WO2022189654A1 - Cellulose microfibrillée pour améliorer les procédés de forage et de gravillonnage - Google Patents

Cellulose microfibrillée pour améliorer les procédés de forage et de gravillonnage Download PDF

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WO2022189654A1
WO2022189654A1 PCT/EP2022/056388 EP2022056388W WO2022189654A1 WO 2022189654 A1 WO2022189654 A1 WO 2022189654A1 EP 2022056388 W EP2022056388 W EP 2022056388W WO 2022189654 A1 WO2022189654 A1 WO 2022189654A1
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mfc
cellulose
fluid
fibrils
use according
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PCT/EP2022/056388
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Hans Henrik ØVREBØ
Otto Soidinsalo
Li Jiang
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Borregaard As
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/50—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls
    • C09K8/504—Compositions based on water or polar solvents
    • C09K8/506—Compositions based on water or polar solvents containing organic compounds
    • C09K8/508—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
    • C09K8/514—Compositions based on water or polar solvents containing organic compounds macromolecular compounds of natural origin, e.g. polysaccharides, cellulose
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/03—Specific additives for general use in well-drilling compositions
    • C09K8/035—Organic additives
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/50—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls
    • C09K8/516—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls characterised by their form or by the form of their components, e.g. encapsulated material
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B33/00—Sealing or packing boreholes or wells
    • E21B33/10—Sealing or packing boreholes or wells in the borehole
    • E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
    • E21B33/138—Plastering the borehole wall; Injecting into the formation
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/02—Subsoil filtering
    • E21B43/04—Gravelling of wells
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
    • C09K2208/08—Fiber-containing well treatment fluids
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
    • C09K2208/12—Swell inhibition, i.e. using additives to drilling or well treatment fluids for inhibiting clay or shale swelling or disintegrating
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
    • C09K2208/28—Friction or drag reducing additives

Definitions

  • the present invention relates to microfibrillated cellulose (MFC) for improving drilling and gravel packing processes.
  • MFC microfibrillated cellulose
  • Oil and gas hydrocarbons are naturally occurring in subterranean formations.
  • Subterranean formations containing such oil and gas hydrocarbons which are usually referred to as “reservoir”, can be located under land or offshore at very different depths, ranging from a few hundreds of feet (shallow reservoirs) to a few tens of thousands of feet (deep or ultra-deep reservoirs).
  • one or more wellbores a “wellbore” is herein also referred to as “borehole” are usually drilled into or adjacent to the reservoir.
  • drilling of earth formations typically employs a rotary drilling apparatus including a drill string and a drill bit attached thereto.
  • a drilling fluid also referred to as “drilling mud”
  • drilling mud is usually circulated through the drill string and drill bit into the wellbore and returned to the surface through the annulus surrounding the drill string.
  • Drilling fluids play a crucial role in drilling operations and fulfil a series of essential functions. For example, drilling fluids reduce the heat buildup in the drilling apparatus and cool, lubricate, and clean the drill bit. Further, drilling fluids are used for borehole cleaning by suspending the cuttings and transporting them from beneath the drill bit all the way up to the surface and out of the wellbore. Ideally, the drilling fluid suspends the cuttings even when the drilling operation stops and thereby prevents any settlement of solid particles. Thus, it is generally desired that drilling fluids provide for a stable cuttings suspension, ideally even when the drilling operation stops.
  • drilling fluids stabilize the borehole by exerting hydrostatic pressure on the formation surrounding the borehole.
  • drilling fluids should be carefully designed by selecting the appropriate additives to meet the requirements of the drilled formations and downhole conditions and to maintain the required properties of the drilling fluids. Those properties include density, viscosity, gel strength, filtration, pH, and other necessary rheological properties.
  • drilling fluids usually contain clays and/or other dispersed solids which are employed to impart desired rheological properties to the drilling fluids.
  • these clays and/or other suspended solids impart desirable thixotropic properties to the drilling fluid, they also serve to coat the walls of the well with a thin and relatively impermeable sheath, commonly referred to as “filter cake”, which retards the flow of fluid from the borehole into the surrounding subterranean formations.
  • a drilling fluid For stabilizing the borehole, a drilling fluid is usually designed in a way that it exerts a hydrostatic pressure that (slightly) exceeds the pressure of the surrounding formation.
  • a drilling fluid may contain one or more weighting agents which function to increase the density of the drilling fluid to a level which will offset high formation pressures encountered at different depth during the drilling operation.
  • suitable weighting agents include heavy minerals such as barite.
  • one particular problem commonly encountered during wellbore drilling operations is the occurrence of fluid loss, worse lost circulation, in which a part or all of the drilling fluid is not returned to the surface.
  • This problem may manifest itself anywhere from moderate losses of the drilling fluid, which results in consequences including unnecessary materials cost and more severely inability to continue the drilling project, to substantial or even total losses of the drilling fluid such that little or none of the drilling fluid is returned to the surface.
  • a formation zone is identified in which unacceptably large amounts of drilling fluid is lost, such formation zone is commonly termed a “thief zone”, “loss zone” or a “loss circulation zone.” While there are many causes for fluid loss and/or lost circulation, non-limiting examples include those situations where the well encounters a formation of unusually high permeability or one which has naturally occurring horizontal or vertical fractures or fissures. Also, the formation may be fractured accidentally by the hydrostatic pressure exerted by the drilling fluid, particularly when a change over to a relatively heavy and/or viscous fluid is made in order to control high formation pressures.
  • fluid loss control is to substantially reduce the permeability of the matrix of the surrounding formation with a fluid loss control material (also referred to as “fluid loss additive” or “fluid loss control additive”) that blocks the permeability at or near the face of the rock matrix of the formation.
  • a fluid loss control material also referred to as “fluid loss additive” or “fluid loss control additive”
  • the fluid loss control material may be a particulate that has a size selected to bridge and plug the pore throats of the formation material. All else being equal, the higher the concentration of the appropriately sized particulate, the faster bridging will occur.
  • the fluid loss control material bridges the pore throats of the formation material and builds up on the surface of the borehole or fracture face or penetrates only a little into the matrix.
  • the buildup of solid particulate or other fluid loss control material on the walls of a wellbore or a fracture is referred to as a “filter cake”.
  • a filter cake may help block the further loss of a fluid phase (referred to as a filtrate) into the subterranean formation.
  • a fluid loss control material is specifically designed to lower the volume of a filtrate that passes through a filter medium.
  • fluid loss control additives are usually added to drilling fluids to minimize the invasion of fluid filtrate and solid particles and reduce the formation damage. Further, fluid loss control additives generally enhance filter cake buildup on the face of the formation to inhibit fluid flow into the formation from the wellbore. Fluid loss control additives can include, for example, a filter cake forming material, a filter cake bridging material, and a lost circulation material to block larger openings in the formation. These and other materials are known in the art as fluid-loss control additives.
  • fluid loss control additives include synthetic polymeric thickening agents such as partially hydrolyzed polyacrylamide, polyelectrolytes such as an ionic polysaccharide, various gums such as locust bean gum and guar gum, various starches, and carboxymethyl cellulose (CMC), carboxyethyl cellulose (CEC) hydroxyethyl cellulose (HEC), hydroxypropyl guar, hydroxyethyl guar.
  • synthetic polymeric thickening agents such as partially hydrolyzed polyacrylamide, polyelectrolytes such as an ionic polysaccharide, various gums such as locust bean gum and guar gum, various starches, and carboxymethyl cellulose (CMC), carboxyethyl cellulose (CEC) hydroxyethyl cellulose (HEC), hydroxypropyl guar, hydroxyethyl guar.
  • drilling fluids are effective for many applications, they have limited capability and may not be suitable for some current (as well as some future) drilling operations due to the increased and still increasing challenging conditions in terms of geological and operational restrictions.
