NO163058B - BROWN CIRCULATING LIQUID, A NON-CIRCULATING LIQUID OR DRILLING LIQUID FOR USING DURING BURNER. - Google Patents

Description

The present invention is aimed at well circulating

fluids/ non-circulating fluids or drilling fluids for use in drilling wells, especially oil and gas

wells, where the liquid is a suspension or an emulsion which includes a polymer which is soluble in the liquid, and optionally, one or more of the following components, a hemicellulose, a clay and a ballast agent.

Circulating fluids used when drilling underground wells are complex suspensions or liquid emulsions.

The purposes of circulating fluids are many, in that the fluid serves to cool and lubricate the drilling equipment, to carry cuttings away from the drill bit to the surface, and to regulate formation pressure and conditions at the bottom of the hole. Because of. the varying geological formations encountered during oil and gas extraction require frequent maintenance of drilling fluids; they are usually mixed to order so that the specific rheology and other properties required in each situation can be provided. In recent years, the tendency has been towards drilling deeper wells. This tendency has increased the demands placed on the function of the drilling fluid in that significant formation variations are often encountered in a single well and the temperature range experienced during drilling can be relatively large - often more than an order of magnitude. In addition, the increased depth of certain wells and the tendency to look for oil and gas in areas with significant geological pressure place strict requirements on the drilling fluids. I.e. that such fluids must increasingly be able to function under conditions of high temperature, high density and high salinity.

Non-circulating fluids useful in oil and gas extraction are generally used after the initial drilling of a production well. Such fluids include completion and overhaul fluids, fill fluids f fracturing fluids, stimulation fluids, water retention agents useful in drilling cements, and other fluids. Each of the preceding types of non-circulating fluids requires special, well-known properties to achieve good performance. Like the circulating fluids, the non-circulating fluids are often made to order, or mixed to order, to meet the particular requirements of a particular well or geological formation, and each fluid must be able to perform under increasingly difficult conditions.

The preceding and other fluids used when drilling after,

and production of oil and gas and in other well-drilling applications are well known to the person skilled in the art. Furthermore, the qualities required to ensure good performance for each of the preceding fluids are also well known. Further explanation of these properties and an overview of fluids useful in oil and gas production may be obtained by reviewing the articles "Composition and Properties of Oil Well Drilling Fluids", 4th Edition, G.R. Gray,

Gulf Publishing Co., Houston (1980); and "Drilling and Drilling Fluids", Developments in Petroleum Science, 11, Chilingarian et al., Elsevier, New York (1981).

In order to provide circulating and non-circulating fluids for use in the production of oil and gas, one wants to use materials which are able to provide desirable rheological and other properties in the fluids. It is of crucial importance that such materials are able to provide defined viscosities for varying downhole conditions including widely varying temperatures, pH, pressure, salinity, and geological conditions. At the same time, the materials used for the production of adhesives for circulating and non-circulating fluids should be compatible with other fluid components and additive products, such as e.g. clays, surfactants, ballasts, salt solutions, oil-containing fluid components, and other materials.

Among the main properties that one wants to incorporate in the materials that are suitable for the production of circulating fluids are • the ability to contribute to the viscosity so that i.a. the fluid's ability to remove cuttings from a well during drilling is improved.

In addition, such materials should preferably be able to seal porous geological structures through which the well extends so that the losses of circulating fluid to the geological formation are minimized or eliminated Preferably, such filtration control should not be accompanied by irreversible phenomena so that the formation porosity can again be exposed to the well shaft if desired. The aforementioned properties should ideally be able to be maintained under extreme conditions regarding pH, temperature, salt content, etc. which may occur during operation on oil fields. Furthermore, such compositions should also exhibit beneficial rheological and filtration control properties in the presence of other common circulating fluid additives and components. Accordingly, compositions suitable for achieving the aforementioned objectives have long been sought after within the crude oil producing part of the industry.

Non-circulating fluids for oil and gas production also have specified rheological and other properties that should also be possessed by mixtures to be used for the composition of such non-circulating fluids. E.g. fracturing fluids should be capable of suspending proppants by maintaining a high viscosity and gel strength, where viscosity and carrying capacity are maintained under high pressure conditions and for the range of conditions that may occur downhole. Complementary

and overhaul fluids impose other requirements well known to those skilled in the art, including the need for viscosity to be maintained over a wide temperature range and other conditions.

These properties which are important for a particular type of circulating or non-circulating fluid for downhole operations are well known to those skilled in the art. Reference to the aforementioned publications will provide further insight into such requirements. Accordingly, compositions suitable for maintaining viscosity have

tet and other rheological properties, for control of fluid loss to geological layers, and for suspension of particulate proppant etc., and for delivery of acid stimulants to a formation, for maintaining the pressure at the bottom of the hole to avoid blowouts in the case of inclusions of ballast liquids, and for numerous other applications to which oil and gas •fluids may be subjected, long sought after within the crude oil producing part of the industry.

Numerous cellulosic materials have been proposed as components for fluids designed for use during the production of oil and gas. It is known that cellulosic ether derivatives, such as e.g. Carboxymethylcellulose, CMC, are useful components in drilling fluids used for oil and gas production. More specifically, CMC has been used as a viscosity modifying agent or drilling additive to control fluid loss in circulating fluids. U.S. patents 3,476,795,

3,471,402, 3,727,688, 4,043,921, 4,068,720, 4,110,226, 4,110,231, 3,506,644, 3,668,122, 3,954,628 and others describe carboxymethyl cellulose and related cellulosic materials for such applications. Other hydroxyalkyl celluloses and alkyl ether-substituted celluloses have also been used to thicken clay-based drilling fluids and the like. Such materials are chemically modified celluloses which, in general, form high molecular weight water-soluble polymers whose dissolution properties may include high viscosity. Such modified celluloses are described, e.g., in U.S. Pat. Patent Nos. 4,290,899, 4,155,410, 4,169,818, 4,239,629, 4,299,710, 4,096,074, 4,172,055 and 4,239,629.

Cellulosic plant material has been included in certain

oil and gas fluids. E.g. described in the U.S. patent 4,082,677 certain phosphorylated agricultural by-products for use in drilling fluids. U.S. patent 3,042,608 is directed to the use of ground down particulate heat-set plastic material and plant material as materials for circulation control. U.S. patent 3,441,528 describes pentosan-containing lignocelluloses such as e.g. seed husks, .bagasse or corn cobs for the production of elastic gel useful as drilling mud. U.S. patent 2,912,380 is directed to fibrous vegetable material which together with plastic material for control of fluid loss in wells. U.S. patent 3,788,405 provides for re-plugging of wellbore formations by circulating cellulose masses such as e.g. wood pulp through the well. Numerous other, earlier, formation plugging materials are also described in the latter patent.

U.S. patent 3,852,200 describes microcrystalline cellulose, MCC, as a thickening and gelling agent for suspension of abrasive particles used in a special drilling technique.

Certain non-cellulosic vegetable materials and gums have been described in connection with oil production fluids. U.S. patent 4,142,595 describes e.g. linseed gum as a shale-stabilizing component of a drilling fluid. Xanthan gum in a calcium chloride, carboxymethyl cellulose supplement liquid is described in U.S. Pat. patent 3,625,889. Certain compositions containing particulate wax are described for fluid loss control in U.S. Pat. patent 3,882,029.

As discussed above, particulate, ground cellulosic material is known in the drilling art to combat circulation loss in wells. Lost circulation occurs when the surrounding formation that is being drilled into is unconsolidated, highly porous, or contains hollow voids where the drilling mud can enter. Examples of vegetable materials that have been used for re-plugging such formations include ground wood, ground walnut shells, shredded paper or shredded vegetable material such as e.g. corn stalks, sugar cane, bagasse, or sugar beet pulp. These materials are added to the drilling fluids to provide bridging seals consisting of large particles that alone, or together with smaller particles, plug porous or fractured formations. Such materials can also be used as a cheap bulk filler for naturally occurring cavities.

