Cuttings Transport Research Articles

Cuttings transport in maxi HDD boreholes with front reaming and one way drilling mud return technologies

Cuttings transport becomes critical important when horizontal directional drilling (HDD) technology has been used more often in long distance and large diameter oil and gas pipeline construction in rocks. Front reaming (FR) and one way drilling mud return (OWDMR) were not new in oil and gas well drilling, but they were rarely used in HDD industry compared to the traditional back reaming (BR) and two way drilling mud return (TWDMR). FR and OWDMR technologies, when they were used in HDD, were designed mainly for highly non-leveled HDD projects to overcome some difficulties such as the recycling of drilling mud. Along with these technologies is that the cuttings need to travel longer distance to the ground surface. In addition, the effect of the drill rod rotation on the cuttings transport does not exist because hole bottom mud motor is usually used in FR. To find a solution for this problem, the cuttings transport mechanism was analyzed based on the drilling mud hydraulics, and then, an equation of cuttings transport distance was derived. It found that the average drilling mud velocity in the annulus and the consistency index of drilling mud are the two most important factors related to the cuttings transport distance. To help with the cuttings transport, a new MMH drilling mud system, which provides a high consistency index and a low flow index, was used in rock HDD projects, instead of the common Bentonite-water drilling mud system.

Numerical Simulation on Cuttings Transport with Drillpipe Rotation in Extended Reach Well

Computational Fluid Dynamics (CFD) is used to simulate the solid-liquid two-phase flow in the annulus. The results show that the mixture of liquid and solid moves in spiral in horizontal annulus, and the solid phase distributes asymmetrically in the annulus. The distribution of solid volume fraction and the velocity of liquid phase and solid phase in annulus are given. The thickness of cuttings bed of rotating drill pipe is 1/3 of that of non-rotating drill pipe. Main factors which influence the cuttings transport in the annulus are analyzed, and the following results are got: the thickness of cuttings bed changes sensitively when the rotation speed of drill pipe ranges from 80rpm to 120rpm, the rotation of drill pipe disturbs the flow of liquid and solid in annulus, improving the cleaning of annulus.

Rapid ice drilling with continual air transport of cuttings and cores: General concept

This article describes the investigation of the feasibility of rapid drilling in ice sheets and glaciers to depths of up to 600 m, with cuttings and cores continually transported by air reverse circulation. The method employs dual wall drill rods. The inner tubes provide a continuous pathway for the chips and cores from the drill bit face to the surface. To modify air reverse circulation drilling technology according to the conditions of a specific glacier, original cutter drill bits and air processing devices (air-cooled aftercoolers, air receivers, coalescing filters, desiccant dryers) should be used. The airflow velocity for conveying a 60-mm diameter and 200-mm long ice core should not be lower than 22.5 m/s, and the minimal airflow rate for continual chip and cores transport is 6.8 m3/min at 2.3–2.6 MPa. Drilling of a 600-m deep hole can be accomplished within 1.5 days in the case of 24 h drilling operations. However, to avoid sticking while drilling through ice, the drilling depth should to be limited to 540 m at a temperature of −20 °C and to 418 m at a temperature of −10 °C.

Predicting fiber drag coefficient and settling velocity of sphere in fiber containing Newtonian fluids

In petroleum industry, fiber containing fluids are widely used as drilling fluids or fracturing fluids to improve the efficiency of cuttings transport during drilling or proppant transport during fracturing. Accurate prediction of fiber drag coefficient and settling velocity of sphere in fiber containing fluids is beneficial to design and optimization of fiber drilling/fracturing fluids applications. In this paper, a visualization apparatus and high-speed camera system are used to record the settling process in fiber containing Newtonian fluids. 283 tests involving different fiber concentrations (0.00%–0.10%), sphere diameters (1–10 mm), particle densities (2680, 4450 and 7960 kg/m3) and fluid viscosities are conducted. The fiber drag force is redefined to be suitable for spheres with different density. The effects of fiber length and fiber concentration on fluids viscosity and particle settling are investigated. The relationship between fiber drag coefficient and particle Reynolds number is obtained based on the experimental data. An explicit settling velocity equation which directly predicts settling velocity of sphere in fiber containing Newtonian fluids is proposed by correlating the total drag coefficient with the dimensionless sphere diameter. The average relative error is 4.4%, which indicates predictions of settling velocity are in good agreement with measured settling velocity. The models for predicting fiber drag coefficient and settling velocity are valid with particle Reynolds number ranging from 0.05 to 167 and fiber concentration ranging from 0.00% to 0.10%. Besides, a trail-and-error procedure and an illustrative example are presented to show how to calculate fiber drag coefficient and settling velocity in fiber containing fluids. Results of this study may provide some basis for the better field applications of fiber containing fluids.