  • Many of the conventional micro and/or macro particle-based drilling fluids have limited functional capabilities due to size effect, plus low area-to-volume ratios and lack of fluid retention features are difficult to manipulate to prepare tailor-made particles with custom-made properties, predominant role of physical and gravitational forces in the particle behavior and have a lack of quantum effect due to trivial boundary effects.
  • gravel packing where gravel is typically packed between a sand screen and the formation to act as a kind of filter to reduce the amount of formation sand reaching the screen and the wellbore.
  • the gravel particles are usually larger than the formation sand particles but small enough so that the voids between the gravel particles are too small for the formation sand particles to pass through them.
  • a number of different gravel packing techniques have been developed and usually involve mixing gravel with a carrier fluid (also referred to as “gravel packing fluid”), and pumping the slurry down the wellbore and into the annulus between a screen and the wellbore.
  • the gravel is deposited in the annulus around the screen where it becomes tightly packed, forming a “gravel pack”.
  • Proper selection of the gravel packing fluid is essential to a gravel packing process.
  • the gravel packing fluid shall not cause any permeability reduction of the formation.
  • the gravel packing fluid must also have sufficient viscosity to suspend and carry the gravel during placement.
  • microfibrillated cellulose MFC
  • the present invention relates to the use of microfibrillated cellulose (MFC) for controlling fluid loss and/or stabilizing cuttings suspension in a wellbore drilling process.
  • the present invention relates to a method for controlling fluid loss and/or stabilizing cuttings suspension during a wellbore drilling process.
  • the present invention relates to the use of microfibrillated cellulose (MFC) for carrying, placing, and circulating gravel packing materials in a gravel packing fluid during a gravel packing process.
  • MFC microfibrillated cellulose
  • the present invention relates to a gravel packing fluid comprising microfibrillated cellulose (MFC).
  • MFC microfibrillated cellulose
  • the present invention relates to a gravel packing process.
  • the microfibrillated cellulose is characterized in that it results in gel-like dispersion that has a zero shear viscosity, h 0 , of at least 2000 Pa*s, preferably of at least 3000 Pa*s or 4000 Pa*s, further preferably of at least 5000 Pa*s, further preferably at least 6000 Pa*s, further preferably at least 7000 Pa*s, as measured in polyethylene glycol (PEG)/water as the solvent (65% PEG and 35% water), and as measured at a solids content of the MFC of 0.65%, wherein the measurement method is as described below.
  • PEG polyethylene glycol
  • the zero shear viscosity, h 0 ⁇ “viscosity at rest’) is a measure for the stability of the three-dimensional network making up the gel-like dispersion. Without wishing to be bound by theory, it is believed that a high zero shear viscosity is of particular advantage for stabilizing suspensions used in wellbore drilling processes.
  • the microfibrillated cellulose has a water holding capacity (water retention capacity) of more than 30, preferably more than 40, preferably more than 50, preferably more than 60, preferably more than 70, preferably more than 75, preferably more than 80, preferably more than 90, further preferably more than 100.
  • the water holding capacity describes the ability of the MFC to retain water within the MFC structure and this again relates to the accessible surface area. The water holding capacity is measured as described below.
  • DP degree of polymerization
  • Figure 1a shows a microscopy image (magnification: 40 x) of MFC as obtained in accordance with a process using a Microfluidics homogenizer (0.17% of MFC, by weight, in water).
  • Figure 1b shows MFC as shown in Figure 1a, but now at a magnification of 100 x.
  • Figure 2a shows an optical microscopy image of “bifurcated” MFC as described herein and as described in WO 2015/180844 (magnification 40x, 0.17% by weight of MFC in water), wherein the MFC was obtained according to Example 1 of WO 2015/180844.
  • Figure 2b shows a microscopy picture of “bifurcated” MFC as described herein and as described in WO 2015/180844 at a higher magnification (100 x) (same MFC concentration as in Figure 2a).
  • Figure 3 shows shear rate sweeps of 0.50 wt% fluid systems in water at 70 °F (MFC, HEC, xanthan gum, CMC, guar gum). Shear rate sweeps were performed from 0.1 to 100 s 1 followed by reverse scan.
  • Figure 4 shows comparison of shear rate viscosities of MFC in propylene glycol versus water at 70 °F. Shear rate sweeps were performed starting at 100 s 1 and decreasing to 0.1 s 1 .
  • Figure 5 shows static dispersion tests at 150 °F for comparison to room temperature tests. Tests also used 1.0 wt% MFC dispersed in water or 100,000 mg/L TDS brine. Under temperature, the dispersions stably supported 0.5 ppg of 20/40 sintered bauxite proppant over 48 hours.
  • the present invention is at least partly based on the surprising finding that MFC as described herein is a highly efficient drilling fluid additive for controlling fluid loss and stabilizing cutting suspension in a wellbore drilling process as well as a highly efficient gravel packing fluid additive for carrying, placing, and circulating gravel packing materials in a gravel packing process.
  • MFC as described herein is a highly efficient drilling fluid additive for controlling fluid loss and stabilizing cutting suspension in a wellbore drilling process as well as a highly efficient gravel packing fluid additive for carrying, placing, and circulating gravel packing materials in a gravel packing process.
  • the rheological properties of MFC in particular the extremely shear thinning properties of MFC, lead to an excellent control of fluid loss, stabilization of cuttings suspension, as well as propensity of carrying, placing, and circulating gravel packing materials.
  • drilling fluid refers to a fluid that is circulated into a wellbore, usually through the inside of a drill string and through a drill bit, and up to the surface through the annulus between the drill string and the wellbore to facilitate the drilling operation.
  • Drilling fluids can be any of a number of liquid and gaseous fluids and mixtures of fluids and solids (as solid suspensions, mixtures and emulsions of liquids, gases and solids) used in operations to drill well bores into the earth.
  • the drilling fluid of the present invention is a liquid drilling fluid.
  • (Liquid) drilling fluids usually comprise a base fluid and different additives, e.g. solids and are mainly classified into three categories: water, oil, and gas base, based on the nature of the base fluid. The first two categories are predominant in common operations.
  • a “drill-in fluid” is a special type of drilling fluid designed for drilling through the reservoir section of a wellbore.
  • drilling fluid includes drill-in fluids.
  • the drilling fluid is a drill-in fluid.
  • MFC Microfibrillated cellulose
  • Microfibrillated cellulose (also known as “reticulated” cellulose or as “superfine” cellulose, or as “cellulose nanofibrils”, among others) is a cellulose-based product and is described, for example, in US 4481 077, US 4 374 702 and US 4341 807. According to US 4 374 702 (“Turbak"), microfibrillated cellulose has distinct properties vis- a-vis cellulose products not subjected to the mechanical treatment disclosed in US 4 374 702. In particular, the microfibrillated cellulose described in these documents has reduced length scales (diameter, fiber length), improved water retention and adjustable viscoelastic properties. MFC with further improved properties and/or properties tailor-made for specific applications is known, among others, from WO 2007/091942 and WO 2015/180844.
  • cellulose which is the starting product for producing microfibrillated cellulose within the meaning of the present application (typically present as a "cellulose pulp'), no, or at least not a significant or not even a noticeable portion of individualized and "separated” cellulose "fibrils” can be found.
  • the cellulose in wood fibres is an aggregation of fibrils.
  • pulp elementary fibrils are aggregated into microfibrils which are further aggregated into larger fibril bundles and finally into cellulosic fibres.
  • the diameter of wood-based fibres is typically in the range of 10-50 pm (with the length of these fibres being even greater).
  • cellulose fibres are microfibrillated
  • a heterogeneous mixture of “released” fibrils with cross-sectional dimensions and lengths from nm to pm may result. Fibrils and bundles of fibrils may co-exist in the resulting microfibrillated cellulose.
  • Fibril is to be understood as relating to (aggregates of) cellulose molecules/fibrils with cross-sectional dimensions (diameters) from 2 nm to 1 pm, including both individual fibrils and fibril bundles. Fibril bundles or aggregates exceeding 1 pm in diameter are considered as ‘residual fibre fragments’ throughout the present disclosure.
