NL8903077A - METHOD FOR PROVIDING A STABLE SUSPENSION OF NON-SWELLING PARTICULATE MATERIAL - Google Patents

Description

A method of providing a stable suspension of non-swelling particulate material.

The invention relates to a method for providing a suspension in a given fluid of a non-swelling particulate material. The slurry is used to achieve increased and continued viscosity in the fluid, which is used for drilling, completing or reprocessing an underground oil or gas well.

A rotary system is the most common form of drilling an underground well. This system depends on the rotation of a column or drill pipe on the bottom of which is attached a multi-fork drill bit. The drill bit cuts into the soil and causes the cuttings to accumulate as drilling proceeds. As a result, a drilling fluid must be used to carry these cuttings to the surface for removal, and the bottom of the hole can be kept clean and free of cuttings at all times.

Generally speaking, fluids used for drilling, completing or reprocessing underground wells have been either of the water-in-oil emulsion type or of an aqueous base, in which tap water, sea water, a brine, or the like is used as the predominant base fluid to which a weighting agent is added such as barite, a clayey substance such as "body" bentonite, filtration control agents, dispersants, flocculants and other additives well known to those skilled in the art.

Recently, environmental considerations have severely limited and, in some circumstances, banned the use of invert emulsions and other hydrocarbon-based fluids, particularly in offshore drilling applications. In some instances, the alternative available to the industry, ie the use of the conventional water-based fluids, has not been entirely satisfactory because of, for example, the lack of lubricants, filtration control agents, and the like, operating at the higher temperatures and pressures in environments one so often comes across in today's drilling activities. Hence, industry has significant interest in so-called "synthetic" aqueous fluids which are non-polluting and exhibit many of the beneficial properties of the hydrocarbon based fluids such as lubrication, filtration control and the like, all at significantly higher temperatures than typical operating parameters of water-based fluids Some of such synthetic fluids are described in co-pending Serial No. 07 / 128,798 filed December 4, 1987 entitled "Modified Non-Polluting Liquid Phase Shale Swelling Inhibition Drilling Fluid and Method of Using Same", which describes and claims are deemed to be included herein Such fluids include a liquid phase to which a water-soluble component has been added The liquid phase may be fresh water, seawater, brine, simulated brine, or mixtures thereof The water-soluble component may be a polyalcohol, glycerine, a glycol, a glycolet it may be a polypropylene glycol, a polyethylene glycol, an ethylene oxide-propylene oxide copolymer or an alcohol-initiated ethylene oxide-propylene oxide copolymer or mixtures thereof or other similar components, with the water-soluble component constituting between about 5 and about 50% by volume of the total of the liquid phase of the fluid.

Such "synthetic" fluids often require the addition of certain fibrous, non-swelling particulate material, such as asbestos, attapulgite, sepiolite, and other minerals and materials well known to those skilled in the art to build viscosity, and others known purposes. Such particulate material is relatively insensitive to surface hydration, inner layer swelling and osmotic swelling. In contrast to clayey and other substances that do swell in liquids, such a non-swelling particulate material does not have a lattice type structure that allows a liquid to be absorbed between the layers as well as on the particle surface. Moreover, such a non-swelling particulate material is also relatively insensitive to osmotic swelling that occurs in lattice type structures because the surface ions are more concentrated than in the liquid itself.

It was noted that in attempting to provide a suspension of such non-swelling particulate material in solvents therefor for subsequent introduction into such synthetic fluids, considerable difficulties are encountered in forming a suspension of the material in the fluid. Depending on the selected fluid and the particulate material, it sometimes happens that initially a slurry will be formed, but it is not stable and the particulate material from the slurry will precipitate in the fluid with time. It is necessary to form a slurry of such particulate material in order to use the material for various drilling fluid applications, including improving and increasing viscosity.

