Frictional Pressure Loss Research Articles

Ohmic Heating of Liquid Whole Egg: Rheological Behaviour and Fluid Dynamics

Although ohmic heating is used as an alternative heating method for liquid egg products commercially, there is a lack of information on the change of rheological properties and fluid dynamics characteristics of ohmically heated liquid whole egg in the literature. The change of rheological behaviour of the ohmically heated liquid whole egg, across a temperature range of 4–60 °C, was determined by using a concentric rotational viscometer. The ohmic heating was conducted by applying the voltage gradient (20 V/cm) at 50 Hz. The temperature dependency of the electrical conductivity of liquid egg was linear (R2 = 0.999). The rheological behaviour was found to be shear thinning since power law model had higher regression coefficient and lower χ2 and root mean square error values than Newtonian model. Ohmically heated liquid whole egg exhibited higher degree of thixotropic index indicating the occurrence of the protein denaturation at 60 °C. The flow behaviour of liquid whole egg in the continuous ohmic heating system was predicted as laminar (GRe range of 87.59–538.87) for the mass flow rate range of 0.0056–0.0166 kg/s. The friction factors and pressure losses in the system in those mass flow rates were also assessed. The result of this study will give necessary information on flow characteristics of liquid whole egg for the modelling, designing and the scaling up of the continuous ohmic heating systems for pasteurisation of liquid egg products.

Maximizing Energy at Coalface for Coalbed-Methane Fracturing

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 114974, "Maximizing Energy at Coalface for Coalbed-Methane- Fracturing Operations," by Abbas Mahdi, SPE, Schlumberger; Mike Yu, SPE, EnCana; Doug Pipchuk, SPE, Craig Wasson, SPE, Jim Nguy, SPE, and Nathan Kathol, Schlumberger, originally prepared for the 2008 CIPC/ SPE Gas Technology Symposium Joint Conference, Calgary, 16–19 June. The paper has not been peer reviewed. Nitrogen coiled-tubing (CT) fracturing is the predominant method for completing and stimulating dry-coalbed-methane (CBM) formations, such as the Horseshoe Canyon in the west-ern Canadian sedimentary basin. Currently, energy that can be delivered to the coalface of these dry-CBM wells has been limited by the frictional pressure loss through CT. The full-length paper discusses the development of a technique that releases a large-volume pressure pulse downhole during the fracturing process to create an order-of-magnitude change in available energy at the fracture face. Introduction The Horseshoe Canyon dry-coal formations have been exploited commercially since late 2000. The Horseshoe Canyon CBM play is a unique CBM play, in that it consists of a dry underpressured coal, which does not require dewatering before production. The coal consists of multiple thin seams, ranging from 10 to 30 seams per well, that are treated individually. Coal-seam thick-ness ranges from 0.1 to 2.5 m. The production rates from these CBM wells dictate that an efficient drilling and completion model be adopted to be economic. The wells are drilled with CT drilling rigs, cased, and cemented. Wireline perforating crews perforate the zones of interest in a rigless operation. The individual coal seams then are stimulated by injection of dry nitrogen at high rates through a CT reel equipped with a fracturing isolation tool. The dry coal has not responded well to any other form of stimulation. To optimize the completion process, high-rate nitrogen-pumping units were developed to reduce the footprint and cost and to increase efficiency of the operation to the point where one and a half to two wells can be stimulated per day. Since the introduction of that change, various optimization initiatives have been attempted. The optimization of nitrogen-pumping rates and pumped volumes has been the focus of these attempts. High rates have been limited by the inside diameter of the CT string. Several CT sizes have been used for this application. Economics and logistics have limited the CT size for CT fracturing to 2 7/8 in. for deeper wells and 3 1/4 in. for shallow wells. The migration to bigger pipe did pro-vide some reduction in frictional pressure loss, but effective pressure at the coalface still was not transported from the surface efficiently.

