobi R﹠D corp (Indonesia)	Water base	As soil+sepiolite+NaCL+ caustic soda+polymkeric substance+cotton fibre+sulfonated lignin+sodium bicarbonate	(1) replaces barite with Nacl, got rid of and to have been dissolved by basic solvent the deleterious solid phase of core analysis (2) cotton fibre	(1) contains that to remove the initial filter loss of soil (2) big
3	BAKER HugHes INTEQ	Water base	Saturated brine+starch+carry stick+sterilant+high temperature and high pre ssure filtration control agent	(1) saturated brine has the clay mineral of core and suppresses stabilization preferably	(1) dehydration just is bigger
								Oil base	Crude oil+the emulsifying agent of modification (working when water intrusion)+oil-base mud is carried stick+weighting agent	(1) not moisture, can not change core wettability and water saturation	(1) preparation maintenance requirement height (2) rheological property is difficult for reaching requirement (3) and has environmental issue

Last tabular has gone out Halliburton, Mobi R﹠amp; D corp (Indonesia), five kinds of core drill well liquid formula of BAKER Hughes Inteq three companies; Wherein the water-base drilling fluid of Halliburton company has better effect aspect stabilizing borehole, helps improving coring recovery rate, but can not satisfy greatly because of containing clay and filter loss * * requirement of oil company.

Mobi R﹠amp; The water-based mud of D corp (Indonesia) company has been considered can be by the cotton fibre of dissolution with solvents with NaCL replacement barite and use, and this respect can be our and uses for reference.The water-base drilling fluid of BAKER Hughes INTER company has been considered the stability of clay mineral in the core preferably, but is saturated brine because of what use, is being restricted aspect the density control, and the initial dehydration of adding it is bigger, thereby can not satisfy the demand.The oil base drilling fluid principle of Halliburton and BAKER Hughes INTEQ two companies is very perfect, the water saturation of the core that is taken out in theory, rate of permeation, how many wettabilitys do not have and changes, but in fact they have all added emulsifying agent in advance, exactly because oil base drilling fluid will suffer in actual application inevitably or from local water or from the pollution of the surface water, this situation is in case occur, emulsifying agent will work, and in a single day emulsifying agent works and will form some weak soaps, these weak soaps can pollute core, make oil base drilling fluid can not reach its purpose.

Domestic core drill well liquid system commonly used

Sequence number	Type	Explanation	Advantage	Shortcoming
					1	The modification drilling fluid system	Before getting core, the use drilling fluid is carried out modification and handle, make it become a kind of drilling fluid of protection core	Cost is low, and technology is simple, and certain effect is arranged, and is widely used	Contain more harmful solid phase
2	Low bentonite polymer drilling fluid system	Before getting core, bentonite content in the drilling fluid is reduced to a proper range	Solid load is low, and core is had certain protective role	Also have wilkinite to exist
					3	The stifled temporarily type drilling fluid system of no wilkinite polymkeric substance	This system does not contain wilkinite and contains temporary plugging agent particle and weighting agent	Eliminated the core infringement that clay mineral causes	Filtrate still can cause the core infringement
4	The oil-in-water drilling fluid system	With water is external phase, and oil is disperse phase, the oil-in-water emulsion drilling fluid	Density is low, stable performance	Easily cause environmental pollution to contain emulsifying agent and may cause wettability modification
					5	No solid phase clear brine drilling fluid system	Salt solution is added additive after filtering	Basically can eliminate solid phase damages core	(1) there is the inorganic scale infringement in domestic shortage suitable polymers additive (2) filter loss big (3)
6	The cationic polymer drilling fluid system	Containing molecular weight in the system is that hundreds of thousands of to millions of macrocation polymkeric substance and molecular weight is that hundreds of arrives thousands of small cation quaternary ammonium salts	Stoped the reservoir CLAY MINERALS AND THEIR SIGNIFICANCE to expand	Properties Control is safeguarded relatively difficulty
					7	The positive colloid drilling fluid system	Contain mixed metal layer hydroxide compound MMH in the prescription	Have unique rheological and extremely strong solids-carrying capacity	Filter loss is bigger

Last table is present domestic 7 kinds of typical core drill well liquid system, wherein:

1, the modification drilling fluid system is simple because of technology, and cost is low, and application at present is comparatively extensive, but just progressive to some extent on common drilling fluid basis, and the target of distance protection core also has big gap.

2, low bentonite polymer drilling fluid system has been considered the harm of wilkinite to core, but others do not add consideration.

3, the stifled temporarily type drilling fluid system of no wilkinite polymkeric substance has been eliminated the injury of the relative core of drilling fluid medium clay soil, but the filtrate of drilling fluid still can cause the injury of core.

4, oil-in-water drilling fluid system disadvantage is to contain emulsifying agent, and it can make rock wettability change.

5, no solid phase clear brine drilling fluid system be not argillaceous and particle diameter greater than the solid phase of 2 μ m, substantially can eliminate the infringement of solid phase to hydrocarbon zone, filtrate is certain density salts solution, and the hydration swelling of clay mineral is had certain restraining effect, can the basically eliminate water sensitive damage.But this system complex process requires height to filter plant, and leakage is serious, and domestic suitable polymers additive shortage, has weak points such as inorganic scale infringement.

6, the cationic polymers drill in fluid can prevent that the expansion of mud shale medium clay soil from causing that the swelling clay mineral in slump in and the reservoir causes water sensitive damage, but this system performance maintenance difficulty, performance is wayward.

7, the positive colloid drill in fluid has the stratum of inhibition yield, prevents that slump in is effective, and solids-carrying capacity is strong; But because of fluid loss causes damage to core than conference, the compatibleness of this system treatment agent imperfection also simultaneously.

Summary of the invention

Technical assignment of the present invention is at existing technology status, and a kind of invasion depth is shallow, environment do not had influence harm-free core-drilling fluid and preparation method and application are provided.The objective of the invention is to realize by following technical scheme:

A kind of harm-free core-drilling fluid, form by the component of following weight proportion:

Water 100000-160000 part NaCl 15000-19000 part Na ₂CO ₃200-400 part

NaOH 50-150 part CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL 150-550 part

Xanthan gum FLOWZAN 200-600 part water retaining starch Stacrch 1200-1800 part

Modifying asphalt SOLTEX 1200-1800 part Baracarb (5) lime carbonate a 2000-4000 part

Baracarb (50) lime carbonate b 2000-4000 part Baracarb (600) lime carbonate c

2000-4000 part

A kind of harm-free core-drilling fluid, form by the component of following weight proportion:

Water 120000-140000 part NaCl 16000-18000 part Na ₂CO ₃250-350 part

NaOH 70-110 part CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL 200-500 part

Xanthan gum FLOWZAN 300-500 part water retaining starch Stacrch 1400-1600 part

Modifying asphalt SOLTEX 1400-1600 part Baracarb (5) lime carbonate a 2500-3500 part

Baracarb (50) lime carbonate b 2500-3500 part Baracarb (600) lime carbonate c

2500-3500 part

A kind of harm-free core-drilling fluid, form by the component of following weight proportion:

17000 parts of Na of 130000 parts of NaCl of water ₂CO ₃75 parts of 297 parts of NaOH

400 parts of 382.5 parts of xanthan gum FLOWZAN of CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL

1500 parts of 1500 parts of modifying asphalt SOLTEX of water retaining starch Stacrch

3000 parts of Baracarb (5) 3000 parts of Baracarb of lime carbonate a (50) lime carbonate b

4000 parts of Baracarb (600) lime carbonate c

A kind of harm-free core-drilling fluid, wherein, the particle diameter of Baracarb (5) lime carbonate a is at 0.5～150um, and the particle diameter of Baracarb (50) lime carbonate b is at 5～600um, and the particle diameter of Baracarb (600) lime carbonate c is at 60～1200um.

