Cuttings Transport Research Articles

Investigation on horizontal and deviated wellbore cleanout by hole cleaning device using CFD approach

AbstractThe application of the hole cleaning device in downhole is a new technology for removing cuttings bed, and it can increase the efficiency of cuttings transport. This paper mainly studies the effects of the helical angle and the rotational speed of the blade of the hole cleaning device on the swirl strength of decaying swirl flow and drilled cuttings deposition behavior. A three‐dimensional computational fluid dynamics (CFD) model is established using the Eulerian‐Eulerian two‐fluid model, Realizable k‐ε turbulence model, and Sliding Mesh technique for simulating the two‐phase fluid flow. The results have been compared with available data in the literature, and a good agreement is found. In order to understand the decay behavior of the swirl flow along the flow direction, the initial swirl strength, the swirl number, and the decay rate of swirl are analyzed in detail in single phase. The effects of the swirl flow induced by the blade on the deposition behavior of drilled cuttings under different rotational speed and helical angle are studied. A new deposition index is used to evaluate the effective distance and hole cleaning efficiency of the swirl flow under various parameters. It has been observed that using the hole cleaning device can improve the hole cleaning performance. The research results of this paper is instructive to the design of the hole cleaning device using in the drilling engineering.

Investigating the Jet Comminuting Process in Cuttings Transport by Coupling the CFD/DEM Method and Bonded-Particle Model

Summary Jet comminuting technology has proved to be an effective means of solid particle pulverization, and current research attempts to introduce it for drilling work to reduce cuttings size, because smaller cuttings are easy to circulate out of the bottom, thus can effectively prevent the formation of cuttings bed, especially in horizontal drilling. In this paper, the feasibility of cuttings’ comminution by jet is studied by means of numerical simulation with secondary development. The coupling analysis methods—including the computational–fluid–dynamics/discrete–element–model (CFD/DEM) modeling for the interaction between fluid and cuttings and the particle replacement and bonding modeling for cuttings breakage—are used to characterize the jet comminuting process of cuttings. Input parameters of simulation are reliable and verified by uniaxial compression tests. Case studies presented here indicate that cuttings can be considerably accelerated by 20 to 30 m/s through the throat, which provides a good effective speed for the cuttings. After being accelerated by the fluid and crushed with the target, the vast majority of cuttings results in smaller debris. Also, increasing the inlet speed affects the crushing efficiency. The inclination of the target at near 65° shows good results. This paper proposes a new perspective to introduce the jet comminuting technique for drilling operations, and its findings could help in guiding engineering design in the future.

Experimental investigation of the effect of henna leaf extracts on cuttings transportation in highly deviated and horizontal wells

Henna leaf extracts (HLE) was used to formulate henna water-based mud (HWBM) and its performance on cuttings transport efficiency (CTE) was compared with bentonite water-based mud (BWBM) and fresh water. Tests were conducted in a laboratory-scale flow-loop equipped with a 16-ft-long test section consisting of a concentric annulus outer casing (3.5-in. ID) and a static inner drill-pipe (2.4-in. OD) at hole-angles of 0°, 45°, 60°, 75° and 90° with annular fluid velocities (1.1, 1.54, 1.98 and 2.31 ft/s) using a cuttings size diameter of 1.0 mm. Experimental results showed that HWBM have better rheological and filtration properties before and after thermal aging tests than BWBM. Plastic viscosity (PV) was 7.4 cP for BWBM and 6.5 cP for HWBM. Apparent viscosity (AV) of BWBM was 12.7 cP and 13 cP for HWBM. The yield point (YP) of BWBM was 10.5 lb/100 ft2 and 12.2 lb/100 ft2 for HWBM, while high pressure high temperature (HPHT) filtrates volume of HWBM was increased by 70.4% from 5.4 to 9.2 ml but, that of BWBM was increased by 94.4% from 7.1 to 13.8 ml. After heating, the PV of BWBM and HWBM decreased by 6.76% and 1.54%, respectively. The YP of BWBM and HWBM was reduced by 21% and 4.1%, respectively. 45° was the most challenging hole-angle, which needs attention while preparing drilling mud. The findings reported in this study could open new areas of research, in particular HLE additive to boost the drilling industry.

