Simulation Research on Coal-Water Slurry Gasification of Oil-Based Drill Cuttings Based on Fluent

In this paper,based on Fluent software,a five-nozzle gasifier reactor was established to simulate the gasification process of oil-based drill cuttings coal-water slurry.The influence of concentration and oxygen/carbon atomic ratio on the gasification process of oil-based drill cuttings coal-water slurry was investigated.The results show that when the oxygen flow is constant,the outlet temperature of gasifier decreases,the content of effective gas increases,and the carbon conversion rate decreases with the increase of concentration;When the ratio of oxygen to carbon atoms is constant,the effective gas content rises and the temperature rises with the increase of the concentration,and the carbon conversion rate reaches the maximum value when the concentration of oil-based drill cuttings coal-water slurry is 65%;When the concentration is constant,the effective gas content decreases and the outlet temperature rises with the increase of the oxygen/carbon atom ratio,and the carbon conversion rate reaches 99.80%when the oxygen/carbon atom ratio is 1.03.It shows that this method can effectively decompose the organic matter in oilbased drill cuttings and realize the efficient and cooperative treatment of oil-based drill cuttings.

Study of Oil-Bearing Drill Cuttings Cleaning and De-Oiling Treatment Method for Shale Gas Reservoirs

Due to its extensive use in shale gas exploration and development,oil-based drilling fluids generate large amounts of oil-bearing drill cuttings during the drilling process.The large amount of oil-bearing drill cuttings generated during the drilling process can lead to serious secondary contamination.In this study,a wetting agent FSC-6 with good hydrophobic and oleophobic properties was synthesized to construct an efficient oil removal system.For the first time,the mechanism of this system was analyzed by using the theory of adhesion function,interfacial tension and wettability.At the same time,a combined acoustic-chemical treatment process was applied to the wastewater and slag generated after the cleaning of the oil-bearing drill cuttings.The experimental results show that the application of this pollution-free technology can effectively solve the environmental pollution and resource recovery problems of oil-bearing drill cuttings.It meets the standard of drilling chips with oil content less than 2%in SY/T7422-2018“Oil-based drilling fluid drilling chips treatment system for oil and gas drilling equipment”.

Cuttings transport: Back reaming analysis based on a coupled layering-sliding mesh method via CFD

Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this study.To this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively.The dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe rotation.The back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been conducted.The results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings concentration.In addition,the cuttings concentration is observed to decrease significantly with the pipe rotation speed.Furthermore,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings.Conversely,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation.The“bulldozer”effect of the connector causes a more severe impact on hole cleaning.In both cases,increasing the tripping velocity only mildly affects the cuttings concentration.It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation.Furthermore,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter,such as the bottom hole assembly.This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.

Solidification and utilization of water-based drill cuttings to prepare ceramsite proppant with low-density and high performance

Water-based drill cuttings(WBDC)and bauxite are used as raw materials to prepare proppants with low density and high performance.The effects of sintering temperature,sintering period,mixture ratios of materials,doping with iron oxide,and acid modification of WBDC on the properties of proppants are discussed.The proppant performance is evaluated according to the national standard SY/T5108-2014.The morphology of the proppant is analyzed using scanning electron microscopy(SEM).The crystal phase structure of the proppant is studied using X-ray diffraction(XRD).Thermal analysis of the proppant sintering process is performed using thermogravimetry(TG).Proppant Z-23 completely satisfied the SY/T5108-2014 standard.This study provides a new perspective for the resource utilization of water-based drill cuttings and preparation of low-density proppants.

Prediction method for risks of coal and gas outbursts based on spatial chaos theory using gas desorption index of drill cuttings

Based on the evolution of geological dynamics and spatial chaos theory, we proposed the advanced prediction an advanced prediction method of a gas desorption index of drill cuttings to predict coal and gas outbursts. We investigated and verified the prediction method by a spatial series data of a gas desorption index of drill cuttings obtained from the II3112 coal roadway at the Shitai Mine. Our experimental results show that the spatial distribution of the gas desorption index of drill cuttings has some chaotic characteristics, which implies that the risk of coal and gas outbursts can be predicted by spatial chaos theory. We also found that a proper amount of sample data needs to be chosen in order to ensure the accuracy and practical maneuverability of prediction. The relative prediction error is small when the prediction pace is chosen carefully. In our experiments, it turned out that the optimum number of sample points is 80 and the optimum prediction pace 30. The corresponding advanced prediction pace basically meets the requirements of engineering applications.