It has been found that a stable suspension of such a non-swelling particulate material in selected synthetic drilling fluids can be provided by contacting the non-swelling particulate material with a sufficient amount of a member preferably selected from the class consisting of water and glycerol to provide a "paste" of that particulate material. By using the word "paste", it is intended herein to refer to the resulting product in which a material is exposed to a fluid to the extent that it is wetted to form a tacky, plastic type material thereafter, which is kneaded with a resulting liquid content that causes the particulate material to form a mass ranging from a stiff putty-like material to a tacky paste, yet contacting and exposing the amount of the member, such as water, etc., used to form the paste is insufficient for the particulate material to be suspended or dispersed or to appear to be separated from the fluid.

After the formation of the paste, such a paste is introduced into a predetermined amount of the synthetic drilling fluid, with stirring, to form a slurry of the particulate material in an initial paste form, so that an increased viscosity can be achieved and maintained in time through the suspension in the fluid.

The non-swelling particulate material used in the present invention can be any fibrous material that does not have a lattice type structure, such as the structure typically found in bentonite and other clayey type materials. The particulate material can be either a mineral or other substituent, such as asbestos. Sepiolite and attapulgite are typical of such non-swelling minerals. The amount of particulate material used in the slurry is not as important as the amount of the fluid member that can be a solvent for it and that is used to form the paste. The fluids suitable for use in the present invention include water and glycerol, and mixtures thereof. When water is used as a selected fluid member, it can be either a brine, brackish water, tap water, sea water or the like. In some instances, deionized water can be used, but its ability to form a satisfactory paste may be somewhat reduced due to lack of proper ionization. Although this is not fully understood, it is believed that ion exchange between the lid fluid and the particulate material may have something to do with the reaction that occurs between the particulate material and the fluid lid used to form the paste.

The amount of the fluid member used in the present invention will of course depend on the particulate material selected. Generally speaking, the fluid member should be provided in an amount of between about 1.3% to about 20% by weight of the total amount of the fluid / lid composition. In field applications, the amount of the fluid member can be easily calculated prior to the formation of the paste, and the particulate material can be contacted with the fluid member by lightly spraying with a hose or nozzle and exposing the surfaces of the particulate material to the limb fluid, or in other known and corresponding ways to ensure that only a paste is formed.

The paste can be introduced into the synthetic fluid base in an off-site vessel for subsequent transport to the rig, either by boat, truck or otherwise, or it can be introduced into such a fluid when in fact it is already circulating in the well , or at the site of the well and in a conventional mud preparatory well or hopper. In any case, the paste is introduced into a predetermined amount of the fluid with stirring, such as using a commercially available mud "gun". A Hamilton Beach stirrer can be used in laboratory preparation. The determination of a satisfactory suspension can be determined by visual indication, or with viscosity data indicating that the viscosity has been established and maintained over time. Typically, the viscosity of a synthetic fluid must be increased by the slurry by at least about 4 times higher than the viscosity of the synthetic fluid without addition of the slurry, as determined by conventional testing, as indicated in the American Petroleum Institute Standard Bulletin 13- B, Paragraph 2.4, for calculation and determination of starting and 30 minute gel points. Such a test has been used in the tests indicated below. Conducting such a test and calculating such gel strengths are well known to those skilled in the art and are set forth in the American Petroleum Institute Standard Bulletin L3-B, Paragraph 2.4, dated September 1, 1988.

While other known fluids can be used to form a synthetic drilling fluid using the slurry mounting method of the present invention, the present invention is particularly useful for preparing a slurry of such non-swelling particulate material in a synthetic fluid base selected from the class consisting of glycol, glycol ethers, polypropylene glycols, polyethylene glycols, glycerine, ethylene oxide-propylene oxide copolymers, alcohol-initiated ethylene oxide-propylene oxide copolymers and / or mixtures thereof. Preferably the tripropylene glycol bottom product is used, to which is added the slurry containing a non-swelling particulate material in paste form.