A kind of harm-free core-drilling fluid, its preparation method is made up of following steps:

(a), in water, add a certain amount of Na in weight proportion ₂CO ₃, be used in water, adding a certain amount of NaOH then again except that contained calcium Ca in anhydrating, be used for except that contained magnesium Mg in anhydrating;

(b) in weight proportion, need slowly in treated water, to add xanthan gum FLOWZAN with the shearing pump of high shear rate,, be about 35s generally until viscosity in aqueous solution with 20 minutes/bag speed adding, yield value value 10pa;

(c) in weight proportion, add NaCL this moment again, and NaCL will add at twice: add NaCL for the first time density is carried to 1.06g/cm ³The system that has certain viscosity and certain density like this will help the adding and the suspension of stifled material (modifying asphalt SOLTEX, Baracarb (5) lime carbonate a, Baracarb (50) lime carbonate b, Baracarb (600) lime carbonate c) temporarily, after temporarily stifled material adds, to further add NaCL according to the density situation, also have CL up to system density ^-Meet the requirements till (51331ppm), temporarily stifled material slowly adds from mixing hopper during preparation, accomplishes evenly not precipitate;

(d) in weight proportion, add starch and CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL again, starch and CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL are powdered granules, need to add by mixing hopper, adding speed should be principle not produce " flake " particle;

(e) through above operation, harmless core drill well liquid is prepared substantially and is finished, and just drilling fluid density only is 1.11G/cm ³So, suitably add Nacl again, adjust, form product at last.

A kind of harm-free core-drilling fluid, this harm-free core-drilling fluid well can protection core, protection environment, well cleaning, lubricated, suppress to use in the field such as drilling cuttings aquation dispersion.

Drilling fluid of the present invention grows up on no solid phase biological polymer base.No solid phase is a kind of mode of the protection core that adopted of domestic and international a lot of core drilling liquid; it has avoided solid phase in the drilling fluid; soil particle is to the infringement of rock core particularly, and biological polymer particular rheological properties energy and low toxicity, good biological degradability become the inevitable choice of this system host polymer.Be determined by experiment 0.228% concentration and can have satisfied requirement of engineering.

It is the key that system is determined that water retaining is selected.It is different that dehydration mechanism falls in starch (Starch) and PAC-SL.Starch be utilize self not charging property characteristic and stop up all holes all-pervasively and reach the leak-off effect of falling; And PAC-SL utilizes itself charging property that water molecules is polarized, and it is stabilized in the filter cake hole, thereby effectively reduces filter cake pore diameter.Starch and PAC-SL use together and can play synergistic effect, promptly when their effects when it falls dehydration effect considerably beyond any independent use when (10: 1 or 9: 1) collocation is used according to a certain percentage, in addition, they are arranged in pairs or groups together and use the temperature resistance ability that can also increase system.Limit temperature resistance is 115 ℃ when using starch separately, has risen 25 ℃ and mixed use back ultimate temperature by 10: 1 or 9: 1, reaches 145 ℃.Under the guidance of above-mentioned theory, being determined by experiment its dosage in system is 2.28% and 2.285%.

The temporary plugging agent adding is worked both ways: the one, and can be as " clay " substitute.Because of what use is no solid phase biological polymkeric substance, and its API filtration can be controlled at about 15ml, the particularly difficulty that seems toward descending again, and key is that instantaneous dehydration is big.After adding temporary plugging agent, be actually mud cake formation basic substance is provided, effectively reduce instantaneous dehydration, filter loss can be controlled at about 5ml through suitable preparation.

It is to be theory with " 1/3rd " rule of building bridge that temporary plugging agent adds, if promptly during d hole＜3d particle, particle can form filter cake at rock surface by bridging action, thereby may infiltrate the stratum hardly.

Temporary plugging agent is selected and dosage is determined to determine by three groups of experiments: (1) only adds Baracarb in the base slurry; (2) add Baracarb and Soltex in the base slurry; (3) add Baracarb, soltex, starch, PAC-SL in the base slurry.

Wherein the base slurry is: 4% salt solution+0228%FLOWZAN

By above three groups of experiments as can be seen: second group of experiment is better than first group of experiment plugging effect, filter loss reduces more obvious, explanation adds soft particle Soltex in Baracarb can make temporarily stifled effect that bigger improvement is arranged, but the anti-effect of arranging is also not very good, illustrates that this prescription also is not optimized.

The 3rd group has been tested actual is to add rigidity temporary plugging agent Baracarb in the base slurry, soft deformable particles Soltex and have a fibrous Starch of long-chain, PAC-SL, under three's acting in conjunction, not only stifled temporarily better effects if, anti-row also is more prone to, and illustrates that this prescription can be used as our actual use prescription.

Each additive, particularly temporary plugging agent add affiliation mud property are produced great influence, and this is that we must consider.By experiment, after the discovery temporary plugging agent adds, plastic viscosity, density etc. all change, and these can be revised by adjusting other additive dosage.In addition, add back apparent viscosity and yield value and also can rise, but this is within the system tolerance interval.

In actual applications, for reducing core drill well liquid cost and reducing core drill well liquid environmental pollution, take the quantification technology, drilling fluid lowest volume demand when coring is calculated in strictness, and prepares with this.During preparation, according to the each component characteristics, the order of additive adding and the method for adding have been carried out suitable design: at first handle and join the slurry water, calcium, magnesium ion concentration and pH value are adjusted to scope of design, joining in the pulp-water after processing, add biological polymer by shearing pump slow (being controlled at 1 bag/20 minutes), prevent that " flake " forms, and the yield value value is assigned to about 10pa; In system, add suitable salt NaCL again, density is carried to 1.06g/cm ³, the drilling fluid that has certain viscosity and density like this will help the adding and the suspension of next step temporary plugging agent.

In the core drilling liquid for preparing, add tracer agent D again ₂O, add-on adds 2.75L by per 100 barrels.Obtain the mud sample by certain program during coring, after the end of coring this mud sample is delivered to relevant laboratory with rock core, so that measure the damage of mud rock core.

Core drill well liquid will prevent its pollution when going into well.Before for slurry, prepare same density (1.14g/cm earlier ³) salt solution is as spacer pad so that will as soil paste and get the core slurry separately, and play the effect of the flushing borehole wall, help simultaneously judging and finish situation for slurry.

Performance is controlled than difficult in following several respects during core drilling:

(1) solid phase control.Be the control solid phase, the vibratory screening apparatus of U.S. Derrick company and desanding, silt remover have been installed, (can not use whizzer) because of containing Baracarb in the system, vibratory screening apparatus wire screen reaches 210 orders or 265 orders, and dilute by adding the new slurry of low density, keep solid phase, density in scope of design thereby reach.

(2) pH value, Ca ²⁺, Mg ²⁺

Layer position exists limestone and anhydrite owing to core, and it is acid that anhydrite shows, and then pH value easily descends, and calcium, magnesium ion easily rise.With NaOH, Na ₂CO ₃Preparation together by a certain percentage, thus reach control pH value, CA ²⁺, Mg ²⁺Purpose.

(3) shear force YP, dehydration are safeguarded

For safeguarding shear force about 10pa, the API dehydration needs in the core drilling to replenish according to the depletion of additive situation about 5ml, needs when replenishing additive is carried out pregelatinated, in case not molten particle infringement rock core in the additive stops up vibration wire screen.

To discuss each additive and dosage below in detail determines:

NaCL brinish optimum concn is determined:

After the filtrate with certain salinity was invaded rock core, the expansion that its filtrate can effectively be suppressed contained clay mineral in core and the hole disperseed.Following method can determine to suppress stratum medium clay soil material dispersive NaCL optimum concn.

The filtration time of filtration parameter decision increases with hydrate inhibitor concentration and reduces.Some back is constant to be reduced to certain, and minimum filtration time is that mud suppresses and expand to suppress to the absorption that clay composition reaches maximum, further improves hydrate inhibitor concentration, can not improve mud absorption or aquation inhibition ability.

In order to determine the optimum concn of NaCL in the core drill well liquid, the landwaste that we determine to collect with the NaHR-UmR stratum is as test specimen, and its lithology is shale and lime.

Below be our process of the test:

Used instrument: press filter press among the API

Process of the test

I: prepare difference [cl respectively ^-] the NaCL salt solution of concentration: 0mg/L, 3000mg/L, 12000mg/L;

31194mg/L, 40847mg/L, 50013mg/L, 55074mg/L, each 500mL of 66249mg/L.