  • the fibrils of the MFC preferably have a diameter in the nanometer range and a length in the pm range.
  • the diameter of the MFC fibrils making up the MFC is in the range from 1 nm to 1000 nm, preferably, and on average, from 10 nm to 500 nm.
  • a comparatively small portion of larger (“residual”) cellulose fibers may still be present in the MFC product and may therefore coexist with the microfibrillated fibrils or fibril bundles.
  • microfibrillated cellulose As described throughout the present disclosure, individual fibrils or fibril bundles can be found and easily discerned by way of conventional optical microscopy, at a magnification of 40 x (see Figure 1 , showing “conventional” MFC as obtained from a Microfluidics homogenizer). These fibrils and bundles of fibrils are also described as "(micro)fibrils”. In accordance with the present invention, any reference to “fibrils” also includes bundles of such fibrils.
  • the magnification of 40 x was chosen to have a reasonable number of fibrils in the given area of the image to be counted, at the given concentration of the MFC-material.
  • individual fibrils or fibril bundles or fibre fragments with cross sectional diameter larger than approximately 200 nm can be studied. Fibrils with cross-sectional diameter below this range cannot be fully resolved or seen, but will be present, coexisting with the fibrils or fibril bundles that can be resolved by optical microscopy as described herein.
  • any type of microfibrillated cellulose can be used in accordance with the present invention, as long as the fiber bundles as present in the original cellulose pulp are sufficiently disintegrated in the process of making MFC so that the average diameter of the resulting fibers/fibrils is in the nanometer-range and therefore more surface of the overall cellulose-based material has been created, vis-a-vis the surface available in the original cellulose material and so that the water retention and/or viscosity are sufficient to stabilize suspensions used in wellbore drilling processes.
  • MFC microfibrillated cellulose
  • the raw material for the cellulose microfibrils may be any cellulosic material, in particular wood, annual plants, cotton, flax, straw, ramie, bagasse (from sugar cane), suitable algae, jute, sugar beet, citrus fruits, waste from the food processing industry or energy crops or cellulose of bacterial origin or from animal origin, e.g. from tunicates.
  • wood-based materials are used as raw materials, either hardwood or softwood or both (in mixtures). Further preferably softwood is used as a raw material, either one kind or mixtures of different soft wood types.
  • the microfibrillated cellulose in accordance with the present invention is characterized, among others, by at least one of the following properties:
  • the microfibrillated cellulose is characterized in that it results in gel-like dispersion that has a zero shear viscosity, h 0 , of at least 2000 Pa*s, preferably of at least 3000 Pa*s or 4000 Pa*s, further preferably of at least 5000 Pa*s, further preferably at least 6000 Pa*s, further preferably at least 7000 Pa*s, as measured in polyethylene glycol (PEG)/water as the solvent (65% PEG and 35% water), and as measured at a solids content of the MFC of 0.65%, wherein the measurement method is as described below
  • the zero shear viscosity, h 0 (“ viscosity at rest’) is a measure for the stability of the three-dimensional network making up the gel-like dispersion. Without wishing to be bound by theory, it is believed that a high zero shear viscosity is of particular advantage for stabilizing suspensions used in wellbore drilling processes.
  • the "zero shear viscosity" as disclosed and claimed herein is measured as described in the following. Specifically, the rheological characterization of the MFC dispersions is performed with PEG 400 as the solvent. “PEG 400” is a polyethylene glycol with a molecular weight between 380 and 420 g/mol and is widely used in pharmaceutical applications and therefore commonly known and available.
  • the rheological properties in particular zero shear viscosity is measured on a rheometer of the type Anton Paar Physica MCR 301.
  • the temperature in all measurements is 25 °C and a "plate-plate" geometry is used (diameter: 50mm).
  • the rheological measurement is performed as an oscillating measurement (amplitude sweep at a frequency of 1 Hz) to evaluate the degree of structure in the dispersions and as rotational viscosity measurements, in which case the viscosity is measured as a function of the shear rate to evaluate the viscosity at rest (shear forces ® 0), as well as the shear thinning properties of the dispersions.
  • the measurement method is further described in PCT/EP2015/001103 (EP 3 149241).
  • the microfibrillated cellulose has a water holding capacity (water retention capacity) of more than 30, preferably more than 40, preferably more than 50, preferably more than 60, preferably more than 70, preferably more than 75, preferably more than 80, preferably more than 90, further preferably more than 100.
  • the water holding capacity describes the ability of the MFC to retain water within the MFC structure and this again relates to the accessible surface area.
  • the water holding capacity is measured by diluting the MFC samples to a 0.3% solids content in water and then centrifuging the samples at 1000 G for 15 minutes. The Clearwater phase was separated from the sediment and the sediment was weighed.
  • DP degree of polymerization
  • microfibrillated cellulose in accordance with the present invention may be unmodified in respect to its functional groups or may be physically modified or chemically modified, or both.
  • Chemical modification of the surface of the cellulose microfibrils may be achieved by various possible reactions of the surface functional groups of the cellulose microfibrils and, more particularly, of the hydroxyl functional groups, preferably by: oxidation, carboxylation, carboxymethylation, silylation reactions, etherification reactions, condensations with isocyanates, alkoxylation reactions with alkylene oxides, or condensation or substitution reactions with glycidyl derivatives.
  • Chemical modification may take place before or after the defibrillation step, preferably after the defibrillation step since the functional groups to be modified (in particular -OH groups) are sterically better available after defibrillation.
  • the MFC is unmodified MFC or is physically modified MFC, preferably unmodified MFC. Also preferably, the MFC does not comprise a lignin coating.
  • “Unmodified MFC”, as referred to herein, relates to MFC that comprises only “naturally occurring functional groups”.
  • naturally occurring functional groups refers to functional groups that are already present (or, more precisely, have already been present) when the cellulose is present in the cellulosic material from which the MFC is derived (e.g. wood, annual plants, cotton, flax, straw, ramie, bagasse (from sugar cane), suitable algae, jute, sugar beet, citrus fruits, and so on) and to functional groups that are introduced (or, more precisely, have been introduced) by means of a pulping process such as sulfite pulping or Kraft pulping.
  • the MFC is derived from a pulping process and subsequent defibrillation and has not been subjected to a post-pulping chemical functionalization step.
  • a “post-pulping chemical functionalization step” is a dedicated step of treating MFC obtained from a pulping process with another reagent in a chemical reaction such that the MFC functional groups that are present before said chemical reaction (mostly -OH groups) are converted into different functional groups.
  • the term “dedicated” in the expression “dedicated step of treating MFC” means that the step of treating MFC is a deliberate step that is performed with the aim of modifying the functional groups.
  • the “post-pulping chemical functionalization step” (which has preferably not been applied to the MFC of the present invention) is an oxidation reaction, a carboxylation reaction, a carboxymethylation reaction, a reaction of adding cationic functional groups, and a reaction of grafting a second polymer onto the MFC.
  • the MFC has not been subjected to a (dedicated) oxidation reaction, a carboxylation reaction, a carboxymethylation reaction, a reaction of adding cationic functional groups, and a reaction of grafting a second polymer onto the MFC.
  • the MFC has not been subjected to a chemical functionalization step after the defibrillation step.
  • That “chemical functionalization step” is a dedicated step of treating the MFC (after the defibrillation step) with another reagent in a chemical reaction such that the MFC functional groups that are present before said chemical reaction (mostly -OH groups) are converted into different functional groups.
  • the MFC has not been subjected to an oxidation reaction, a carboxylation reaction, a carboxymethylation reaction, a reaction of adding cationic functional groups, and a reaction of grafting a second polymer onto the MFC, before and/or after the defibrillation step.
  • the cellulose microfibrils may, in principle, also be modified by a physical route, either by adsorption at the surface, or by spraying, or by coating, or by encapsulation of the microfibril.