The purpose of the present invention is to provide well circulating fluids, non-circulating fluids or drilling fluids for use in drilling wells, especially oil or gas wells, where the fluid is a suspension or an emulsion that includes a polymer that is soluble in the fluid and, optionally , one or more of the following components, a hemicellulose, a clay and a ballast agent, which is characterized in that it further contains parenchymal cell cellulose.

It has been discovered that circulating and non-circulating fluids for use in drilling and in the production of oil, gas and other "wells" can be advantageously obtained by utilizing parenchymal cell cellulose. Such fluids have been found to provide excellent viscosity control, good control of fluid loss, and to be compatible with common components and additives for oilfield and other fluids.Furthermore, such fluids can be composed so that they provide good stability with regard to temperature, pH, density and salt content.

Such fluids can be supplemented by the presence of certain polymers, especially anionic polymers, which have been found to provide synergistic results in combination with parenchymal cell cellulose in controlling fluid loss in porous subsurface formations. In connection with the present description, the terms regulation of liquid loss and filtration regulation are used interchangeably. According to another preferred embodiment, parenchymal cell cellulose and anionic polymer can be advantageously produced by alkali release from parenchymal cell cellulose from sugar beet pulp and certain other parenchymal sources.

Furthermore, a synergistic system for improving fluid loss regulation with circulating drilling fluids can be achieved by using parenchymal cell cellulose, a soluble polymer, preferably an anionic polymer, and one or more clays. The unique structure of parenchymal cell cellulose is believed to have properties that are particularly well-suited for interaction with clay particles and certain polymers, so that a variety of different underground porous structures can be sealed, thereby minimizing fluid loss to such formations.

In addition, non-circulating fluids and methods for using, including filler fluids, completion fluids, overhaul fluids, stimulation fluids, fracturing fluids, and many other well-known non-circulating fluids can also advantageously use parenchymal cell cellulose according to the present invention. In all of the foregoing applications, one can take advantage of parenchymal cell cellulose's excellent stability over a wide range of chemical and physical conditions.

New drilling fluid mixtures which eliminate most, if not all, of the disadvantages associated with mineral or clay-based drilling fluids are provided by the present invention. Broadly speaking, the invention describes mixtures of drilling and other well fluids, including non-circulating fluids, which are obtained by dispersing a new, particulate form of cellulose derived from parenchymal cell tissue of certain plants, especially sugar beet and citrus, in water, oil or saline solutions. The mixture may also preferably contain various amounts of hemicellulosic materials in modified or original form as well as polymers, especially anionic polymers and other beneficial minerals, salts and organic materials. Methods for producing dispersed preparations of parenchymal cell-derived cellulose are described in US Patent No. 4,629,575.

Parenchymal cell-derived cellulose (PCC) has been found to be unique among natural cellulose isolates in that it forms viscous, gravity-stable suspensions with low solids content. In the concentration range from 0.5 to 3.0% w/w, PCC forms a gel-like, aqueous suspension that exhibits pseudoplasticity. This behavior can be approximated by Bingham's plastic model, which is used to describe strongly flocculated clays. This unusual rheology is believed to be associated with the unique micromorphology of PCC. PCC mainly exists as a dispersed collection of thin, flexible cellulosic membranes resulting from the breakdown of parenchymal cell complexes that are characteristic of certain plant materials, especially sugar beet, citrus, Jerusalem artichoke, etc., so that the parenchymal cell material is released from the fibrous cellulose it is associated with and from hemicellulose and other components of the complex. The rheology of the PCC suspension has been found to be very stable over

for the effects of mechanical shear forces, pH, high temperature and dissolved salts.

The micromembrane geometry of PCC enables thin films

of the cellulosic structure is stacked or packed in layers so that films with low liquid permeability are formed at porous interfaces and filtration surfaces such as pore diameters greater than 0.149 mm. These films act as primary filters for small suspended clay particles or interacting polymers that can be retained on the film and thus further reduce permeability. This property is highly desirable for drilling fluids since the presence of porous formations in newly drilled parts of the well that are not lined, combined with the high hydrostatic pressure of the fluid column in the wellbore, often causes fluid loss into the adjacent formation by a filtering effect. The result is, if the fault is not corrected, that the suspension fluid penetrates into the formation and leaves a suspension with

increased solids content. The suspension with a higher solids content often shows significantly changed rheology, this leads to poorer sludge circulation and other undesirable properties. This phenomenon is a serious problem with simple clay-based drilling fluids. Clay-based drilling fluids are also believed to be the main cause of the irreversible damage to producing formations which is due to significant penetration of fine clay particles into the production formation which blocks the capillary structure in the formation and prevents the flow of gas and oil into the header pipe.

It has further been discovered that the inclusion of certain other polymeric constituents of the parenchymal cell complex, called hemicelluloses,

HC, in the PCC suspension can contribute to synergistic improvement of the regulation of fluid loss under certain conditions. These hemicellulose components can either be isolated simultaneously with PCC,

or isolated separately and later combined with this to provide improved performance of the PCC-based drilling fluid.

It is believed that pectinic and polygalacturonic acid or pectinic acid are important components of such hemicelluloses in this respect. Additive compatibility or synergism of the PCC/HC system with numerous other filtration and rheology control additives or polymers has also been discovered. Other polymers, especially soluble, anionic polymers can also act synergistically in this respect.

The above-mentioned properties of the PCC/HC complex make it so

an ideal agent for aqueous drilling fluids in that it forms gels with a low solids content that show good suspension properties for particulate material such as e.g. sand or rock fragments, but still has a low viscosity under conditions with high shear stress corresponding to the conditions found at the drill bit. The PCC/HC complex is also thermally stable and has a rheology which

is stable against varying salt content, and provides further resistance to fluid loss into porous formations below the surface.

Sugar beet pulp, which is a known precursor of sheet material for the production of parenchymal cell cellulose, has, as indicated earlier, been known for use in connection with oil drilling, yet the most closely related material known for such applications is completely different from the materials that are useful in connection with the present invention. E.g. hydrates sugar beet pulp when placed in water, e.g. in the torn form known from prior art, to a mushroom-like and sponge-like mass of plant tissue in the form of thin bands which can be several centimeters long, or "beet slices". While parenchymal cell cellulose can be derived from spent sugar beet pulp, there is neither physical nor chemical similarity between the two materials except for the fact that one is a precursor to the other. As a structural and compositional analogy for the relationship between sugar beet pulp and parenchymal cell cellulose and other components that can be derived from this, chopped wood that is used to regulate circulation loss and the converted products derived from it that can be useful in drilling fluids can be mentioned. Such materials may include cellulose ethers and lignosulfonates.

A similar comparison can be used to distinguish between precursors and natural forms of cellulose that can be useful as materials for regulating lost circulation in drilling fluids and processed cellulose preparations derived therefrom that are useful for regulating the basic rheology of drilling fluids. I.e. fibrous versions of natural celluloses, such as cotton and wood, find application as materials for regulating lost circulation in a manner analogous to raw sugar beet pulp. Such cellulosic materials are precursor materials useful in the manufacture of microcrystalline cellulose, a particulate cellulose with large dimensions two to three orders of magnitude smaller than the original form of cellulose from which it is derived. Numerous patents belonging to Battista, referenced in US-PS No. 4,629,575 describe the use of dispersed microcrystalline cellulose, MCC, in the preparation of drilling fluids, particularly for injection drilling.

Consequently, parenchymal cell cellulose must be kept separate from material from which it is produced, i.e. raw sugar beet or citrus pulp. In addition, parenchymal cell cellulose must be kept separate from non-parenchymal materials such as wood pulp and from cellulosic materials such as e.g. microcrystalline cellulose, MCC, which can be derived from it. A partial explanation of the aforementioned differences can be found in the reference "Cellulose and Other Natural Polymer Systems, Brown ed., Plenum (1982).

A more thorough explanation of the above-mentioned relationships

can be found in US Patent No. 4,629,575.

A further distinction must be made with the particulate celluloses for use in drilling fluids described in U.S. Pat. patent 4,356,096. This reference describes the use of treated, mechanically degraded linters to serve as a hydrophobic, organophilic, water-wettable absorbent, which together with certain lubricant additives can be useful in the formation of a high lubricant film around a wellbore. This organophilic, absorbent form of cellulose is morphologically and functionally distinct from parenchymal cell cellulose.

