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Collaborating Authors
Seheult, J.M.
Abstract Xanthan gum has been used extensively as a viscosifier in the oil industry for different applications due to its unique rheological properties. In this paper we describe the properties of two previously introduced bio-polymers for use in drilling, drill-in, completions, spacer fluids and coiled tubing applications. The first bio-polymer yields higher viscosities and better temperature stability at lower polymer concentrations than welan and xanthan gum due to its higher molecular weight; this polymer is particularly effective in low salt fluids. The second bio-polymer has improved solubility in high density CaCl2 brines. Viscosity data over a wide shear rate range in different brine systems is presented comparing the new bio-polymers with xanthan and welan gum at temperatures between 75ยฐF to 330ยฐF. The effect of different types of solids and friction pressure tests in coiled tubing are presented, showing diutan's friction reduction properties. Introduction Since its introduction in 1964 xanthan gum has been used extensively in the oil industry as a viscosifier for different applications due to its unique rheological properties. These applications include drilling, drill-in, completions, coiled tubing and fracturing fluids. Similarly, welan gum (introduced in 1985) has been used in drilling fluids and cement spacers, due to its compatibility with oil field cement formulations. Navarrete et al. introduced two new bio-polymers which have improved performance in some of the applications where xanthan and welan gum have been traditionally used. The first polymer is a new bio-fermented polymer produced by a newly isolated naturally-occurring bacterial strain of the Sphingomonas genus. This bio-polymer has been given the generic name of diutan gum. The chemical structure of the monomer is shown in Fig. 1. The tertiary structure is a double-helix. The diutan structure is closer to that of welan gum (Fig. 2) than that of xanthan gum. However, there are important differences. Diutan has an average molecular weight of 5ร10, which is much higher than those of welan and xanthan. This is why the length of the diutan molecule is larger than that of welan or xanthan (Fig. 3). The second polymer is a pyruvate-free variant of xanthan gum, or Non-Pyruvylated Xanthan (NPX) gum, produced from Xanthomonas campestris. The chemical structure of the NPX monomer is shown in Fig. 4. NPX is similar in structure to xanthan gum on all other respects aside from the absence of the pyruvic acid group which reduces anionic character. The unique structures of these two bio-polymers give them different properties in solution. Some of these properties can be advantageous in the design of water-based drilling, drill-in, completions, coiled tubing and spacer fluids. These properties are presented in this paper. Experimental Rheological Measurements. Rheological measurements were performed using a Brookfield PVS viscometer which can measure shear viscosity between 0.05 to 1,000 s, at temperatures up to 350ยฐF and pressures up to 1,000 psi. A pressure of 300 psi was used in all tests. Different geometries can be used with this instrument. The ones used here were the single annulus B1-R1 Couette geometry, and the triple annulus TA5 Couette geometry. Other viscometers used at ambient temperature were the FANN 35 (B1-R1 Couette) and the Brookfield DV-II (wide gap Couette).
Abstract Xanthan gum has been used extensively as a viscosifier in the oil industry for different applications due to its unique rheological properties. In this paper we introduce two bio-polymers for use in drilling, drill-in, completions, spacer fluids and coiled tubing applications. The first bio-polymer yields higher viscosities and better temperature stability at lower polymer concentrations that welan and xanthan gum due to its higher molecular weight; this polymer is particularly effective in low salt fluids. The second bio-polymer has improved solubility in high density CaCl2 brines. Viscosity data over a wide shear rate range is presented comparing the new bio-polymers with xanthan and welan gum at temperatures between 75ยฐF to 300ยฐF. Viscoelastic measurement and settling test are presented to demonstrate the effect of elasticity of the bio-polymers on solids transport and suspension capabilities. Fluid-loss, formation damage tests and friction pressure tests in coiled tubing are also shown. Introduction Since its introduction in 1964 xanthan gum has been used extensively in the oil industry as a viscosifier for different applications due to its unique rheological properties. These applications include drilling, drill-in, completions, coiled tubing and fracturing fluids. Similarly, welan gum (introduced in 1985) has been used in drilling fluids and cement spacers, due to its compatibility with oil field cement formulations. Here two new bio-polymers are introduced which have improved performance in some of the applications where xanthan and welan gum have been traditionally used. The first polymer is a new bio-fermented polymer produced by a newly isolated naturally-occurring bacterial strain of the Sphingomonas genus. This bio-polymer has been given the generic name of diutan gum. The chemical structure of the monomer is shown in Fig. 1. The tertiary structure is a double-helix. The diutan structure is closer to that of welan gum (Fig. 2) than that of xanthan gum. However, there are important differences. Diutan has an average molecular weight of 5ร10, which is much higher than those of welan and xanthan. This is why the length of the diutan molecule is larger than that of welan or xanthan (Fig. 3). The second polymer is a