II: in the brine sample of above different concns, add the ground landwaste of 35g; And high-speed stirring 10min.

III: above mud sample is carried out the filter loss test respectively, and 20mL filtrate required time collected in record.

Collect the used time of filtrate

cl - mg/L	Collect the used time min of 20ml filtrate
		0	15
3000	13.5
		12000	12
31194	11.2
		40847	10.9
50013	10.1
		55074	9.6
61249	9.6

The optimum concn that obtains of this test further increases [cl between 55074-61249mg/L as can be seen from the table ^-] content is helpless to improve its inhibition.

We get adsorbed clay mineral in the mesoporosity, sandwich layer position with approximate the seeing of the clay mineral in the chip sample of being tested, and like this, we have just obtained keeping [cl ^-] be not less than the concentration of 55000mg/L.

Temperature and pressure influences brinish:

Because well temperature and pressure are not stationary values, they all change with well depth, and they study carefully to compete to understand which type of influence of generation to brinish density, and to this, Britain a company had done research, and (used salt is Cacl ₂/ CaBr mixed brine).

Temperature and pressure influences salt solution

Depth(ft) Density(ppg)	Temp F		Pressnre(psi)
				0	60	0	13.19
2000	93	1365	13.13
				4000	127	2723	13.05
6000	161	4074	12.98
				8000	194	5416	12.91
10000	228	6751	12.83
				12000	262	8078	12.75
14000	295	9397	12.68
				16000	329	10108	12.6
18100	365	12083	12.5

From showing as seen, different well depths place brine density difference, average out to 12.85ppg, this explanation temperature and pressure has certain influence to brine density, but influence is not very big.

Biological polymer xanthan gum FLOWZAN and dosage are determined:

Harmless core drill well liquid select biological polymer FLOWZAN as host polymer be based on following some: 1, can in seawater or NaCL salt solution, use, and have unique rheological property 2 of satisfying coring process, can drop to bottom line 3, good lubricating property 4, low toxicity and high biodegradability to core damage.

Get limestone fracture development in the core stratum, good penetrability, core is easily cracked, for obtaining satisfied coring recovery rate, getting the core design all limits ROP (drilling well speed), brill dish drilling speed, mud speed rate, particularly relevant flow velocity with mud, design only is 125 ~ 250 gallon per minute, being scaled the metric system that we have the knack of is 7.88L/S ~ 15.77L/S, with this discharge capacity, mud speed rate only is 0.287m/s ~ 0.575m/s in protector string, and low like this flow velocity requires to finish the well cleaning, carry the salt bits, mud yield value YP remains on about 10Pa at least.And this can cause problem on the other hand: obtain high shear force like this, often apparent viscosity can reach more than the 60mpas, and following table is that host polymer commonly used is mixed with shear force YP apparent viscosity table when being 10Pa

The performance when shear force of several host polymer preparations is 10Pa:

The polymkeric substance title	Yield value Pa	Apparent viscosity mpas	Ф6/Ф3	Gelpa/pa
					PMHA-II	10	68	8/7	3.5/6

Fa367	10	76	8/7	3.5/6
					HPAM	10	81	9/7	3.5/6.5
FLOWZAM	10	37	11/9	4.5/9
					Annotate: above polymkeric substance all is to prepare in fresh water.

From last table as seen, when yield value reached 10Pa, the apparent viscosity of PMHA-II, FA367, HPAM all was more than the 60mpas, had only FLOWZAN only to be 37mpas.Too high apparent viscosity can cause bit balling, and hydraulic bit horsepower is low, pump pressure height, not harm such as easy-clear of solid phase.Therefore, select biological polymer FLOWZAN as host polymer.It below is the typical rheological property of different dosage FLOWZAN that FLOWZAN supplier provides.

The FLOWZAN dosage is to the polymer drilling fluid rheology impact

FLOWZAN dosage %	AV mpas	PV mpas	YP pa	Φ6/Φ3	Gel Pa/Pa
						0	31	25.5	5.5	3/2	1.5/20
0.02	32	23.5	8.5	7/5	2.5/4.5
						0.04	34	19.5	14.5	11/9	4.5/9.5
0.06	36	17.5	18.5	15/11	5.5/12.5
						0.08	36	19.5	16.5	19/13	7.0/17.5
Wherein fill a prescription: 4% sodium bentonite seawater slurry+0.i%PF-plus+0.1%PAC-R+0.3%PAC-SL+1.5%DFD+FLOWZAN

As seen from the table, increase with the FLOWZAN dosage, the drilling fluid apparent viscosity changes little, but drilling fluid yield value, gel strength obviously increase, and when the FLOWZAN dosage was 0.04%, the drilling fluid rheology performance was fine, can satisfy the picture horizontal well, get the needs of special operation such as core.

The FLOWZAN protection reservoir mechanism of action:

1. high purity prevents formation damage

When this high-quality biological polymer of development, be originally as a kind of well workover and well-completion practice additive of being applied to it.If prepare properly, the impurities and the solid phase particles that can leach are seldom in this highly purified additive.This will help preparing real clay-free drilling fluid, thereby reach the protection reservoir, the effect of protection core.

2. prevent the reservoir fine migration

Fine migration causes that the process that reservoir permeability reduces is divided into starting, migration, deposition obstruction three phases.And the starting of particulate under liquid flow impact is the first step of fine migration, also is a crucial step.Because the FLOWZAN molecular chain length can be pulled in several particulates together, thereby form the critical starting velocity that bigger particle improves particulate; FLOWZAN also with rock hole wall and particulate effect, particulate is fixed on the hole wall, prevent or reduce the fine migration of reservoir.

3. reduce submicron rice particle

Adopt laser particle analyzer to research and analyse under the different FLOWZAN dosage situations, the mass percent of submicron particles changes in the drilling well, adding along with FLOWZAM, the median particle size of drilling fluid system increases, particle diameter reduces less than 2 microns submicron particles mass percent, increase gradually again after reaching minimum value, dosage surpasses at 0.2% o'clock, and the median particle size of FLOWZAN drilling fluid system and the mass percent of submicron particles are close with the base slurry.Therefore can reduce submicron particles in the drilling fluid system by control FLOWZAN dosage, reduce injury reservoir.

The rejection of biological polymer FLOWZAN:

The rejection of FLOWZAN is by the rolling process furnace, understands rock sample dispersing property in FLOWZAN solution through dispersion experiment, and experimental procedure is as follows:

(1), take by weighing the rock sample 50g of granularity 2-5mm, put into the high-temperature tank that fills 350ml distilled water;

(2), when checking ne-leakage, high-temperature tank is put into 80 ℃ rolling process furnace, take out behind the rolling 16h;

(3), be cooled to room temperature, in water, sieve and wash 1min with 40 mesh sieves, will tail over rock sample in 105 ℃ of oven dry;

(4), take out rock sample, place 24h under the room temperature, weigh;

(5), utilize following formula to calculate rock sample and disperse rate of recovery R ₄₀=W/50 * 100%;

In the formula: R ₄₀---roll and disperse the rate of recovery (crossing 40 mesh sieves)/%;

W---cross the rock sample weight/g of 40 mesh sieves;

Following table is when adding different concns FLOWZAN in 4% salt solution, Arab " D " core once, the secondary recovery rate.Hot roll experiment condition is 100 ℃ * 16h, the survey 40 landwaste rate of recovery now.

The landwaste rolling rate of recovery under the different FLOWZAN dosages

Prescription	Primary recovery %	Secondary recovery rate %
			4%NaCL base slurry+5gArab " D " landwaste	52.4	9.4
4%Nacl base slurry+0.0285%FLOWZAN+50gArab " D " landwaste	53.2	18.4
			4%Nacl base slurry+0.0855%FLOWZAN+35gArab " D " landwaste	57.2	22.3
4%Nacl base slurry+0.143%FLOWZAN+50gArab " D " landwaste	67.4	25.8
			4%Nacl base slurry+0.2%FLOWZAN+50gArab " D " landwaste	81.2	50.3
4%Nacl base slurry+0.228%FLOWZAN+50gArab " D " landwaste	89.6	57.7

As can be known from the above table when the FLOWZAN dosage is 0.228% once, the secondary recovery rate reaches 89.6%57.7% respectively, illustrates in concentration to be that the inhibition ability of 0.228% o'clock FLOWZAN is better, can satisfy requirement of engineering.