In order to elaborate on the beneficial properties obtained by using parenchymal cell cellulose, either with or without the addition of certain polymers, especially hemicelluloses, in the production of circulating and non-circulating well fluids, the following examples are provided. It is assumed that an average person skilled in the art will readily realize the great applicability of the drilling fluids and the methods described. Such a person will also understand that the number of examples is necessarily limited, one will further understand that the materials, methods and ideas described here have great potential applicability in the production of oil and gas and for other well drilling and production applications.

A further description of examples of well fluids that may advantageously include the PCC of the present invention can be found in "Production Operations 1 - Well Completions, Workover and Stimulation", Thomas 0. Allen and Alan P. Roberts, Oil and Gas Consultants International, Tulsa, Oklahoma (1982); and "Well Completions, Volume 1" - SPE Series 5a published by The Society of Petroleum Engineers, Dallas, Texas, 2nd Edition (1980). The following examples serve the above-mentioned purpose.

It should be emphasized that, at the time of filing the present application, no underground applications of circulating or non-circulating fluids according to the present invention had taken place. Nevertheless, the materials according to the present invention have shown excellent performance in standardized tests, such as e.g. the fluid loss control experiment developed by American Petroleum

in Institute, A.P.I., the conclusion of which is that underground application is likely to be very successful. Similarly, standardized viscosity and other rheological tests lead to a similar conclusion regarding the impact of the application of parenchymal cell cellulose in underground fluids, where rheological properties are of significant importance.

EXAMPLES

The following illustrative examples describe specific embodiments of the present inventions. Unless otherwise stated, all percentages are based on weight to volume and viscosity is in centipoise at indicated viscometer rotation speeds. The liquid cosimeter readings were, unless otherwise stated, taken at apparent steady state to minimize the time-dependent factors due to thixotropic effects. Filtration regulation was determined using standard low pressure A.P.I. the attempt. The liquid loss data were collected with Baroid Model 301 low pressure filtration cells or similar equipment.

The following materials and additives were used in the examples.

PCC: A crude parenchymal cell cellulose derived from sugar beet or citrus pulp. Materials isolated from such cellulose have been shown to consist mainly of membrane structures that exhibit the desired rheology when dispersed in aqueous media. See Examples 1 and 8 of US Patent No. 4,629,575 regarding the preparation of this material.

PCC-BC: A ClC>2 bleached preparation of PCC that is mechanically graded to remove fiber-like or undispersed cellulose particles. See Examples 2 through 5 of US Patent No. 4,629,575 for example methods.

PCC-C: An unbleached preparation of PCC classified as in Example 5 of US Patent No. 4,629,575 to separate fibers and undispersed cellulosic particles.

HC: The soluble hemicellulose complex isolated from sugar beet pulp. See Examples 6-8 of US Patent No. 4,629,575.

HC-S: An alkaline saponified preparation of the hemicellulose complex isolated from sugar beet pulp according to example 8 in US patent no. 4,629,575.

SAP: An alkaline converted sugar beet pulp in which both particulate PCC and soluble HC-S are present. The ratio of HC-S to PCC non-volatile solids depends on the manufacturing method, but typically ranges from 1 to 2.

PG: A polygalacturonic acid derived from citrus pectin.

Rev-Dust: An aluminosilicate containing kaolinite (74.1*), a-quartz (17.3*) and a-cristobalite (7.6$) as main components. It is believed to be representative of drilling mud solids of the kaolinite class for addition to experimental mud mixtures. The average particle size for this preparation is 2 µm, 93 µm of the material passing through a 0.044 mm mesh sieve. A trademarked clay of Milwhite Co., Inc., Houston, Texas.

Grundite: A mainly illitic clay containing illite (41.4*), illite montmorillonite (24.3*), a-quartz (18.5*) and kaolinite (7.2*) as major components. It is considered representative of drilling mud solids of the illitic class for addition to drilling mud mixtures. A trademarked clay of Macobar Dlvision, Dresser Industries, Houston, Texas.

Impermex: A commercial version of drilling slurry that is used as a fluid loss control agent. A trademarked product of Baroid Dlvision, NL Industries, Houston, Texas.

Aquagel: A commercial A.P.I. quality high yield sodium montmorillonite clay used for drilling fluid rheology and filtration control. A trademarked product of Baroid Dlvision, NL Industries, Houston, Texas.

Zeogel: A commercial A.P.I. grade of attapul git clay for rheology control in brine based drilling fluids. A trademarked product of Baroid Dlvision, NL Industries, Houston, Texas.

Calcium ium carbonate

CaCC^: A high purity limestone ground down to 95*,

passes through a sieve with a mesh size of 0.044 mm.

Klerzym L-100: A commercial pectinase enzyme preparation. A trademarked product of Miles Laboratories, Elkhart, Indiana.

Pectinol 60B: A pectinase enzyme preparation. A trademarked product of Corning Glass Works, Corning, New York.

Barytt: A Commercial A.P.I. specified quality of barium sulphate which is used as a ballast agent in well fluids.

Hematite: A commercial product of iron oxide that is used as a ballast agent in well fluids.

Lignite: A commercial grade of lignite that has a high content of humic acid. It is used as a thermophilic diluent, emulsifier and fluid loss additive for both oil and water-based drilling fluids.

CMC^V: Sodium salt of carboxymethyl cellulose having a viscosity of 25-50 cp at 25°C in a 2% w/v solution.

Drispak: A polyanionic cellulose used as an additive to control fluid loss in freshwater or saltwater drilling fluids. A trademarked polymer product of Drilling Specialties Company, Bartlesville, Oklahoma.

XC: A commercial grade of Xantomonas useful as a rheology control agent in circulating well fluids.

All other reagents, additives or chemicals are either commercial qualities that can be obtained through chemical retailers or, if they are trademark registered products, the source is indicated.

EXAMPLE 1

Thermal effects on PCC rheology and stability of PCC at high temperatures

A 0.8% w/v suspension of a bleached and graded cellulose preparation (PCC-BC) was homogenized for 15 minutes in a "Waring" mixer at high speed. The pH of the homogeneous suspension measured at 26°C was 4.6. The temperature of the homogeneous suspension after the mixing process was approx. 80°C and the temperature was systematically reduced before the subsequent viscosity measurement. The viscosity profile was recorded over the range from 100 to 600 rpm. minute on a "model 30 Fann" viscometer and at 60 revolutions per minute on a "Brookfield viscometer model LVF" using spindle No. 3. The Brookfield viscosities are normalized and expressed as a percentage of the viscosity at 21°C. The Fann readings were not taken until a stable value was obtained (usually within 5 minutes) and the Brookfield reading typically required 15 to 30 minutes before a stable value was obtained. The latter is probably due to thixotropic effects during radial relaxation of the deformable PCC particles in response to shear forces from the viscometer spindle. Minor evaporation losses at 50°C to 80°C were regulated by periodic, precise additions of water. The results are summarized in table 1.

These results suggest that the viscosity of PCC varies inversely with temperature. The relationship is not linear and the apparent viscosity is approximately halved over an interval of 50°. This reflects that the viscosity has a relatively low thermal coefficient. The plastic viscosity shows a doubling over these temperature ranges and appears to have a plateau at 25°C. The flow limit triples over the same area.

PCC has high thermal stability as revealed by a comparative static incubation at 177°C against xanthan gum (XC). The concentrations of PCC and XC were respectively 1.67% w/v and 1.0% w/v, where the weights for the non-volatile, particulate cellulose solids are not corrected for ash content. Both polymer preparations were homogenized for 15 minutes at high speed on a "Waring" mixer, cooled to room temperature and the pH was adjusted to 9.0. In the case of the XC polymer, the homogenized product contained 3 drops of a commercial antifoam agent (Dow 544)

per 600 ml to control foaming. The static incubation was carried out in a stainless steel tubular container at 177°C for 14 hours. The contents were not vented and the volumetric ratio between the top space and the liquid-filled space inside the incubation container was approximately 1, this results in a highly oxidizing environment. After the incubation, the contents of the incubation container were re-homogenized for 5 hours and

The pH was adjusted to 9.0 before the rheological study at 26°C. The results are summarized in table 2.