Development and Evaluation of Various Drilling Fluids for Slim Hole Wells

Abstract Slim hole drilling has gained wide acceptance, however, it presents a new set of challenges and problems. One such challenge is reducing annular pressure losses (APLs). Due to the reduced annular clearance in slim hole wells, the APL is usually high, translating to a high equivalent circulating density which can lead to fracturing the formation and lost circulation. Fifty-three fluids were evaluated for their APLs using three different wellbore configurations under atmospheric conditions and at 150?F. Each fluid was characterized using the Bingham Plastic and Power Law rheological models. It was observed that the partially hydrolyzed polyacrylamide (PHPA) viscosified brines gave the lowest frictional pressure losses of all fluids tested. However, the xanthan viscosified brines exhibited better carrying capacity due to their high viscosities. As expected, APL gradients were reduced at high temperatures due to reduced viscosities which led to reduced carrying capacities of the fluids. Introduction Drilling cost optimization has always been, and will continue to be, the most important issue in the petroleum drilling industry. Using slim hole technology is one of the sure ways to achieve substantial cost savings. The basic difference between conventional wells and slim hole wells is the wellbore geometry. While the hole diameter of the production interval in a conventional well ranges from 6? in to 95/8 in, that of a slim hole well ranges from 3? in to less than 6 in. Recent advances(1–3) in slim hole technology include the development of drilling fluids to reduce the APLs because 60% of the pressure loss occurs in the annulus of slim hole wells(1). Some developments in slim hole drilling fluids design have included the works of Downs et al.(2) They formulated formate brine-based fluid with xanthan gum as a viscosifier. Randolph et al.(3) developed a unique weighting agent for slim hole drilling. In general, low solids-fluids are used to prevent the plating out of solids inside the drill string, and the fluids should have low viscosity to avoid an excessively large equivalent circulating density (ECD). These systems are very costly, thereby reducing the cost savings significantly. The purpose of this study was to develop a low-cost, low viscosity fluid that will reduce the annular pressure loss significantly while maintaining a gauged hole. Study Methodology his study involved the development of several fluids and their rheological characterizations with Bingham Plastic and Power Law models. The data were used for calculating APL gradients for three slim hole geometries and carrying capacities of the fluids. The fluids developed were water-based because they are cheap, environmentally accepted and they require little effort when detecting gas kicks. Two main groups of fluids were tested: bentonite (clay)-based fluids and viscosified brines. Salts were added to the fluids for wellbore stability. The two types of salts used in this study are potassium chloride (KCl) and potassium formate (KF). Xanthan and PHPA (partially hydrolyzed polyacrylamide) polymer were used as viscosifiers in the brines in order to investigate their effects on annular pressure losses.

Interfacial-Area Transport Equation at Reduced-Gravity Conditions

The interfacial-area transport equation is of practical importance for two-phase flow analyses at reduced-gravity conditions. In view of this, the interfacial-area transport equation, which takes the gravity effect into account, is studied in detail. The constitutive equation for the sink term of the interfacial-area concentration due to wake entrainment has been developed by considering the body acceleration due to frictional pressure loss. A comparison of the newly developed interfacial-area transport equation with various experimental data taken at normal-gravity and microgravity conditions shows a satisfactory agreement. An example computation of the newly developed interfacial-area transport equation has been performed at various gravity conditions such as 0, 1.62, 3.71, and 9.80 m/s 2 , which correspond to zero-gravity and the lunar, Martian, and Earth surface gravities, respectively. It has been revealed that the effect of the gravity on the interfacial-area transport in a two-phase flow system is more pronounced for low-liquid-flow and low-void-fraction conditions, whereas the gravity effect can be ignored for high-mixture-volumetric-flux conditions.

Modeling of Equalizer Production System and Smart-Well Applications in Full-Field Studies

Summary Equalizer production systems and inflow control devices are used to mitigate water or gas-coning problems for mature fields. We have developed new modeling methods to simulate equalizer and interval control valve (ICV) performance in full-field multimillion-cell reservoir models under a parallel computational environment. The authors present single-well performance predictions with and without an equalizer, and the results are significantly different in some cases. Full-field modeling with equalizers and ICV controls for several examples has been conducted. In such cases, many individual wells would have significantly improved performance. At full-field level, however, using equalizers or smart well applications without total field optimization would not improve performance much, for reasons discussed in this paper. The frictional pressure loss across an equalizer can be considered as a skin, and we have developed an analytical well equation to include it. With this theoretical development, it is now possible to confirm or monitor equalizer performance in terms of pressure drop from pressure transient analysis.