Numerical Simulation and Experimental Study of Cuttings Transport in Narrow Annulus

With the development of petroleum industry, it needs an efficient drill method such as under balanced drilling (UBD) to enhance the rate of penetration (ROP). However, borehole instability is a problem that UBD must face. The coiled tubing partial underbalanced drilling (CT-PUBD) is proposed to try to solve this problem while keeping an underbalanced condition with high ROP. This paper analyzes the laws of cuttings transport in the narrow annulus focus on this new technique through the simulations and experiments. From the results of simulations, it obtains that the particle velocity declines with the increase of rotational speed and increases with the increase of flow rate. The particles become concentrated as the flow rate increases, and the high flow rate limits particles in a small area. The particle distribution undergoes a process of concentration, dispersion, and concentration as the rotational speed increases. The high rotational speed makes particles deviate from the high fluid velocity area, which causes low particle velocity. The relationships between particle velocity and rotational speed and between particle velocity and flow rate are fitted through the equations, respectively. The phenomenon of collision of particles, sinking and rising of particles, and variation of particle velocity are observed in the experiments. The error between the particle velocity in the experiment and numerical simulation is less than 8.5%. This paper is an exploratory study conducted for the cuttings transport in narrow annulus.

Experimental investigation of hole cleaning in directional drilling by using nano-enhanced water-based drilling fluids

Inadequate hole cleaning often leads to challenges in drilling and well completion operations such as low rates of penetration, pipe sticking, losing tools, difficulties in liner/casing placements, etc. Designing a drilling fluid with improved rheological properties would be a solution to increase cuttings transportation efficiency. This study investigates the performance of nanosilica water-based drilling fluids for the hole cleaning process in directional drilling operations. Different inclination angles have been considered in a flow loop system with different rotational speeds (0 and 150 rpm) to simulate the drilling conditions in a wellbore. The performance of nano-enhanced drilling fluids in the cuttings removal process was compared with conventional water-based drilling fluids, and it was found that silica nanoparticles increased the cuttings transport efficiency in all experiments. The results indicated that the presence of nanosilica in the mud increased the colloidal interactions with cuttings and contributed to the improvements in cuttings transportation efficiency by 30.8–44% for different nano-enhanced water-based drilling fluids used in this study. The implementation of nanosilica in water-based drilling fluids showed promising results in the hole cleaning process which demonstrates the feasibility of using them in extended reach drilling operations.

Simulation of steady-state cuttings transport through a horizontal annulus channel

The current study is devoted to simulating cuttings transport by drilling fluid through a horizontal section of borehole with an annular cross section. Drill pipe rotates in fixed eccentric position. Steady-state flow is considered. Cuttings are rigid spheres with equal diameters. The carrying fluid is drilling mud with Herschel-Bulkley rheology. Suspension rheology depends on local shear rate and particles concentration. Continuous mixture model with algebraic equation for particles slipping velocity is used. Two hydrodynamic regimes are considered: axial flow without drill pipe rotation and with drill pipe rotation. In the case of axial flow was shown that increasing of power index n and consistency factor k increases pressure gradient and decreases cuttings concentration. Increasing of yield stress leads to increasing of pressure gradient and cuttings concentration. Cuttings concentration achieves constant value for high yield stress and not depends on it. Rotation of the drill pipe significantly changes the flow structure: pressure loss occurs and particles concentration decreases in the cross section. Two basic regimes of rotational flow are observed: domination of primary vortex around drill pipe and domination secondary vorticity structures. Transition between regimes leads to significant changes of flow integral parameters.