Temperature and pressure effects of drilling fluid on cutting transport using CFD simulations

AbstractSimulation of liquid–solid flow in annulus of oil wells is of a great importance to predict the two‐phase flow field in wellbore accurately. In this paper, direct effects of drilling fluid rheological properties by Herschel–Bulkley model on cuttings transportation, pressure drop, and other parameters of two‐phase flow are numerically investigated at different temperatures and pressures. Recent studies have not addressed these effects. Thus, a 3D form of a steady‐state and isothermal model is used to simulate the two‐phase flow in various temperatures and pressures of drilling fluid, flow rates, and drilling pipe rotations. The governing equations created a system of coupled partial differential equations solved using the iterative finite volume method. The comparisons between the results of the model and experimental data and also analytical relation showed that the model can accurately predict two‐phase flow in the annulus. The results indicated that the elevation of temperature and reduction of pressure contributes to a decrease in the cuttings transportation. For drilling fluid velocity of 0.75 m/s, the cuttings transportation has been decreased 2.08% by increasing temperature from 70°C to 90°C in 0.1 MPa, whereas in pressure of 10 MPa, about 1.63% reduction on the transportation of cuttings yielded. © 2017 Curtin University and John Wiley & Sons, Ltd.

Simulation on Cuttings Transport with Drillpipe Rotation in Highly-Inclined Well Section

Hole cleaning is one of the key techniques of extended reach drilling. Compared with horizontal and vertical well section, the cuttings transport in inclined section is more complicated and difficult to be solved analytically, especially affected by drill pipe rotation. Computational fluid dynamics method is used to simulate the cuttings-mud two-phase flow in the annulus of inclined section. Simulation result shows that back flow is a remarkable feature of cuttings transport in inclined well section. Drill pipe rotation turns the axial motion of cuttings in annular into the helical motion. Drill pipe rotation can not only reduce the total cuttings concentration in annular, but also increase the average cuttings velocity. Section with 40 ～ 60 degree of deviation angle is the most difficult cleaned section, where cuttings concentration and pressure drop are also bigger than the rest sections.

Biopolymer Substitution and Impact on Cuttings Transport of a Lightweight Water-Based Drilling Fluid

Abstract The aim is to determine the impact of substitution of a local material for another, on rheological properties and hole cleaning capability. A local biopolymer Mucuna solannie was used as a substitute for another biopolymer, Detarium microcarpum, primarily as a viscosifier in a water-based drilling fluid. Tests were carried out using standard equipment and specifications. Variations in transport efficiency and required minimum fluid flow rate at same cuttings concentration (CC) were recorded in the 12¼ in vertical hole section, while in the 8½ in directional section, the maximum ROP that can be sustained while still maintaining adequate hole cleaning was obtained by graphical method. Yield stress values of 2.7, 3 and 12.4 lb/100ft 2 were calculated based on different approaches. In the 12¼ in section, TE of 99.98% and CC of 5.002 vol.% were observed at 300 ft/h with minimum fluid flow rate of 657 gpm for the Mucuna solannie mud, from a MATLAB cuttings transport program, compared with TE of 99.98 and 98.55% at same CC of 5.002 vol.% for the Detarium microcarpum and XCD/Polymer muds respectively used as control samples. Required minimum fluid flow rates are 612.4 and 621.3 gpm respectively. In the 8½ in section, with the Herschel-Bulkley mud, an ROP of about 8.2 ft/h was obtained as the maximum drilling rate at 40° inclination. The lightweight mud exhibited good cuttings transport in the vertical well, and might not be suitable for highly deviated wells. Comparison of this kind is necessary for evaluation of respective constituents in a mud formulation where several local materials are combined, in a wholly-replaced-bentonite mud. Different models and approaches yielded various yield stress values; hence, comparison of accuracy of models in predicting yield stress is necessary. Keywords: Cutting carrying index, cuttings transport, lightweight mud, Mucuna solannie. Cite this Article Uwaezuoke N, Onwukwe SI, Igwilo KC et al. Biopolymer Substitution and Impact on Cuttings Transport of a Lightweight Water-Based Drilling Fluid. Journal of Petroleum Engineering and Technology. 2017; 7(2): 54–64p.

