Cuttings Transport Research Articles

Comparison of computational intelligence models for cuttings transport in horizontal and deviated wells

Improper cleaning of the horizontal and deviated wellbores is one of the major problems encountered during drilling process. Cuttings bed thickness is a key parameter to determine hole cleaning. In this study, computational intelligence techniques including k-Nearest Neighbor (kNN), Support Vector Regression (SVR), Linear Regression and Artificial Neural Network (ANN) were employed to estimate cuttings bed thickness inside a wellbore with and without drill pipe rotation. Cuttings transport measurements for hole inclinations from horizontal to 60°, rates of penetration from 0.0013 to 0.0038m/s, flow velocities from 0.64m/s to 1.59m/s, and pipe rotations from 0 to 120rpm were recorded to train the computational intelligence techniques. More than three hundred different datasets were performed and corresponding cuttings bed thickness values were obtained. The prediction results of computational intelligence techniques were satisfactory, when compared with experimental data. A t-test was conducted and insignificant difference between experimental and predicted data was concluded. ANN provided slightly better performance than the other models when they were compared with their RMSE, AAE, and AAPE values. However, K-nearest neighbor (kNN) can be modeled a lot faster than the other computational intellegence techniques.

Effect of Yield Power Law Fluid Rheological Properties on Cuttings Transport in Eccentric Horizontal Narrow Annulus

Narrow annular drilling such as casing-while-drilling technique is gaining popularity due to its ability to mitigate nonproductive time during oil and gas drilling operations. However, very little is known about the flow dynamics in narrow annular drilling. In this study, the Eulerian-Eulerian two-fluid model was used to examine the influence of Yield Power Law fluid rheological properties on cuttings transport in eccentric horizontal narrow annulus. The flow was assumed as fully developed, laminar, and transient state. The present simulation model was validated against experimental data, where a mean percent error of −1.2% was recorded. Results revealed an increase in the radial distribution of cuttings transport velocity in the wide annular region as the consistency index, K, and the flow behavior index, n, increase. Nonetheless, increasing the yield stress, τo, had insignificant effect on the cuttings transport velocity. Three-dimensional profiles showed how cuttings preferred to travel in less resistant flow area, whereas cuttings concentration builds up in the narrow annular region. Furthermore, annular frictional pressure losses also increased as K, n, and τo increased. This study serves as a guide to properly optimize drilling fluid rheological properties for efficient cuttings transport and equivalent circulating density (ECD) management in narrow annular drilling.

Optimization of Hole Cleaning In Iraqi Directional Oil Wells

Efficient cuttings transport and hole cleaning are very important factors for obtaining an effective drilling operation. In an inclined and horizontal drilling, hole cleaning issue is a common and complex problem.
 The scope of this research is to study the drilling parameters which affect hole cleaning in Iraqi directional wells through studying and analyzing some drilled wells ( vertical , directional (30 degree) , directional (60 degree) and horizontal ).An excel sheet is prepared to calculate carrying capacity index which represents an indicator for good hole cleaning in different sections. The study indicated through the field investigations, practical experiences and theoretical calculations that the most effective drilling parameters for optimum hole cleaning were flow rate, yield point, mud weight, plastic viscosity, rotation of the drill string, and pH.

Development of a mixer-viscometer for studying rheological behavior of settling and non-settling slurries