As can be seen from the results, XC completely degrades in the high temperature and oxidizing environment of this experiment, but PCC retains a significant degree of its original viscosity at 600 rpm.

EXAMPLE 2

Stability of PCC in salt solution at high temperature

PCC also shows high thermal stability in the presence of saline solution. Two preparations of PCC were used to demonstrate this fact

- one bleached and graded, PCC-BC, and the other mechanically graded but unbleached, PCC-C. The particulate solids in the cellulose pulp contained some inorganic material which appeared as an ash residue of 5%. Both PCC preparations were prepared at 1% weight/volume in either saturated NaCl solution or water. The preparations were homogenized at high speed in a "Waring" mixer for 15 minutes, cooled to room temperature, and the pH was adjusted to 9.0 with concentrated NaOH. In the case of the NaCl solution, the pH was corrected for effects of salt on the glass electrode in the pH meter. In contrast to the high temperature incubation in Example 1, the incubation at 177°C in this case was carried out in a non-oxidizing atmosphere. The PCC preparations were several times degassed by vacuum extraction and pressurized to 7.0 kp/cm<2> with N2 in situ for three cycles. After incubation for 16 hours, the contents of the incubation bombs were cooled to room temperature, and the Fann profile designated "No. 1" was registered. The pH of the samples was then adjusted to 9.0 and the samples were homogenized for 5 minutes at high speed in the "Waring" mixture before another Fann profile "No. 2" was recorded. The results are tabulated in table 3.

Both forms of graded PCC, bleached and unbleached, show similar behavior upon high temperature incubation in the presence of saturated NaCl. Both lose approx. 50% of the viscosity measured using the Fann viscometer at 600 rpm, and the resulting homogenized preparations show little shear dependence of the apparent viscosities. Under these test conditions, the bleached classified PCC shows approx. 1.5 times the viscosity of the unbleached preparation at an equivalent solids concentration.

EXAMPLE 3

The effect of homogenization after the reactor treatment and alkali treatment on the liquid loss control of a PCC/HC composition

A 1.5% w/v (particulate solids basis) suspension

of a PCC/HC mixture was prepared from an acid-converted beet pulp according to Examples 6 and 7 of US Patent No. 4,629,575. The total non-volatile solid content of the suspension was 3.7% w/v and is uncorrected for inorganic ash content.

The initial pH of the slurry was 3.0. Equal parts

of the acid-converted pulp suspension was subjected to the following treatments:

1. Control - homogenized without further treatment.

2. Not homogenized, pH adjusted to 11.2 and the slurry incubated for 3.5 hours to achieve saponification. Final pH

was 9.7.

3. Saponified as in 2., with homogenization after incubation.

4. Saponified as in 2., incubated overnight at room temperature, homogenized and pH regulated from 9.1 to a final pH of

6.5.

Homogenization was achieved by mixing 300 ml portions in a "Waring" mixer at high speed for approx. 5 minutes. The resulting homogenized products were foamy but were not degassed prior to examination. Rates of fluid loss were measured; Saponification or alkali treatment of a slurry of acid-converted beet pulp is desirable to improve liquid loss regulation none. Further homogenization of the reactor slurry improves

also the filtration regulation. The filtration rate seems to be relatively independent of pH in the range from pH 6.5 to 9.7.

EXAMPLE 4

Maintenance of PCC rheology and fluid loss regulation under conditions of varying pH

Two converted pulp suspensions with approx. 1% weight/volume content

of cellulose-containing solid in particulate form was prepared in the following way. A slurry of acid-converted beet pulp with 5.2% w/v (non-volatile solids are not corrected for inorganic ash content) was saponified at room temperature by two additions of ION NaOH so that the total concentration of added base was 0.3N. A 500 ml portion containing 3 drops of antifoam agent (Dow 544) was diluted 2.5 times, homogenized in a "Waring" mixer for 5 minutes at high speed and allowed to stand at room temperature for 24 hours to obtain a PCC/HC- S.

The original slurry of acid-converted pulp was pressed to remove HC, bleached and mechanically classified on a 0.169mm/0.074mm two-stage sieve. The bleached PCC/BC was diluted to 1% w/v (non-volatile solids not corrected for inorganic ash content).

Both preparations above were homogenized

in a "Hamilton" submerged shaft mixer at high speed and defoamed by the addition of 100 ppm antifoam. The pH of the final saponified PCC/HC-S preparation was 11.8 and it contained an estimated 0.8% w/v particulate cellulose solids and 1.2% w/v soluble hemicellulose. The pH of the homogenized PCC-BC was adjusted to pH 11.9 with concentrated NaOH. The viscosity profiles were obtained at 23°C with a "Brookfield viscometer model LVF" using spindle No. 2 at 60 rpm. The viscosities are specified as time-independent limit values. The results are tabulated in table 5.

The results indicate that the viscosity of the solution regulated by PCC is independent of the hydrogen ion concentration over a range of 10 orders of magnitude. The unit viscosities for both preparations are almost identical if they are corrected for the difference in concentration of particulate cellulose solids e.g.

An A.P.I. static filtration tests at low pressure were performed

with both the homogenized preparations at the high and low pH extremes. In table 6 below are the results of an abbreviated A.P.I. test (7.5 minutes against the normal 30 minutes) listed

for the two preparations.

In contrast to the viscosity profile results, the fluid loss rate for the homogenized PCC/HC-S is pH sensitive. The presence of HC-S is believed to exert a synergistic, beneficial effect on fluid loss regulation at high pH. In the acidic range below a small pK of 3-4 for the pectic acid component in HC, the filtration regulation effect disappears and the filtration rate approaches the rate for PCC alone.

EXAMPLE 5

Shear stability of PCC

The overall rheology of dispersed forms of native, isolated parenchymal cell cellulose approaches a stable limit value when the material is subjected to high shear stresses. This is assumed to

be associated with dissociation and dispersion of the membrane complex. Raw PCC, such as the presscake isolated from an acid-converted pulp containing both membrane- and fiber-like forms of cellulose, as well as purified forms of PCC, such as bleached/graded suspensions of PCC-BC containing only the membrane fraction show this phenomenon. 1.5% and 1.2% weight/volume suspensions of PCC-BC and PCC, were prepared and the pH was in each case regulated to 11.0. The solids content is stated as non-volatile solids and is not corrected for inorganic ash content. 5 drops of antifoam agent (Calgon CL-371) were added to 700 ml of each cellulosic suspension and they were mixed at high speed in a "Waring" mixer for specified periods of time. The contents of the sealed mixing containers accumulated

considerable thermal energy and during the mixing time they approached boiling. Corrections for small evaporation losses were made by adding water after homogenization where required. The samples were then cooled to room temperature and degassed by vacuum extraction before instrumental examination. Measurements of liquid loss at low pressure were carried out according to A.P.I. specifications. The viscosity of the homogenized preparations was examined with a "Fann viscometer model 35" at room temperature.

The data in Table 7 show that the rheology of an unhomogenized PCC suspension exhibits an initial time-dependent shear effect that quickly levels off and remains relatively constant after 30 minutes in a "Waring" mixer. These initial time-dependent effects are believed to be a consequence of dispersion of collapsed or aggregated parenchymal cell walls/membranes. Dispersion of small amounts of vascular, fiber-like cellulose components is also assumed to take place if such are present in the solution.

Although examination before and after homogenization under a light microscope shows no clear systematic change in the size of the dispersed membrane fraction for some preparations, the size of the smaller, fiber-like component in the case of PCC appears to be significantly reduced - possibly to a more elementary level. Better liquid loss control for the homogenized raw press cake compared to the bleached and classified

The higher PCC-BC is probably the result of a wider particle size distribution and the presence of smaller amounts of HC-S.

An alternative to using high speed mixers for dispersing PCC is to use annular high pressure homogenizers in the process. Colloid mills are also useful,

but not as effective as impact valve devices in the process. An alkaline converted pulp, SAP, with 5.0% w/v total non-volatile solids content, uncorrected for inorganic ash content was homogenized in the untreated state and diluted three times or homogenized after a threefold dilution.