Biological polymer FLOWZAN good lubricating property:

Biological polymer presents fabulous natural lubricity, does not add any lubricant in the horizontal well with FLOWZAN construction, any complexity and accident that causes because of lubrication problem do not occur.

Following table is a FLOWZAN lubricity test card

The FLOWZAN lubricity

Prescription	The coefficient of friction resistance	Coefficient of friction resistance reduced rate %
			The base slurry	0.2325
Base slurry+0.0285%FLOWZAN	0.1635	29.7
			Base slurry+0.0855%FLOWZAN	0.1433	38.4
Base slurry+0.143%FLOWZAN	0.1232	47
			Base slurry+0.2%FLOWZAN	0.1023	56
Base slurry+0.228%FLOWZAN	0.0963	58.6
			Base slurry+0.228%FLOWZAN+3% machine oil	0.0923	60.3
Base slurry+0.228%FLOWZAN+5% crude oil	0.0948	59.22

The mud coefficient of friction resistance of base slurry 0.228%FLOWZAN only is 0.0963 as can be seen from the table, than more than the base slurry coefficient of friction resistance drop by half.And on this basis, add 3% machine oil and 5% crude oil, the coefficient of friction resistance only has slight variations, illustrate that FLOWZAN system mud lubricity itself possesses, needn't add any lubricant in addition, and this performance can guarantee not have in the core drill well liquid mineral oil, tensio-active agent etc. to change the additive of rock wettabilities, thereby provides assurance for harmless core drill well liquid.

Fluid loss agent Starch, PAC-SL and dosage are determined:

The front is narrated, and this harmless core drill well liquid is to be the base slurry with the sodium chloride solution, and next we will select fluid loss agent for body series, so that satisfy the requirement of " the low intrusion ".Fluid loss agent is selected, must be met the following conditions:

1. can in the sodium chloride salt aqueous solution, use, can resist salt;

2. high efficiency promptly can play a role under lower dosage;

3. can not significantly increase simultaneously the viscosity of system in the control dehydration;

4. drilling cuttings there is not dispersiveness.

According to above condition, we will fall filter and determine on non-ionic type fluid loss agent starch and two kinds of products of anionic water retaining PAC.

Non-ionic type fluid loss agent starch storage crop mechanism and performance:

The filter cake that the slip-stick artist of MB mud company once formed mud such as starch PAC-SL was made hole research, its result such as following table.

The capillary dimensions of starch, PAC-SL filter cake

Fluid loss agent

Diameter μ m

	Water mud	NaCL mud
				10	30
Starch	10	35
			PAC-SL	3	6

Last table explanation, when filter loss dropped to the cardinal principle par, the line style anionic polymer had the effect of dwindling filter cake pore diameter, and non-ionic starch does not then have this effect.Therefore, non-ionic polyalcohol starch can only be by self charging property and stop up all spaces and reach the leak-off effect of falling not all-pervasively.This character has determined that the characteristics of non-ionic type fluid loss agent are insensitive to ionogen, and stronger salt tolerant and anticalcium ionic ability are arranged.

On the other hand, have a large amount of polar groups in the molecule of non-ionic polyalcohol starch, they produce polarization and form hydration layer water molecules, thereby reduce the free movement energy of water molecules, reach the purpose that reduces filter loss.And just because of this mechanism, the viscosity shear force of mud is risen after making starch add again.Following table is that starch slurry adds the back performance test.

The starch slurry performance

Fluid loss agent	Dosage %	AV mpas	YP pa	Pa ingresses	Egress pa	FL ml
							Starch	0	2.5	3.5	2.8	3.0	25.0
1.0	5.5	14.3	11.1	12.8	12.5
						2.0		9.0	28.0	22.9	24.2	8.5
3.0	13.0	36.5	29.7	31.7	7.0
						4.0		16.0	54.5	40.4	45.0	6.2
5.0	26.0	75.5	55.7	62.3	6.0

From last table as seen, the starch dosage reaches 2.0% o'clock filter loss promptly significantly to be reduced, and shear force YP is greatly improved, and apparent viscosity AV is also to a certain degree improved.

The mechanism of action and the performance of anionic fluid loss agent PAC:

The anionic fluid loss agent mechanism of action is to improve the filter cake negative charge density by absorption, and water molecules is polarized is stabilized in the filter cake hole it to be difficult for passing through then.Also because of such characteristic, PAC can effectively reduce the size of filter cake pore diameter.

When adding Nacl, the average aperture diameter of mud cake has increased 5 times, but PAC has still realized the good control to filter loss.The ability of PAC combination water has obviously remedied the detrimentally affect that brings because of the pore diameter increase.Reason that PAC can use in the Nacl brine system that Here it is.

PAC has two kinds of ranks, i.e. PAC-R (common) and PAC---SL (low sticking).Below be Baroid drilling fluid company to PAC-R and PAC---the typical performance test that SL did.

The performance of PAC-R under different dosages

Dosage	AV CP	PV CP	YP 1b/100f t 2	10s gel 1b/100f t 2	10min gel 1b/100f t 2	PH	API30 ml
								0	9.5	3	13	6	6	7.4	41
0.143	75	7	1	0	2	7.6	9.5
								0.285	15	12	6	1	4	7.8	6.3
0.57	44	27	34	9	38	7.6	4.0

The performance of PAC-SL under different dosages

Dosage	AV CP	PV CP	YP 1b/100f t 2	10see gel 1b/100f t 2	10min gel 1b/100f t 2	PH	API30min ml
								0	9.5	3	13	6	6	7.4	41
0.143	6	6	1	0	1.5	7.5	12
								0.285	10.5	10	9	0.5	3	7.6	7.5
0.57	13	12	12	2	7	7.6	6

Below then experiment is to serve as that base slurry is tested with 4%Nacl salt solution+15lb/bbl prehydration colloidal sol.

From above two tables as can be known, when dosage was 0.285%, PAC-R and PAC-SL reduced dehydration effectively, and PAC-R is promoted to 15CP with apparent viscosity from 9.5CP, and PAC-SL only is promoted to 10.5CP from 9.5CP.Root we to falling the choice criteria of filtering agent, we will select effectively to reduce dehydration, significantly not increase the PAC-SL of system viscosity again as fluid loss agent.

The synergistic effect of starch and PAC-SL:

Starch and PAC-SL itself is water retaining, but when they by a certain percentage (10: 1 or 9: 1) can sharply reduce fluid loss when using together, and can make the temperature resistance of system improve the performance of synergistic effect that Here it is.Following table is that we use starch, the test that PAC-SL and starch+PAC-SL did respectively.

The synergistic effect test of starch and PAC-SL

Starch

PAC-SL

Starch+PAC-SL

Dosage	APT dehydration ml	Dosage	APT dehydration ml	Dosage	APT dehydration ml
						0	110	0	110	0	110
1.4	72	0.14	91	1.4% starch 0.14%PAC-SL	32
						2.8 5	60	0.28 5	76	2.85% starch 0.285%PAC-SL	26

More than test is to test in 4%NaCL salt solution 0.228%FLOWZAN starches for base.After using in 10: 1 ratio, PAC-SL can reduce dehydration from the visible starch of last table rapidly.

At starch and PAC-SL synergistic effect corresponding test has been done in the raising of starch temperature resistance;

Accompanying drawing mixes the thetagram that the starch temperature resistance is improved with PAC-SL for starch in salty mud.

Namely when separately using starch, its ultimate-use (limiting service) temperature be 115 ℃ and by mix at 10: 1 use after ultimate-use (limiting service) temperature risen 25 ℃, reach 145 ℃.