Slurry transport has become a subject of interest in several industries, including oil and gas. The importance of slurry/solid transport in the oil and gas industry is evident in areas of cuttings transport, sand transport and, lately, hydrates. There is therefore a great need to develop instrumentation capable of characterizing fluids with high solid content. Presence of solids in fluids makes the rheological characterization of these systems difficult. This is because available rheometers are designed with a narrow gap and cannot prevent solids from settling. The main aim of this paper is to present a step-by-step procedure of converting torque and shaft speed into viscosity information by applying the Couette analogy, equivalent diameter and inverse line concepts. The use of traditional impeller geometries such as cone and plate may be challenging due to their narrow gap and inability to prevent settling. Therefore, the use of non-conventional impeller geometry is imperative when dealing with settling slurries and suspensions. The most challenging task using complex geometry impeller is data interpretation especially when dealing with complex rheology fluids. In this work, an autoclave is transformed into a mixer-type viscometer by modifying its mixing, cooling and data acquisition systems. Mathematical models relating the measured torque to shear stress and the measured shaft speed to shear rate were developed and expressed in terms of the equivalent diameter. The shear rate and shear stress constants were expressed in terms of equivalent diameter and measureable parameters such as impeller speed and torque. The mixer-type viscometer was calibrated using four Newtonian and four Power-Law fluids to determine the rheological constants (equivalent diameter, shear rate and shear stress constants). The concept of inverse line was used to identify the laminar flow regime. The calibrated instrument was used to characterize two Power-Law fluids. This procedure can be extended to any rheological model. Methods developed in this work can be used to characterize fluids with high solid content. This is particularly important when dealing with complex rheology slurries such as those encountered in food processing, oil and gas and pharmaceuticals.

Theoretical derivation of the cuttings transportation trajectory for lunar sampling auger drilling

Theoretical derivation of the cuttings transportation trajectory for lunar sampling auger drilling

A Method for Optimizing Jet-Mill-Bit Hydraulics in Horizontal Drilling

Summary Efficient cuttings transport is a major challenge in horizontal drilling; one can use a new type of jet-mill bit to overcome the challenge fundamentally. However, currently, there is no available method for optimizing jet-mill-bit hydraulics, which restricts the jet-mill bit from being widely used. In this paper, on the basis of the high-pressure water-jet comminution and jet-pump theory, a basic performance model of the jet-mill bit is developed. Then, the optimal parameter model for the jet-mill bit is presented according to the multivariable limitation theory; meanwhile, a method for optimizing jet-mill-bit hydraulics is also developed. With the method, one can determine the optimal jet-mill-bit hydraulics. Theoretical analysis and discussion show that the impact angle and the friction-loss coefficient are the key factors affecting the efficiency of the jet-mill bit; the impact angle is suggested to be set at approximately 70 ° and the optimal flow-rate ratio at appoximately 1.0; and the effect of rate of penetration (ROP, m/h) is not obvious, and one can ignore it. The optimal area ratio is almost not related to friction-loss coefficient and ROP, but it is related to the impact angle significantly. It provides drilling engineers a practical tool for determining the optimal jet-mill-bit hydraulics in horizontal drilling and promotes the jet-mill bit to be widely used.

Root-Cause Analysis of Drilling Lost Returns in Injectite Reservoirs

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 174848, “Root-Cause Analysis of Drilling Lost Returns in Injectite Reservoirs,” by Scott Buechler, Jing Ning, Nidheesh Bharadwaj, Kaustubh Kulkarni, Caleb DeValve, Carsten Elsborg, Timothy Head, and Arnout Mols, ExxonMobil, prepared for the 2015 SPE Annual Technical Conference and Exhibition, Houston, 28–30 September. The paper has not been peer reviewed. The work presented combines a fundamental-physics approach with field data to identify the root cause of drilling failures in Paleocene and Eocene injectite-sand intervals. Study results showed that unfavorably oriented sand/shale interfaces, which can occur more frequently at the top of an injectite reservoir, can reopen at equivalent circulating densities (ECDs) below predicted fracture gradients, but above the minimum stress, and can result in massive losses. Theoretical Approach and Application Diagnosing narrow-margin drilling challenges in injectite sands has proved to be extremely difficult because of the convoluted nature of available drilling data, statistically small data sets, and often contradictory “apples-to- apples” comparisons made on the basis of simple metrics. Two mechanisms have seemed probable: (1) suboptimal hole cleaning leading to packoff and subsequent lost returns, or (2) lost returns leading to suboptimal hole cleaning and subsequent packoff. Wellbore Cleaning. In this work, wellbore cleaning is evaluated with a proprietary transient-hydraulics and –hole-cleaning model. This model is based on first-principle equations of mass and momentum transport for drilling fluid and cuttings along the wellbore in the annular space between the drillpipe and casing (or open hole). The key physical effects during the cuttings-removal process are captured through constitutive models for frictional pressure drop in a circulating mud, heat transfer between the formation and drilling fluid, cuttings deposition/ erosion, and particle/liquid drag force. The partial-differential equations of mud and cuttings transport are discretized along the wellbore, and the entire system of equations is solved simultaneously in an implicit manner for each timestep. With this approach, the efficiency of hole cleaning can be characterized for these wells. Additionally, the effect of both lost returns and breakout can be incorporated into the models.