Friction pressure correlations for turbulent flow of drag reducing polymer solutions in straight and coiled tubing

Accurate determination of friction pressure losses of dilute drag reducing polymer solutions remains to be a challenge in many practical applications. These include a wide variety of hydraulic operations performed on a daily basis in the oil and gas industry. Most drilling, completions, and stimulation jobs require pumping fluids at high flow rates, which in turn generates high frictional pressure losses, enhanced by the use of small diameter tubing or coiled tubing. Curvature in this latter is believed to generate secondary flows and thus extra flow resistance. Therefore, good drag reduction characteristics of fluids are desirable. In this study, energy dissipation by eddies in turbulent flow of viscoelastic fluids is assumed to be the mechanism causing drag reduction. Various concentrations of Nalco ASP-700 and Nalco ASP-820 dilute polymer solutions are tested at ambient temperature in laboratory-scale and full-scale flow loops installed with straight and coiled tubing sections exhibiting different values of diameter, curvature ratio and pipe roughness. In addition, flow tests are conducted at 100 °F and 130 °F using the laboratory-scale flow loop. Effects of concentration, temperature, curvature ratio, and pipe roughness on drag reduction are discussed in light of Fanning friction factor versus solvent Reynolds number plots. Results show that drag reduction in coiled tubing is lower than in straight tubing. As curvature ratio increases, drag reduction decreases. The effect of increasing temperature is to decrease drag reduction in straight tubing and increase it in coiled tubing. In turn, the effect of increasing pipe roughness is to slightly decrease drag reduction in straight tubing up to a certain Reynolds number value and then it starts to increase. For coiled tubing, the effect of increasing pipe roughness is to decrease drag reduction. In this study, generalized correlations for the prediction of drag reduction in dilute polymer solutions flowing in straight and coiled tubing are developed on the basis of the energy dissipation of eddies in turbulent flow field and a shear rate dependent relaxation time. In addition, correlations are validated using experimental data for a low concentration guar fluid flowing through full-scale flow loop.

Estimating Flow Patterns and Frictional Pressure Losses of Two-Phase Fluids in Horizontal Wellbores Using Artificial Neural Networks

Underbalanced drilling achieved by gasified fluids is a very commonly used technique in many petroleum-engineering applications. This study estimates the flow patterns and frictional pressure losses of two-phase fluids flowing through horizontal annular geometries using artificial neural networks rather than using conventional mechanistic models. Experimental data is collected from experiments conducted at METU-PETE Flow Loop as well as data from literature in order to train the artificial neural networks. Flow is characterized using superficial Reynolds numbers for both liquid and gas phase for simplicity. The results showed that artificial neural networks could estimate flow patterns with an accuracy of ±5%, and frictional pressure losses with an error less than ±30%. It is also observed that proper selection of artificial neural networks is important for accurate estimations.

G0501-1-5 垂直粗面管を上昇するマイクロバブルの流動特性(キャビテーション,マイクロバブル)

The fluid characteristics of vertically upward micro-bubble flow through the rough-surfaced tube were investigated experimentally. An experiment was performed for the Reynolds number in the range of 1000 up to 20000. In our experiment, we measured average void ratio at the outlet of the tube and the frictional pressure loss through the tube of 20mm in ID. The surface wall inside test sections consisted of the tube with no roughness or with roughness. The micro-bubble flow was formed in micro bubbles of almost 60 micrometer in diameter. It was found that the micro-bubble flow can delay laminar-turbulent transition and then the friction factor has minimum value at Re_1=5000, and that the effect of roughness on friction factor has a negligible small, in other words, the friction-reduction effect of the micro-bubble flow is especially effective against roughness.