A study on non-spherical cuttings transport in CBM well drilling by coupled CFD-DEM

ABSTRACTDue to the specificity of coal rock containing CBM (coal bed methane), large-sized cuttings from coal bed drilling present abnormal appearances which make the transport of cuttings more troublesome. Simulations of the transport of large-sized and non-spherical drilling cuttings in the horizontal well-bore annulus possesses both theoretical challenges and engineering worth. In this work, a coupled CFD-DEM model is developed and a multi-sphere method is adopted to construct the non-spherical cuttings particles including cubic and long flaky particles. Validation with the experimental data reveals the well applicability of the developed CFD-DEM model. The movements as well as the sedimentations of cuttings are discussed in detail. The influences of fluid velocity and particle shapes on the transport efficiency of cuttings are studied and more attention is paid to flaky cuttings. The results show that, with a consistent equivalent volume, relatively good performance happens to the 20 mm spherical particles while local piled bed appears to the flaky particles; however, cuttings in cubic particles behave the worst. In the chosen conditions, transport efficiency drops dramatically when the volume fraction of the flaky cuttings exceeds 10%. Work in this paper is expected to be able to be applied to CBM drilling engineering.

Metabolic nitrogen and carbohydrate pools as potential quality indicators of supply chains for ornamental young plants

The plasticity and physiological functions of metabolic nitrogen (N) and carbohydrate pools in the tissues of axillary shoot tip cuttings are poorly understood despite their pivotal role in pre-harvest growth, post-harvest abiotic stress resilience, survival and adventitious root (AR) formation in young plant supply chains for ornamental crops. Therefore, we studied the N and carbohydrate pools in response to contrasting experimental environments by both the graduated N supply of stock plants and the different dark storage amounts of the cuttings as well as during multi-seasonal transport of commercial cuttings from low-latitude stock plant facilities.The initial survey of cuttings from the supply chains confirmed species-specific optimal total nitrogen (Nt) levels and indicated further species differences both in Nt allocation to metabolic N pools and in the total carbon (Ct)/Nt ratio in Chrysanthemum (CHRY), Euphorbia (POI), Impatiens (IMP), Osteospermum (OSTEO) and Pelargonium (PEL). For CHRY and PEL, frequency distributions of the Nt content revealed that a significant percentage of commercial cuttings is not optimally supplied. The PEL cuttings responded to experimental dark storage with a gradual increase in mobile organic N pools at the expense of the proportion of Nt of the matrix protein pool, which corresponded to reduced survival and rooting capacity, whereas the Nt and nitrate levels remained unchanged. Analyses of commercial cuttings confirmed regular incidents of shifts in Nt allocation from insoluble protein-N to mobile N pools; these shifts coincided with severe carbohydrate depletions during transport. Therefore, compared with leaf tissues, stem tissues displayed a higher resilience against carbohydrate depletion.In conclusion, monitoring deviation ranges and changes among N pools in addition to carbohydrates and Nt is suggested. This monitoring is appropriate not only during growth before harvest but also throughout postharvest and helps to identify risks of low survival rate and low rooting before cuttings are planted. As a first parameter, a set of indicators for decision support is suggested. In this regard, the potential of near-infrared spectroscopy (NIRS) is discussed as rapid diagnostic tool that can easily be applied at critical points of the supply chains.

Transportation of Cuttings in Inclined Wells

One of the most important functions performed by drilling fluid is the removal of cutting from the bottom of the hole to the surface. This function must be performed efficiently if not, the cuttings produced during drilling process will accumulate in the annulus. This problem in directional drilling is featured by gravitational forces. Problems resulting from inefficient cutting transport include pipe stuck, wear of bit, reduction in penetration rate, high torque and drag with many other problems encountered. In high angle deviated wells, the cutting goes through a complex path to the surface where some of the cuttings gravitate to the low side of the well. Reduction in any problem associated with improper cutting transport require good understanding in cutting transport mechanisms. This research focuses on calculating the minimum annular velocity of drilling fluid and minimum pump flow rate which is required to achieve hole- cleaning and lifting of the cutting to the surface, taking into consideration the main parameters that affect the coring capacity of the drilling fluid, for this purpose, data of a deviated well (X) located in Kurdistan region of Iraq is collected to determine slip velocity, annular velocity, critical flow rate and carrying capacity index taking in consideration the mud used and the angle of the deviation using the drilling formula spread sheet V1.6.

