Drilling Tests Research Articles

Study on Fracture Characteristics and Controlling Factors of Tight Sandstone Reservoir: A Case Study on the Huagang Formation in the Xihu Depression, East China Sea Shelf Basin, China

Abstract Natural fractures are not only the key to affect the natural productivity of tight sandstone reservoirs but also one of the important factors to control the fracturing effect. If the local strata are affected by multistage tectonic movement and diagenesis, it will lead to the complexity of fracture types and characteristics, which makes it difficult to accurately identify natural fractures, thus, seriously affect the development of fractured reservoirs and the fracturing effect. In this paper, the macroscopic fractures were studied by combining core, conventional logging, imaging logging, petrophysical logging, logging, drilling, and gas test data. The microscopic fractures were analyzed by casting thin sections and scanning electron microscopy and cathodoluminescence. The effect of fractures on hydrocarbon migration was analyzed by fluid inclusions in fractures. The core can be used to visually study the opening fracture, but when the color of the filling inside the fracture is similar to the surrounding, the filling fracture is not easy to be found. Imaging logging has high identification accuracy for filling fractures, but it can hardly be used as a means of identifying high-angle opening fractures. The opening fracture zone in the noncoring section can be studied by conventional logging, mud logging, drilling, and rock mechanical parameter. The macroscopic structural fractures are obviously directional, which is controlled by the tectonic stress field. The occurrence and density of macroscopic structural fractures are controlled by buried depth, lithology, rock thickness, sedimentary facies, distance from the fault, and structural location. The opening fractures are all of high angle, indicating that the inclination angle is an important factor affecting the filling degree of fractures. The direction of intragranular fractures is chaotic, which is affected by the mechanical weak surface of the mineral particles, particle morphology, and particle contact relationship and stress. Effective fractures provide channels for the migration of oil and gas and acidic fluids in the historical period, which promote the occurrence of hydrocarbon accumulation and dissolution.

E&P Notes (July 2021)

E&P Notes (July 2021)

Application of Vertical Electrical Sounding for Groundwater Investigation in the Premises of the Sabaragamuwa University of Sri Lanka

Growing social, as well as development activities in the premises of Sabaragamuwa University of Sri Lanka (SUSL) and its surroundings, have reformed the natural landscape of the area. Consequently, water demand is increasing. Therefore, an understanding of the subsurface geology and their potential as beneficial aquifers help to overcome the impending water demand because surface water scares in the area. In view of assessing the groundwater potential of the area, an initial study was conducted using topographic and satellite maps followed by a geo-electrical resistivity survey, consisting of vertical electrical sounding (VES) and electrical profiling. Results revealed three subsurface layers in most places. The resistivity of the topsoil layer is ranging between about 50 to 2800 Ωm and the average thickness between 1 m to 15 m. The second layer is characterized by resistivity between about 16 to 9760 Ωm. The resistivity of the third layer ranges from about 2 to 5600 Ωm, and extending to a depth of more than 100 m. Most of the curves were identified as K type. The rest of the curves were H, Q, and A types. Out of 18 VES points, nine locations were identified as possible locations for groundwater abstraction. Groundwater could be located at a depth of between 25 to 60 m. Resistivity data indicate that the regolith mostly forms the aquifers in the area along with some weathered rock aquifers at depth. Most of the points close to or at valleys were found to be deep aquifers. Considering all the geological, structural, and morphological features, nine locations were identified as most convincing and could be recommended for test drilling.

Small Unconventional Hydrocarbon Gas Reservoirs as Challenging Energy Sources, Case Study from Northern Croatia

Small possible hydrocarbon gas reservoirs were analysed in the Bjelovar Subdepression in Northern Croatia. This area includes the Neogene–Quaternary, mostly clastics, sequences, reaching 3000+ metres in the deepest part. The shallow south-eastern part of the Drava Depression contains a subdepression characterised with several, mostly small, discovered hydrocarbon fields, where the majority are located on the northern subdepression margin. The reason is the large distance from the main depressional migration pathways and main, deep, mature source rock depocenters. However, two promising unconventional targets were discovered inside the subdepression and both were proven by drilling. The first are source rocks of Badenian, of kerogen type III in early catagenesis, where partially inefficient expulsion probably kept significant gas volumes trapped in the source rock during primary migration. Such structures are the Western Bjelovar (or Rovišće) and the Eastern Bjelovar (or Velika Ciglena) Synclines. The second promising unconventional reservoir consists of “tight” clastic lithofacies of mostly Lower Pontian located on the north-eastern margin of the subdepression. These are fine-grained sandstones with frequent alternations in siltites, silty and clayey sandstones. They are located on secondary migration pathways, but were never evaluated as regional reservoirs, although numerous drilling tests showed gas “pockets”.