Hole-cleaning performance comparison of oil-based and water-based drilling fluids

Cuttings transport is a topic of great interest in the oil and gas drilling industry. Insufficient cuttings transport leads to several expensive problems. Knowledge and selection of the drilling fluids is one of the important factor for efficient hole cleaning. It has been observed, however, that the hole cleaning performance of drilling fluids can be different even if the fluid rheological properties are similar as measured in accordance with API specifications. The reasons for stated difference in the behavior of drilling fluids are not well understood. The main objective of present work is to evaluate hole cleaning efficiency of an oil-based drilling fluid (OBM) and a water-based drilling fluid (WBM) whose viscosity profiles are similar as per API specifications.Hole cleaning efficiency of an oil-based drilling fluid and a water-based drilling fluid whose viscosity profiles are similar was investigated. The fluids tested were industrial fluids used in the field and were sent to us after reconditioning. Experimental studies were performed on an advanced purpose-built flow-loop by varying flow velocities and drill string rotation rates. The flow loop had a 10 m long annulus section with 4″ inner diameter wellbore and 2″ outer diameter fully eccentric drill string. Pressure drop and sand holdup measurements were reported. Rheological investigations of the same fluids were used to understand the difference in the behavior of the drilling fluids tested. Higher pressure drop was observed for WBM compared to OBM, and for both fluids, the pressure drop increased with drill string rotation speed. In case of no drill string rotation, better hole cleaning performance was observed with the oil-based fluid compared to the water-based fluid. With the presence of drill string rotation, hole cleaning performance of both the fluids was nearly the same.

Viscoelastic properties of drilling fluids and their influence on cuttings transport

Cleaning the wellbore from drilled material is important to continue drilling efficiently and to prevent high torque and drag, as well as reducing down time due to reaming operations. Drilling fluids used for this purpose are complex fluid systems, generally with water or oil as a base substance. Water-based and oil-based drilling fluids are performing differently in terms of hole cleaning, even when their density and viscosity are fairly similar. Comparative studies performed by several research groups have resulted in diverse outcomes, showing superior behavior of either water- or oil-based drilling fluids, or no significant differences between the fluids at all.In the present study, a water-based and an oil-based drilling fluid have been investigated regarding their viscoelastic properties, using the Anton Paar rheometers MCR 102 and MCR 302. Amplitude sweep tests, 3-intervall-thixotropy tests, temperature sweep tests, and low-shear rate flow curves with controlled shear stress and shear rate were performed and analyzed. Cuttings transport experiments in a flow loop with a 10 m long test section and a free-whirling inner-rotating drill string were conducted with the same fluids to study the hole-cleaning efficiency of different drilling fluids. The results from both experimental parts are presented. The rheometer results are used to interpret the cuttings transport behavior in the flow-loop experiments. The water-based drilling fluid was a KCl brine based fluid, and the oil-based fluid a water-in-oil emulsion. Both fluids are actual field fluids, used during drilling operations on the Norwegian Continental Shelf and have similar viscosities and densities.The oil-based drilling fluid showed better hole-cleaning abilities during the flow-loop experiments, leaving a lower sand bed in the test section. This fluid displayed viscoelastic properties, such as a yield stress and a linear viscoelastic range. The water-based drilling fluid showed no yield stress and a 50–100% higher elasticity than the oil-based drilling fluid.