A Statistical Model for Hole Cleaning and Cuttings Transport Efficiency During Drilling of Wells

This paper is about evaluating the minimum efficiency of hole cleaning and cuttings transport during drilling of vertical and deviated wells by a statistical-regression model using the Buckingham Pi theorem of dimensional analysis technique. The model will be evaluated by deriving the unknown proportionality constant and five exponents utilizing the statistical - regression curve of the least- squares fitting method and using the prepared field data from five drilled wells in the Gulf of Suez Company (GUPCO) fields. Then, the model's equation will be differentiated partially with respect to one of the independent parameters which are average annular velocity of drilling fluid, drilling rate of penetration, drill string rotation, drilling fluid density, yield point, plastic viscosity, density of drilled-cuttings, and coefficient related to hole deviation angle. Then it will be evaluated over a range of values for these parameters. From the parametric study, it is found that the hole cleaning efficiency increases as the average annular velocity, yield point, plastic viscosity, drill string rotation, density of drilling fluid increase. It is found also that efficiency decreases when drilling rate, cuttings density, hole deviation angle increase. Finally, it is recommended that the model can be applied in oil well drilling industry in different fields and horizontal wells rather than the vertical and deviated wells used in the paper.

Cellulosic Cyperus esculentus L. as a filtrate loss modifier in field applicable aqueous and non-aqueous drilling fluids

The design and formulation of drilling fluids require additives that are cost-effective and environmental friendly in line with international best practices. This study was conducted to investigate the potentials and effects of Cyperus esculentus (Tiger Nut) as a filtrate loss modifier in field applicable aqueous and non-aqueous drilling fluids. Sixteen (eight aqueous and eight non-aqueous) drilling fluid systems were formulated, four aqueous and non-aqueous had Cyperus esculentus as a filtration additive, while the others do not contain the additive. The rheological properties, as well as the fluid filtration properties of the drilling muds, were investigated and compared with standard drilling mud. To ascertain validity, the results obtained were validated with the classic filtration model to ensure fit. Results obtained showed that the formulated mud systems had rheological properties that favored the suspension and transportation of drill cuttings, as well as the prevention of flocculation and clogging of drill strings. The rheological properties also showed a progressive trend as the concentrations of the additive were increased from 2 to 8 ppb. It was also further observed from the API and HPHT filter press test that the increase in the concentration of the additive exhibits a progressive trend that can be compared with the standard. In addition, it was observed from the classic filtration model that the experimental results from both mud systems were fit for the adopted model.

An Eulerian-Lagrangian CFD study of a particle settling in an orthogonal shear flow of a shear-thinning, mildly viscoelastic fluid

For improving CFD models of particle transport in wellbore flows, i.e. cuttings transport, we have extended the Lagrangian Discrete-Particle-Model model of the commercial code ANSYS Fluent 17.2 to describe the motion of a particle settling in an orthogonal shear flow of a shear-thinning, mildly viscoelastic fluid. Essentially, the fluid strain rate as the magnitude of the fluid deformation rate tensor is corrected by a particle-induced shear rate. This corrected strain rate is used to compute an apparent viscosity. The fluid is treated as a Generalized Newtonian Fluid using Cross and Carreau material functions. Different drag laws are investigated, including one which accounts for the fluids viscoelastic wake structure behavior via a correction term. We validate the model with eight different particle trajectories representing different combinations of particle diameters, fluid flow rates and rheological properties (water and polymeric solutions) provided by Khatibi et al. [1].In general, the experimental trajectories are satisfactorily replicated by the CFD model. However, for small particles a trajectory mismatch is observed close to the lower channel wall. We find this mismatch to be a consequence of unexpectedly high particle x-velocities in the experimental data. Various possible causes are identified and discussed. More detailed experimental near-wall data of both particle and fluid velocities as well as more sophisticated modeling of the fluids rheology, including the rheology effect on the forces acting on the particles, may be required to minimize the mismatch.In addition, we further conclude that in case of the polymeric solutions particle drag is the dominant particle force, that the viscoelastic wake of the particle is not significantly affecting the trajectories, and that a Newtonian drag law may be used as long as the particle-induced shear rate is estimated with ‖vr‖/dp and a material function accounting for the limiting zero-shear Newtonian viscosity is applied.