A High-Mathematical Model Optimizing Cuttings Transport in Oil Drilling Engineering

With special drilling operation equipment and specific conditions of geology, how does drilling fluid carry cuttings effectively? So far, it is still an urgent problem for drilling researchers to study. This work just aims at the actual engineering background to develop studying model. In this paper, according to non Newtonian fluid mechanics, the law of the solid liquid, two phase fluid flow and actual drilling engineering, the major factors affecting cuttings transport are drilling fluid velocity, hole inclination and fluid rheological properties. Getting a clear understanding of the law of drilling fluid and its cutting taking mechanism, this paper puts forward a model for analysis of field data and quantitative forecast of cutting taking capability of drilling fluid. The full scale annular test section was 6.1 m with 76 and 114 mm drillpipe in a 203 mm ID (wellbore diameter). Hole angle varied from 0° to 90°.

Fracture development during disposal of hazardous drilling cuttings by deep underground injection: A review

Drilling fluids with complicated compositions are becoming more common as the oil and gas industry develops. The production of hazardous cuttings is increasing, which not only stifles the oil and gas industry’s development but also poses a severe environmental threat. Deep underground re-injection is a cost-effective and efficient method for dealing with hazardous cuttings. Numerous experiments and numerical studies on cuttings re-injection have been conducted in the past thirty years. However, there is still a divergence of views on the fracture development in the process of cuttings re-injection. A comprehensive review of existing studies is necessary to help researchers advance this technology. This paper provides a review of the fundamental studies on fracture behaviors during the deep underground re-injection of drilling cuttings. The limitations of the existing studies are also discussed to inspire new research endeavors.

Optimization of ice cuttings transportation by cable-suspended core auger drills

Ice cores contain an abundance of information about the Earth's climate in the past,and recovered from shallow drilling down to 300--350 m give sufficient information for reconstructing of the last climatic changes and for monitoring of pollution from human being. Cable-suspended core auger drills use an armored cable with a winch to provide power to the down-hole motor system and to retrieve the down-hole unit. Because of their lightweight,convenient transportation and installation,high penetration rates and low power consumption,core auger drills are widely used for shallow drilling in ice. Nowadays at least 14 types of auger electromechanical drills were designed and tested in different foreign and national glaciological laboratories. However,auger options were usually determined by experience,and the main parameters( helix angle of the fights and rotational speed) are varied in a wide range from drill to drill. If parameters of auger are not chosen properly,poorly engineered drills had troubles with low efficiency of cuttings transportation,jam of ice cuttings,repeated fragmentation,cutters icing and stop penetration,abnormal power consumption,high rotation torques,and so on.Thus,this paper presents the method of optimization of ice cuttings transportation of cable-suspended core auger drill on the base of the theory of rotary auger. As the result,the optimal helix angle was determined corresponding to the rotational speed from the transportation efficiency point of view.

A novel predictive model of drag coefficient and settling velocity of drill cuttings in non-Newtonian drilling fluids

In oil and gas well drilling operations,it is of great significance to accurately predict the drag coefficient and settling velocity of drill cuttings in non-Newtonian drilling fluids.In this paper,the free-falling of 172 groups of spheres and 522 groups of irregular-shaped sand particles in Newtonian/non-Newtonian fluids were investigated experimentally.It was found that the drag coefficient calculated based on Newtonian correlations can result in a significant error when the particle settles in the non-Newtonian fluid.Therefore,predictive models of drag coefficient were established respectively for different types of fluids.The validity of the proposed drag coefficient model of spheres was verified by comparing it with the previous works.On this basis,the drag coefficient model of irregular-shaped sand particles was established by introducing a shape factor.The models do not use the shape factor that requires detailed threedimensional shape and size information.Instead,two-dimensional geometric information(circularity)is obtained via image analysis techniques.The present new models predict the settling velocity of sand particles in the power-law fluid and Herschel-Bulkley fluid accurately with a mean relative error of5.03%and 6.74%,respectively,which verifies the accuracy of the model.

