Application and development of numerical simulation for under- ground horizontal directional drilling

In coalmines of China, horizontal directional drilling （HDD） is an increasingly popular method for underground in-seam gas drainage. Numerical simulation, especially finite element analysis, is often used as an effective method to improve HDD operation. These improvements focus on rock-breaking efficiency, directional precision, stability of the borehole wall, and reliability of the drill equipment. On the basis of underground drilling characteristics, typical numerical simulation exam- ples in drilling techniques and equipment are summarized and analyzed. In the end, the future development trends of numerical simulation in underground in-seam drilling are proposed.

Surface settlement induced by horizontal directional drilling

Horizontal directional drilling(HDD)is a widely used trenchless method for underground utility connections.The associated ground settlement triggered by HDD depends on the size,types,and surface texture of pipe,diameter of borehole,and soil conditions.The pre-sent study investigates the surface settlement due to the construction of a 1067 mm diameter HDD,which will replace an existing sewer siphon under the SR-60 highway in Chino,California using empirical,and numerical methods.Based on the results obtained from the subsurface investigation,an empirical analysis was conducted first.followed by numerical modeling of the HDD using PLAXIS 2D soft-ware.A careful comparison between two different methods indicated closer values of surface settlement between the empirical method(7.3 mm)and the numerical modeling(4.6 mm).In addition,the shape of surface settlement and horizontal settlement curves for the empirical and numerical methods was found to be similar.The minor discrepancy between the two methods resulted as the numerical model can host several soil layers whereas the empirical equation can use only one type of soil.Finally,a parametric study was conducted to evaluate the effect of borehole cover depth,size,and soil parameters on surface settlement.It was observed that soil strength param-eters yielded a greater effect on surface movement,whereas modulus of elasticity has a relatively smaller influence with zero contribution from Poisson’s ratio.

Laboratory study of fluid properties owing to cutting intrusions during horizontal directional drilling

During horizontal directional drilling installations,a primary function of drilling fluids is to yield drill cuttings and lubricate the product pipe.This paper presents the results of a research study of drilling fluid parameters,and the filter cake properties associated with drill cutting intrusions.Different sand meshes and field cutting sizes were added to the drilling fluids.Based on the laboratory experiments of eighteen samples including testing drilling fluid rheology and filter cake properties,the influence of drill cuttings on low solid-phase drilling fluid systems were obtained.The results reveal that drilling fluid plastic viscosity values increase with sand content and particle size.The 100-mesh sand exhibits a larger plastic viscosity compared to the 200-mesh sand.This suggests that the coarser the sand,the greater is the plastic viscosity.By contrast,drilling fluids with 200-mesh sand exhibit greater shear forces than the 100-mesh sand.When the sand content is4%,the shear dilution ability of the drilling fluid begins to weaken.The thinnest filter cake is formed after 6 h with a 100-mesh cutting size and 4%sand content.However,when the cutting size changed to 150-mesh and 2%content,the largest filter cake toughness and strength after rolling for 12 h were obtained.Simultaneously,the combination of 200-mesh and 150-mesh with 2%–4%content rolling for 12–24 h indicate different results.For the filter cake thickness,cutting content is the primary influencing factor followed by particle size and gradation.The factor with the least influence is rolling time.We found that rolling time and gradation were the most significant factors affecting the toughness of the filter cake,followed by cutting content.Conversely,particle size exhibits the least influence on filter cake toughness.These results are important to better understand the solid-phase control of drilling fluids in the field.

Effect of Low Frequency Electromagnetic Field on Macrosegregation of Horizontal Direct Chill Casting Aluminum Alloys

The horizontal direct chill (HDC) casting process is a well-established production route for aluminum alloy ingot but the ingot may suffer from macrosegregation sometimes. In order to control the defect, a low frequency electromagnetic field has been applied in HDC casting process and the relevant influence has been studied. The results show that application of low frequency electromagnetic field can reduce macrosegregation in HDC casting process; and two main parameters of electromagnetic field density and frequency, have great influences on the solution distribution along the diameter of ingot. Moreover, the mechanisms of reduction of macrosegregation by electromagnetic field have been discussed.