Numerical study on cuttings transport in vertical wells with eccentric drillpipe

Abstract In this paper, hydrodynamic of drilling mud and cuttings in a vertical well has been studied numerically. For solid–liquid two-phase flow simulation, the mixture model including continuity and momentum equations was used. To describe the rheological behavior of drilling mud, Herschel Bulky model was implemented. Then, a numerical code was developed to calculate flow field parameters (i.e. liquid phase velocity components, solid phase volume fraction, and solid phase velocity components in the annulus) and pressure drop. The results have been compared with available data in the literature and good agreement was found. Moving mud at entrance of the annulus and developed flow length were studied and pressure drop was calculated. Annular flow velocities in this study varied from 0.4 to 1.4 m/s. Then the effects of velocity, fluid type, pipe rotation, drilling cuttings and eccentricity on pressure drop were investigated. The pressure drop in the annulus increased while eccentricity and rotation of drill pipe increased. Rotation of the drill pipe shifts maximum fluid velocity location toward cornel space of the concentric annulus. After ensuring the accuracy of the simulation, the effects of drilling mud type, mud axial velocity, drilling rotation, fluid density and cuttings size on cuttings transport were studied. Finally, mud capacity for keeping cuttings was calculated in stasis. Then, with considering shape factor for cuttings, the velocity profile of cuttings, the mud capacity of the drilling flow and slip velocity were calculated. Slip velocity profile of cuttings in the annulus increased as cutting size increased. This indicates that cutting transport in the annulus enhances as velocity, mud density, viscosity and rotation of drill pipe increase. Eccentricity and cutting size have a negative effect on cutting transport.

Distribution features of cuttings bed and sensitivity analysis of major drilling parameters for cuttings transport in gas drilling horizontal wells

AbstractIn the current engineering methods for the gas horizontal drilling, the distribution features of cuttings bed remain an issue to be cleared, and the gas horizontal drilling is still in early stages of development. For on-site drilling, a 3-D transient model is established in this paper to simulate the distribution features and the transport mechanism of the cuttings bed, based on the gas-solid two-phase flow theory. The effects of major drilling parameters, such as the gas velocity, the drill pipe rotation, the cutting size and the eccentricity, on the cuttings transport efficiency are analyzed. The major findings of this study include that the cuttings begin to settle down and build up a fixed cuttings bed, in the most evident regions in front and behind the connector, the dominant parameter of the wellbore cleaning is the gas velocity, and, as the cutting size is increased, the thickness of the cuttings bed developed in the wellbore increases significantly. In addition, the eccentricity has some influence on the cuttings transport, and the drill pipe rotation has little effect on the cuttings transport.

A FEM-DEM technique for studying the motion of particles in non-Newtonian fluids. Application to the transport of drill cuttings in wellbores

We present a procedure for coupling the finite element method (FEM) and the discrete element method (DEM) for analysis of the motion of particles in non-Newtonian fluids. Particles are assumed to be spherical and immersed in the fluid mesh. A new method for computing the drag force on the particles in a non-Newtonian fluid is presented. A drag force correction for non-spherical particles is proposed. The FEM-DEM coupling procedure is explained for Eulerian and Lagrangian flows, and the basic expressions of the discretized solution algorithm are given. The usefulness of the FEM-DEM technique is demonstrated in its application to the transport of drill cuttings in wellbores.