Improving hole cleaning using low density polyethylene beads at different mud circulation rates in different hole angles

In oil and gas exploration and development, drilling a hole is one of the first and most expensive operations. The continuous demand from industry to reduce costs and operational problems has resulted in numerous innovative drilling technologies that allow us to drill directionally. Nevertheless, hole cleaning has become a problematic issue in directional drilling because drill cuttings tend to be deposited on the lower side of the deviated hole. Excess accumulation of cuttings significantly reduces the rate of penetration and indirectly increases the operational cost. To improve the cuttings transport efficiency in a deviated hole, low-density polyethylene (LDPE) beads were introduced into water-based mud for hole cleaning. LDPE beads travel rapidly through the mud column due to buoyancy and move the cuttings forward by drag and collision. The interaction between the LDPE beads and cuttings facilitates the cuttings transport process and prevents the cuttings from settling. In this study, different concentrations of LDPE beads (i.e., 1% to 5% by volume) and different flow rates (i.e., 0.4 L/s, 0.6 L/s, and 1.0 L/s) were used to determine the effects on cuttings transport efficiency. In addition, the hole angle was varied from vertical to horizontal to evaluate the significance of LDPE beads in assisting in transporting cuttings. The results denote that more cuttings can be removed from a hole with higher concentrations of LDPE beads in water-based mud. This finding is due to the higher frequency of collisions, which in turn produces larger impulsive force. In addition, the improvement in cuttings transport efficiency enabled by LDPE beads is more significant in a vertical hole than in a highly deviated hole. In summary, LDPE beads are a promising additive for drilling mud to effectively remove drilled cuttings from a hole.

Effect of orbital motion of drill pipe on the transport of non-Newtonian fluid-cuttings mixture in horizontal drilling annulus

The effect of orbital motion of drill pipe on the transport of non-Newtonian fluid and cuttings is simulated by means of the two-fluid model in combination with the kinetic theory of granular flow in the horizontal wellbore annulus. The drill pipe self-rotates around its own axis while pursuing a circular orbit around the axis of the wellbore annulus, in which the orbital radius is the eccentric distance of the drill pipe from the axis of the wellbore. The embedded sliding mesh method is adopted to achieve the effect of the orbital movement of the drill pipe wall on the liquid-solid mixture. The cuttings transport ratio (CTR) which is defined as the ratio of the concentration of injected cuttings to the concentration of cuttings retained in the annulus is chosen as the measurement to evaluate hole cleaning. Cuttings transport behaviors in the annuli with the four motion states of drill pipe are investigated respectively. Simulations indicate that if the drill pipe is not concentric, there must be the fluid force that causes the lateral movement of drill pipe when it rotates. The orbital motion of drill pipe improves cuttings transport ratio in the annulus due to the periodical stirring and entrainment effect on cutting particles. The tangential flow within the annulus is dominated by the orbital motion of drill pipe rather than the self-rotation. The secondary flow appears especially when the self-rotation and orbital motion of drill pipe are in the opposite direction. With the increase of the orbital radius, the cuttings transport ratio is improved and the pressure drop is reduced because of the agitation of the drill string against the flow field. Increasing the rotating speed of the drill pipe contributes to a better wellbore cleaning, while an excessive rotating speed causes a higher pressure drop. Although the orbital motion of the drill pipe improves the hole cleaning, it also greatly increases the resistance and resultant moment exerted by the liquid-solid mixture, especially at high rotation speeds and eccentricity ratios.