Research on Reliability of Desorption Indexes of Drilling Cuttings(K_(1)andΔh_(2)):A Case-Based on Pingdingshan Mining Region,China

To accurately predict the risk of coal and gas outburst and evaluate the reliability of desorption indexes of drilling cuttings(K_(1) andΔh_(2))in No.16 coal seam of Pingmei No.12 coal mine,two sets of coal samples were selected from the target coal seams for proximate analyses,methane adsorption/desorption tests,and desorption indexes of drilling cuttings tests.The results indicated that the desorption volume in the initial stage of desorption is large,and increases slowly in the later stage.The methane desorption volume of PMD1 and PMD2 coal samples accounts for 15.14%-18.09%and 15.72%-18.17%respectively in the first 1 min,and 43.92%-48.55%and 41.87%-52.25%respectively in the first 10 min in the 120 min desorption tests.Both K_(1) andΔh_(2) present power function relationships with methane pressure.Similarly,the power function relationships also can be found between the initial desorption characteristics(Q1 and Q4-5)and the methane pressure.Finally,the average relative error between the measured value and the calculated value of Q1 based on K_(1) is less than that of Q4-5 based onΔh_(2),which indicates that K_(1) is a more reliable index thanΔh_(2) to predict the risk of coal and gas outburst in the No.16 coal seam of Pingmei No.12 coal mine.

Method for predicting cuttings transport using artificial neural networks in foam drilling

Foam is used widely in underbalanced drilling for oil and gas exploration to improve well perfor-mance.Accurate prediction of the cutting transport and pressure loss in the foam drilling is an important way to prevent stuck pipe,lost circulation and to increase the rate of penetration(ROP).In foam drilling,the cuttings transport quality may be defined in terms of cuttings consistency and downhole pressure loss,which are controlled by many factors.Therefore,it is very difficult to establish the mathematical equation that reflects nonlinear relationship among various factors.The field and experimental measurements of these parameters are time consuming and costly.In this study,the authors suggest a cuttings transport mathematical modeling using BPN(back propagation network),RBFN(radial basis function network)and GRNN(general regression neural network)based on various experiment data of cuttings transport of previous researchers and compared the result with experiment data.Results of this study show that the GRNN has a correlation coefficient of 0.99962 and an average error of 0.15 in training datasets,and a correlation coefficient of 0.99881 and an average error of 0.612 in testing datasets,which has higher accuracy and faster training velocity than the BP network or RBFN network.GRNN can be used in many mathematical problems for accurate estimation of cuttings consistency and downhole pressure loss instead of field and experimental measurements for hydraulic design in foam drilling operation.

Cooling and Crack Suppression of Bone Material Drilling Based on Microtextured Bit Modeled on Dung Beetle

In recent years,the number of patients with orthopedic diseases such as cervical spondylosis has increased,resulting in an increase in the demand for orthopedic surgery.However,thermal necrosis and bone cracks caused by surgery severely restrict the development and progression of orthopedic surgery.For the material of cutting tool processing bone in bone surgery of drilling high temperature lead to cell death,easy to produce the problem such as crack cause secondary damage effects to restore,in this paper,a bionic drill was designed based on the micro-structure of the dung beetle's head and back.The microstructure configuration parameters were optimized by numerical analysis,and making use of the optical fiber laser marking machine preparation of bionic bit;through drilling test,the mathematical model of drilling temperature and crack generation based on micro-structure characteristic parameters was established by infrared thermal imaging technology and acoustic emission signal technology,and the cooling mechanism and crack suppression strategy were studied.The experimental results show that when the speed is 60 m/min,the cooling effects of the bionic bit T1 and T2 are 15.31%and 19.78%,respectively,and both kinds of bits show obvious crack suppression effect.The research in this paper provides a new idea for precision and efficient machining of bone materials,and the research results will help to improve the design and manufacturing technology and theoretical research level in the field of bone drilling tools.