Experimental and numerical simulation of cuttings transportation in coiled tubing drilling

Coiled tubing technology (CTT) showed its capabilities in oil and gas (O&G) drilling in many cases. Some of the advantages of CT drilling are rapid mobilization/demobilization and rig up/down times, faster tripping in and out of the hole, small hole size capability, faster drilling operation, and less environmental footprint. Because the CT does not rotate, a down-hole motor/turbine, which needs high flow rate, is required to rotate the drill-bit. The cuttings transport in the small size annulus space is the core part of this research study. This was done through both laboratory experiments using a flow loop and numerical modeling.The results of flow loop experiments determined the minimum transportation velocity (MTV) to effectively bring all the cuttings to the surface. Directional boreholes were tested and the effect of cuttings size as well as mud properties was investigated. Testing actual cuttings in CT drilling presented different results than those observed in the literature for conventional O&G drilling. The different outcomes, for instance on the effect of rheology on cuttings transportation, necessitates conducting this research to develop a model for cuttings transportation in CT drilling.Computational fluid dynamics numerical simulation with Eulerian Granular approach was applied in this study to investigate the effect of different parameters in cuttings transportation. The simulation results were validated against the experimental results of the flow loop. Various flow patterns were simulated by changing different parameters.

The return of drilling fluid in large diameter horizontal directional drilling boreholes

The return of drilling fluid (drilling mud) in large diameter horizontal directional drilling (HDD) boreholes is a very important issue related to mud pressure, cuttings transport and pull back force, but this problem has not been fully solved in previous research due to the complexity and uncertainty of downhole conditions. The calculation methods of mud pressure loss in the borehole annulus are briefly introduced and the equation using a Power Law model is adopted to study the drilling mud return. A typical reaming hierarchy of a large diameter HDD project has been used to study the return direction of drilling mud and volumes of drilling mud return to the exit and entry points. The research results disclosed that the drilling mud can return to both exit and entry points at the same time, with a large majority of the drilling fluid returning to the exit point if the reamer is closer to the exit point, and vice versa. A parametric study has been conducted to find out the effect of changing parameters in the calculation equation on the drilling fluid return. The drilling mud return for those boreholes with the exit point and entry point located at different elevations has also been discussed. Finally, different types of reamers and other factors such as borehole collapse and borehole shape were taken into the consideration of drilling mud return.

CFD simulation of viscosity modifier effect on cutting transport by oil based drilling fluid in wellbore

In this study particle transportation has been predicted in a wellbore for an oil based drilling fluid containing viscosity modifier using CFD simulation. The effects of fluid viscosity on particle transport capacity of fluid were studied by considering various particle parameters such as density, diameter, shape, and initial particle concentration and wellbore inclination through using the Algebraic Slip Mixture (ASM) model. Rheology of the drilling fluid was expressed by Herschel–Bulkley non-Newtonian fluid model. The influence of viscosifier concentration on fluid rheology show that it improves carrying capacity of particles but its effect attenuates in higher concentration. For 2 ppb of viscosifier in drilling fluid, the cutting transport capacity has been increased almost 12% whereas adding 4 ppb of viscosifier, only created about 14% escalation on the transportation of cuttings. Against this positive effect viscosity modifier make more pressure drop that was a costly effect for operation and this effect had constant rate (for each ppb viscosifier, pressure drop growth is equal to 200 kPa/m approximately). Also, the results indicate higher particle density or larger particle size results in less particles transportation in the wellbore. Increasing initial solid loading has an adverse impact on the transmission of solid particles in wellbore.