Experimental Study on the Wellbore-Cleaning Efficiency of Microhole-Horizontal-Well Drilling

SummaryMicrohole-drilling technology is a high-efficiency and low-cost technology that has developed rapidly in recent years. However, during microhole-horizontal-well drilling, cuttings are easy to deposit at the bottom of the wellbore because of gravity and nonrotation of drillpipe. Inadequate drill-cuttings removal can cause costly problems such as excessive drag, and even mechanical pipe sticking. Therefore, many laboratory studies as well as field observations have been directed toward addressing the cuttings-transport problem. In the present study, a full-scale horizontal-cuttings-transport flow loop was set up and a total of 136 experiments were conducted. By analyzing the cuttings volumetric concentration and the dimensionless height of the cuttings bed, the effects of flow rate (0.00058–0.00078 m3/s), cuttings diameter (0.0003–0.005 m), rate of penetration (ROP) (0.00211–0.00636 m/s), eccentricity (0–0.8), and wellbore diameter (0.04–0.08 m) on wellbore-cleaning efficiency were obtained. It was found that cuttings-transport efficiency increased first and then decreased as cuttings diameter increased. Flow rate was the main parameter. Higher flow rate, lower ROP, lower eccentricity, and smaller drillpipe/wellbore-diameter ratio all led to higher wellbore-cleaning efficiency in microhole horizontal wells. In addition, a model for estimating the cuttings volumetric concentration and the cuttings-bed height was proposed by dimensional analysis dependent on the thorough understanding of the effects of various variables. The predictions were good when they were compared with the experimental data obtained. Major factors influencing cuttings transport in the field during microhole drilling and conventional rotary drilling were compared, and the reasons for their differences were discussed. The limitations of the proposed model in this study were also discussed. These results could provide a factual basis for improving microhole-drilling hydraulics.

Cuttings-Transport Simulation Combined With Large-Scale-Flow-Loop Experimental Results and Logging-While-Drilling Data for Hole-Cleaning Evaluation in Directional Drilling

SummaryThe authors have developed a 1D two-layer-model transient-cuttings-transport simulator that predicts the transient behaviors of cuttings transport, including the concentration and slip velocity of suspended cuttings, bed height of cuttings, annular pressure, and equivalent circulating density (ECD) along the entire trajectory of a complex extended-reach well. Model parameters, such as annulus-friction factor, cuttings-deposition rate, and re-entrainment rate, were determined from numerous experiments previously performed by use of a large-scale cuttings-transport flow-loop apparatus. This apparatus simulates the complex flows in borehole annuli at various inclination angles, ranging from vertical to horizontal. In this study, the authors validate the model and analyze the cuttings transport by use of field data in a directional well, in which the annular ECD was measured by logging while drilling (LWD), and the rate of the returned cuttings was measured at the surface. On the basis of the simulation study, the potential of the developed transient-cuttings-transport simulator for the predrilling- and post-drilling-phase analyses is discussed. Moreover, the authors evaluate the transient-hole-cleaning conditions and the ECD behavior from the LWD data.

CFD-DEM modeling of cuttings transport in underbalanced drilling considering aerated mud effects and downhole conditions

This paper presents a developed CFD (Computational fluid dynamics)-DEM (Discrete elements method) model to study the cuttings transportation in aerated mud drilling process for inclined annuli at downhole conditions. The model is conducted to determine the effects of liquid flow rate, air injection rate, annulus inclination angle, elevated temperature and pressure on the cuttings transport efficiency. The motion of the fluid is computed using CFD based approach with gas–liquid interface capturing provided by the volume-of-fluid (VOF) method. The dynamics of cutting phase is studied by DEM using soft sphere approach in order to take into account the particle collision phenomenon. The continuum and dispersed phases are strongly coupled via the interaction forces such as drag force, lift force and pressure gradient force, which are considered in the developed CFD-DEM model. In addition, the real gas law governs the dynamics of injected air and the gas-liquid viscosity is assumed to be temperature dependant. The predicted results have been compared with the experimental data and fair agreement has been established. The results have indicated that in addition to the liquid flow rate, the cuttings transport efficiency is affected by gas-liquid ratio, ambient temperature and injection pressure.