pyruvate-free variant of xanthan gum, or Non-Pyruvylated Xanthan (NPX) gum, produced from Xanthomonas campestris. The chemical structure of the NPX monomer is shown in Fig. 4. NPX is similar in structure to xanthan gum on all other respects aside from the absence of the pyruvic acid group which reduces anionic character. The unique structures of these two bio-polymers give them different properties in solution. Some of these properties can be advantageous in the design of water-based drilling, drill-in, completions, coiled tubing and spacer fluids. These properties are presented in this paper. Experimental Rheological Measurements. Rheological measurements were performed using a Brookfield PVS viscometer which can measure shear viscosity between 0.05 to 1,000 s, at temperatures up to 350ยฐF and pressures up to 1,000 psi. A pressure of 300 psi was used in all tests. Different geometries can be used with this instrument. The ones used here were the single annulus B1-R1 Couette geometry, and the triple annulus TA5 Couette geometry. Other viscometers used at ambient temperature were the FANN 35 (B1-R1 Couette) and the Brookfield DV-II (wide gap Couette). Rheological Measurements. Rheological measurements were performed using a Brookfield PVS viscometer which can measure shear viscosity between 0.05 to 1,000 s, at temperatures up to 350ยฐF and pressures up to 1,000 psi. A pressure of 300 psi was used in all tests. Different geometries can be used with this instrument. The ones used here were the single annulus B1-R1 Couette geometry, and the triple annulus TA5 Couette geometry. Other viscometers used at ambient temperature were the FANN 35 (B1-R1 Couette) and the Brookfield DV-II (wide gap Couette).
- North America > United States > Texas (0.46)
- North America > United States > Oklahoma (0.34)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
Experiments in Fluid Loss and Formation Damage with Xanthan-Based Fluids While Drilling
Navarrete, R.C. (Kelco Oil Field Group of Pharmacia Corporation) | Dearing, H.L. (OGS Laboratory) | Constien, V.G. (Constien & Assoc.) | Marsaglia, K.M. (Westport Technology Center International) | Seheult, J.M. (Kelco Oil Field Group of Pharmacia Corporation) | Rodgers, P.E. (Kelco Oil Field Group of Pharmacia Corporation)
Abstract Formation damage is a concern when attempting to control fluid loss during drilling operations. The usual approach is to use bridging agents and high polymer loadings to reduce fluid loss. However, these additives contribute to formation damage. In this paper we explore the fluid loss characteristics of xanthan-based fluids, including starch and calcium carbonate, during the drilling process. Fluid loss while drilling is a complex process where fluid is lost underneath the bit and through the surface of the wellbore. A unique laboratory scale drilling simulator was used to determine the leakoff and formation damage of xanthan-based drilling fluid formulations. The fluid was circulated as in a conventional drilling operation, through the microbit and up the annulus under overbalanced conditions. Thin section analysis and environmental SEM were performed on rock samples to identify the different components of the fluid system. Sandstones up to 1,000 md were used. Cleanup sequences, which include enzymes and oxidizers, were also evaluated after the cores were drilled. The cleanup efficiencies were compared to conventional QC-testing techniques used by operators for filtercake removal. The results showed that most of the fluid is lost underneath the bit in a continuous spurt condition while drilling. The filtercake formed during drilling does not pose a resistance to flow during production, but poses a strong resistance during leakoff. Xanthan gum contributes to fluid loss reduction, while combinations of CaCO3, starch and xanthan gave the lowest leakoff and formation damage. Wellbore soaking procedures do improve production after drilling. Introduction The issue of formation damage has always been a concern when attempting to control fluid loss during drilling operations. The use of bridging agents and high polymer loadings to reduce fluid loss has been the common approach. However, these additives have the potential to contribute to formation damage. Xanthan gum has been used extensively as a viscosifier in drilling, drill-in and completion fluids because of its unique rheological properties. In this paper we explore the fluid loss characteristics of xanthan-based fluids, including starch and calcium carbonate during the drilling process. Fluid loss while drilling is a complex process where a significant part of the fluid is lost underneath the bit under continuous spurt conditions while drilling. The spurt loss appears to occur where new surface area is being generated, i.e. where the rock is being crushed and removed. During the initial spurt loss, an internal filtercake is formed, which eventually leads to and external filtercake. The composition of the filterake is made up of bridging agents (drill fines, CaCO3, and starch) and viscosifying polymer (xanthan gum, HEC) that covers the porous wellbore. This filtercake is beneficial since it can significantly reduce the fluid loss rate preventing further damage to the wellbore. During the spurt phase, however, fluid enters the formation resulting in potential damage. The depth of the invasion and the reduction in permeability in the invaded zone will determine the skin and overall effect on production. A significant effort has been placed into removing the external filtercake by means of soaking the wellbore with breaker solutions intended for the bio-polymer and the bridging agents. The idea is to dissolve the filtercake to reduce potential damage during production.