  • Preferred modified microfibrils can be obtained by physical adsorption of at least one compound.
  • the MFC may also be modified by association with an amphiphilic compound (surfactant).
  • surfactant amphiphilic compound
  • the microfibrillated cellulose is not physically modified.
  • MFC is a highly efficient thickener in solvent systems, in particular water systems, and builds large three dimensional networks of fibrils which are stabilized by hydrogen bonds.
  • the fibrils of MFC have hydroxyl groups on the surface that are fully dissociated (to form hydroxyl ions, O ), at a high pH and cause intra and inter-particular interactions, stabilizing the overall network (stabilizing by “chemical” and/or “physical” interactions).
  • MFC has high water holding capacity.
  • the MFC is prepared or obtainable by a process, which comprises at least the following steps:
  • step (b) subjecting the mechanically pretreated cellulose pulp of step (a) to a defibrillation step, which results in fibrils and fibril bundles of reduced length and diameter vis-a-vis the cellulose fibers present in the mechanically pretreated cellulose pulp of step (a), said step (b) resulting in m i crofi bri 11 ated cellulose; wherein the defibrillation step (b) involves compressing the cellulose pulp from step (a) and subjecting the cellulose pulp to a pressure drop.
  • the mechanical pretreatment step preferably is or comprises a refining step.
  • the purpose of the mechanical pretreatment is to "beat" the cellulose pulp in order to increase the accessibility of the cell walls, i.e. to increase the surface area.
  • a refiner that is preferably used in the mechanical pretreatment step comprises at least one rotating disk. Therein, the cellulose pulp slurry is subjected to shear forces between the at least one rotating disk and at least one stationary disk.
  • step (b) which is to be conducted after the (mechanical) pretreatment step, the cellulose pulp slurry from step (a) is passed through a homogenizer at least once, preferably at least two times, as described, for example, in PCT/EP2015/001103, the respective content of which is hereby incorporated by reference.
  • the homogenizer may be a Microfluidics homogenizer.
  • the cellulose fiber suspension is subjected to a pressure differential by passing through Z- and/or Y-shaped channels, which are arranged within a chamber.
  • the cellulose fiber suspension is typically passed through at least two Z- and/or Y-shaped channels with various diameters that are connected in series, firstly, typically one Z- or Y- shaped channel with a large diameter (for example 400 pm) and secondly, one Z- or Y- shaped channel with a small diameter (for example 100-200 pm) to avoid clogging of the smaller channels.
  • the defibrillation of the cellulose fibers to fibrils and/or fibril bundles is achieved because of the pressure differential due to the small diameter in the channels and the turbulence created within the channels.
  • MFC obtained by using a Microfluidics type of homogenizer generally leads to MFC of comparatively low water retention and/or zero shear viscosity and also generally shows no or very little bifurcation of fibril ends.
  • “Bifurcation” of fibril ends should be understood as the pattern at the end of a main fibril with brush like appearance of smaller fibrils being partly released at one or two of the end points of a main fibril, but still being attached to the main core fibril. Both ‘main’ fibrils and their ‘brush-like’ end bifurcations are easily discernible in the optical microscopy pictures of Figures 2a and 2b, both showing “bifurcated MFC”, which is one kind of MFC preferably used in the present invention (see below).
  • the MFC comprises fibril bundles and/or individual fibers, wherein at least a fraction of the fibril bundles and/or individual fibrils of the MFC has bifurcations on at least one end of the main fibrils into secondary fibrils, preferably bifurcations into three or more secondary fibrils, further preferably bifurcations into four or five or more secondary fibrils, wherein said secondary fibrils have a smaller diameter than the non-bifurcated main fibril.
  • a significant part of the fibrils or fibril bundles of the MFC does not terminate in an end point, but the “main” fibril rather bifurcates at this end point, at least once, preferably two or more times, further preferably three or more times, further preferably five or more times into secondary fibril segments of a smaller diameter than the "main" fibril.
  • the number of said bifurcated ends of fibrils/fibril bundles is at least 60 bifurcated ends of fibrils per mm 2 , as measured in accordance with the optical light microscopy method as described herein, at a magnification of 40 times, preferably at least 80 bifurcated ends of fibrils per mm 2 , further preferably at least 100 bifurcated ends of fibrils per mm 2 .
  • the ratio of the number of bifurcated ends of fibrils / fibril bundles of the MFC relative to the number of bifurcated ends of fibrils / fibril bundles of a reference MFC, that has been homogenized in a conventional Microfluidics homogenizer, as described herein, is at least 5, preferably at least 10, further preferably at least 15, wherein the number of bifurcated ends of fibrils / fibril bundles is measured in accordance with the optical light microscopy method as described herein, at a magnification of 40 times.
  • the conventional fluidizer/homogenizer as used as a reference is of the type "Microfluidizer M-110EH" as offered by Microfluidics Corp. and as commonly known in the field.
  • An example of a homogenizing process utilizing a microfluidizer is described, for example, in application WO 2007/091942.
  • microscopy method used herein is as follows:
  • the MFC is diluted in water as the solvent, at a solids content of 0.17%.
  • a droplet of this sample is put on a microscopy slide and an optical microscopy image of the individual fibrils, fibril bundles in solution is taken, at a magnification of 40 x.
  • a field of view of 0.14 mm 2 is chosen. Then, the number of bifurcations into two or more smaller fibril segments at at least one of their respective endpoint(s) is counted. A fibril is counted as one fibril showing such a bifurcation if a bifurcation is found at one end or at both ends.
  • the MFC samples were dispersed at a solids content of 0.17% in water and viewed in an Olympus BX51 microscope by using phase contrast and magnifications ranging from 10 to 200 times. For counting and comparison purposes, a magnification of 40x was used.
  • For each of the MFC samples two individual samples with a 0.17% solid content of MFC in water were prepared, and from each of these, 2-4 samples were prepared for imaging by placing a droplet on a microscope slide with size 1.5 (0.17mm thick) glass cover slip. The samples were studied by an Olympus BX51 microscope at 40x magnification with phase contrast.
  • the magnification of 40x was chosen to have a reasonable amount of fibrils/fibril bundles in the given area to be counted (see further details in regard to the evaluation of the number of “brushes” as discussed below). Using this magnification, the whiplash/brush like end structures are well visible and it is possible to also count the ⁇ 10 micron fibrils/fibril bundles, wherein the 10 micron refers to the length of the fibrils/fibril bundles.
  • the location of the images taken on the sample (drop of MFC dispersion in water on a microscope slide) was chosen randomly, providing images representing a reasonably large amount of fibrils, and up to eight images are taken for each sample preparation.
  • the MFC of comparatively high water retention and/or comparatively high zero shear viscosity as described above may be prepared by a process that comprises the following steps:
  • step (b) subjecting the mechanically pretreated cellulose pulp of step (a) to a homogenizing step, which results in fibrils and fibril bundles of reduced length and diameter vis-a-vis the cellulose fibers present in the mechanically pretreated cellulose pulp of step (a), said step (b) resulting in m i crofi bri 11 ated cellulose; characterized in that the homogenizing step (b) involves compressing the cellulose pulp from step (a) and subjecting the cellulose pulp to a pressure drop, by expanding the cellulose through at least one orifice, providing said pressure drop between a volume segment, preferably a chamber, that is located upstream of said orifice, and another volume segment, preferably a chamber, that is located downstream of said orifice, area, wherein said pressure drop is at least 1000 bar, preferably more than 2000 bar, preferably more than 2500 bar, further preferably more than 3000 bar, and wherein the cellulose fibrils are subjected to a turbulent flow regime in said volume segment, preferably a chamber
  • the MFC used in the present invention is prepared by said process.
  • said process does not comprise a step of chemically functionalizing the MFC, preferably does not comprise a step of oxidation, carboxylation, carboxymethylation, adding cationic functional groups, and grafting a second polymer onto the MFC.