Investigation of active vibration drilling using acoustic emission and cutting size analysis

This paper describes an investigation of active bit vibration on the penetration mechanisms and bit-rock interaction for drilling with a diamond impregnated coring bit. A series of drill-off tests(DOTs) were conducted where the drilling rate-of-penetration(ROP) was measured at a series of step-wise increasing static bit thrusts or weight-on-bits(WOBs). Two active DOTs were conducted by applying 60 Hz axial vibration at the bit-rock interface using an electromagnetic vibrating table mounted underneath the drilling samples, and a passive DOT was conducted where the bit was allowed to vibrate naturally with lower amplitude due to the compliance of the drilling sample mountings. During drilling, an acoustic emission(AE) system was used to record the AE signals generated by the diamond cutter penetration and the cuttings were collected for grain size analysis. The instrumented drilling system recorded the dynamic motions of the bit-rock interface using a laser displacement sensor, a load cell, and an LVDT(linear variable differential transformer) recorded the dynamic WOB and the ROP, respectively. Calibration with the drilling system showed that rotary speed was approximately the same at any given WOB, facilitating comparison of the results at the same WOB. Analysis of the experimental results shows that the ROP of the bit at any given WOB increased with higher amplitude of axial bit-rock vibration, and the drill cuttings increased in size with a higher ROP. Spectral analysis of the AEs indicated that the higher ROP and larger cutting size were correlated with a higher AE energy and a lower AE frequency. This indicated that larger fractures were being created to generate larger cutting size. Overall, these results indicate that a greater magnitude of axial bit-rock vibration produces larger fractures and generates larger cuttings which, at the same rotary speed, results in a higher ROP.

Predictive Modeling and Parameter Optimization of Cutting Forces During Orbital Drilling

To optimize cutting control parameters and provide scientific evidence for controlling cutting forces,cutting force modeling and cutting control parameter optimization are researched with one tool adopted to orbital drill holes in aluminum alloy 6061.Firstly,four cutting control parameters(tool rotation speed,tool revolution speed,axial feeding pitch and tool revolution radius)and affecting cutting forces are identified after orbital drilling kinematics analysis.Secondly,hybrid level orthogonal experiment method is utilized in modeling experiment.By nonlinear regression analysis,two quadratic prediction models for axial and radial forces are established,where the above four control parameters are used as input variables.Then,model accuracy and cutting control parameters are analyzed.Upon axial and radial forces models,two optimal combinations of cutting control parameters are obtained for processing a13mm hole,corresponding to the minimum axial force and the radial force respectively.Finally,each optimal combination is applied in verification experiment.The verification experiment results of cutting force are in good agreement with prediction model,which confirms accracy of the research method in practical production.

Exploring the potential of drill cuttings for reservoir characterization:A case study from the Volga-Ural basin,Russia

The research objectives are to assess the possibility of using drill cutting analysis to obtain information about the mineralogical and geochemical properties of the reservoir rocks.Drill cutting samples were collected from a vertical well that penetrated the Domanik sediments(Semiluksk Formation)in one of the oil fields in the Volga-Ural petroleum province.Thin sections from drill cuttings were examined using an optical polarizing microscope(Axio Imager A2).X-ray diffraction(XRD)analyses were performed using a Brucker D2 Phaser X-ray powder diffractometer.Thermophysical properties were studied using an STA 449 F3 Jupiter instrument.The pyrolytic studies were performed using the Rock-Eval method.Visual inspection showed that the studied sediments are alternations of carbonates and siliceous-carbonate rocks.Thin section examinations revealed that the carbonates are mainly limestone(mudstone and wackestone)and are characterized by a dense texture and up to 30%organic residues.The siliceous-carbonate rocks are dominated by siliceous mudstones and are characterized by dark colours,layered structure,and an enrichment in organic matter.XRD analyses showed that the carbonate rocks are mainly composed of calcite,dolomite,quartz,feldspar,and mica,which are minor components.The siliceous-carbonate rocks are dominated by quartz,followed by calcite,although they also contain feldspars,mica,dolomite,and pyrite as impurities.According to the simultaneous thermal analysis,the average total hydrocarbon in the carbonate and siliceous-carbonate rocks is 13.6%(for the core samples)and 11.5%(for the drill cutting samples).The content of heavy hydrocarbons in the rocks is higher than the content of light hydrocarbons,indicating the immature nature of organic matter.Kerogen is found sporadically in siliceous-carbonate rocks.According to the pyrolytic studies,average S1 is 4.4 mg/g and average S2 is 19.8 mg/g(for the core samples);average S1 is 2.1 mg/g and average S2 is 17.8 mg/g(for the drill cutting samples),which indicated that the studied sediments have very good to excellent generation potential.The average Tmax of 425.7℃(for the drill cutting samples)and 427.9℃(for the core samples)indicate immature organic matter that generated only heavy oils.Comparing the results of the analysed drill cutting samples with the results of the analysed core analysis from the same reservoir interval in the neighbouring wells showed a good correlation,which proves that this technique is a valid tool that provides an alternative,cost-effective method to determine the rock's characteristics from drill cuttings.