Efficient method for rapid multiplication of clean and healthy willow clones via in vitro propagation with broad genotype applicability

Willow is a versatile crop with considerable potential as a source of renewable biomass for bioenergy. Although breeding new varieties takes less time compared with some other tree species, producing new willow varieties is still a slow, labour-intensive process, partly because clonally propagating the results of each cross is a bottleneck early in the breeding scheme. In this paper, we describe a facile, rapid method for the in vitro culture of a wide range of willow genotypes. We have developed a combination of media and methods for efficient tissue-culture propagation to rapidly multiply individual plants and simultaneously produce clean, stock germplasm applicable to a wide range of willow genotypes that can be phytosanitary tested to demonstrate their disease-free status. The micropropagation method described could generate in the order of 5000 viable, transplantable clones from a single plant in just 24 weeks and was used to produce phytosanitary tested breeding material for export to overcome restriction on the international transport of woody cuttings. This method could represent a valuable biotechnology adjunct to willow breeding programmes and could accommodate early selection via molecular or biochemical markers.

Modeling and Experimental Study of Solid–Liquid Two-Phase Pressure Drop in Horizontal Wellbores With Pipe Rotation

Determining pressure loss for cuttings-liquid system is very complicated task since drillstring is usually rotating during drilling operations and cuttings are present inside wells. While pipe rotation is increasing the pressure loss of Newtonian fluids without cuttings in an eccentric annulus, a reduction in the pressure loss for cuttings-liquid system is observed due to the bed erosion. In this study, cuttings transport experiments for different flow rates, pipe rotation speeds, and rate of penetrations (ROPs) are conducted. Pressure loss within the test section and stationary and/or moving bed thickness are recorded. This study aims to predict frictional pressure loss for solid (cuttings)–liquid flow inside horizontal wells using computational fluid dynamics (CFD) and artificial neural networks (ANNs). For this purpose, numerous ANN structures and CFD models are developed and tested using experimental data. Among the ANN structures, TrainGdx–Tansig structure gave more accurate results. The results show that the ANN showed better performance than the CFD. However, both could be used to estimate solid–liquid two-phase pressure drop in horizontal wellbores with pipe rotation.

Identifying practices likely to have impacts on grapevine trunk disease infections: a European nursery survey

A questionnaire covering all aspects of grapevine propagation including cultural and sanitation practices in mother blocks and harvest and transport of cuttings from mother blocks to nurseries, nursery operations and field nursery management, was mailed to all Management Committee members of the European COST Action FA1303 “Sustainable Control of Grapevine Trunk Diseases” for distribution to the identifiable nurseries in each European country. The main objective was to develop understanding of the current propagation practices and to identify those likely to have the greatest impacts on the quality of planting material, especially with regard to the control measures used against fungal trunk pathogen infections. The questionnaire was sent to 666 vine nurseries, and 146 replies were received (21.9% response rate) The study identified several risks factors which could increase infection by fungal trunk pathogens during the propagation processes, as well as a clear need for further research into the effects of treatments on grapevine viability, including hot water treatment, and the potential of biological agents and other strategies such as ozonation to control grapevine trunk diseases in nurseries.

Size distribution and shape characteristics of ice cuttings produced by an electromechanical auger drill

The size distribution and shape characteristics of ice cuttings have a large influence on the efficiency of the transportation of cuttings by electromechanical auger drills and eventually determine the maximum possible rate of penetration. The size of ice cuttings is usually controlled and estimated by visual examination, but this is insufficient for the precise control and prediction of performance of ice cutting removal. To determine the patterns of ice cuttings, sixteen ice cuttings were sampled in the course of drilling in natural lake ice by an electromechanical auger drill at a temperature below −5°C. The cutter is 19mm in width, with a rake angle of 45° and a relief angle of 15°. Sensors are employed to measure the drilling-depth, drilling-time and rotation speed of the coring auger. This paper presents the size distribution and shape characteristics of cuttings under various drill head rotation speeds and rates of penetration by using a sieving and computer image-based method. The size distribution of the cuttings has an asymmetrical shape similar to a chi-square distribution. Approximately half of the ice cuttings by weight are classified as small sized (<0.6mm). In all of the sieving samples, the ice cuttings have prolate form with a ratio between the major and minor axis within the range of 1.35 to 1.97, averaging ~1.55.