Development of a Downhole Separator and Intensifier for Coiled Tubing Jetting

Abstract Wells often build scale deposits on the inside of their tubulars that can impede production or interfere with a workover operation. When this scale buildup is over long intervals, coiled tubing (CT) is often the conveyance system used to deliver acid, drilling or jetting technologies to remove the scale. Acidizing through coil can be effective only if the scale is acid soluble and it can be expensive. Drilling with motors can be very effective, but motors are susceptible to performance issues, especially if high nitrogen ratios are required. Jetting the scale is possible, but this technology also faces challenges. Delivering sufficient downhole hydraulic pressure to overcome the scale's threshold pressure is very difficult due to the limited pressure capacity of CT and frictional pressure losses in long CT strings. Further, if nitrogen is required to ensure returns, the gas phase quickly disperses the fluid jet as it exits the jetting tool, and very little power is delivered to the scale face. Recent technical advances in CT jetting technology include a rotary separator to separate the nitrogen from the fluid and a downhole pressure intensifier to take the separated water and increase the hydraulic pressure delivered to the jetting tool. The paper first discusses measurements of the threshold pressure required for removal of oilfield scales. The development of a gas separator and downhole intensifier are discussed next, followed by the results of testing these tools. Introduction Mineral scale deposits inside of production tubing can reduce production or interfere with workover operations. Coiled tubing is used to remove this scale using motors or jetting tools. Jet milling of scale is an attractive option because fluid jets will not damage tubulars or other downhole equipment. Jet milling capabilities are limited by the threshold pressure required to initiate milling and by fluid jet dissipation. The jet pressure delivered to the scale surface determines the ability of the jet to cut a given scale. The jet power then determines the rate at which the scale can be removed. The pressure that can be delivered to a jetting tool through CT is limited by fatigue limits of the coil and the pressure capabilities of available pumps. The jet power, which determines milling rates, is further limited by friction pressure loss in the CT. These losses become more significant in deep wells. One approach to cutting scale at the pressure available using coil is to add abrasives(1), however, this approach adds cost and complexity to the operation. Another approach is to boost the pressure of the jets with a downhole intensifier. In the 1990s, the FlowDril Corporation manufactured a large-scale downhole intensifier pump to drill 77/8 in to 83/4 in holes with jet assisted roller cone bits(2). The unit was designed to work with a conventional rotary drill string and run on drilling mud. The intensifier ratio was 14:1, delivering 84 l/min at 200 MPa from mud supplied at 1,260 l/min and 23 MPa. A similar approach would allow CT pressure to be boosted to a level capable of milling hard scale. The effectiveness of fluid jetting tools is further limited by dissipation of the jet in the high pressure well environment. Submerged, non-cavitating fluid jets are subject to rapid dissipation due to turbulent mixing of the fluid. The maximum length of the high pressure jet core produced by an ideal jet under these conditions is under seven nozzle diameters(3). Intense turbulence persists to a range of around 20 nozzle diameters. By contrast, water jets in air can be effective at ranges of over 1,000 nozzle diameters. Jet dissipation effects

Analytical prediction of pressure loss through a sudden-expansion in two-phase pneumatic conveying lines

Estimation of separation or minor pressure losses for pipe fittings of a pneumatic conveying system at design stage is critical as much as determination of frictional pressure losses through it. The flow in many pneumatic conveying systems is a two-phase flow; it is so complex and difficult to be investigated by experimental techniques. The static pressure recovery and the minor loss coefficient through an axis-symmetric, circular cross-section, sudden-expansion fitting of a horizontal pneumatic conveying line with air–solid particle flow are analytically studied. The theoretical models proposed in the literature are scarce, and do not confirm the experimental studies. The well-known homogeneous and separated flow models proposed in the literature are initially applied to the case by means of mass and momentum conservation laws. The predictions of both the models on the pressure recovery were compared with the experimental and the numerical data in the literature and a bad agreement was observed between them; therefore, a new original analytical model is proposed by the present study. The new model is called as the slip flow model, which takes into account the slip velocity between gas and solid phases evaluated by coupling the well-known separated flow model with the empirical slip ratio predictions in the literature. The predictions of the proposed slip flow model on both the pressure recovery and minor loss coefficient are found in good agreement with the corresponding data in the literature.