Be 233  (112 ℃) although do not surpass the operating limit temperature of starch according to log data DK-597 well getting core stratum bottom temp, but for preventing the high temperature degradation effect that starch may occur, we think that further to improve the starch temperature resistance by synergistic effect necessary.

Diverting agent Baracarb and Soltex and dosage are determined:

Why harmless core drill well liquid introduces diverting agent, mainly contains the Main Function of two aspects: the one, use as " clay " substitute, and be used for forming filter cake, reduce filtrate intrusion; The 2nd, form by " shading ring ", core is played shielding, temporarily stifled effect, prevent harmful solid invasion.

Baracarb is as the use of " clay " substitute, the press filtration vector can be controlled at about 15ml in common without the solid phase biological polymer drilling fluid 30 minutes, then seem particularly difficult toward decline again, its key issue is large without the instantaneous dehydration of solid phase biological polymer, the introduction of Baracarb, for the formation without solid phase biological polymer mud cake provides material base, its instantaneous filter loss greatly reduces, through suitable preparation, can in 30 minutes, press dehydration to drop in the 5ml.

Next be the test of Barracacb dosage, this dosage test is the test of being carried out as the base slurry take without the solid phase biological polymer.

The base slurry formula:

1# salt solution+0.228%Baracarb+1.14%Soltex+2.28% starch+0.285%PAC-SL

2#：1#+1％Barracacb(5)+1％Barracacb(50)+1％Barracacb(600)

3#：1#+1.5％Barracacb(5)+2％Barracacb(50)+2％Barracacb(600)

4#：1#+1.71％Barracacb(5)+2.85％Barracacb(50)+2.85％Barracacb(600)

Its performance is as shown in the table.

The experiment of Barracacb dosage

Prescription	ρ g/cm 3	FL ml	FLHTHP ml
				1#	1.06	26.0	35
2#	1.08	13.0	22
				3#	1.10	5.5	13
4#	1.11	5.0	12

When using the 4# prescription, press dehydration to reduce to 5.0ml among the API as can be known from the table data, and the HTHP dehydration only is 12ml, illustrate that 4# prescription can satisfy low requirement of invading, again in conjunction with following pollution evaluation test, we will fill a prescription 4# as the prescription of our practice of construction use.

Barracacb is as the use of bridge particle:

When from the front is discussed, we know in our the employed solid phase that does not contain artificial interpolation in without the solid phase biological polymer drilling fluid, but the landwaste that still contains porphyrize in this drilling fluid, when core drill well liquid contacts with reservoir, because the pressure imbalance in the well between liquid notes and the stratum, the minimum solid particle (landwaste) of particle diameter can be invaded reservoir in these outside fluids before mud cake forms, thereby blowhole, crack etc. is resulted in blockage, and reservoir permeability is significantly reduced. This ponding is relevant time of contact with filtration property, solid concentration, pressure reduction and fluid and the stratum of fluid.

" 1/3rd particle diameters are built bridge regular "

Abroms etc. point out if the d hole＜and during the 3d particle, particle can form filter cake at rock surface by bridging action, thereby may infiltrate the stratum hardly; If granulometric range is 3d particle＜d hole＜10d particle, the solid phase particles in the drilling fluid is easy invaded formation then; Form internal filter cake, reservoir is caused larger infringement, this moment, depth of invasion was generally ~ 2cm, if granularity further attenuates, reached 10d particle＜d hole, then can invade deeper layer, caused even more serious infringement.

The results showed that inner in order to prevent that solid phase particles from invading reservoir, particle diameter is equal to or greater than the particle proportion of stratum average pore size 1/3 in the outside fluid, should be no less than 5% of solid phase cumulative volume in the fluid.

According to above discussion, we will select Baracarb (5), Baracarb (50), Baracarb (600) as filling particle and bridge particle.

The test of diverting agent pollution evaluation:

In getting the core process, if the fracture pore size of the size of the solid phase particles of drilling fluid and reservoir is not mated, under the condition of positive differential pressure, drilling fluid will be invaded crack and hole inevitably. In the ordinary course of things, if drilling fluid does not form effective bridge blinding at the crack arrival end, then depth of invasion can be calculated with rice office, and the obstruction of the degree of depth is difficult to be disengaged like this. Therefore, in getting the core process, it is very necessary that fracture one porous reservoir is implemented effectively to protect.

Not adding temporarily stifled material drilling fluid is not adding in the temporarily stifled material situation the core pollution condition for estimating core drill well liquid the core pollution condition. Use 3 BH-23 well Arab " D " core to test. Drilling fluid composition is as follows:

5% bentonite+0.2238%Flowzan+2.28% starch+0.285%PAC-R+ baryta (this slurry is taken from Tu Jing slurry as the well section) experiment condition: confined pressure 5MPa, circulation of drilling fluid is pressed and is 3.5MPA, and shear rate is 150S¹, the circulation of drilling fluid time is 1 hour.

Experimental arrangement is as follows:

(1) by cutting, measure, washing oil vacuumizes, and with simulated formation water soaking 24h. Wherein simulated formation water is based on BH-23 well formation water sample analysis, preparation situation such as following table: preparation 2L)

The formation water preparation

Material	Dosage g
		Salt	219.5
Cacl 2	1.774
		MgCL 2	48.44
Na 2SO 4	0.51
		NaHCO 3	1.4

(2) measure original permeability K1 with simulated formation water forward

(3) on multifunctional high-temperature high pressure dynamic filtration apparatus, by above-mentioned experiment condition, use drilling fluid to be reversed dynamic pollution experiment.

(4) after pollution finished, then maintenance core 24h took out rock sample, scrapes off outer mud cake, again with the permeability K2 after the simulated formation water forward measurement infringement

Experimental result sees Table

Do not add diverting agent drilling fluid damage evaluation experimental

The core numbering	K1×10 3     Um 3	K2×10 3Um	K2/K1％
				1	103.6	3.23	3.12

2	102.5	3.72	3.62
				3	107.4	4.01	3.73

Can see the not enough original permeability 4% of the permeability after the infringement, average out to 3.49% from table. Obviously this mainly be since in the drilling fluid solid phase particles and crack, hole do not mate and cause solid phase particles to invade in a large number, in the crack, form internal filter cake, make anti-row's permeability reduction. This shows that the drilling fluid fracture that does not add diverting agent, the infringement that the hole rock sample causes are quite serious.

The screening of temporarily stifled material and dosage:

Be the effect of each additive adding to stopping up in the appraisement system, we have designed three groups of experiments take 4%Nacl salt solution+0.228%Flowzan as the base slurry:

1. base slurry+1.71%Baracarb (5)+2.85%Baracarb (50)+2.85%Baracarb (600)

2. base slurry+1.71%Baracarb (5)+2.85%Baracarb (50)+2.85%Baracarb (600)+1.14%SOLTEX

3. base slurry+1.71%Baracarb (5)+2.85%Baracarb (50)+2.85%Baracarb (600)+1.14%SOLTEX+2.28% starch+0.285%PAC-SL

(1) first group of test: the obstruction result who adds separately Baracarb.

According to the solid phase laws for plugging, the Baracarb that adds particle diameter 0.5 ~ 1200 μ m blocks up temporarily, and experimental result sees the following form

Add separately temporarily stifled experimental result of Baracarb

Core number	Dynamically temporarily stifled experiment			Temporarily stifled intensity		Flow ml/min under different anti-row pressures are poor
													P  mpa	T  mi  n	FL   ml	P   Mp   a	Flow ml/m in	0.5  Mpa	1.0  Mpa	1.5  Mpa	2.0  Mpa	2.5  Mpa	3.0  Mpa	4.0Mpa
	1	3.5	15	0.   9	6.   5	0	0.0  8	0.0  8	0.0  8	0.0  9	0.1	0.1													0.1
2													3.5	15	0.   8	6.   5	0	0.0  8	0.0  8	0.0  8	0.0  8	0.0  9	0.0  9	0.1
	3	3.5	15	0.   9	6.   5	0	0.0  8	0.0  9	0.0  9	0.0  9	0.1	0.1													0.1

As can be known, after the Baracarb that has used particle diameter 0.5 ~ 1200um, shading ring can bear the pressure of 6.5Mpa from table, but anti-row is difficult for. Be owing to block up excessively deeply on the one hand, be likely on the other hand owing to do not add the result that the soft particle of deformable causes.