Example 1

Tests were conducted and results evaluated to determine the ability of the present method to produce a stable suspension of certain non-swelling particulate matter in lid fluids used in the test. In the testing, a "blank" test was conducted in which the non-swelling particulate material had not been prepared in the form of a paste for introducing into a fluid in an attempt to prepare the suspension. In preparing such a "blank" material for use in such a process, all chemicals were weighed out and tripropylene glycol bottoms were added to a Hamilton Beach bar blender. The tripropylene glycol bottoms product was stirred in such a mixture for 2 minutes, then tap water from Houston, Texas was added. After this addition of the water, the selected non-swelling particulate material was added and mixed in the mixer for 20 minutes. The procedure used for the test in which a paste of the non-swelling particulate was first prepared before introduction into the liquid was as follows: all chemical materials were weighed and the tripropylene glycol bottoms product was added to the mixture and mixed for 2 minutes . The selected non-swelling particulate material was contacted with water from Houston, Texas by spraying this light until a paste was formed. The paste was introduced into the mixer before mixing for 20 minutes. In all cases, 10% of the calculated fluid volume of tap water was used to form the paste. After the formation of the paste, it was introduced into the tripropylene glycol bottom product prior to measuring the rheological properties. Rheological properties of each material were then determined at room temperature using a Fann 35 A viscometer, and rheological properties were determined in a known manner along with initial and 20 minute gel strengths. The amount of the non-swelling particulate material used to prepare both the "blank" and the paste material was an amount equal to 10 pounds per barrel of such particulate material.

After the introduction of the paste into the fluid, a suspension thereof was immediately visually noted. Also, no suspension of the non-swelling particulate material in the fluid in the "blank" format was noted. The rheological readings indicated that viscosity increase had been established and that a stable suspension had been provided in the test procedure using the paste-forming method, initial and 30 minute gel readings, which had significantly increased over the gel readings for the "blank" tests.

The results of this test are set forth in Table 1 below.

Table 1

Trial No. 1 Trial No. 2 dry, dried additives in test, moist, moistened 1 2 Products "blank" "blank" __ ___

600 RPM

reading 72 112 68 86 150 150 TPGB (g)

300 RPM

reading 38 68 39 53 P.V. cps 34 44 29 33 4.8 Sepiolite (g) y.p.

# / 100 square foot 4 24 10 20 presence gel 2 8 3 7 4.8 Attapul pour (g) 30 min. gel 3 12 4 8 17 17 Tap water (g)

Example II

Tests were performed and results were evaluated as in Example I, changing the amount of sepiolite and attapulgite, as well as the amount of tap water used to form the paste. In one run (Run 3-Example II), glycerol was used instead of tap water to form the paste, and in another run (Run 4-Example II), octanol (a material not within the scope of the invention) ) used to form the paste. In all such tests, a satisfactory paste was formed and a suspension in the tripropylene glycol bottoms material was noted visually prior to obtaining rheological readings. In all tests except test 4, compared to the "blank" preparation and the test, enlarged rheological readings were obtained, and the initial and 30 minute gels were increased above those of the "blank" test and the material, which indicated that a satisfactory suspension had been established over time and that such suspension had resulted in an increased viscosity within such a tripropylene glycol bottoms fluid The results of this test are set forth in Table 2, below:

Table 2

Trial no. 1 Test no. 2 Test no. 3 Test no. 4 dry / pasta dry / pasta dry / pasta dry / pasta "blank" "blank" "blank" "blank"

600 RPM

reading 78 153 68 124 68 163 63

300 RPM

reading 40 93 35 71 35 100 32 P.V. cps 38 60 33 53 33 63 31 Y.P.