Pipe-Rotation Effect on Hole Cleaning for Water-Based Drilling Fluids in Horizontal and Deviated Wells

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 114965, "Effect of Pipe Rotation on Hole Cleaning for Water- Based Drilling Fluids in Horizontal and Deviated Wells," by M.E. Ozbayoglu, Middle East Technical University; A. Saasen, StatoilHydro; M. Sorgun, Middle East Technical University; and K. Svanes, StatoilHydro, prepared for the 2008 IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition, Jakarta, 25-27 August. The paper has not been peer reviewed. A major concern while drilling horizontal and directional wells is proper hole cleaning. For a stationary bed of drilling cuttings in the annulus, generally, an increase in the fluid velocity will erode the bed significantly. However, depending on the drilling conditions, very-high fluid velocities are needed for bed removal, which may not be possible because of hydraulic and physical limitations. In such cases, pipe rotation may enhance cuttings transport mechanically, and effective hole cleaning may be achieved even at fluid velocities lower than the critical annular fluid velocities required to prevent stationary-bed development. The effect of pipe rotation on hole cleaning was investigated. Introduction Increasing the fluid viscosity or flow rates for vertical wells can improve the cuttings-transport performance. However, as hole inclination progresses from vertical to horizontal, additional challenges arise, such as cuttings-bed development. At inclinations between 40 and 60°, hole cleaning is most difficult because of back sliding of the cuttings inside the wellbore. Such cases require higher flow rates. Also, for inclined wellbores, fluids with high viscosities do not clean the hole as observed in vertical cases. Also, during drilling operations, the drillstring usually is rotating, which increases the complexity of the drilling-fluid behavior and cuttings transport inside the wellbore. Although many studies on the relationship between the pipe rotation and cuttings-transport performance are available in the literature, there is a lack of understanding about the contribution of pipe rotation to hole cleaning. This study provides detailed information on the effects of pipe rotation on hole cleaning. The basis of the information was experimental work conducted by varying major drilling parameters. Theory Many drilling variables influence hole cleaning. For realistic modeling, all variables that affect cuttings transport should be taken into consideration. From the point of view of hole cleaning, pipe rotation will affect not only the cuttings-distribution scheme inside the wellbore but also the fluid properties and pipe alignment, especially in eccentric cases. Use of all data will increase the difficulty of predicting the contribution that pipe rotation makes in cuttings transport and hydraulics. For example, in an eccentric annulus, frictional pressure loss will decrease as the pipe eccentricity increases, if all other parameters are kept constant. However, when the pipe is rotated, frictional pressure loss increases, most probably because of the orbital motion. It is more difficult to predict the behavior of pressure loss with the presence of cuttings in the system. However, the volume of stationary bed decreases with increased pipe rotation, which leads to an increased fluid-flow area. Thus, frictional pressure losses might decrease as pipe rotation is increased.

Experimental Study of gas–liquid two-phase flow affected by wall surface wettability

To evaluate the effect of wall surface wettability on the characteristics of upward gas–liquid two-phase flow in a vertical pipe, an experimental study was performed using three test pipes: an acrylic pipe, a hydrophilic pipe and a hydrophobic pipe. Basic flow characteristics such as flow patterns, pressure drop and void fraction were measured in these three pipes. In the hydrophilic pipe, a slug to churn flow transition boundary was shifted to a higher gas velocity at a given liquid velocity, whereas a churn to annular flow transition boundary was shifted to a lower gas velocity at a given liquid velocity. In the hydrophobic pipe, an inverted-churn flow regime was observed in the region where the churn flow regime was observed in the acrylic pipe, while a droplet flow regime was observed in the region where an annular flow regime was observed in the acrylic pipe. At a high gas flow rate, the mean void fraction in the hydrophobic pipe was higher than in the acrylic pipe. The effect of surface wettability on frictional pressure loss was confirmed to be insignificant under the present experimental conditions.