Experimental investigation of the effects of silica nanoparticle on hole cleaning efficiency of water-based drilling mud

Effective cuttings transports and hole cleaning is crucial for obtaining an efficient drilling operation. Recently, the use of nanotechnology have been exploited to improve rheological and filtration properties of water-based mud. Herein, water-based mud (WBM) was formulated with nanosilica to enhance cuttings and solid particles transports from the wellbore to the surface. Different weight percent concentrations of nanosilica (0.001–1.5 wt%) at three different flow rates in litres/seconds (0.4, 0.6 and 1.0) and cuttings sizes (small, medium and large) were used to investigate the formulated water-based mud lifting capacity of the drilled cuttings. Experimental results show that addition of the nanosilica concentrations to the WBM enhances the viscosity, thereby increasing the muds carrying and circulating capacity. Moreover, nanosilica water-based mud (n-WBM) displays improved mud stability with high propensity to prevent intrusion of formation fluids. The effect of cuttings size on the wellbore cleaning is minimal. The large cuttings size shows a lower degree of cuttings transportation compared with the small and medium cutting size. Accordingly, the small cuttings size has higher cuttings recovery to the surface. Finally, though increase in flow rate leads to more cuttings recovery, there is every tendency that much fluid flow rate will cause an increase in frictional pressure losses and equivalent circulating density, high pump pressure requirement and potential hole erosion.

Computational intelligence models for PIV based particle (cuttings) direction and velocity estimation in multi-phase flows

In multi-phase flow, the gas phase, the liquid phase and the particles (cuttings) within the liquid have different flow behaviors. Particle velocity and particle direction are two of the important aspects for determining the drilling particle behavior in multi-phase flows. There exists a lack of information about particle behavior inside a drilling annular wellbore. This paper presents an approach for particle velocity and direction estimation based on data obtained through Particle Image Velocimetry (PIV) techniques fed into computational intelligence models, in particular Artificial Neural Networks (ANNs) and Support Vector Machines (SVM). In this work, feed forward neural networks, support vector machines, support vector regression, linear regression and nonlinear regression models are used for estimating both particle velocity and particle direction. The proposed system was trained and tested using the experimental data obtained from an eccentric pipe configuration. Experiments have been conducted at the Cuttings Transport and Multi-phase Flow Laboratory of the Department of Petroleum and Natural Gas Engineering at Middle East Technical University. A high speed digital camera was used for recording the flow at the laboratory. Collected experimental data set consisted of 1080 and 1235 data points for 15° inclined wellbores, 1087 and 1552 data points for 30° inclined wellbores and 885 and 1119 data points for horizontal (0°), wellbores respectively to use in estimation and classification problems. Results obtained from computational intelligence models are compared with each other through some performance metrics. The results showed that the SVM model was the best estimator for direction estimation, meanwhile the SVR model was the best estimator for velocity estimation. The direction and speed of the particles were estimated with a reasonable accuracy; hence the proposed model can be used in eccentric pipes in the field.

Experimental investigation of multiphase flow behavior in drilling annuli using high speed visualization technique

Imaging with high definition video camera is an important technique to visualize the drilling conditions and to study the physics of complex multiphase flow associated with the hole cleaning process. The main advantage of visualizing multiphase flow in a drilling annulus is that the viewer can easily distinguish fluid phases, flow patterns and thicknesses of cutting beds. In this paper the hole cleaning process which involves the transportation of cuttings through a horizontal annulus was studied. The two-phase (solid-liquid) and the three-phase (solid-liquid-gas) flow conditions involved in this kind of annular transportation were experimentally simulated and images were taken using a high definition camera. Analyzing the captured images, a number of important parameters like velocities of different phases, heights of solid beds and sizes of gas bubbles were determined. Two different techniques based on an image analysis software and MATLAB coding were used for the determinations. The results were compared to validate the image analyzing methodology. The visualization technique developed in this paper has a direct application in investigating the critical conditions required for efficient hole cleaning as well as in optimizing the mud program during both planning and operational phases of drilling. Particularly, it would be useful in predicting the cuttings transport performance, estimating solid bed height, gas bubble size, and mean velocities of bubbles/particles.