Non-destructive determination of carbohydrate reserves in leaves of ornamental cuttings by near-infrared spectroscopy (NIRS) as a key indicator for quality assessments

The importance of carbohydrate reserves in leaves for rooting performance of ornamental cuttings is well-known. Especially under environmental conditions unfavourable for photosynthesis, sufficient reserves are indispensable for an undisturbed adventitious root formation and to prevent senescence of leaves during rooting. However, due to time and costs, established methods for carbohydrates analysis are not suitable for implementation in global production chains of ornamentals. Near-infrared spectroscopy (NIRS) might be a valuable alternative. To explore the suitability of this technique, NIR spectra were taken from intact cuttings as well as from upper and lower side of detached leaves of chrysanthemum and pelargonium cuttings and partial least squares (PLS) calibration models were developed for glucose, fructose, sucrose and starch in leaves, which were analysed by a stepwise enzymatic-photometric method. Presumably because of a high percentage of cuttings with very low amounts of glucose, fructose and sucrose, calibration models for single soluble sugars and sum of soluble sugars were poor (RCV2 ≤ 0.5, RPDCV ≤ 1.5), while prediction performance for starch and sum of starch and soluble sugars was quite good (R2 > 0.8, RPD > 2.0, RER > 10). The high number of cuttings with depleted reserves of soluble sugars seems to have been at least partly caused by transportation of cuttings, before NIR analysis, from stock plant facilities in Africa and Latin America to Central Europe. The quite low levels of leaf carbohydrates on delivery at rooting facilities cannot be detected by NIRS properly. Thus, NIRS seems to be more suitable for monitoring of leaf carbohydrates in stock plants to optimise crop management than for assessment of cutting quality before rooting.

Uncertainty quantification for cuttings transport process monitoring while drilling by ensemble Kalman filtering

The aim in this work was to develop a method to draw our conclusions for the uncertain quantities of interest in a real problem in oilfield, namely the cuttings transport problem, given the limited data available. The cuttings transport process is subject to disturbances and is influenced by various factors in a stochastic and uncertain manner. In addition, the drilling environment is very complex to understand fully, and to model efficiently and accurately. An experiment was conducted to monitor the process in real-time via time-series measurements of distributed pressure transducers along the drillstring. A mathematical model describing the dynamic process of cuttings transport is developed, which aims to capture the dominant characteristics of the process, without attempting to model reality perfectly; modeling and measurement errors are represented by uncertainties in model inputs, parameters, and states. The proposed model is described in detail, and is incorporated in the Bayesian framework (via ensemble Kalman filtering) to make our best estimate about the location and amount of cuttings transported along the wellbore in real time, given the available data. The estimations of the uncertain process parameters are described.

Modeling of the Critical Deposition Velocity of Cuttings in an Inclined-Slimhole Annulus

SummaryA coupled computational-fluid-dynamics/discrete-element-method (CFD/DEM) theory is developed to simulate the transportation of cuttings in an inclined-slimhole annulus. In this theory, the liquid phase is governed by the Eulerian continuum equation and the Navier-Stokes momentum-conservation equation. The collisions between particle and wall, between particle and drillstring, and among particles are treated as the spring-damping system, and the particle-contact model is then established. The particle-governing equation based on Newton's second law is established by analyzing the forces on the particles. The CFD/DEM theory is developed by analyzing the forces on the dispersed particles per unit volume, which is the source term in the coupling. Using this CFD/DEM coupling algorithm, cuttings transportation in slimhole drilling is investigated, and the particle velocity and distributions are calculated. The calculated annular cuttings concentration is in good agreement with experimental data from the literature (Kim et al. 2014). The effects of the annular-fluid velocity, angle of inclination, cuttings concentration in feeding, and rotation speed of the drillstring on the annular cuttings concentration are also investigated. A correlation of critical deposition velocity has been proposed by use of dimensional analysis and nonlinear regression analysis. The correlation of annular cuttings concentration is also concluded. The new method proposed in this work is of great significance to hole-cleaning calculation and hydraulic-parameter design in slimhole drilling.

A Fast Graphic Approach To Estimate Hole Cleaning for Directional Drilling

SummaryIn this paper, a set of charts is developed to allow drilling engineers to quickly estimate the cuttings volumetric concentration in the wellbore. The most-important parameters for hole cleaning are divided into several ranges on the basis of their sensitivity to cuttings concentration in the wellbore. A series of charts is obtained by running a hole-cleaning simulator, which is based on a large number of experimental and modeling studies of cuttings transport. The difference between the charts’ prediction results and experimental data is within 20%. Drilling engineers can quickly estimate the cuttings volumetric concentration by looking up the charts and conducting very-simple calculations.