Two-phase minor loss in horizontal bubbly flow with elbows: 45° and 90° elbows

The present study investigates the geometric effects of a 45° elbow on the pressure drop due to the minor loss in horizontal bubbly flow. A round glass tube with inner diameter of 50.3 mm is employed as a test section, along which a 45° elbow is installed at L/D = 353.5 from the two-phase mixture inlet. In total, 15 different flow conditions are examined. The local static pressures are measured at four axial locations at L/D = 197, 342, 363 and 419 from the two-phase mixture inlet. The effect of the elbow is clearly demonstrated in the pressure data along the axial direction. In the data analysis, the pressure data previously acquired with a 90° elbow is also utilized as well. The conventional Lockhart–Martinelli correlation with parameter C = 30 predicts the overall two-phase frictional pressure loss between the inlet and exit of the test section relatively well for both the 90° and 45° elbow experiments. However, it fails to predict the pressure loss across the elbows, because the existing model does not account for the additional loss due to the flow restrictions. In view of this, a new correlation analogous to Lockhart and Martinelli’s is developed for the two-phase frictional pressure loss across the elbows. The new correlation with the parameter C = 65 and the minor loss factors of k = 0.58 and k = 0.35 for the 90° and 45° elbows, respectively, yields the best fit to the data. The average percent differences between the predictions made by the new correlation and the data are ±2.1% and ±1.3% for 90° and 45° cases, respectively.

Hole Cleaning During Underbalanced Drilling in Horizontal and Inclined Wellbore

Summary This paper is an extended work of SPE 90038. An aerated non-Newtonian flow and an inclined wellbore section were added to the previous model to study the hole-cleaning problem while drilling an underbalanced well. This new mechanistic model for cuttings transport was developed by combining two-phase hydraulic equations, turbulent boundary layer theory, and particle transport mechanism. It is shown that the model is useful for predicting minimum annular velocity and cuttings bed thickness in horizontal and inclined wellbore geometry. Effects of temperature, bottom hole pressure, liquid flow rate, gas injection rate, cuttings size and density, inclination angle, and rheological properties of drilling mud on hole cleaning are analyzed using this mechanistic model. The model is validated by available experimental data. Computer simulation indicates that cuttings bed thickness is very sensitive to the liquid phase flow rate. It dominates cuttings transport efficiency. However, during underbalanced drilling, increase of liquid phase fraction may not always be feasible while trying to keep a low equivalent circulating density (ECD). Meanwhile, injection of gas has positive effects on cuttings transportation depending on the flow patterns and drilling mud viscosity. Elevated temperature causes a significant increase of bed thickness, and it is important to recognize this negative effect, especially when drilling high-pressure/high-temperature (HPHT) wells. The effect of pressure on cuttings concentration is negative. Larger size and heavier cuttings make hole cleaning more difficult and require higher pump rates for low-viscosity fluids. Increases of liquid phase density result in better hole cleaning. The range of hole angles from approximately 35° to 60° (from vertical) is the most difficult for cuttings transport. Frictional pressure losses in a deviated wellbore highly depend on cutting bed thickness. Simulation results are compared to available experiment data and show good agreement. In summary, this paper presents a model that is useful for practical hole cleaning during underbalanced drilling (UBD).

Effects of Friction and Thickness on Long-Term Consolidation Behavior of Osaka Bay Clays

The objective of this study is to empirically clarify the scale effect in long-term consolidation behavior. Frictional pressure loss arising at the interface between the consolidation ring and the specimen must be considered, when the specimen thickness increases. This study uses a special oedometer that can evaluate the quantity of the frictional pressure loss. Incremental loading oedometer tests are carried out in order to evaluate the frictional pressure loss in the normal oedometer test using a specimen with a height of 20 mm. The frictional pressure loss ratio generally exceeds 0.2 when the consolidation pressure is less than approximately 300 kPa, rather than the overconsolidation range. Consequently, a series of inter-connected type consolidation tests, in which the frictional pressure loss can be minimized by limiting the thickness of each specimen element, are carried out in order to investigate the scale effect of the specimen thickness in the range of 20-200 mm. The end of primary consolidation (EOP) can be clearly identified in the excess pore pressure dissipation. The law of squared H is essentially valid for the pore water pressure dissipation. However, the EOP becomes unclear in the strains when the specimen thickness decreases. The compressive strain at the EOP stays constant or slightly increases with the specimen thickness.