The pH of the diluted homogenized suspension was 6.0 and the concentration of particulate solids after dilution was

0.75% weight/volume.

The homogenizer used was a "Gaulin model 15M"

and the colloid mill was a "Gaulin 2F". A feed pressure of 2.81 kp/cm<2> was used at the homogenizer and a gravity feed was used for the colloid mill. The viscosity was measured at 23°C with a "Brookfield model LVF" viscometer at 60 rpm. with a No. 2 spindle using a 20 second reading. The results are summarized in table 8.

A single pass through the homogenizer at relatively low pressures (211 to 352 kp/cm<2>) is sufficient to generate a stable dispersion of hydrated forms of PCC. Further passes at high pressure (562 kp/cm<2>) do not change the rheology of the homogenized PCC. In-line homogenization has been found to be useful in rehydrating spray slurries of PCC-BC, although two or more passes may be required to fully restore the optimal functionality of the homogenous slurry.

EXAMPLE 6

The dependence of the liquid stasis regulation _ and rheology on the prr-k«- mantras ion

A concentrated PCC suspension prepared from a press cake acid-converted beet pulp was incubated overnight at pH 11.0 and 80°C. Several dilute PCC suspensions were then prepared, these varied in concentration from 0.5 to 2.0% w/v; The pH of the suspensions was adjusted to 7.8. The concentration of non-volatile organic solids is not corrected for inorganic ash content. Homogenization was achieved using a "Waring" mixer at high speed for several minutes. The viscosities were measured at 20°C with a "Brookfield viscometer model LVF" using spindle no. 2 at 60 rpm. The viscosities

are specified as time-independent limit values. Data for fluid loss at low pressure were also recorded.

In the range from 0.5 to 1.5% weight/volume, the viscosity of well-dispersed PCC preparations varies approximately linearly with the concentration of particulate matter. PCC tends to

form zero gels at solids concentrations above 2.0% weight/volume. The deviation from a linear solid/viscosity relationship that begins in this area is probably a consequence of non-linear particle/particle interaction. The filtration rates are relatively independent of the concentrations below 1% weight/volume and seem to increase at higher concentrations for the pressures of 7.03 kp/cm<2> that are used.

EXAMPLE 7

The effect of the HC-S concentration on the filtration regulation for PCC

A 30% w/w HC was diluted to 5% w/v and adjusted to 0.1N in NaOH. The solution was partially saponified by reaction overnight at 75°C. On cooling, a sticky loose gel had formed which could easily be stirred out and poured. A sufficient amount of the 5% gel was added to a PCC suspension prepared from an alkaline converted pulp containing no HC or HC-S to form a dispersed mixture of 1% w/v PCC (the non-volatile cellulose content is not corrected

for inorganic ash content) with three different HC-S concentrations. The slurries were then homogenized by mixing at high speed in a "Waring" mixer for several minutes. The resulting PCC dispersion was slightly alkaline and had a pH

of 7.8. The viscosity was measured using a "Brookfield model LVF" viscometer with spindle No. 3 at 60 rpm and 23°C. The procedure for the examination of fluid tapsis regulation was the standard A.P.I. method. The results are summarized in table 10.

The saponified HC-S appears to have an important synergistic effect on liquid loss control for PCC, as it approximately halves the filtration rate for a 1% PCC dispersion at an equivalent solids concentration. Further improvement is observed by increasing the HC-S/PCC ratio. The ratio of 1.5 is approximately equal to the distribution between soluble and particulate matter resulting from alkaline conversion of beet pulp at high temperatures. These results suggest that a homogeneous HC/PCC product (SAP) resulting from thermomechanical treatment at high pH of beet pulp, as described e.g. in Example 8 of U.S. Patent No. 4,629,575, may be particularly useful as a fluid for both rheology and fluid loss control for drilling fluids. In contrast to an HC-S that is saponified at high temperature, the saponified HC-S used in this example seems to partially contribute to the viscosity.

EXAMPLE 8

Rheological effect of alkali converted beet pulp in saline solution or water as a drilling fluid mixture

An alkaline converted beet pulp (SAP) was prepared as in Example

8 of US Patent No. 4,629,575 by reaction between the mass at 163°C and 0.2N NaOH for 57 seconds. The resulting mass contained approx.

40% particulate material and 60% soluble bulk solids.

The pH of the converted pulp slurry was 11.8 and it appears to be indefinitely stable when stored at room temperature in this condition. The following experiments were carried out using a 1% w/v particulate PCC suspension containing 1.5% w/v

weight of saponified hemicellulose form HC-S and the other stated ingredients. The PCC/HC-S suspensions containing 5 drops of antifoam agent (Calgon CL-371) were mixed for 5 minutes in a "Waring" mixer at high speed, cooled to room temperature, and degassed by vacuum suction prior to instrumental examination. The results of the series of basic experiments designed to

confirm its suitability for use as a proposed drilling fluid is re-

given in Table 11. A "Fann model 35" viscometer was used for the viscosity measurements and the "Baroid, model 301" filtration equipment was used for liquid loss control measurements.

The data suggest good compatibility with solids present in drilling muds and common fluid loss control agents.

Table 12 shows data from an identical series of surveys

performed in saturated NaCl solution. It is noteworthy that the results suggest that both the viscosity and filtration regulation of homogenized SAP appear to be improved in saturated saline solutions. As with freshwater dispersions, the addition of representative solids from drilling mud at low concentrations improved filtration regulation, except for CaCO2. As expected, bentonite was less effective, and starch unaffected by the salt water solution.

EXAMPLE 9

Rheological properties and filtration regulation in saturated salt solution of alkali converted pulp, SAP

The alkali-converted mass, SAP, described in the previous example 8 was used and a corresponding experimental setup was used. Table 13 reproduces the basic series of drilling fluid experiments, in this example in saturated NaCl where the concentration of SAP was varied. The weight ratio of SAP is expressed based on a particulate PCC basis. The material also contains approx. 1.5 times the PCC content of HC-S solids. While the rheological properties systematically deteriorate with increasing content of solids in the alkaline mass, the filtration control is improved. An optimum point appears to be reached in the vicinity of 0.75% w/w based on the content of particulate PCC. These mixtures, especially those containing representative solid drilling fluid components, are expected to perform very well as drilling fluids.

3

EXAMPLE 10

Synergistic fluid loss regulation by PCC. and low viscosity CMC

in fresh water

The particulate fraction from an acid-converted beet pulp was bleached and mechanically divided to obtain a PCC

BC preparation that did not contain HC. PCC-BC alone, CMC alone

and a PCC-BC/CMC mixture was homogenized for 5 minutes in a "Waring" mixer at high speed, cooled to room temperature and degassed by vacuum suction. One drop of antifoam agent was added per 100 ml of homogenized suspension to facilitate degassing. The pH of the homogenized suspension was regulated to approx. 11. Table 14 reproduces the results of a basic series of experiments with respect to rheology and filtration control for these samples. Neither PCC nor CMC^v alone provide adequate regulation of fluid loss. The combination shows significant synergistic improvement; however, there is an increase in viscosity that exceeds the additive effect that was expected. Corresponding synergistic results were observed for the PCC and HC-S combinations in the previous example 7.

EXAMPLE 11

The effects of saturated NaCl solution and other additives on the rheology and filtration properties of a homogenized alkali-converted beet pulp

Different mixtures of an alkali-converted beet pulp (SAP)

and various substances from drilling mud, filtration control additives and calcium salts were prepared in the following manner.

About. 3 drops of an antifoam agent were added per 600 ml of the SAP suspensions containing 1% w/v PCC and 1.7% w/v saponified HC-S (the stated solids content is not corrected for inorganic ash content). The mixtures were mixed at high speed in a "Waring" mixer for 5 minutes, the pH was adjusted to 11.0, and the resulting homogeneous suspensions were mixed for an additional 10 minutes. The homogenized preparations were aged at 20°C for 16 hours, at which time they were degassed by vacuum suction and the pH was, if necessary, again adjusted to 11.0. All pH readings in saline were corrected for Na<+->concentration effects on the glass electrode of the pH meter.