(2) second groups of tests: the obstruction effect that adds Baracarb and SOLTEX. The SOLTEX main component is deformable yellow pitch particle, and under certain well temperature, these particles can soften, be out of shapes, thus with the Baracarb acting in conjunction, produce better obstruction effect, experimental result sees the following form:

The temporarily stifled experimental result of magma+Baracarb+SOLTEX

Core number	Dynamically temporarily stifled experiment			Temporarily stifled intensity		Flow under different anti-row pressures are poor
													P  mpa	T  mi  n	FL  ml	P   Mp   a	Flow ml/m in	0.   5   Mp   a	1.   0   Mp   a	1.5   Mpa	2.0  Mpa	2.5  Mpa	3.0  Mpa	4.0Mpa
	1	3.5	15	0.7	6.   5	0	0	0	0	0.0  1	0.0  2	0.0  2													0.02
2													3.5	15	0.6  5	6.   5	0	0	0	0	0	0.0  1	0.0  2	0.02
	3	3.5	15	0.7	6.   5	0	0	0	0.0   1	0.1	7.0	The anti-merit of lining up

It can be seen from the table, filter loss has largely decline than first group of test, illustrates that adding SOLTEX first group of experimental basis can make temporarily stifled effect that larger improvement is arranged. Wherein a core has successfully been realized anti-row. But the anti-effect of arranging is also not very good, illustrates that this prescription also is not optimized. The anti-merit of lining up means that flow increases suddenly under a certain anti-row pressure is poor, and this moment, drill core permeability rate returned to close to the original permeability before the drilling fluid contamination. Obviously, if required anti-row's pressure reduction is less, show that the infringement that is caused by drilling fluid is easier to be disengaged.

(3) the 3rd groups of tests: add the obstruction effect behind Baracarb, SOLTEX, Starch, the PAC-SL in the base slurry.

Starch, PAC-SL belong to respectively nonionic filtrate loss reduction additive and polyanion filtrate loss reduction additive.

Stop up effect such as following table.

Magma+Baracarb+SOLTEX+Starch+PAC-SL is stifled experimental result temporarily

Core number

Dynamically temporarily stifled experiment

Temporarily stifled intensity

Flow under different anti-row pressures are poor

	P   Mpa	T   mi   n	FL   ml	P  Mpa	Flow ml/m in	0.   5   Mp   a	1.0  Mpa	1.   5   Mp   a	2.   0   Mp   a	2.   5   Mp   a	3.   0   Mp   a	4.0Mpa
													1	3.5	15	0.   2	7.0	0	0.   1	0.3	8	The anti-merit of lining up
2	3.5	15	0.   2	7.0	0	0.   1	0.3  5	8
									3	3.5	15	0.   2	7.0	0	0.   1	0.3	8

By experimental result as seen, in base slurry, add respectively Baracarb, SOLTEX, Starch, PAC-SL after, formed shading ring can bear the pressure reduction of 7.0mpa, and its permeability is 0, shows such shading ring " surely stifled ". Only need when anti-row that the anti-row pressure of 2.0Mpa is poor just can eliminate shading ring, show again such shading ring " Yi Fanpai ". Therefore, utilize this formed shading ring of filling a prescription to satisfy simultaneously " surely stifled " and " Yi Fanpai " these two specification requirements.

Temporarily stifled degree of depth evaluation:

The temporarily stifled degree of depth is to weigh an important indicator of temporary shielding method ,barrier building temporary seal incores. The requirement of temporary shielding method ,barrier building temporary seal incores is: one is exactly shallowly stifled, namely cooperatively interacts between bridge particle, particle filled composite and the soft particle, forms not only thin but also fine and close internal filter cake on the nearly borehole wall of oil reservoir or core surface, i.e. shading ring.

BH-23 well Arab " D " oil reservoir core is selected in experiment, blocks up temporarily experiment with drilling fluid composition in above-mentioned the 3rd group of experiment first, then removes the core of certain-length along temporarily stifled end-grain cutting, by with the permeability of above-mentioned same experimental arrangement mensuration remaining part core. If the permeability of remaining core with pollute before the permeability of core suitable, the length that then cuts part can be similar to as shading ring thickness or the temporary stifled degree of depth, experimental result sees the following form

Test with the temporarily stifled degree of depth that the drilling fluid in the 3rd group of test carries out

Core number	K 1×10 3  μm 3	L 1cm	K 2×10 3μm 3	L 2cm
					1	104.5	0  1.0	22.43  103.9	＜1.0
2	101.1	0  1.10	19.54  101.2	＜1.10
					3	101.5	0  1.10	21.65  101.5	＜1.10

K wherein₁，L ₁Be respectively original permeability, the core length of clipping.

K ₂，L ₂Be respectively the residue drill core permeability rate, temporarily the stifled degree of depth.

From upper table data as seen, after once cutting, the permeability of 3 cores is recovered basically fully. The formed shading ring thickness of drilling fluid that shows this prescription is less.

The adding of diverting agent is on the impact of property of drilling fluid:

The design of harmless core drill well liquid will reach the protection purpose to core on the one hand, will satisfy on the other hand the needs of engineering construction. Diverting agent adds and may exert an influence without the solid phase biological polymer performance to former, and its influence degree will be used for judging the intermiscibility between diverting agent and the former drilling fluid. Following table is for adding diverting agent 1.71 %Baracarb (5)+2.85%Baracarb (50)+2.85%Baracarb (600) front and back performance comparison situation:

Property of drilling fluid contrasts after adding diverting agent

The sampling order	ρ   g/cm    3	PV   mpa   S	YP     pa	AV     mpas	n	K     Pn.s     n	FL   ml	FL HTHP     ml	PH
										Before the adding	1.06		10	37			26.0	35
After the adding	1.11		11.5	47			5.0	12

As can be known, after adding diverting agent, density is by 1.06g/cm from upper table Data Comparison³Rise to 1.11 g/cm³, plastic viscosity rises to some extent. This is that they have certain impact to plastic viscosity because Baracarb is inert material, also is weighting material simultaneously, and mud density is risen, and on this respect impact, we can make density meet designing requirement by regulating salt (Salt) dosage.

Apparent viscosity AV rises to 47mpas by 37mpas. In front we discussed the viscosity of core drill well liquid can not be too high, but the apparent viscosity of 47mpas is still our acceptable scope.

Yield value is slight the rising just, and impact is little.

Press dehydration to drop to 5.0ml by 26ml among the API, the HTHP dehydration drops to 12ml by 35ml, and this is our desired result just. In sum, diverting agent and without mixing between the solid phase biological polymer, some adverse effects that produce between them can be eliminated by the dosage of regulating other inorganic agents.

Beneficial effect:

Harmless core drill well liquid lubricity is good, and is outstanding in aspect performances such as well cleaning, the dispersions of inhibition drilling cuttings aquation.

Compatibility is good between each inorganic agent of harm-free core-drilling fluid, and starch and PAC-SL have synergism when using together; Diverting agent Bacacarb and Soltex replenish mutually, form effective temporarily blocking layer at core surface, and with macromolecule starch, when PAC-SL used jointly, effect was more obvious, had controlled completely effectively the intrusion of harmful solid phase and filtrate.

According to tracer D₂The mensuration of O, core drilling liquid filtrate depth of invasion is 0.6cm to the maximum, has reached the purpose of the low intrusion of specific oil company requirement fully.

Environment protecting is good. According to analysis and mensuration to chemical toxicity, bio-toxicity and the biodegradability of additive, harm-free core-drilling fluid satisfies the requirement of relevant environmental acceptability fully. Additive FLOWZAN, starch, PAC-SL etc. can both be very fast by this biodegradation in the harmless core drill well liquid, Baracarb pulverizes the inorganic additive that is processed into by marble, environment is not polluted, because adopting drilling fluid quantification technology, discharge capacity is controlled in the minimum atmosphere in addition.