Rheological and Hydraulic Properties of Welan Gum Fluids in Straight and Coiled Tubings

Abstract This study involves experimental investigation of the hydraulic characteristics of aqueous based welan gum fluids of concentrations 1.4kg∕m3, 2.9kg∕m3, 5.7kg∕m3, and 8.6kg∕m3 in both straight and coiled tubings at 21°C, with particular emphasis on the effect of polymer concentration and coiled tubing curvature ratio. The flow loop available at the Well Construction Technology Center of the University of Oklahoma, consisting of 1.27cm straight and coiled tubings (with curvature ratios of 0.01, 0.019, and 0.031), was utilized. It was observed that for all welan gum fluids investigated, friction losses in coiled tubing were significantly higher than those in straight tubing. In addition, increasing coiled tubing curvature ratio brings about higher friction loss for all fluids investigated. Rheological data for these fluids were obtained using a Model 35 Fann viscometer. Friction pressure data gathered from flow experiments are analyzed and correlations for friction pressure loss prediction of welan gum fluids have been developed for both straight and coiled tubings. These correlations, which represent the industry’s first attempt in the fundamental investigation of friction loss prediction of welan gum fluids, are found to provide good accuracy when compared to the experimental data. Flow behavior of welan gum fluids is compared with 4.9kg∕m3 guar fluid. It is found that in both straight and coiled tubings, the guar fluid exhibited higher drag reduction when compared to the welan gum fluids investigated in this study.

Polymer Reduction Leads to Increased Success: A Comparative Study

Summary Recent advances in guar and crosslinker technologies have resulted in the development of high-viscosity crosslinked borate-fracturing fluids without increasing polymer loadings. These low polymer (LP) borate fracturing fluids are being used successfully in various formations previously believed to be too hot and or too deep for LP fracturing fluids. Historically, polymer loadings of 3.6 to 4.2 kg/m3 (30 to 35 lbm/1,000 gal) were commonly pumped in the Western Canadian Sedimentary basin (WCSB) for formations deeper than 2500 m and bottomhole temperatures greater than 80°C. These same formations are now fracture stimulated using the LP fluids with loadings as low as 1.8 kg/m3 (15 lbm/1,000 gal) with exceptional results. This paper demonstrates that LP fracture fluids can be used in place of fluids requiring higher polymer loadings with minimal changes to the overall design of the fracture treatment. The new fluid can be pumped on-the-fly at conventional pump rates and proppant concentrations because of the fluid's improved shear and temperature stability. The advantages of using a reduced-polymer fracturing fluid include increased production, lower treatment costs, and lower frictional pressure loss. This paper illustrates these advantages as it compares the LP fracture fluid with HP fracture fluids in more than 200 wells in the WCSB. The formations where LP fluids were used have depths of up to 3250 m and reservoir temperatures reaching over 100°C.

Production Operations: Inflow-Control Devices

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 108700, "Inflow-Control Devices: Application and Value Quantification of a Developing Technology," by F.T. Al-Khelaiwi, SPE, and D.R. Davies, SPE, Heriot-Watt U., prepared for the 2007 SPE International Oil Conference and Exhibition in Mexico, Veracruz, Mexico, 27–30 June. The paper has not been peer reviewed. Horizontal and multilateral completions are a proven, superior development option in many reservoir situations. However, they are susceptible to coning toward the heel of the well despite their maximizing of reservoir contact. This is a result of frictional pressure drop and/or permeability variations along the well. Annular flow, leading to severe erosion and screen plugging, is another challenge. Inflow-control devices (ICDs) were proposed as a solution to these difficulties in the early 1990s. ICDs have gained popularity recently and are being applied to a wider range of field types. Their ability to control the well inflow profile has been confirmed by a variety of field monitoring techniques. Introduction ICDs are a new sandface completion technology specifically developed to help balance the inflow contribution along horizontal wellbores. Extensive flow-loop testing and subsequent field experience have proved the potential of ICDs to extend well life by extending the plateau period, minimizing water and gas coning, minimizing annular flow, and increasing recovery. Historical Development Norsk Hydro introduced the ICD technology in the early 1990s to enhance the performance of horizontal wells in the Troll field, a giant gas field on the Norwegian shelf of the North Sea. The field contains a thin oil column (4 to 27 m thick) overlain by a large gas cap and underlain by an aquifer. The field was developed originally as a gas field in the "thin-oil-column" part of the field because the production of such a thin oil column was deemed nonviable with conventional wells. Two horizontal wells then were drilled, and long-term well tests were conducted to determine the ability of such wells to drain the oil economically. The wells were completed with large-diameter prepacked slotted liners to reduce the effect of frictional pressure losses along the wellbores. The long-term-test results indicated that a significant oil-production potential existed. The initial flow rate of the first well was four times that expected from a vertical well. The well productivity index was very high, at approximately 6000 std m3/d/bar, which is 5 to 10 times higher than that expected from a vertical well. This also meant that a small pressure drop of only 0.5 to 1.0 bar is sufficient drawdown pressure to produce the well at a target rate of 3000 to 5000 std m3/d. A new field-development plan was put in place that used horizontal wells. However, production logging of the first test well indicated that 75% of the contribution was coming from the first half of the horizontal section. This is indicative of the significant effect frictional pressure losses can have on the performance of horizontal wells once this frictional pressure drop is of the order of magnitude of the drawdown.