  • a homogenizer suitable for preparing the “bifurcated MFC” comprises the following components:
  • At least one volume segment preferably at least one chamber, which is located downstream of the orifice, in which the microfibrillated cellulose is subjected to a turbulent flow regime, wherein said homogenizer is suitable to subject a cellulose slurry to a pressure drop between the volume segment located upstream of said orifice, and the other volume segment located downstream of said orifice, wherein said pressure drop is at least 1000 bar, preferably more than 2000 bar, preferably more than 2500 bar, further preferably more than 3000 bar.
  • a commercially available high water retention / high zero shear viscosity MFC as described in WO 2015/180844 is MFC available under the trade designation Exilva ® from Borregaard and is one example of MFC of improved water retention and viscosity that is particularly suitable for the uses in accordance with the present invention. Exilva is “unmodified” MFC within the meaning of the present application.
  • microfibri Hated cellulose of particularly high water retention capability and/or zero shear viscosity such as the MFC as described herein and in WO 2015/180844 is particularly useful for controlling fluid loss and stabilizing cuttings suspension in a wellbore drilling process as well as for carrying, placing, and circulating gravel packing materials in a gravel packing fluid during a gravel packing process.
  • high water retention or high viscosity MFC such as “bifurcated MFC” is advantageous over “usual” MFC as for example prepared in a conventional Microfluidics homogenizer.
  • MFC that provides increased stability to three-dimensional networks of fibrils, for example due to a "brush"-like bifurcated end structure of the fibrils or fibril bundles, allows to enclose more water and thus improves the water holding capacity of the resulting suspension, and also increasing the viscosity at rest.
  • the bifurcated/brush like end structures in the MFC of this invention contribute to 'nest' the fibrils, fibril bundles and aggregates more tightly together, and to build a more rigid and stable three-dimensional network measured as the improved rheological properties and the increased zero shear viscosity in particular, compared to conventional MFC.
  • a tight three-dimensional network of the MFC as obtained according to processes described herein may entrap or bind water more strongly within the aggregates, leading to an increased surface area and a higher amount of reactive OH-groups being exposed to water through the more structured ends of the fibrils.
  • the present invention relates to the use of microfibrillated cellulose (MFC) for controlling fluid loss and/or stabilizing cuttings suspension in a wellbore drilling process.
  • MFC microfibrillated cellulose
  • the MFC is as set out above, and preferably is “bifurcated MFC” as described above and as described in WO 2015/180844.
  • the MFC is comprised in a composition comprising said MFC and a solvent, wherein the MFC is preferably comprised in the composition in an amount of 1.0 to 20 wt%, preferably 2.0 to 10 wt.%, based on the total weight of the composition.
  • the solvent is preferably selected from the group consisting of water and a hydrocarbon solvent such as an alcohol, preferably a glycol, or a combination thereof.
  • a hydrocarbon solvent such as an alcohol, preferably a glycol, or a combination thereof.
  • the MFC is comprised in a wellbore drilling fluid, which comprises water and one or more components selected from (a) clay such as a bentonite clay, wherein the bentonite clay is preferably added in the form of a prehydrated bentonite slurry,
  • the wellbore drilling fluid comprises at least two of components (a)- (e), preferably at least three of components (a)-(e), more preferably at least four of components (a)-(e), even more preferably each of components (a)-(e).
  • the wellbore drilling fluid comprises water in an amount of 40 to 80 wt.%, based on the total weight of the wellbore drilling fluid, preferably 50 to 70 wt.%, more preferably 60 to 70 wt.%, even more preferably 62 to 68 wt.%. It has been found that this amount of water leads to particularly good results, in particular in combination with “bifurcated MFC” as described herein and in WO 2015/180844.
  • the clay component (a) is present in the wellbore drilling fluid in an amount of 0.5 to 5.0 wt.%, based on the total weight of the wellbore drilling fluid, preferably 0.5 to 4.0 wt.%, more preferably 0.5 to 3.0 wt.%, even more preferably 1.0 to 2.8 wt.%, even more preferably 1.5 to 2.2 wt.%. It has been found that this amount of clay leads to particularly good results, in particular in combination with “bifurcated MFC” as described herein and in WO 2015/180844.
  • the shale stabilizer component (b) is present in the wellbore drilling fluid in an amount of 5.0 to 40.0 wt.%, based on the total weight of the wellbore drilling fluid, preferably 5.0 to 30.0 wt.%, more preferably 10.0 to 30.0 wt.%, even more preferably 20.0 to 30.0 wt.%. It has been found that this amount of shale stabilizer leads to particularly good results, in particular in combination with “bifurcated MFC” as described herein and in WO 2015/180844.
  • the friction-lowering agent (c) is present in the wellbore drilling fluid in an amount of 2.0 to 15.0 wt.%, based on the total weight of the wellbore drilling fluid, preferably 3.0 to 14.0 wt.%, more preferably 4.0 to 13.0 wt.%, even more preferably 5.0 to 12.0 wt.%. It has been found that this amount of friction-lowering agent leads to particularly good results, in particular in combination with “bifurcated MFC” as described herein and in WO 2015/180844.
  • the starch component (e) is present in the wellbore drilling fluid in an amount of 2.0 to 10.0 wt.%, based on the total weight of the wellbore drilling fluid, preferably 3.0 to 9.0 wt.%, more preferably 4.0 to 8.0 wt.%, even more preferably 5.0 to 7.0 wt.%. It has been found that this amount of starch component leads to particularly good results, in particular in combination with “bifurcated MFC” as described herein and in WO 2015/180844.
  • the clay is a bentonite clay and is added to the wellbore drilling fluid in the form of a prehydrated bentonite slurry, wherein the prehydrated bentonite slurry has a bentonite content of 1.0 to 5.0 wt.%, based on the total weight of the bentonite slurry, preferably 1.5 to 4.0 wt.%, more preferably 2.0 to 3.0 wt.%. It has been found that the use of a prehydrated bentonite slurry as a source of clay is particularly useful for readily preparing a stable dispersion.
  • the MFC is present in the wellbore drilling fluid in an amount of 0.05 to 5.0 wt.%, based on the total weight of the wellbore drilling fluid, preferably 0.1 to 4.0 wt.%, more preferably 0.1 to 3.0 wt.%, even more preferably 0.1 to 2.0 wt.%, even more preferably 0.1 to 1.5 wt.%, even more preferably 0.2 to 1.5 wt.%, even more preferably 0.2 to 1.0 wt.%, even more preferably 0.2 to 0.8 wt.%, even more preferably 0.3 to 0.6 wt.%, alternatively 0.05 to 0.6 wt%
  • the wellbore drilling fluid further comprises sodium lignosulfonate and/or lignite, preferably both of sodium lignosulfonate and lignite.
  • fluid loss can be significantly reduced as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC.
  • fluid loss can be reduced by 90% or more.
  • fluid loss is reduced by at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, even more preferably at least 70%, even more preferably at least 80%, even more preferably at least 90%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC. Fluid loss is determined as described in the examples section.
  • the fluid loss volume as determined in a HTHP filtration test as described in the examples section is less than 12 ml_, which is significantly lower than the fluid loss volume of a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC.
  • the wellbore drilling fluid provides for a fluid loss volume of less than 17 ml_, preferably less than 16 ml_, even more preferably less than 15 ml_, even more preferably less than 14 ml_, even more preferably less than 13 ml_, even more preferably less than 12 ml_, after 30 minutes in a HTHP filtration test as described in the examples section.
  • filter cake thickness can be significantly reduced as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC.
  • filter cake thickness can be reduced by more than 50% as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC.
  • the use of the first aspect is preferably characterized in that filter cake thickness is reduced by at least 30%, more preferably at least 40%, more preferably at least 50%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC.
  • Filter cake thickness is determined as set out in the examples section.
  • the wellbore drilling fluid provides for a filter cake thickness of less than 3.5 mm, preferably less than 3.0 mm, more preferably less than 2.5 mm, even more preferably less than 2.0 mm, even more preferably less than 1.8 mm, after 30 minutes in a HTHP filtration test conducted at 200 °F and a back pressure of 100 psi, wherein the HTHP filtration test is carried out as described in the examples section.