- Geology > Geological Subdiscipline (0.46)
- Geology > Rock Type (0.36)
Abstract Xanthan gum has been used extensively in the oil industry as a viscosifier for different applications due to its unique rheological properties. In this paper we explore how the rheological behavior of xanthan-based fluids can be used to control fluid loss. Linear and radial flow tests were performed in 100โ1,00 md rocks. The rheological characteristics of xanthan gum were measured in linear core flow tests. This constitutive flow behavior was used in a radial flow simulator to predict the invasion profile of xanthan gum in the formation. Radial flow tests were performed to validate the predictions from the simulator and to observe the effect of fluid loss additives such as starch and ground Berea. A laboratory scale drilling simulator was used to determine the leakoff and formation damage of xanthan-based drilling fluids. The fluid was circulated through tubing and cuttings were removed from the annulus. Thin section analysis and environmental SEM were performed on rock samples taken at different distances from the wellbore to determine the nature and depth of the damage. Results show that fines generated during the drilling process form an external filter cake which in combination with xanthan gum results in considerable fluid loss reduction. Damage due to xanthan gum is small and limited to a narrow thickness around the wellbore, resulting in negligible skin factors. The use of starch can lead to considerable damage and large skin factors if allowed to invade the formation. Introduction The rate of leakoff is of critical importance during drilling, completion operations (i.e. sand control) and stimulation treatments, such as acid treatments and hydraulic fracturing. In all of these cases, fluid loss control has been achieved by two basic mechanisms: Increasing the overall viscosity of the fluid using high polymer concentrations or by crosslinking the polymer. Developing an internal and/or external filter cake using fluid loss additives (starch, sized CaCO3, mica, silica flour, oil soluble resins, etc.) to plug the pore-throats of the formation. Both fluid loss control mechanisms may result in a loss of permeability when flow is initiated in the production mode. Furthermore, if fluid loss additives are not used properly, they can cause significant loss of permeability due to their plugging mechanism if they enter the formation. Xanthan gum has been used extensively as a viscosifier in the oil field for drilling, drill-in and completion fluids due to its unique rheological properties. In this paper we explore the rheological properties of xanthan-based fluids in Berea sandstone rocks and how these properties can be used to control fluid loss. Prior attempts to simulate the flow of non-Newtonian fluids in porous media have not been entirely satisfactory because of the lack of an adequate correlation between the deformation rates inside the pore-throats and the velocity of the fluid. Linear and radial flow tests were performed in 100 to 1,000 md rocks. The rheological behavior of xanthan gum was measured in linear core flow tests. This constitutive flow behavior was used in a radial flow simulator to predict the invasion profile of xanthan gum in the formation. Radial flow tests were performed to validate the predictions from the simulator. Simulations of field scale wellbore invasion profiles are presented using both xanthan gum and HEC. The effect of fluid loss additives, such as starch and sized CaCO3 was also studied in radial flow leak-off tests. The damage left over associated with those additives was quantified and compared to pure xanthan-based fluids.
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (1.00)
- Geology > Geological Subdiscipline > Geomechanics (0.46)
- Geology > Mineral > Silicate (0.46)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
Predicting the Fluid Loss of Drilling, Workover, and Fracturing Fluids into a Formation With and Without Filter Cake
Carlson, E.S. (The University of Alabama) | Venkataraman, M. (The University of Alabama) | Clark, P.E. (The University of Alabama) | Sifferman, T.R. (Kelco, A Unit of Monsanto Company) | Coffey, M.D. (Kelco, A Unit of Monsanto Company) | Seheult, J.M. (Kelco, A Unit of Monsanto Company)
SPE 35227 Predicting the Fluid Loss of Drilling, Workover, and Fracturing Fluids into a Formation With and Without Filter Cake E.S. Carlson, SPE, M. Venkataraman, P.E. Clark, SPE, The University of Alabama, T.R. Sifferman, SPE, M.D. Coffey, SPE, J.M. Seheult, Kelco, A Unit of Monsanto Company Copyright 1996, Society of Petroleum Engineers, Inc. Introduction An evaluation of the tests described in the American Petroleum Institute's Recommended Practice "Standard Procedure for Testing Drilling Fluids" would probably lead to the conclusion that the control of fluid loss during drilling or completion operations requires the use of a wall-building fluid. As we will show in this paper, this is not a valid conclusion because power-law fluids can be very effective for invasion control. The lack of a standard test for the invasion characteristics of a power-law fluid is understandable, because the invasion behavior for these fluids depends on both fluid and formation properties. In this paper, we describe the theory of non-Newtonian fluid invasion from a wellbore to a formation, and discuss a computer model that we developed which is based on this theory. We present computational results which validate the model against analytical and