EFFECT OF LOW-FREQUENCY ELECTROMAGNETIC FIELD ON THE AS-CASTING MICROSTRUCTURES AND MECHANICAL PROPERTIES OF HDC 2024 ALUMINUM ALLOY

The influences of the low frequency electromagnetic field on the horizontal direct chill casting process were investigated experimentally. Ingots of 2024 aluminum alloy with a cross size of 40 mm× 200 mm were produced by the conventional horizontal chill casting process and low frequency electromagnetic horizontal chill casting processre- spectively. The as-cast structures and the mechanical property of the ingots were examined. The results showed that the low frequency electromagnetic field could sub- stantially refine the microstructures and pronouncedly reduce the macrosegregation in the horizontal direct chill casting process. Moreover, the surface quality of the ingot was prominently improved by the low frequency electromagnetic field. The fracture strength and elongation percentage of the ingot was increased with the low frequency electromagnetic field.

Estimation of the horizontal in-situ stress magnitude and azimuth using previous drilling data

Oil exploration and production,well stability,sand production,geothermal drilling,waste-water or CO_(2) sequestration,geohazards assessment,and EOR processes such as hydraulic fracturing,require adequate information about in-situ stresses.There are several methods for analyzing the magnitude and direction of in-situ stresses.The evaluation of tensile fractures and shear fractures in vertical oil and gas wellbores using image logs is one of these methods.Furthermore,when image logs are run in boreholes,they can be extremely costly and possibly stop the drilling.The data for this study were gathered from seven directional wells drilled into a strike-slip fault reservoir in southern Iran.Vertical stress,minimum horizontal stress,pore pressure,Poisson's ratio of formations,and 233 mud loss reporting points make up the entire data.This is the first time maximum horizontal stress direction has been calculated without referring to image log data.In addition,the points of lost circulation were categorized into natural and induced fracture.The results revealed that,the maximum horizontal stress direction of the reservoir was calculated at 65northeast-southwest.The error rate is roughly 10when comparing the results of this investigation to those obtained from the image log.The maximum horizontal stress direction is calculated precisely.In terms of tensile fracture pressure,the in-situ stress ratio identifies the safest as well as the most critical inclination and azimuth for each well.

Effect of casting speed on surface quality of horizontal direct chill casting 7075 aluminum alloy ingot

7075 aluminum alloy ingot with the diameter izontal direct chill casting in different casting of 100 mm has been produced by horspeed. The effect of the casting speed on the ingot surface and subsurface layer was studied by surface observation and subsurface structure analysis. It was found that increasing the casting speed results in the adding of segregation knots in the ingot surface. The thickness of the dendrite microstrueture layer in the subsurface reduces with increasing the casting speed. And the elements of Zn, Cu and Mg enrich in the coarse dendrite microstructure layer of the ingot.

Robust multi-objective optimization of rolling schedule for tandem cold rolling based on evolutionary direction differential evolution algorithm

According to the actual requirements,profile and rolling energy consumption are selected as objective functions of rolling schedule optimization for tandem cold rolling.Because of mechanical wear,roll diameter has some uncertainty during the rolling process,ignoring which will cause poor robustness of rolling schedule.In order to solve this problem,a robust multi-objective optimization model of rolling schedule for tandem cold rolling was established.A differential evolution algorithm based on the evolutionary direction was proposed.The algorithm calculated the horizontal angle of the vector,which was used to choose mutation vector.The chosen vector contained converging direction and it changed the random mutation operation in differential evolution algorithm.Efficiency of the proposed algorithm was verified by two benchmarks.Meanwhile,in order to ensure that delivery thicknesses have descending order like actual rolling schedule during evolution,a modified Latin Hypercube Sampling process was proposed.Finally,the proposed algorithm was applied to the model above.Results showed that profile was improved and rolling energy consumption was reduced compared with the actual rolling schedule.Meanwhile,robustness of solutions was ensured.

BIM for the Underground-An enabler of trenchless construction

The subsurface space in urban areas is an important asset.However,the information available on this environment is relatively poor compared to above ground information.This paper proposes a Building Information Model(BIM)for underground applications as means to address this information gap.The creation and progressive update of BIM for a constructed artefact ensures that data on the structures is available and can be used throughout its lifetime.A BIM for underground applications integrates data on surface structures,such as buildings,and subsurface infrastructures,such as pipes,along with details of the surrounding ground,the associated soil and rock properties and groundwater regime into a single framework.This approach is demonstrated by applying it to trenchless construction operations,including a microtunnelling project for a new sewer.The data from this extended BIM concept can be interactively used with analysis packages to conduct risk assessments for new construction activities.It also shows how BIM for the Underground can be used throughout the planning,construction and post-construction stages of a project,and,importantly,how this information can be available for future projects.