  • MFC dispersions based on polar organic solvents other than water may be of interest for drilling muds and other oilfield fluid applications, particularly when sensitivity of a high value formation to water is a critical factor.
  • MFC was found to readily disperse into a polar organic solvent phase using low to moderate mixing shear to create smooth, homogenous dispersion.
  • the abundance of hydroxyl groups in the MFC allow for the complete and uniform mixing of MFC in, for example, propylene glycol (PG) which also contains hydroxyl groups which renders the mixtures fully compatible.
  • PG propylene glycol
  • the present invention also relates to all uses as described herein, in particular the use of MFC for controlling fluid loss and/or stabilizing cutting suspensions in a wellbore drilling process, wherein the microfibrillated cellulose is dispersed in a polar organic solvent.
  • said polar organic solvent includes ethylene glycol, propylene glycol or a mixture thereof.
  • the polar organic solvent includes ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, or any mixture of two or more thereof;
  • water and one or more polar organic solvents are blended in a volume ratio of 1 :9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2 or 9:1.
  • the present invention relates to a method for controlling fluid loss and/or stabilizing cuttings suspension during a wellbore drilling process.
  • the method is characterized in that at least a part of the wellbore is contacted with a wellbore drilling fluid comprising MFC.
  • a wellbore drilling fluid comprising MFC.
  • the method is preferably characterized in that
  • fluid loss is reduced by at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, even more preferably at least 70%, even more preferably at least 80%, even more preferably at least 90%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC, wherein fluid loss is determined as set out in the examples section, and/or
  • filter cake thickness is reduced by at least 30%, more preferably at least 40%, more preferably at least 50%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC, wherein filter cake thickness is determined as set out in the examples section.
  • the present invention relates to the use of microfibrillated cellulose (MFC) for carrying, placing, and circulating gravel packing materials in a gravel packing fluid.
  • MFC microfibrillated cellulose
  • the MFC is as set out above, preferably “bifurcated MFC” as described above and in WO 2015/180844.
  • the MFC is comprised in a gravel packing fluid in an amount of 0.05 to 2.0 wt.%, based on the total weight of the well treatment fluid, preferably 0.25 to 1.75 wt.%, more preferably 0.50 to 1.50 wt.%, even more preferably 0.75 to 1.25 wt.%, alternatively 0.05 to 0.5 wt%.
  • the present invention relates to a gravel packing fluid comprising microfibrillated cellulose (MFC).
  • MFC microfibrillated cellulose
  • the MFC is as set out above, preferably “bifurcated MFC” as described above and in WO 2015/180844.
  • the gravel packing fluid is characterized in enhanced static viscosity, thermal stability and easy to transport feature, of which the bifurcated MFC differentiates itself among commonly used polysaccharides such as xanthan, scleroglucan, diutan, succinoglycan, guar, hydroxyethylcellulose, and modifications, c ellulose based biopolymers such as cellulose acetate (CA), cellulose acetate butyrate (CAB), and cellulose acetate propionate (CAP) derivatives, and combinations thereof.
  • CA cellulose acetate
  • CAB cellulose acetate butyrate
  • CAP cellulose acetate propionate
  • the present invention relates to a gravel packing process.
  • the gravel packing process is characterized in that a gravel packing fluid as defined herein is contacted with at least a part of a wellbore.
  • the MFC is as set out above, preferably “bifurcated MFC” as described above and in WO 2015/180844.
  • MFC microfibrillated cellulose
  • microfibrillated cellulose is characterized in that it results in gel-like dispersion that has a zero shear viscosity, h 0 , of at least 2000 Pa*s, preferably of at least 3000 Pa*s or 4000 Pa*s, further preferably of at least 5000 Pa*s, further preferably at least 6000 Pa*s, further preferably at least 7000 Pa*s, as measured in polyethylene glycol (PEG)/water as the solvent (65% PEG and 35% water), and as measured at a solids content of the MFC of 0.65%, wherein the measurement method is as described in the description.
  • PEG polyethylene glycol
  • microfibrillated cellulose is characterized in that it has a water holding capacity (water retention capacity) of more than 30, preferably more than 40, preferably more than 50, preferably more than 60, preferably more than 70, preferably more than 75, preferably more than 80, preferably more than 90, further preferably more than 100, wherein the water holding capacity is measured as described in the description.
  • water holding capacity water retention capacity
  • the MFC comprises fibril bundles and/or individual fibers, wherein at least a fraction of the fibril bundles and/or individual fibrils of the MFC has bifurcations on at least one end of the main fibrils into secondary fibrils, preferably bifurcations into three or more secondary fibrils, further preferably bifurcations into four or five or more secondary fibrils, wherein said secondary fibrils have a smaller diameter than the non-bifurcated main fibril.
  • step (b) subjecting the mechanically pretreated cellulose pulp of step (a) to a homogenizing step, which results in fibrils and fibril bundles of reduced length and diameter vis-a-vis the cellulose fibers present in the mechanically pretreated cellulose pulp of step (a), said step (b) resulting in microfibrillated cellulose; characterized in that the homogenizing step (b) involves compressing the cellulose pulp from step (a) and subjecting the cellulose pulp to a pressure drop, by expanding the cellulose through at least one orifice, providing said pressure drop between a volume segment, preferably a chamber, that is located upstream of said orifice, and another volume segment, preferably a chamber, that is located downstream of said orifice, area, wherein said pressure drop is at least 1000 bar, preferably more than 2000 bar, preferably more than 2500 bar, further preferably more than 3000 bar, and wherein the cellulose fibrils are subjected to a turbulent flow regime in said volume segment, preferably a chamber, that is located downstream of said
  • At least one volume segment preferably at least one chamber, which is located downstream of the orifice, in which the microfibrillated cellulose is subjected to a turbulent flow regime, wherein said homogenizer is suitable to subject a cellulose slurry to a pressure drop between the volume segment located upstream of said orifice, and the other volume segment located downstream of said orifice, wherein said pressure drop is at least 1000 bar, preferably more than 2000 bar, preferably more than 2500 bar, further preferably more than 3000 bar.
  • the diameter of the MFC fibrils making up the MFC is in the range from 1 nm to 1000 nm, preferably, and on average, from 10 nm to 500 nm. 13. The use according to any one of the preceding embodiments, wherein the MFC does not comprise a lignin coating.
  • the MFC is comprised in a composition comprising the MFC and a solvent, wherein the MFC is comprised in the composition in an amount of 1.0 to 20 wt%, preferably 2.0 to 10 wt.%, based on the total weight of the composition.
  • the solvent is selected from the group consisting of water and a hydrocarbon solvent such as an alcohol, preferably a glycol, or a combination thereof.
  • clay in particular a bentonite clay or smectite, kaolinite, chlorite, illite, wherein the clay is preferably added in the form of a prehydrated slurry,
  • a shale stabilizer in particular potassium chloride, sodium chloride, choline chloride, tetramethylammonium chloride, or partially hydrated polyacrylamide/polyacrylate copolymer,
  • a friction-lowering agent in particular montmorillonite, mica, chlorite, serpentine, or talc,
  • a pH-adjusting agent in particular sodium hydroxide, sodium bicarbonate or sodium carbonate,
  • the wellbore drilling fluid comprises at least two of components (a)-(e), preferably at least three of components (a)-(e), more preferably at least four of components (a)-(e), even more preferably each of components (a)-(e).
  • the wellbore drilling fluid comprises water in an amount of 40 to 80 wt.%, based on the total weight of the wellbore drilling fluid, preferably 50 to 70 wt.%, more preferably 60 to 70 wt.%, even more preferably 62 to 68 wt.%. 19.