experimental results. Using average parameters that were determined from experiments, we show that formation invasion can be effectively controlled using power-law fluids. We also show that the power-law fluid characteristics which lead to good invasion control do not necessarily lead to long-term restrictions to well productivity. Theory We have searched exhaustively to find invasion models which are comparable to the those presented in the following sections. Many models exist which describe invasion characteristics of wall-building fluids. There are papers which discuss the flow of power-law fluids through linear cores, and other papers which discuss transient pressure behavior of power-law fluids in a reservoir. However, we have not found any which rigorously evaluate the invasion behaviors of power-law fluids. Flow of Non-Newtonian Fluids in Porous Media Unlike Newtonian fluids, which exhibit a constant apparent viscosity, general non-Newtonian fluids have an apparent viscosity which depends on the shear rate, and the shear rate depends on the fluid velocity. For power-law fluids, the apparent viscosity can be given by (1) where app is the apparent viscosity in cp, n is the flow behavior index, K is the consistency index in dyne.sn/cm2, and is the shear rate in s-1. For a given power-law fluid, it is a routine matter to measure n and K. When a rotational viscometer is used, shear stress is measured as a function of rotational speed. The shear rate is directly proportional to the rotational speed, and the apparent viscosity is the ratio of shear stress to the corresponding shear rate. P. 643
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
SPE Members Abstract Achieving optimal fluid performance with biopolymer viscosifiers, xanthan and welan, depends on reaching or exceeding a minimum or critical polymer concentration (CPC). CPC is affected by a variety of fluid and wellbore conditions, including: temperature and salinity, average shear rate, shear history, velocity gradients, hole angle, polymer configuration and rigidity, and the size, density, and concentration of suspended solids. The suspension and transport properties of xanthan and welan correlate directly properties of xanthan and welan correlate directly to low-shear-rate-viscosity (LSRV) and elasticity (G'), properties which cannot be quantified with a conventional field viscometer. LSRV and G' are qualitatively related to a polymer's molecular rigidity and configuration, and quantitatively to the number of physical and chemical polymer chain associations, referred to as polymer networks and structures. Introduction Compared to other conventional oilfield viscosifiers xanthan and welan provide enhanced static suspension and dynamic transport of suspended solids. This has resulted in their preferential use in Alaska's high-angle and horizontal drilling and workover operations. Their unique rheology and flow profiles minimize the formation of cuttings beds, decrease bed compaction, and promote erosion and removal of existing beds, particularly when used at or above the CPC. The differential rheology of these polymers, above and below their CPC, is not generally polymers, above and below their CPC, is not generally understood or utilized in oilfield drilling or workover operations due to the limitations of conventional viscometers. To be a useful predictor of fluid performance, rheological data should correlate to fluid behavior and field results. LSRV and G' correlate to the suspension and transport properties of fluids viscosified with the subject biopolymers. LSRV is a near-zero steady shear rate measurement taken in the range of 0.06 sec-1, and measures both viscous and elastic components of viscosity. G' is the elastic, structural or gel-like, component of viscosity. G' is quantified with oscillatory rather than rotational shear measurements, taken over a range of small strains and low frequencies. G' increases with salinity and biopolymer concentration and represents the suspensional component of viscosity. LSRV and G' result from quantitative formation of polymer networks, and qualitative molecular characteristics such as size, shape, and rigidity, which determine the structural integrity of the networks. Under static conditions in high-angle and horizontal wellbores. LSRV and G' correlate to suspension, reduced radial settling, and reduced potential for the formation of cuttings beds. Under dynamic conditions in these wellbores, LSRV and G' correlate to modified fluid flow profiles, which improve suspension and transport minimize radial slip of drilled and suspended solids, and promote cuttings bed erosion. The effects of temperature and salinity in determining CPC are researched, as well as the effects of size, density, and concentration of suspended and drilled solids. Comparisons are made to other conventional oilfield viscosifiers, including: bentonite, hydroxyethylcellulose (HEC), and partially hydrolyzed polyacrylamide (PHPA). partially hydrolyzed polyacrylamide (PHPA). Laboratory studies include the effects of polymer concentration on LSRV, G', sand suspension, yield points, and "n" values. LSRV is shorn to be a points, and "n" values. LSRV is shorn to be a valuable new data point for evaluating biopolymers, measurable with a compact, field-durable viscometer. LSRV and G' are shown to correlate to sand suspension, and conventional oilfield viscosity measurements are shown to lack reliable correlation.
- North America > United States > Alaska (0.34)
- North America > United States > Texas (0.28)