Drilling fluid filtrate is on the washing away of rock core, drop to minimum on the impact of the permeability of rock core.

Do not contain in the drilling fluid and can not dissolve and compressible solids, solid in the drilling fluid can be reduced to minimum to the packing action of core hole.

Can not change the wetability of rock. By MB mud company to BH-23 well Arab " D " core employment well before, get in the core process, get the mud dipping behind the core, and measure its wetability, the result shows that basic change does not occur wetability.

Embodiment

Next explain below a kind of harm-free core-drilling fluid of the present invention being done.

Embodiment 1:

Water 100000kg NaCl 15000kg Na ₂CO ₃200kg NaOH 50kg

CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL 150kg xanthan gum FLOWZAN 200kg

Water retaining starch Stacrch 1200kg modifying asphalt SOLTEX 1200kg

Baracarb (5) lime carbonate a 2000kg Baracarb (50) lime carbonate b 2000kg

Baracarb (600) lime carbonate c 2000kg

A kind of preparation method of harm-free core-drilling fluid:

(a), in water, add a certain amount of Na in weight proportion ₂CO ₃, be used in water, adding a certain amount of NaOH then again except that contained calcium Ca in anhydrating, be used for except that contained magnesium Mg in anhydrating;

(b) in weight proportion, need slowly in treated water, to add xanthan gum FLOWZAN with the shearing pump of high shear rate,, be about 35s generally until viscosity in aqueous solution with 20 minutes/bag speed adding, yield value value 10pa;

(c) in weight proportion, add NaCL this moment again, and NaCL will add at twice: add NaCL for the first time density is carried to 1.06g/cm ³The system that has certain viscosity and certain density like this will help the adding and the suspension of stifled material (modifying asphalt SOLTEX, Baracarb (5) lime carbonate a, Baracarb (50) lime carbonate b, Baracarb (600) lime carbonate c) temporarily, after temporarily stifled material adds, to further add NaCL according to the density situation, also have CL up to system density ^-Meet the requirements till (51331ppm), temporarily stifled material slowly adds from mixing hopper during preparation, accomplishes evenly not precipitate;

(d) in weight proportion, add starch and CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL again, starch and CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL are powdered granules, need to add by mixing hopper, adding speed should be principle not produce " flake " particle;

(e) through above operation, harmless core drill well liquid is prepared substantially and is finished, and just drilling fluid density only is 1.11g/cm ³So, suitably add Nacl again, adjust, form product at last.

Embodiment 2:

Water 160000kg NaCl 19000kg Na ₂CO ₃400kg NaOH 150kg

CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL 550kg xanthan gum FLOWZAN 600kg

Water retaining starch Stacrch 1800kg modifying asphalt SOLTEX 1800kg

Baracarb (5) lime carbonate a 4000kg Baracarb (50) lime carbonate b 4000kg

Baracarb (600) lime carbonate c 4000kg

Its preparation method is with embodiment 1.

Embodiment 3:

Water 120000kg NaCl 16000kg Na ₂CO ₃250kg NaOH 70kg

CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL 200kg xanthan gum FLOWZAN 300kg

Water retaining starch Stacrch 1400kg modifying asphalt SOLTEX 1400kg

Baracarb (5) lime carbonate a 2500kg Baracarb (50) lime carbonate b 2500kg

Baracarb (600) lime carbonate c 2500kg

Its preparation method is with embodiment 1.

Embodiment 4:

17000 parts of Na of 130000 parts of NaCl of water ₂CO ₃75 parts of 297 parts of NaOH

400 parts of 382.5 parts of xanthan gum FLOWZAN of CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL

1500 parts of 1500 parts of modifying asphalt SOLTEX of water retaining starch Stacrch

3000 parts of Baracarb (5) 3000 parts of Baracarb of lime carbonate a (50) lime carbonate b

4000 parts of Baracarb (600) lime carbonate c

Its preparation method is with embodiment 1.

Harm-free core-drilling fluid well of the present invention can clean, suppress the drilling cuttings aquation in well and disperse, protects in the core field and use.

Specifically discuss the analysis of harmless core drill well solution additive environmental acceptability below:

Drilling fluid additive chemical toxicity monitoring analysis result:

Measure Pb, Cd, Cr, As and Hg in the various drilling fluid additives commonly used, it the results are shown in following table

The chemical toxicity analytical results of harmless core drill well solution additive

Classification	The sample title	Measurement result/(mg/kg)					Estimate
										Pb	Cd	Cr	As	Hg
Flocculation agent	FLOWZA N	1.63	0.45 9	25	4.6 9	0.00 3
							Alkaline agent	NaHCO 3	2.41	0.13 8	0.25 0	4.1 4	0.03 5
Fluid loss agent	PAC-SL	3.13	0811	15.6	3.3 3	0.01
							Fluid loss agent	STARCH	10.8	2.07	48.0	5.9 2	0.00 9
Fluid loss agent	SOLTEX	1.88	28.9	625	4.7 2	0.00 3									Cr slightly exceeds standard
							Alkaline agent	Na 2CO 3	0.63 4	0.82 4	12.7	5.0 5	0.00 3
Temporary plugging agent	BARACA RB	3.64	5.27	2.37	6.1 4	0.01 6									Cd slightly exceeds standard

As seen from table, the content difference of Pb, Cd, Cr, As and Hg five heavy metal species pollutents is very big in the various drilling fluid additives.The content range of Pb is 0.634-3.64 in the wherein various additives, and the content range of Cd is 0.138-28.9, and the content range of Cr is 0.250 ~ 625, and the content range of As is 3.33-6.14, and the content range of Hg is 0.003 ~ 0.035.Wherein the Cr of fluid loss agent SOLTEX exceeds standard, and the Cd of Baracarb exceeds standard, and this may be relevant with the basic raw material of these additives, but they in actual use concentration can not be 100%, so nontoxic in actual use.

Core drill well solution additive biological degradability is analyzed:

Select BOD ₅/ COD _CrThe ratio assessment method, measure the COD of various drilling fluid additives _CrAnd BOD ₅, judge its biological degradability, it the results are shown in Table.

Core drill well solution additive biological degradability A+E result

The additive sequence number	BOD 5(mg/l)	COD Cr(mg/l)	BOD 5/COD Cr(％)	Biodegradability is judged
					FLOWZAN	271.77	972	28.7	Easily
PAC-SL	139.34	892	15.6	Easily
					NAHCO3	-1.82	30	--	--
NACO3	--	--	--	--
					STARCH	137.79	528	26.1	Easily
SOLTEX	122.57	830	14.7	Difficult
					BARACARB	--	--	--	--

As seen from table, SOLTEX has restraining effect to microorganism in the harmless core drill well liquid additive therefor.Also have several samples not measure its COD in addition because of water insoluble or stable inorganics _CrAnd BOD ₅

The drilling fluid additive bio-toxicity is analyzed:

According to the photogenic bacterium method, measure the bio-toxicity of specific oil field drilling fluid additive sample commonly used, its measurement result sees Table.

Drilling fluid additive oxicity analysis test result

The sample title	Working concentration	EC 50(ppm)	Toxicity grading
					(％)
FLOWZAN	0.228	＞10 5	Nontoxic
				PAC-SL	0.285	＞10 5	Nontoxic
SOLTEX	1.14	＞3.1×10 4	Actual nontoxic
				Na 2CO3	1.0	＞10 5	Nontoxic
NaHCO3	0.2	＞10 5	Nontoxic

As seen from table, the EC50 value of the additive SOLTEX that harmless core drill well liquid is used is lower slightly, but meets nontoxic standard, and other treatment agents EC50 value is all greater than 3 * 10 ⁴The suggestion emission standard, generally, harmless core drill well liquid has been controlled the use of toxic substance well, has environmental acceptability preferably, has satisfied the protection core, the protection environment purpose.

Tracer agent D ₂The adding of O:

D ₂D is a radio isotope among the O, adds in the mud by measuring the degree of depth and the relative concentration of D, can to calculate mud filtering layer invasion depth and quantity along with filtrate enters the stratum.