  • shale stabilizer component (b) is present in the wellbore drilling fluid in an amount of 5.0 to 40.0 wt.%, based on the total weight of the wellbore drilling fluid, preferably 5.0 to 30.0 wt.%, more preferably 10.0 to 30.0 wt.%, even more preferably 20.0 to 30.0 wt.%.
  • the clay is a bentonite clay and is added to the wellbore drilling fluid in the form of a prehydrated bentonite slurry, wherein the prehydrated bentonite slurry has a bentonite content of 1.0 to 5.0 wt.%, based on the total weight of the bentonite slurry, preferably 1.5 to 4.0 wt.%, more preferably 2.0 to 3.0 wt.%.
  • the wellbore drilling fluid further comprises sodium lignosulfonate and/or lignite, preferably both of sodium lignosulfonate and lignite.
  • the MFC is comprised in a wellbore drilling fluid and:
  • fluid loss is reduced by at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, even more preferably at least 70%, even more preferably at least 80%, even more preferably at least 90%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC, wherein fluid loss is determined as set out in the description, and/or
  • the wellbore drilling fluid provides for a fluid loss volume of less than 17 ml_, preferably less than 16 ml_, even more preferably less than 15 ml_, even more preferably less than 14 ml_, even more preferably less than 13 ml_, even more preferably less than 12 ml_, after 30 minutes in a HTHP filtration test conducted at 200 °F and a back pressure of 100 psi, wherein the HTHP filtration test is carried out as described in the description, and/or
  • filter cake thickness is reduced by at least 30%, more preferably at least 40%, more preferably at least 50%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC, wherein filter cake thickness is determined as set out in the description, and/or
  • the wellbore drilling fluid provides for a filter cake thickness of less than 3.5 mm, preferably less than 3.0 mm, more preferably less than 2.5 mm, even more preferably less than 2.0 mm, even more preferably less than 1.8 mm, after 30 minutes in a HTHP filtration test conducted at 200 °F and a back pressure of 100 psi, wherein the HTHP filtration test is carried out as described in the description.
  • a method for controlling fluid loss and/or stabilizing cuttings suspension during a wellbore drilling process characterized in that at least a part of the wellbore is contacted with a wellbore drilling fluid comprising MFC, wherein the MFC and the wellbore drilling fluid are defined as set out in any one of embodiments 2 to 25.
  • fluid loss is reduced by at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, even more preferably at least 70%, even more preferably at least 80%, even more preferably at least 90%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC, wherein fluid loss is determined as set out in the description, and/or
  • filter cake thickness is reduced by at least 30%, more preferably at least 40%, more preferably at least 50%, as compared to a reference wellbore drilling fluid of identical composition but comprising hydroxyethyl cellulose or polyanionic cellulose instead of MFC, wherein filter cake thickness is determined as set out in the description.
  • MFC microfibri Hated cellulose
  • solvent is selected from the group consisting of water and a hydrocarbon solvent such as an alcohol, preferably a glycol, or a combination thereof.
  • a gravel packing fluid comprising microfibrillated cellulose (MFC).
  • a gravel packing process characterized in that a gravel packing fluid as defined in any one of embodiments 34 to 37 is contacted with at least a part of a wellbore.
  • the polar organic solvent includes ethylene glycol, propylene glycol or a mixture thereof.
  • the polar organic solvent includes ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol methyl ether, diethylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n- butyl ether, or any mixture of two or more thereof;
  • the MFC used in the examples is the commercial product Exilva ® F 01 -V as available from Borregaard A.S. This high water retention and high viscosity MFC was tested against two commonly used cellulose materials, namely:
  • the performance testing of the drilling fluids was conducted in terms of rheology and fluid loss properties.
  • the performance attributes were evaluated in NaCI saturated bentonite mud after ageing overnight.
  • the mud suspensions were prepared in duplicate. One of the suspensions was aged under static conditions and the other one was hot rolled at 200°F overnight.
  • the rheology profile for both samples was determined using a Fann 35 type viscometer and the fluid loss control properties using a Dynamic HTHP Filter Press (available from OFITE, Houston, TX) under 100 psi pressure at room temperature.
  • a prehydrated bentonite was prepared by adding 28.57 g of bentonite (available from SigmaAldrich Co) into 1 liter freshwater and mixed for 4 hours minimum at 1500 rpm. The bentonite was then left to hydrate for 24 hours prior to use. The bentonite suspension was homogenized for 10 minutes prior to use.
  • the drilling fluid was then prepared by mixing, using a Hamilton Beach mixer, 356 g pre-hydrated bentonite, 125 g KCI, 10 g Rev-dust smectite clay (Hydrated Sodium Calcium Aluminosilicate), 2 ml NaOH (10% solution), 4 g Starch and 2 g candidate polymer (active content).
  • the suspension was mixed for a total of 40 minutes. Afterwards, the suspensions were aged as described above.
  • Comparative tests were performed against drilling fluid compositions containing CELLOSIZE QP-3000H (premium quality hydroxyethyl cellulose available from Dow Chemical) and polyanionic cellulose (available from Ashland) as fluid loss additives under the same testing conditions.
  • the formulations for these tests are described in Table 1.
  • prehydrated bentonite slurry serves to lubricate and cool the drilling bits while protecting them from corrosion. Typically, it would take account of 50-70 wt% mass of the entire fluid.
  • Potassium chloride is used as a shale stabilizer which, at a dosage range of 5-30 wt%, helps preserve the integrity of the near wellbore formation.
  • Rev-dust clay is a fine montmorillonite powder used for reducing the pressure induced friction while drilling, normally dosed in the range of 2-15 wt%.
  • Sodium hydroxide is used to modulate the drilling fluid pH in the optimal window and is dosed as needed.
  • Starch is functional as the viscosity modifier and is dosed in the range of 2-10 wt%.
  • HTHP filtration test For each drilling fluid, 450 ml volume was used in the test. The cell was equipped with standard API filter paper backed by ceramic disk. The cell was heated up to 200°F target temperature while being kept under 200 psi pressure against a back pressure of 100 psi. After the cell temperature reached 200°F, the filtration test was conducted over a period of 30 minutes and the filtrate volume was recorded as set out in Table 2: Field trial
  • the vertical well segment at the depth between 315m-1480m, temperature gradient 167-200°F it was typical to exhibit fluid loss up to 30 m3/hr for a heavily fortified KCI-polymer water based drilling fluid, containing prehydrated bentonite (12 Ib/bbl), potassium chloride (50 Ib/bbl), caustic potash (0.5 Ib/bbl), starch (5 Ib/bbl), polyanionic cellulose or hydroxyethyl cellulose (2.0 Ib/bbl), sodium lignosulfonate (5 Ib/bbl) and lignite powder (4 Ib/bbl).
  • prehydrated bentonite (12 Ib/bbl), potassium chloride (50 Ib/bbl), caustic potash (0.5 Ib/bbl), starch (5 Ib/bbl), polyanionic cellulose or hydroxyethyl cellulose (2.0 Ib/bbl), sodium lignosulfonate (5 Ib/bbl) and
  • a total of 250 m 3 drilling mud was prepared according to the above composition except for that the cellulose component was replaced by Exilva.
  • the prepared drilling fluid was circulated for 12 days to keep its homogeneity before it was deployed for the drilling project, with the resultant fluid loss rate under 2 m3/hr which is fully manageable for engineering purposes.
  • Viscosity is a particularly critical indicator of how a fluid behaves under different shear conditions at a given temperature.
  • drilling fluids will have pseudoplastic (shear thinning) as well as thixotropic properties so that the fluid will have a high viscosity at low shear regimes, but then “gets thinner” as higher shear is exerted on the fluid.
  • the shear-thinning feature has several benefits, among them to allow for higher pump rates for better wellbore cleaning with minimal friction pressures and resultant hydraulic horsepower (and associated cost) needed to pump the fluid at the surface.
  • Table 3 show the results of an amplitude sweep test for 0.5 wt% ExilvaTM MFC in water at ambient temperature, compared to the same amount of other cellulose or polysaccharide derivatives including HEC, CMC, guar gum and xanthan gum.