Table 15 compares the rheology and liquid loss profiles for different additives in a fresh water liquid. Corresponding data in a saturated salt water solution is reproduced in table 16.

The results from the 16 hour aging tests suggest that the dissolution rheology of the different homogenized SAP samples,

with few exceptions, is relatively insensitive to a high concentration of dissolved NaCl. The slight increase in viscosity compared to the control sample observed for certain particulate additives is probably due to inherent salt effects on the particulate substances used. This effect can contribute in an additive way to the overall rheology of the mixture. The filtration regulation improves in saline, with the exception of the "Grundite" mixture where the rate showed a slight increase. Differences in liquid loss ranging from 5 to 15 mL are thought, in a first approximation, to be due to the relative efficiency of small particles in bridging or polymer interaction with the primary film of PCC/HC-S at the filtration surface.

EXAMPLE 12

Static aging at 93°C of polymeric drilling fluids based on alkali- or acid-converted beet pulp with a low solids content

An alkali-converted beet pulp concentrate (SAP) was prepared by the high-temperature reaction at high pH of rehydrated beet pulp pellets generally according to US Patent No. 4,629,575. The preparation contained 1.9% w/v cellulosic material in particulate form and approx. 3.2% w/v non-volatile, soluble material which is mainly hemicellulosic solid. The entered in-

keep non-volatile/ , solids not corrected for inorganic ash content. The SAP was diluted with water or saturated NaCl solution so that an uncorrected concentration of particulate cellulose of 1% w/v was obtained. After adding other additives and enough NaCl to saturate the solution,

i, the pH was adjusted to either 9.0 or 11.0 and the mixture was mixed for 15 minutes at high speed in a "Waring" mixer. pH became,

if necessary, again regulated and the homogenized suspension was placed in a stainless steel container for static incubation at 93°C for 16 hours. The cylinders were not degassed and contained an unfilled volume approximately equal to the volume of the liquid contents. After incubation, the contents were cooled, mixed at low speed for 2-5 minutes to disperse any clumped material, the pH was, if necessary, adjusted and the homogenized suspension was degassed by vacuum suction.

Table 17 summarizes the rheology and the liquid loss profiles.

A similar method was used to examine acid-converted pulp prepared according to example 1 in US Patent No. 4,629,575. The effect of various polymers believed to be more temperature stable than the beet pulp endogenous hemicellulose was investigated.

PSS, PVS, PA, PVA represent low to medium viscosity versions of sodium polystyrene sulphate, sodium polyvinyl sulphonate, sodium polyacrylate and polyvinyl alcohol respectively. CMC

is a low viscosity carboxymethyl cellulose. None of the above-mentioned polymer preparations alone show significant regulation of liquid loss or viscosity at the indicated concentrations.

"Grundit" was used as an example of solids in drill bits in an amount of 1% weight/volume. "Grundit" alone shows little, if any, filtration regulation. Tables 18 and 19 summarize the results.

As can be seen from table 17, alkali-converted beet pulp can form the basis for drilling fluids with a low solids content that work well in fresh water or saturated salt solutions. Fluid loss regulation is markedly improved by including typical solids from drilling mud, which is an endogenous component of drilling fluids. At the high pH range of 10-11, the hemi-celluloses slowly break down at 93°C and the filtration regulation decreases accordingly. At pH 9 and below, however, the decomposition is significantly reduced and the alkali-converted mass can probably be used with satisfactory results as a base liquid at temperatures up to 107°C to 120°C.

Tables 18 and 19 show that a number of anionic polymers interact synergistically with PCC so that filtration regulation is improved. These polymers are less affected by temperature and can be used as an additive to an alkali-converted pulp, SAP-based system when used at temperatures exceeding approx. 120°C. The liquids with the addition of synthetic polymers are limited by the inherent thermal stability of the added polymers, which lies in the range from 149°C to 177°C for the systems used in this example. Inclusion of solids from drilling mud also improves fluid tap regulation. Each of the aforementioned polymers appears to act synergistically with PCC in improving the properties that are desirable in drilling fluids.

EXAMPLE 13

High temperature drilling fluid mixture based on PCC

Homogenized PCC from an acid-converted presscake containing high-temperature additives to control liquid loss was prepared by high-speed homogenization in a "Waring" mixer for 15 minutes. To the homogenized suspensions was added

4 drops of antifoam agent per 600 ml; The pH was adjusted to 9.0

after cooling to room temperature. 600 ml samples were statically incubated at 149°C for 16 hours in stainless steel cylinders having a volume ratio between empty space and liquid filled space of 1. No attempt was made to degas or remove oxygen. The lignite used was a commercial ground down API grade AMPS is a high molecular weight homopolymer of 2-acrylamido-2-methyl propanesulfonic acid available through Lubrizol Corp., Cleveland, Ohio. "Miltemp" is a trademarked, sulfonated polystyrene copolymer product of the Milchem Company, Houston, Texas.

After incubation, the contents of the bombs were cooled to room temperature, the pH was adjusted to 9.0 and the mixtures were mixed for 5 minutes with 2 drops of antifoam. Rheology and fluid loss regulation were determined as described in the previous examples. The results are reproduced in table 20.

The results show that PCC has good compatibility with lignite

AMPS and "Miltemp" at 149°C. E.g. it is believed that lignite can regulate the filtration and the PCC rheology. In the case of AMPS, the polymer adds to the rheology and provides a synergistic filtration control effect. AMPS alone shows no fluid loss regulation. "Miltemp" acts synergistically with PCC to regulate the liquid loss, but is not believed to contribute to the rheology of the mixture.

EXAMPLE 14

Potassium-inhibited drilling fluids based on alkali-converted pulp with a low solids content

An alkali-converted beet pulp (SAP) liquid was prepared containing 1.0% w/v particulate PCC and 1.8% w/v

volume of saponified 'HC-S solid (the concentration of non-volatile solids is not corrected for inorganic ash content). The preparation was homogenized on a "Manton-Gaulin Model 15" homogenizer at 211 kg/cm<2> (first stage) to an "ann-limit viscosity" at 600 rpm. The homogenized suspension was diluted 1:1 with tap water, the specified ingredients were added (typical drilling mud solids and KC1) and the mixture was further homogenized in a "Waring" mixer for 5 minutes. 5 drops of antifoam agent were used per 600 ml of homogenized suspension to control foaming. After mixing in the mixer, the homogenized suspensions were degassed by vacuum suction and the pH was adjusted to 9.0. The rheology and liquid loss properties were determined as indicated in the previous examples. Static aging of the preparations at room temperature for 24 hours had no apparent effect on the properties except that the control of the A.P.I. liquid loss was somewhat improved for the mixture, which contained “Rev Dust.” Table 21 summarizes the results.

The Fann rheology profile is insensitive to 3% w/v KC1. The intrinsic filtration regulation, believed to be provided by the interaction between the PCC film and HC-S, appears to be only slightly affected by KC1. Addition of representative Boré solids greatly increases the regulation of liquid loss, as observed in previous examples for saturated salt solutions. It is believed that the suspended sludges provide a sufficient amount of small particles so that a part of the colloidal clays plug the voids in the PCC-based film. HC-S is believed to interact with these clays so that the fluid permeability across the composite film is further reduced.

EXAMPLE 15

HC-prepared bentonite in salt water

Dispersed freshwater preparations of bentonite clay undergo flocculation and later aggregation in the presence of increasing salt concentrations. Flocculation increases gel strength and greatly reduces liquid loss regulation, while aggregation reduces both gel strength and liquid loss regulation. The time and concentration dependence of bentonite-based drilling fluids in saltwater solutions makes regulation of the rheology difficult. Certain polymers, such as e.g. polyanionic celluloses and CMC have been found to improve the fluid loss control characteristic of aggregated clays. Furthermore, these polymers are, in some cases, believed to reduce the interactions that lead to aggregation of both flocculated and dispersed clays. It has now been discovered that the hemicellulose derived from converted sugar beet pulp in an alkaline environment acts in a manner similar to CMC and gives bentonite clays in salt water or saline solutions beneficial properties.