Add D ₂The program of O is as follows:

(1) measures background formation D ₂O concentration.Fixed according to the BH-23 well surveying, background formation concentration is 150ppm, gets the core slip-stick artist and advise preparing 300ppmD in view of the above in mud ₂O.

(2) D ₂The O demand

Need add 2.50LD in per as calculated 100 barrels of mud ₂O.(3.02.KG/15.9M ³)

(3) adding D ₂Before the O, get a mud sample, so that original D in the computation of mud ₂O.

(4) get a mud sample respectively in beginning, centre, the end of getting core for every time.

(5) get core and finish after, institute's mud sample of getting and core will be delivered to relevant laboratory, so that measure the damage to core.

Harmless core drill well liquid is gone into well:

Because of soil paste as in the well before replacing being, for avoid any as soil to the infringement of core, the mixing of soil paste and new slurry as will being strictly on guard against during for slurry, solution is one section spacer pad of design, will as soil paste starch and separate with getting core, and well and sleeve pipe are washed away and clean.Spacer pad adds salt by the well site water, and density is carried to 1.14g/CM ³, spacer pad length is 609ft in the volume 50bbls, well.

Be foundation with the time of calculating on the one hand during actually operating, more shallow because of the spacer pad color on the other hand, judge easily for the slurry performance.

For slurry the time emit well head effusive as soil paste and spacer pad, spacer pad has one section to mix and starch with taking out between the drilling fluid, also with it discharging, being entirely core drill well liquid up to mud can termination of pumping, trip-out.During trip-out, cleaning be in the jar as soil paste, and clean down with washing, pump into harmless core drill well liquid, so that set up circulation.

Performance maintenance when getting core:

Solid control technology for reducing the core infringement, reduces solid phase and invades, and density is strict controlled in 1.137-1.140g/cm in the scope of design ³Between.For this reason, we have been equipped with solid control equipment.(comprise reciprocating sieve; Sand separator; Silt remover)

For preventing that whizzer from removing the Baracarb in the system, therefore getting the core stage without whizzer, we also take following measure in addition:

Drilling cuttings is thinner when (1) boring gypsic horizon, requires reciprocating sieve all to select detailed catalogue wire screen for use, 210 orders or 265 orders.

(2) for avoiding drilling fluid lake sieve, can not add dry powder family macromolecule weight polymers treatment agent in drilling fluid, any additives adds necessary pregelatinated, avoids taking place in the drilling fluid salt crystallization.

(3) since down-hole and ground in the face of the consumption of mud, we need prepare new slurry, only need add small amounts of salts during new slurry preparation or not with salt, CL in the view volume system ^-Content and deciding, promptly new pulp density is low, so just can solid phase density be maintained in the scope of design towards mud in rare recycle system.

(4) adopt drilling fluid quantification technology.Well domestic demand 63.13m as calculated ³, add two necessary circulation tanks of the upper ground surface recycle system, need 158.53m altogether ³, this is to keep getting the suitable mud amount of core, by this volume calculation, sand separator, silt remover are handled a week need only 64.3 minutes.Suitable mud amount has improved the utilization ratio of solid control equipment.

PH value Ca ²⁺, Mg ²⁺Maintenance because formation lithology is limestone and anhydrite, and anhydrite is a tart, very easily causes pH value to reduce Ca ²⁺Concentration increases, and for keeping the scope of pH value at 9.0-9.5, we are with NaOH and Na ₂CO ₃Be formulated in together in the medicine jar, its ratio is by Ca in the system ²⁺Adjust with the pH value size.And they are added in the core drill well liquid PH, Ca with doing little by little without a break ²⁺, Mg ²⁺Be controlled in the scope of design.

Shear force YP, dehydration safeguard that core drill well liquid shear force YP must maintain about 10Pa, on the experience, 1 bag of (25KG) FLOWZAN of every adding can improve about shear force 1Pa in the recycle system, mud amount is enough during actually operating such as in the recycle system, then can pump into old slurry and add FLOWZAN to shearing in the jar, and look the dehydration situation and add starch STARCH and PAC-SL and Baracarb, SOLTEX.Need replenish as mud amount, then in the water of well site, add above additive and safeguard with an amount of salt.

Claims (6)

1, a kind of harm-free core-drilling fluid is characterized in that being made up of the component of following weight proportion:

Water 100000-160000 part NaCl 15000-19000 part Na ₂CO ₃200-400 part NaOH 50-150 part CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL 150-550 part xanthan gum FLOWZAN 200-600 part water retaining starch Stacrch 1200-1800 part modifying asphalt SOLTEX 1200-1800 part Baracarb (5) lime carbonate a 2000-4000 part Baracarb (50) lime carbonate b 2000-4000 part Baracarb (600) lime carbonate c2000-4000 part

2, a kind of harm-free core-drilling fluid according to claim 1 is characterized in that being made up of the component of following weight proportion:

Water 120000-140000 part NaCl 16000-18000 part Na ₂CO ₃250-350 part NaOH 70-110 part CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL 200-500 part xanthan gum FLOWZAN 300-500 part water retaining starch Stacrch 1400-1600 part modifying asphalt SOLTEX 1400-1600 part Baracarb (5) lime carbonate a 2500-3500 part Baracarb (50) lime carbonate b 2500-3500 part Baracarb (600) lime carbonate c2500-3500 part

3, a kind of harm-free core-drilling fluid according to claim 1 and 2 is characterized in that being made up of the component of following weight proportion:

17000 parts of Na of 130000 parts of NaCl of water ₂CO ₃4000 parts of 297 parts of NaOH 75 parts of CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL, 382.5 parts of xanthan gum FLOWZAN, 400 parts of water retaining starch Stacrch 1500 parts of Baracarb of 1500 parts of modifying asphalt SOLTEX (5), 3000 parts of Baracarb of lime carbonate a (50), 3000 parts of Baracarb of lime carbonate b (600) lime carbonate c

4, according to claim 1 or 2 or 3 described a kind of harm-free core-drilling fluids, the particle diameter that it is characterized in that Baracarb (5) lime carbonate a is at 0.5～150um, the particle diameter of Baracarb (50) lime carbonate b is at 5～600um, and the particle diameter of Baracarb (600) lime carbonate c is at 60～1200um.

5,, it is characterized in that its preparation method is made up of following steps according to arbitrary described a kind of harm-free core-drilling fluid of claim 1-3:

(a), in water, add a certain amount of Na in weight proportion ₂CO ₃, be used in water, adding a certain amount of NaOH then again except that contained calcium Ca in anhydrating, be used for except that contained magnesium Mg in anhydrating;

(b) in weight proportion, need slowly in treated water, to add xanthan gum FLOWZAN with the shearing pump of high shear rate,, be about 35s generally until viscosity in aqueous solution with 20 minutes/bag speed adding, yield value value 10pa;

(c) in weight proportion, add NaCL this moment again, and NaCL will add at twice: add NaCL for the first time density is carried to 1.06g/cm ³The system that has certain viscosity and certain density like this will help the adding and the suspension of stifled material (modifying asphalt SOLTEX, Baracarb (5) lime carbonate a, Baracarb (50) lime carbonate b, Baracarb (600) lime carbonate c) temporarily, after temporarily stifled material adds, to further add NaCL according to the density situation, also have CL-to meet the requirements till (51331ppm) up to system density, temporarily stifled material slowly adds from mixing hopper during preparation, accomplishes evenly not precipitate;

(d) in weight proportion, add starch and CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL again, starch and CMC (Sodium Carboxymethyl Cellulose) BP/USP PAC-SL are powdered granules, need to add by mixing hopper, adding speed should be principle not produce " flake " particle;

(e) through above operation, harmless core drill well liquid is prepared substantially and is finished, and just drilling fluid density only is 1.11g/cm ³So, suitably add Nacl again, adjust, form product at last.

6,, it is characterized in that this harm-free core-drilling fluid well can clean, suppress the drilling cuttings aquation in well and disperse, protects in the core field and use according to arbitrary described a kind of harm-free core-drilling fluid of claim 1-3.