ADVANCES IN THEORETICAL RESEARCH ON ANNULAR HYDRAULICS AND CUTTINGS TRANSPORT

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Conservative approach in drilling-cutting tool injuries

Objective: To prevent unnecessary laparotomies by evaluating the effectiveness of conservative approach in abdominal trauma cases due to drilling-cutting instruments.Methods: Demographic data, effected region of the body, additional findings of trauma, hemodynamic parameters, duration of admission, diagnostic methods and treatment modalities were retrospectively evaluated in 217 cases with abdominal injury (lower thoracic region, abdominal wall and back) among 1128 victims with drilling-cutting instrument injuries between January 1, 2012 and December 31, 2017. The conservative approach was based on physical examination, hemogram follow-up and hemodynamic evaluation.Results: Totally 177 (81.6%) cases of 217 patients were followed conservatively while 25 cases were operated at early (1-8 hours) and 15 were operated at late (9-48 hours) periods. Two patients who underwent surgery in the early period and two patients who underwent surgery in the late period were accepted as negative laparotomy while 1 patient in the late operated group was regarded as non-therapeutic laparotomy. Diagnostic laparoscopy was performed in 81 cases. Complications developed in 7 patients who were operated in the early period and 10 patients who were operated in the late period. The mean hospital stay period was 5.3 days (1-33) in all cases, 4.5 days (2-20) in conservative treatment group and 8.4 days (3-33) in the operated patients;and the difference was statistically significant.Conclusions: Detailed physical examination, accurate assessment and effective use of different diagnostic methods reduce the frequency of negative and non-therapeutic laparotomies in abdominal stab wound injuries.

Identifying Optimal Cutting Parameters in Drilling of Titanium Aluminum Vanadium Using Finite Element Analysis

Titanium alloys are widely used in the aerospace industries because of their excellent strength-to-weight ratio, high resistance to corrosion, high chemical reactivity and low thermal conductivity and ability to withstand high temperatures. However, these properties make titanium alloys difficult to machine. Drilling of titanium alloy may generate high temperature and high cutting forces. This paper is aimed at determining the suitable cutting parameters in the drilling of titanium alloys to minimize the cutting temperature and cutting forces. A finite element 3D model of the drilling process is simulated in this research. A combination of drilling speeds and feed rates are simulated to obtain the resulting responses of cutting force and temperature. The central composite design (CCD) is used to generate different combinations of cutting parameters to reduce the number of experiments and optimize the temperature and cutting force responses. Results show at the drilling speed of 5000 rpm with a feed rate of 0.1 mm/rev, temperature and cutting force significantly reduced.

Gas-hydrate formation,agglomeration and inhibition in oil-based drilling fluids for deep-water drilling

One of the main challenges in deep-water drilling is gas-hydrate plugs,which make the drilling unsafe.Some oil-based drilling fluids（OBDF） that would be used for deep-water drilling in the South China Sea were tested to investigate the characteristics of gas-hydrate formation,agglomeration and inhibition by an experimental system under the temperature of 4 ？C and pressure of 20 MPa,which would be similar to the case of 2000 m water depth.The results validate the hydrate shell formation model and show that the water cut can greatly influence hydrate formation and agglomeration behaviors in the OBDF.The oleophobic effect enhanced by hydrate shell formation which weakens or destroys the interfacial films effect and the hydrophilic effect are the dominant agglomeration mechanism of hydrate particles.The formation of gas hydrates in OBDF is easier and quicker than in water-based drilling fluids in deep-water conditions of low temperature and high pressure because the former is a W/O dispersive emulsion which means much more gas-water interfaces and nucleation sites than the later.Higher ethylene glycol concentrations can inhibit the formation of gas hydrates and to some extent also act as an anti-agglomerant to inhibit hydrates agglomeration in the OBDF.