An implicit unsteady hydraulic solver for suspended cuttings transport in managed pressure wells

We present a simulation tool for transient events in complex hydraulic networks. The code includes modelling of the transport of suspended cuttings in near-vertical wells. An unstructured finite volume formulation with implicit time integration has been chosen. The unconditional stability of the integrator makes the method suitable for the simulation of transient events over a wide range of characteristic timescales. It handles both very fast transients (e.g. fluid hammer events) and the long-term evolution of the well (e.g. hole cleaning operations). The software has been developed to address the need of the oil industry for a robust and efficient predictive tool allowing effective well control in managed pressure drilling operations. The physical modelling follows the standard practices accepted by the industry (e.g. mud rheology computations). The mathematical foundation of the algorithm is described followed by validation cases that illustrate its capabilities and accuracy. Finally, a practical industrial application example is provided to demonstrate the real-world performance of the software.

The effect of nanoparticles additives in the drilling fluid on pressure loss and cutting transport efficiency in the vertical boreholes

The effect of nanoparticles of various chemical components and sizes on the rheological behaviour of drilling fluids, pressure loss and cuttings transport in the vertical borehole for a laminar flow regime is considered in the paper. The results of numerical and experimental studies are presented. Silicon, aluminium and titanium oxides nanoparticles are considered. A drilling fluid is Bentonite-water solution with a mass fraction of 5%. The particles concentration in the solution was varied from 0.25 to 2 wt percentages and the particles sizes ranged from 5 to 50 nm. The dependences of the effective viscosity and rheological parameters of the solutions on the nanoparticles concentrations, sizes and materials were obtained. It was shown that nanoparticles in drilling fluid increase cuttings transport by 17% and decrease the average slip velocity of the sludge particles in 1.7–2.0 times, but the pressure losses when pumping the drilling fluid increase in 2.5 times.

A new solution to enhance cuttings transport in mining drilling by using pulse jet mill technique

In horizontal drilling, the cuttings bed is frequently formed to result in severe problems such as backing pressure, binding of bottom hole assembly (BHA) and even sticking of tool. Practice and research show that the smaller particle size is, the more favorable to carry out from bottom of hole in extended reach well or horizontal well. This paper presented a new solution to enhance cuttings transport in mining drilling through a new type of bit called pulsed mill bit (PMB) by using pulse jet mill technique. It provides a promising solution to enhance the efficiencies of rock breaking and cuttings carrying for pulsed jet, sucking cuttings to decrease the chip hold down effect, and reducing cuttings’ diameter to eliminate cuttings bed. The design was supported by the calculation models of Helmholtz resonator natural frequency, optimal drilling fluid flow rate of resonator, drilling fluid flow velocity in forward jet channel, critical impact velocity of cuttings and minimum length of the accelerating cavity. Meanwhile, factors affecting optimal drilling fluid flow rate, critical impact velocity of cuttings and minimum length of accelerating cavity were investigated. Case study showed a good consistency between the calculation results and the related theories. It is concluded that optimal drilling fluid flow rate increases with the increase of inlet and outlet cavity’s diameter, and decreases with the increase of the diameter of the resonant cavity. Critical impact velocity of cuttings increases with the energy conversion factor (β) and ROP, while decreasing with the final size of the cuttings (dt). This effect is obvious when β<0.2, ROP <3.048 m h−1 and dt<0.3 mm. Minimum length of the accelerating cavity decreases with the increase of the resonator’s natural frequency and separation coefficient (α) of drilling fluid flow rate. This study provides a promising solution to remove cuttings bed in horizontal well.