Experimental Study on Cuttings Transport With Foam Under Simulated Horizontal Downhole Conditions

Summary The use of drilling foams is increasing because foams exhibit properties that are desirable in many drilling operations. A good knowledge of cuttings transport efficiency under downhole conditions is essential for safe and economical foam drilling. Previous cuttings transport studies with foam are limited to low pressure and ambient temperature conditions. No experimental study has been conducted under downhole (i.e., elevated pressure and temperature) conditions. This paper presents an experimental study of cuttings transport with foam in a horizontal annulus under simulated downhole conditions. Experiments were conducted to determine the effects of polymer additives, foam quality, flow velocity, temperature, and pressure on foam cuttings transport. Experiments were carried out at elevated pressures (100 to 400 psi) and temperature (80 to 170°F) conditions in a unique full-scale flow loop with a 73-ft long test section (5.76×3.5 in. concentric annulus). A field-tested commercial foam system consisting of surfactant (1% v/v) and hydroxylethylcellulose polymer (HEC) was used in the experiments. Three different polymer concentrations (0.0, 0.25, and 0.5% v/v) were tested. Foam quality was varied from 70 to 90%. During a test, cuttings were injected continuously to the flow loop until a steady state condition was established in the test section. In-situ cuttings volumetric concentration (i.e., the ratio of the volume of cuttings in the suspension and the cuttings bed to the volume of the annulus) in the test section was determined using nuclear densitometers, load cell measurements, and by weighing cuttings flushed out of the flow loop. Test parameters recorded during the experiments were: liquid and gas injection rates, cuttings weight in injection and removal towers, mixture density, friction pressure loss, and pressure and temperature in the annulus. Two flow patterns, stationary cuttings bed, and fully suspended flow, were observed during the cuttings transport tests. The flow pattern depends on polymer concentration, foam quality, and annular velocity. Annular flow velocity, foam quality, and polymer concentration all affect cuttings transport efficiency and frictional pressure loss. This paper will help to better design foam drilling and cleanup operations.

Two-phase flow characteristics across sudden expansion in small rectangular channels

This study examines the two-phase flow pattern change and frictional pressure loss pertaining to the sudden flow area expansion from a small diameter tube into small rectangular channels. It is found that a unique flow pattern “liquid jet-like flow pattern” occurs at a very low quality region of G = 100 kg / m 2 s in a test section of 3 mm × 9 mm . This flow pattern is almost inconceivable for the 3 mm × 6 mm test section. The pressure difference usually increases with vapor quality but a setback is encountered provided that the liquid jet flow pattern prevails. A phenomenal observation suggests that a conceivable reduction of the pressure difference is related to the liquid jet-like flow pattern, yet a flat or level-off of the pressure difference is seen when the liquid jet-like flow is less pronounced. By contrast, an appreciable increase of pressure difference is seen when the liquid jet-like flow pattern is completely gone. The measured pressure differences are compared with existing correlations/models, whereas none of them gives satisfactory predictions against the present data. It is found that a slight modification to the empirical constant K of Wadle’s correlation may give rise to a fair improvement of the predictive ability.