Improving Drilled Cuttings Lifting Using Polypropylene Beads in Water-Based Mud at Different Annular Mud Velocities

An effective drilled cuttings lifting from the bottom hole to the surface improves drilling performance. The transportation of drilled cuttings becomes more challenging when drilling a high angle or horizontal well. A sufficiently high annular mud velocity is essential to prevent drilled cuttings from settling and forming stationary beds on the low side of a hole. This can cause several drilling problems such as high torque and drag, stuck pipe, etc. This problem has been addressed via an experimental work which studied the effect of annular mud velocities on drilled cuttings removal using water-based mud with polypropylene beads in vertical, deviated, and horizontal holes. It was accomplished using a 3.96 m long flow loop which comprised 50.8 mm transparent acrylic section with a simulated drill string. The annular mud velocity was varied from 0.27 in/s to 1.06 m/s at ambient condition. The experimental results showed that increase in annular mud velocity has improved hole cleaning, i.e., cuttings transport ratio experienced an improved performance in the turbulent flow than in laminar flow. The findings further demonstrated that the presence of polypropylene beads in water-based mud has contributed positively to the performance of drilled cuttings lifting in a vertical hole by 9% in a turbulent flow.

A New Mathematical Method for Solving Cuttings Transport Problem of Horizontal Wells: Ant Colony Algorithm

Cuttings transport problem has long been recognized as one of the key difficulties in drilling horizontal wells, and the models in cuttings transport research are usually formulated with highly nonlinear equations set. When using Newton methods to solve real engineering problems with nonlinear equations set, the problems of result dependence on initial values, Jacobian matrix singularity, and variable outflow of its definition domain in iterations are three of the often-encountered difficulties. In this paper, the ant colony algorithm is applied to solve the two-layer cuttings transport model with highly nonlinear equations set. The solution-searching process of solving nonlinear equations set is transformed into an optimization process of searching the minimum value of an objective function by applying ant colony algorithm. Analyzing the results of the example, it can be concluded that ant colony algorithm can be used to solve the highly nonlinear cuttings transport model with good solution accuracy; transforming the solution-searching process of solving nonlinear equations set into an optimization process of searching the minimum value of the objective function is necessary; the real engineering problem should be simplified as much as possible to decrease the number of unknown variables and facilitate the use of ant colony algorithm.

Optimization of Weight on Bit During Drilling Operation Based on Rate of Penetration

Drilling optimization is very important during drilling operation, to save time and reduce cost of operation thus increases the profit. Drilling optimization aims to optimize controllable variables during drilling operation such as weight on bit and bit rotation speed for obtaining maximum drilling rate. In this study had been selected the effects of several parameters during drilling operation. Important parameters such as depth, density, bit weight, rotary speed per minute, efficiently cuttings transported hole is to take into account the factors given in Table 3. It was concluded that average annular fluid velocity is between 414.17 to 581.24ft/min, dominating parameter on cuttings transport, the higher the flow rate. s Another important factor is the mainly the rheological properties of the drilling fluid such as Vis=45-50 s, p.v=12, PH=10, mud weight is between 8.57 ppg to 8.74 ppg. The rate of penetration for the field data had been calculated for several data points. Although the weight on bit has increase from 6600 until 19800 lbs, 1137.41 lbs/in, rate of penetration still in the range of 11.74 ft/hr. The optimized bit weight is 13200 lbs or 1077.55 lbs/in during drilling operation, penetration rate for depth 4330.02 ft is suitable due to formation that is may be high in strength.

A mathematical model for estimating cuttings bed thickness in horizontal and deviated wells

A mechanistic model is presented to estimate cuttings bed thickness in horizontal and inclined wellbores with and without pipe rotation using computational fluid dynamics (CFD). The model described in this work incorporates the effects of the hole inclination and pipe rotation on cuttings bed thickness. In this study, Navier-Stokes equations for turbulent flow are numerically solved using finite differences technique and a computer code is developed for CFD model. Extensive cuttings transport experiments are conducted using a flow loop. The pressure drop and cuttings bed thickness were recorded in addition to the other test conditions. Using the experimental data, the performance of the proposed model is analysed. The prediction results are satisfactory with determination coefficients, R2 = 0.89 and average absolute percent error (AAPE) = 9.78 for cuttings bed thickness. [Received: January 18, 2016; Accepted: July 17, 2016]