Study of Cuttings Transport Using Stable Foam Based Mud in Inclined Wellbore

Drilling of high angle, horizontal and other more complex trajectory wells are common strategies to economically produce hydrocarbon from the reservoirs. During directional drilling, hole cleaning is a vital aspect which needs to be monitored and controlled. For this purpose, foam-based mud using the underbalanced drilling technique (UBD) is employed to obtain a better cutting transport. Solid particle is one of the lubricating agents that is widely used in water-based mud. Previous studies have shown that microbeads could significantly reduce the friction in water-based mud. However, the application of polymer beads in foam-based mud is yet to be proven. Similar to the improvement in the water-based mud, it is expected that polymer beads such as Styrene Methacrylate could enhance the rheological properties of the foam-based mud. The polymer beads might significantly reduce the torque and drag by reducing the coefficient of friction of the foam-based mud. Polymeric particles could act as the foam or emulsion stabilizer which improves the stability of the foam. The half-life of the bubbles could be extended due to the addition of polymers. The fine sizes of the polymer beads will enhance the stability of bubbles. Theoretically, the gas phase in the foam drilling mud will pull the cuttings upward because of their buoyancy, thereby counteracting the gravity force. Therefore, the more stable the bubble in the foam drilling, the better the cuttings transportation will be. Introduction of polymer beads in the foam-based mud will improve the foam stability. Reduction of the torque and drag force will improve the carrying capacity of the cuttings in directional drilling. The suitable lubricating agent can reduce the drilling operation problems such as stuck-pipe. This will result in smooth drilling operation and great benefits in term of economy.

English

This research work presents the experimental results of the effect of polypropylene beads' concentrations in waterbased mud on wellbore cleaning. A comparative study of cuttings transport performance (CTP) of water-based mud and water-based mud with polypropylene beads were carried out at different hole angles of 0°, 30°, 60°. 75° and 90° in a 13 ft (3.96 m) acrylic concentric annulus flow test section, having a 2 in (50.8 mm) casing ID and a fixed 0.79 in (20 mm) inner pipe OD. A total of 100 runs had been accomplished using fine sands (from Tanjung Balau, Johor Bahru, Malaysia), of size ranging from 5/127-6/127 (1.0-1.2 mm) and density 2.4 g/cc (2400 kg/m3), with the mud density and viscosity maintained at 9 ppg (1078 kg/m3) and 5 cp (0.005 Pa.s), respectively, in a flow velocity of 2.1 ft/s (0.64 m/s). Polypropylene beads used in this study have the following properties: 290 kg/cm2 of tensile strength at yield, 0.86 g/cc (860 kg/m3) density, 4 mm (20/127) size, 82 R scale Rockwell hardness, 13,500 kg/cm2 flexural modulus, 85°C heat deflection temperature at 4.6 kg/cm2, 4 g/10 min melt flow rate at 230°C and spherical in shape. The experimental findings showed that commingling the basic mud with polypropylene beads has successfully introduced a buoyant force which was found to have improved the cuttings transport performance by more than 10% when weight concentration of the polypropylene beads was increased to 1.5% as compared with the performance obtained from the basic water-based mud. The improvement of cuttings transport performance was found to be more significant in a vertical hole.

Erratum for “Cuttings Transport Mechanism in a Large-Diameter HDD Borehole” by Biao Shu, Baosong Ma, and Haitao Lan

Erratum for “Cuttings Transport Mechanism in a Large-Diameter HDD Borehole” by Biao Shu, Baosong Ma, and Haitao Lan