A pre-hydrated freshwater bentonite was prepared by aging 100 g of bentonite in 3.5 L of tap water overnight (28.57 g/L or 2.85% w/v). The pre-hydrated bentonite mixture was divided into 5 equal portions of 700 ml and the specified amounts of CMClv or HC were added. The HC used in this experiment was derived from an acid-converted beet pulp and was concentrated up to 30% solids weight/weight (the concentration of non-volatile solids is not corrected for ash content). When isolated from an acid-converted pulp, the pectin component is highly acetylated on the secondary hydroxyl functionality of the pyranose moiety and the uronic acid exists mainly as the methyl ester. The mixtures were allowed to stand at room temperature for 3 hours at a base

pH of 8-11 so that the HC was saponified. After the saponification reaction had essentially ended, as evidenced by a stable pH reading, 35 g of NaCl was added to each of the portions and the slurry was well mixed. The mixtures were statically aged at room temperature for 24 hours and the Fann rheology and fluid loss properties were determined. Table 22 summarizes the results.

HC-S improves the gel strength and filtration control properties of saline bentonite suspensions in a manner similar to CMC. The improvement in fluid loss caused by HC-S shows a semi-logarithmic concentration dependence and, by extrapolation to the results for CMClv, HC appears to be approx. 20% more effective than CMC-^v under the conditions of this experiment on a unit weight basis in the untreated state.

EXAMPLE 16

Application of PCC to suspend ballast agents in high density drilling, completion or overhaul fluids

Medium density liquids were prepared by mixing various amounts of a crude acid-converted pulp press cake with a commercial A.P.I. grade debarite and water or saturated NaCl. The PCC concentrations are expressed as a percentage of the total content of solid, cellulosic materials based on the original liquid volume or weight before addition is discontinued. The volumetric change after barite addition was approx. 40%. The PCC concentrations used varied from 0.75% to 1.5% w/v. The mixture was homogenized in a "Waring" mixer at high speed for 6 minutes, poured into a covered 600 ml "Griffin" beaker and allowed to stand

at room temperature for 4 days. The compositions are given in table 23 which also gives results.

A weak concentration dependence is suggested, but 1% w/v

PCC gives a final suspended volume of barite layer of approx. 83% of the total volume of the homogenized suspension. This is in contrast to the weight packed barite control sample without PCC where the bed volume was only 33% of the total volume. There is apparently no difference between saline- or fresh-water-based suspensions. Homogeneous solutions of PCC-expanded barite showed no evidence of a significant sedimentation gradient or compactor bed. Apparently, the layer of suspended barite contracts in a homogeneous manner until the compressive forces between the particles of the particulate suspension agent are balanced by the gravitational forces on the particles of the ballast agent. The relative error of + 10% that appears at

dispersion in the measured densities is assumed to be caused by volumetric perturbations due to air inclusions in the homogeneous suspensions. Normally, the salt water solutions should be approx. 10% denser than water, but due to a tendency to foam and entrap air, they had approximately the same density as the water-based system. In the case of the control sample where no air was trapped, the density difference was as expected.

A high density ballasted liquid was prepared by mixing to homogeneity 175 ml of a specified homogenized PCC and 332 g of a commercial hematite preparation in a "Brookfield Model L587" mixer. The mixtures contained 3 drops of antifoam agent.

Equal portions of the mixed suspension were placed

in graduated cylinders to the 100 ml mark and covered to prevent evaporation loss during long periods of standing. The ratio between the height and the diameter of the volume of the mixture in the cylinder was approx. 14. The expected density of the hematite mixture was 2.10 kg/l. However, the observed density was somewhat lower, indicating the inclusion of smaller amounts of air. The percentage contraction of the layer is calculated from the amount of standing water above the expanded layer containing the ballast. layers seem to stabilize after standing for 24 hours at room temperature. A clear PCC concentration dependence appears from the results in table 24. The influence of the container geometry, the density of the ballast and the concentration of ballast particles make a quantitative comparison with the barite example difficult. However, the results are qualitatively similar to the results from the barite example; the composition with 1% w/w PCC gives good suspension in high weight systems.

To demonstrate the thermal stability of the suspension, the experiment with 2.04 kg/l hematite was repeated with 1% and 2% w/v PCC, and statically aged at 149°C for 16 hours. The aged suspensions were homogenized for 5 minutes in a "Waring" mixer at high speed and a portion of 100 ml was poured into a 100 ml graduated cylinder for sedimentation. The layer volumes were observed and recorded over a period of 2 weeks. The results are con-

summarized in Table 25. The results indicate that there is very little change in the suspension properties of PCC after it has been exposed to high temperature for 16 hours.

Addition of small amounts of attapulgitite sepiolite typically 1 more

2% w/v, to a homogenized PCC suspension improves the suspension properties of the membrane preparation. This is assumed to

is due to the needle-shaped mineral particles forming bridges between the membranes. This can produce a non-compressible structural component

to the particulate membrane matrix containing the high density ballasts in suspension.

in

EXAMPLE 17

01je- in- water PCC emulsions with low solids content

A 1% PCC w/v (non-volatile cellulosic solids content not corrected for inorganic ash content) homogeneous aqueous suspension of an acid-converted crude press cake was prepared to contain 3% "Rev Dust"

as drilling mud solids. The pH was adjusted to 11.3. A 10% v/v oil-in-water emulsion of the homogenized PCC was prepared by adding 44 mL of diesel oil to a 400 mL portion of the homogenous solution containing 5 drops of a common liquid soap concentrate (linear alkylbenzene sulfonate)

and mixing at high speed in a "Waring" mixer for 5 minutes. The control sample consisted of homogenized PCC without liquid soap

and diesel oil. Both samples were degassed by vacuum extraction. The results of a basic series of drilling mud tests are presented in Table 26. The rheology and fluid loss control profiles were obtained as previously described.

The oil-in-water PCC-based emulsion was stable and showed no observable segregation upon standing for 2 months. The results show that an oil emulsion with a low solids content

and reasonably good filtration regulation can be obtained from homogenized PCC. In contrast to clay-based systems, this liquid should be able to be used in high-temperature environments due to the excellent temperature stable rheology of PCC.

EXAMPLE 18

The effect of chromium lignosulfonate and ferrochromium lignosulfonate on the fluid loss properties of a homogeneous PCC

A 1% w/v PCC pulp (particulate cellulose not corrected for inorganic ash content) was prepared from the press cake of an acid-converted beet pulp by mixing for 15 minutes at high speed in a "Waring" mixer. The pulp was cooled to room temperature and a suitable amount of "Rev Dust" and a commercial grade of either chromium lignosulfonate (CLS) or ferrochromium lignosulfonate (FLS) was added so that the sample became 1% w/v with respect to drilling solids and 1% or 3% w/w /volume with respect to the desired lignosulfonates. The slurries were homogenized for 5 minutes, antifoam added, cooled to room temperature and pH adjusted to 9.0. Each sample was statically aged at 93°C for 16 hours. After cooling to room temperature, each slurry was again briefly mixed and the pH was again adjusted to 9.0. Table 27 shows the results obtained by applying the standard A.P.I. the press for filtration regulation at low pressure and the Fann rheology profile.

PCC does not interact to a significant extent with lignosulfonates so that the rheology changes. The regulation of liquid loss is improved, however, this varies directly with increasing concentrations of lignosulfonates in the concentration range where they are usually used to control the deposition of solids.

EXAMPLE 19

Production of PCC from citrus pulp

PCC and related materials can also be obtained from other vegeta-

automotive material in addition to sugar beet. I.e. that citrus

pulps, Jerusalem artichoke pulps, and many other processed plant residues containing a high proportion of parenchymal material can serve as a source for PCC. Most of these also include useful hemicellulose fractions. A particularly promising source for PCC is citrus. PCC derived from citrus also appears to

could be useful in the production of drill-completion

and overhaul fluids for oil and gas production.

23 kg of a commercial raw material grade of pelletized grapefruit pulp was hydrated with 10% w/w pulp solids. Sufficient 50% w/w NaOH was added to make the slurry 0.1N NaOH with an initial pH of 12.1. The viscous slurry was passed through the tubular reactor apparatus described in US Patent No. 4,629,575 at 165°C. The slurry was pumped at such a rate that it had a 50 second residence time. The linear surface velocity at the outlet opening was approx. 1,000 cm/sec. The product was cooled and the distribution of non-volatile solids obtained by separation and purification through a nylon cloth with a mesh size of 0.074 mm was respectively 38% retained particulate material and 62% soluble/colloidal material.