  • the amplitude sweep from 0 to 100% the amplitude of the deformation is varied while the frequency is kept constant, and the storage modulus G' and the loss modulus G" are plotted against the deformation.
  • gelling agents are essentially polymeric materials with complex viscoelastic characteristics. At G7G” ratio of 1 , it indicates an equal contribution by the storage (elastic) and loss (viscous) modulus respectively.
  • MFC distinguishes itself against other common gelling agents by a significantly greater G7G” ratio, exhibiting superior elastic properties that are fundamental to its uniquely strong dispersing capability, as described throughout this invention.
  • G7G G7G
  • 3.5 (vs HEC) and 10.6 (vs CMC) folds increases in the G7G” ratio over two commonly used cellulose analogues demonstrate the distinctive feature of MFC material routed in its un modified chemical nature and aspect ratio ranges.
  • the storage modulus (G’) is dominant over the loss modulus (G”)
  • Dominant G’ characteristics indicate that the MFC dispersions form a stable network of forces which give the fluid structure. These fluids are gel-like (quasi-solid) in nature and are predicted to have favorable dispersion properties for solid particles (considering particle shape, size and density). In addition, the more concentrated the MFC dispersions, the higher the resulting G’ and G” values.
  • the MFC microfibrils form a three-dimensional network of fibrils connected by physical links and entanglements. This network is dispersed throughout the entire dispersion and increases fluid viscosity while stabilizing other entities (e.g., fines, sand, weighting agents, cuttings) enveloped in the MFC network
  • MFC dispersion based in polar organic solvents other than water becomes a subject of interest, particularly when the sensitivity of a high value formation to water is a critical factor.
  • This study compares the rheological properties of MFC dispersion in PG with those in aqueous solution.
  • a 2.0 wt% starting paste of MFC (Exilva F 01 -L) was used to prepare dilutions of 1.0, 0.50, and 0.25 wt% MFC in PG solvent.
  • MFC was found to readily disperse into the solvent phase using low to moderate mixing shear to create smooth, homogenous dispersion.
  • the abundance of hydroxyl groups in the MFC allow for the complete and uniform mixing in PG which also contains hydroxyl groups which render the mixtures fully compatible.
  • the MFC viscosities in PG do not change as dramatically at the highest shear rate intervals (100 s _1 ), particularly at ambient temperature.
  • the aqueous dispersion has a markedly lower viscosity at higher shear (are more shear-thinning).
  • This characteristic implies that the MFC dispersion in PG can be comparatively thicker when the fluid is moving than water-based dispersion.
  • the operational implication is that the MFC formulation in PG may require more energy at the surface to pump than those formulations in water.
  • the rheology of the MFC systems in PG is shown versus that in water at 70 °F in Figure 4.
  • the viscosity of the systems is shown when the shear rate goes from 100 to 0.1 s 1 .
  • the viscosities of the water-based MFC dispersion are clearly less than those in PG solvent when at higher shear.
  • the aqueous based dispersions demonstrate more shear thinning (pseudoplastic) character in this shear regime because the slopes of the water-based curves are steeper.
  • rheological characterization of MFC based in either PG or water shows that both systems create stable and robust dispersion.
  • the PG-based MFC system appears to have better dispersion properties, i.e., comparable G’ at higher MFC loadings and generally higher viscosities.
  • the rheology was performed in step intervals by running at shear rates of 0.1 , 10, 50, and 100 s _1 for 30 seconds per shear rate, the sweeps were ramped from 0.1 to 100 s 1 and then from 100 to 0.1 s 1 , with each ramp set to collect 13 points at 1 second intervals.
  • Amplitude sweeps were conducted at 0.01 to 100% shear strain at 1 .0 Hz. During the duration of the test, 25 points were collected. Frequency sweeps were performed from 0.1 to 100 rad/sec at 0.5% shear strain with 16 points per measurement.
  • High density, high strength sintered bauxite proppant (20/40 mesh, SG 3.56) was used in all static dispersion tests. Dispersions of 1.0 wt% MFC in water or 100,000 mg/L NaCI brine were prepared as previously described and loaded with 0.5 lb m /gallon (ppg) proppant.
  • MFC Microfibrillated cellulose
  • MFC is highly resistant to mechanical shear degradation, compatible with a wide variety of high TDS brines, and thermally stabile at applicable oilfield temperatures. It is chemically stable and has high water absorbency, owing to its natural chemical functionalities (abundant hydroxyl (-OFI) groups) and its physically high surface area per unit mass.
  • the key by which MFC enables stable dispersion is through chain entanglement of the microfibrils and extensive hydrogen bonding. These physical and chemical interactions form a three-dimensional network, adding strength and structure to compositions.
  • the functional correlation of the rheological properties of MFC dispersions with solids dispersion in practice has been demonstrated.
  • a summary of applicable rheological, chemical, and mechanical properties of MFC dispersion include:
  • MFC yields highly stable dispersion by adding structure to fluid compositions.
  • the rheology of MFC dispersion improves transport of cuttings and other debris to the surface during drilling operations.
  • the material also demonstrates favorable solids dispersion at an idle state over extended time periods.

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Abstract

La présente invention concerne l'utilisation de MFC comme additif de fluide de forage pour réguler efficacement la perte de fluide et/ou stabiliser la suspension de déblais pendant un processus de forage de puits de forage. En outre, la présente invention concerne l'utilisation de MFC pour transporter, placer et faire circuler des matériaux de gravillonnage dans un fluide de gravillonnage.
PCT/EP2022/056388 2021-03-12 2022-03-11 Cellulose microfibrillée pour améliorer les procédés de forage et de gravillonnage WO2022189654A1 (fr)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4341807A (en) 1980-10-31 1982-07-27 International Telephone And Telegraph Corporation Food products containing microfibrillated cellulose
US4374702A (en) 1979-12-26 1983-02-22 International Telephone And Telegraph Corporation Microfibrillated cellulose
US4481077A (en) 1983-03-28 1984-11-06 International Telephone And Telegraph Corporation Process for preparing microfibrillated cellulose
WO2007091942A1 (fr) 2006-02-08 2007-08-16 Stfi-Packforsk Ab Procede de fabrication de cellulose microfibrillee
WO2015180844A1 (fr) 2014-05-30 2015-12-03 Borregaard As Cellulose microfibrillée
US20170253786A1 (en) * 2014-12-19 2017-09-07 Halliburton Energy Services, Inc. Additive of chemically-modified cellulose nanofibrils or cellulose nanocrystals
EP3453798A1 (fr) * 2017-09-07 2019-03-13 Borregaard AS Dilution en ligne de cellulose microfibrillée

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4374702A (en) 1979-12-26 1983-02-22 International Telephone And Telegraph Corporation Microfibrillated cellulose
US4341807A (en) 1980-10-31 1982-07-27 International Telephone And Telegraph Corporation Food products containing microfibrillated cellulose
US4481077A (en) 1983-03-28 1984-11-06 International Telephone And Telegraph Corporation Process for preparing microfibrillated cellulose
WO2007091942A1 (fr) 2006-02-08 2007-08-16 Stfi-Packforsk Ab Procede de fabrication de cellulose microfibrillee
WO2015180844A1 (fr) 2014-05-30 2015-12-03 Borregaard As Cellulose microfibrillée
EP3149241A1 (fr) 2014-05-30 2017-04-05 Borregaard AS Cellulose microfibrillée
US20190284762A1 (en) * 2014-05-30 2019-09-19 Borregaard As Microfibrillated cellulose
US20170253786A1 (en) * 2014-12-19 2017-09-07 Halliburton Energy Services, Inc. Additive of chemically-modified cellulose nanofibrils or cellulose nanocrystals
EP3453798A1 (fr) * 2017-09-07 2019-03-13 Borregaard AS Dilution en ligne de cellulose microfibrillée

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