# / 100 square foot 2 33 2 18 2 37 1

Note 1 13 1 9 1 21 1 30 min gel 1 21 2 19 2 41 2

Additive in test # / bbl 1_2_3_4 _Products 150 150 150 150 TPGB (g) 4.4 4.4 4.4 Sepiolite (g) 4.4 Attapulgite (g) 3 3 Tap water (g) 3.75 Glycerol (g) __ 3 Octanol (g) 2 and 2.4 wt. % wetting additive 10 pounds per Barrel clay.

Example III

Tests were conducted and results were evaluated to determine the ability of the present method to enable non-swelling particulate material to form a suspension in certain fluids to increase viscosity. Except for non-swelling particulate material used, i.e., sepiolite, the procedure was also applied to a material that is not a non-swelling particulate material, i.e., bentonite. The method had no effect whatsoever on such a swellable small material with grid structure.

In the first part of the test, a synthetic drilling fluid was prepared from liquid phase tripropylene glycol bottoms to which a partially hydrolyzed polyacrylamide ("PHPA") was added. In Table 3A, the sepiolite and bentonite were not prepared in the form of a paste prior to introduction into the tripropylene glycol bottoms fluid. When the method of the present invention was used to paste the bentonite and sepiolite materials, as in Table 3B, a viscosity increased and visual observation initially occurred. However, as indicated in Table 3B below, when testing bentonite, initially gphene visual viscosity became visible while such viscosity was evident when the procedure was applied to a non-swelling particulate material, i.e., sepiolite. The results of this test are set out in Tables 3A, 3B and 3C below:

Table 3A

Products g q g g g g PHPA 42.8 47.1 30 TPGB 100 100 100 100 50 180

Sepiolite 10 40 10.8

Bentonite 20

Polyglycol E200 20

Sat. NaCl brine 9.5

Visual viscosity no no no no low no

Table 3B

After moistening the sepiolite with brine, a paste is formed

Products _g g g q q q PHPA 63 63 63 63 TPGB 135 137 133 120

Sepiolite clay 5.4 4 6.7 4 2% NaCl brine 4.7 3.5 5.8 20.8 (3.3%) (2.5%) (4.2%) (14.7%)

Visual viscosity yes yes yes yes

Table 3C

Products g g g g g g PHPA 63.0 63.0 63.0 63.0 TPGB 137.0 137.0 94.0 128.0

Sepiolite clay 4.0 4.0 4.0 2.0

Bentonite clay 12

Polyglycol E200 137.0 2% NaCl brine 10.5 3.5 3.5 41.0 10.0 (7.1%) (2.5%) (2.5%) (30.3%) (7 , 2%)

Visual viscosity no yes yes yes yes

While the invention has been described in terms of specific embodiments set forth in detail, it is noted that this is for illustrative purposes only and that the invention is not necessarily limited thereto, as alternative embodiments and operating techniques will become apparent to those skilled in the art for disclosure . Accordingly, it contemplates modifications that can be made without departing from the spirit of the described invention.

Claims (5)

A method for providing a stable suspension of a non-swelling particulate material in a fluid, characterized in that a non-swelling particulate material is contacted with a sufficient amount of water, glycerol or mixtures thereof, for the providing a paste of this particulate material; and which paste is introduced into a predetermined amount of this fluid, with stirring, providing a suspension of this paste, and increased viscosity can be determined and maintained by this suspension in this fluid. 2. A method according to claim 1, characterized in that the non-swelling particulate material is sepiolite, attapulgite, asbestos, or mixtures thereof. A method according to claim 1 or 2, characterized in that the amount of water, glycerol or mixture thereof is between 1.3% and 20% by weight of the total amount of the composition. 4. A method according to claims 1 to 3, characterized in that the increased viscosity is at least 4 times higher than the viscosity of the fluid without the addition of this suspension. 5. Process according to claims 1 to 4, characterized in that this fluid is glycerine, glycol, glycol ethers, polypropylene glycols, polyethylene glycols, ethylene oxide-propylene oxide copolymers, alcohol-initiated ethylene oxide-propylene oxide copolymers and / or mixtures thereof.