The pH of the press juice was adjusted to 4.5 with HC1 and two

cial pectinases, "Klerzyme L-100" and "Pectinol 60B", were added to the cloudy brown solution, each in an amount of 1% v/v. After several hours of centrifugation, the solution was centrifuged and analyzed using HPLC as in ex. 6. Smaller, and approximately equal, molar amounts of D-glucose and D-fructose were found in the supernatant, but not D-galacturonic acid. The glucose and fructose are presumably due to hydrolysis of endogenous sucrose. The pectates appear to be flocculated, colloidal precipitates resulting from lime treatment of the pulp before drying.

Any low molecular weight uronic acids generated during the hydrolytic enzyme treatment are co-flocculated and sediment during the centrifugation. Useful hemicelluloses in soluble form cannot be easily isolated from citrus pulps that have been treated with lime.

The alkali-converted pulp residue was cleaned and divided by jet spraying against a sieve with a mesh size of 0.149 mm on a collector consisting of a sieve with a mesh size of 0.074 mm. Unlike PCC obtained from sugar beet which almost completely passes through a 0.149 mm mesh sieve, the dimensions of the PCC particles derived from grapefruit pulp are somewhat larger, 76* being retained on a 0.149 mm mesh sieve and 24* remaining on the collector which consists of a sieve with a mesh size of 0.074 mm. The recovered PCC can be easily bleached to a white cellulose pulp using conditions similar to those described in Examples 2-4. The bleached and split PCC from citrus appears to be very similar to the PCC obtained from beet pulp in terms of its rheology of low solids homogeneous suspensions and its film-forming properties. Light microscopy investigations, however, show a considerably greater heterogeneity in the membrane size than observed for beet PCC.

EXAMPLE 20

Relative temperature stability of PCC produced from beet and citrus pulp

Bleached and classified samples of PCC prepared according to examples 2-5 in US patent no. 4,629,575 and the preceding example 19 from respectively beet and citrus pulps, were suspended in water and homogenized at high speed in a "Waring" mixer for 15 minutes. The citrus pulp had a content of particulate PCC of 1.5* weight/volume and the beet pulp had a content of particulate PCC of 0.8* weight/volume, none of the figures are corrected for inorganic ash content. The pH was adjusted to 9.0 for the beet PCC samples and to 10.0 for the citrus PCC samples. The samples were placed in stainless steel incubation cells under high temperature and high pressure and were degassed in situ by repeated vacuum aspiration and nitrogen purging. The cells were pressurized to 7.0 kp/cm<2> with nitrogen, sealed, and subjected to static incubation at the indicated temperature for 16 hours. After incubation, the contents of the cells were cooled and examined. Standard A.P.I. rheology profiles were recorded using a "Fann model 35" viscometer. The results are reproduced in Table 28. 10 minute gel strengths are identical to 10 second gel strengths.

The samples were gradually degraded when the temperature was raised above 160°C. Both PCC preparations behave similarly in that they are very stable at temperatures up to approx. 160°C, and then they appear to undergo an irreversible thermal transformation between 160°C and 190°C, here they lose 50 to 70% of their viscosity in 16 hours measured at 600 rpm. in the Fann viscometer. The improved thermal stability of the PCC in this example compared to example 1 is believed to be due to the fact that the material in this case was not in a highly oxidizing atmosphere.

EXAMPLE 21

Synergistic interaction between saponified citrus pectin and

PCC from citrus pulp

A 2% w/w solution of a commercial grade of citrus pectin was saponified by heating to 65°C with the addition of sufficient alkali to maintain a pH greater than 10 during the ester hydrolysis. The resulting polygalacturonic acid = PG- solution was used to prepare a 1% w/v suspension of the bleached and split PCC prepared from grapefruit pulp as in Example 19, which contained 0.5% w/v PG. The suspension was homogenized for 15 minutes at high speed in a "Waring" mixer, cooled to room temperature and the pH was adjusted to 10. The rheology and filtration control profiles compared to PCC alone are reproduced in Table 29.

These results show that PG acts synergistically with PCC to

to improve filtration regulation and increase viscosity. This suggests that homogeneous suspensions of alkali-converted citrus pulps containing PG derived from endogenous pectin can provide dissolution properties desirable in a base system for a drilling fluid. The masses that would be of greatest interest are those that have not been subjected to liming or other flocculation processes with polyvalent cations that are usually used to facilitate water separation and drying.

EXAMPLE 22

Synergistic interaction between anionic polymers and

PCC derived from citrus pulp

A 1% w/v homogeneous suspension of a bleached and split PCC derived from grapefruit pulp was prepared by a single pass of the suspension through a two-stage "Gaulin Model 15" homogenizer at 352 kp/cm 2 . Various polymers were then added to the base stock and the pH was, if necessary, adjusted to 10.0. Rheology profiles were recorded using the "Fann Model 35" viscometer, and liquid loss control was determined using standard A.P.I. the experiment at low pressure. The results are summarized in table 30.

These results demonstrate a high degree of synergistic interaction between certain anionic polymers and PCC derived from citrus pulp. Both CMC and AMPS improve viscosity, gel strength and filtration regulation. CMC is, for this purpose, an exceptionally effective additive at relatively low concentrations.

EXAMPLE 23

Preparation of citrus pulp suspensions useful in oil-

and gas production/extraction

Wet citrus pulp from Valencia oranges that contained fibers,

peel and stones were led away from the pulp line in a commercial citrus juice factory before lime addition. About. 50 kg of the pulp was mixed and chopped up in a modified food waste disposal unit to give 114 L of a pale yellow slurry. Concentrated NaOH (50% w/w) was added to the slurry

in an amount of 10.6 ml/l. The slurry turned deep orange and had a pH of 11.5.

The alkaline citrus pulp was saponified in a tubular reactor

at 165°C according to US patent no. 4,629,575 by using a residence path in the reactor of approx. 80 seconds. The slurry was released to atmospheric pressure through an outlet opening with a diameter of 0.64 cm, this gives a linear surface velocity of 350 cm/sec. Upon cooling to room temperature, the effluent slurry from the reactor had a pH of 9.0 and formed a thick, gel-like mass.

The saponified mass was diluted to three times the volume, mixed and sieved through a 0.084 mm mesh sieve to remove* minor amounts of fiber-like particles prior to homogenization. The resulting slurry was homogenized at low pressure in a "Gaulin Model 15" homogenizer to give a thick, amber-colored concentrate with a plastic viscosity of 28 cp and a yield strength of 3.03 kg/m<2>. The 30 minute A.P.I. filtrate was 12.5 ml using the standard low pressure static test.

The above alkali-converted pulp suspension was further diluted 1.5 times to obtain a content of non-

volatile solids of 0.8% organic particulate matter (PCC) and 0.8% organic soluble matter (HC-S), both correct-

made for ash content. The pulp was saturated with NaCl by adding 34 g of NaCl per 100 g pulp. The masses were mixed in a "Waring" mixer at high speed for 5 minutes and cooled to room temperature.

raw ride before examination. The effect of starch and CMC on the rheology and filtration regulation before and after static aging for 17 hours at 93°C is reproduced in Table 31.

Claims (3)

1. Well circulating fluid, a non-circulating fluid or a drilling fluid for use in drilling wells, in particular oil and gas wells, where the fluid is a suspension or an emulsion comprising a polymer which is soluble in the fluid and, optionally, one or more of the following components, a hemicellulose, a clay and a ballast agent, characterized in that it further contains parenchymal cell cellulose. 2. Liquid according to claim 1, characterized in that the parenchymal cell cellulose is mechanically finely divided, parenchymal plant material selected from the group consisting of acid-converted, parenchymal material and alkali-converted, parenchymal material. 3. Liquid according to claim 1, characterized in that the parenchymal cell cellulose is derived by alkaline saponification of cellulose material, such as sugar beet or citrus pulp.