Investigation of thrust force in drilling polyphthalamide (PPA) composites

In this study, the drilling process is explored on 30% glass fiber reinforced PPA composite to investigate the influence of drilling parameters on thrust force. HSS, TiN coated HSS and carbide twist drills with 5 mm diameter and 118° point angle are used to perform the drilling tests. The drilling tests were carried out in dry conditions on the 3-axis CNC milling machine. Three different cutting speeds such as 15, 20, and 25 m/min and feed rate such as 0.05, 1.0, and 1.5 mm/rev were selected as drilling conditions. Experimental results indicated that the thrust force increases with increasing the feed rate and in contrast the force decreases with increasing the cutting speed. Statistical Analysis of Variance (ANOVA) method was used to determine the effects of drilling parameters and interactions on the thrust force. According to the analysis, drill materials play the most important role on the thrust force. In addition, mathematical models were developed using the multi-linear regression method. The optical microscope and Scanning Electron Microscopic (SEM) images were used to examine the drilled hole surface of the PPA composite material. According the images of the drilled hole surfaces indicated the existence of matrix crack, fiber pull-out, and shearing of fibers. In order to obtain the best surface quality (in terms of delamination factor and surface roughness) and minimum thrust, it is recommended to use carbide drill bits at the lowest feed rate and highest cutting velocity cutting conditions.

Analytical study and experimental investigation on delamination in drilling of CFRP laminates using twist drills

Delamination in composite laminates is one of the most common and critical defects, it would significantly reduce the stiffness and strength of components. This paper aims at reducing the drilling-induced delamination to improve hole quality. First, drilling tests are carried out to examine the distribution and amplitude of thrust force on drill under different cutting conditions. Empirical thrust force models are developed using experimental data. Then, analytical models of critical thrust force (CTF) are separately established considering two drilling states, considering the actual interactions between the drill and laminate. Anisotropy of composite, tool geometry and load distribution on drill are considered. Comparisons with experimental data and existing models show that the proposed models are capable of predicting CTFs under different loading conditions. In addition, the critical feed rates at different ply locations are determined. This study can provide guidance for the selection of cutting parameters to reduce drilling-induced delamination.

Effect of Cutting Parameters and Tool Geometry on the Performance Analysis of One-Shot Drilling Process of AA2024-T3

Drilling is an important machining process in various manufacturing industries. High-quality holes are possible with the proper selection of tools and cutting parameters. This study investigates the effect of spindle speed, feed rate, and drill diameter on the generated thrust force, the formation of chips, post-machining tool condition, and hole quality. The hole surface defects and the top and bottom edge conditions were also investigated using scan electron microscopy. The drilling tests were carried out on AA2024-T3 alloy under a dry drilling environment using 6 and 10 mm uncoated carbide tools. Analysis of Variance was employed to further evaluate the influence of the input parameters on the analysed outputs. The results show that the thrust force was highly influenced by feed rate and drill size. The high spindle speed resulted in higher surface roughness, while the increase in the feed rate produced more burrs around the edges of the holes. Additionally, the burrs formed at the exit side of holes were larger than those formed at the entry side. The high drill size resulted in greater chip thickness and an increased built-up edge on the cutting tools.

A Comprehensive Investigation on Abnormal Impoundment of Reservoirs—A Case Study of Qionglin Reservoir in Kinmen Island

Leakage is the most serious problem in reservoir operation, because heavy leakage influences reservoir impoundment efficiency and even leads to a complete loss of reservoir functions. Since its completion in 1982, Qionglin Reservoir has never been fully filled with water except in the spring of 1983 when there was heavy rain. The reservoir management unit suspected that its side slopes, bottom or dam might leak and carried out a number of leakage prevention and improvement works, but all of them failed to fulfill the impoundment function of the reservoir. Hence, this study attempts to find out the reasons why the reservoir cannot impound water. A series of tests and investigations are carried out in this study, including electrical resistivity tomography of dam, tracer test, geological drilling test, reservoir water level observation, investigation of reservoir catchment area and field investigation of dam. The test results and investigation results show that no leakage path and leakage are found. According to the analysis, there is no serious leakage of this reservoir. The main reason for the failure of impoundment is that massive improper development in the catchment area influences the runoff into the reservoir.

Design and Experimental Validation of a Miniaturized Robotic Tendon-Driven Articulated Surgical Drill for Enhancing Distal Dexterity in Minimally Invasive Spine Fusion

Steerable drills have the potential to minimize the required dimensions of incisions in minimally invasive spine fusion (MISF). Existing steerable drills mostly rely on flexible continuum mechanisms to create distal tip steerability. However, due to their inherent compliance and underactuation, high stiffness and dexterity cannot be achieved at the same time, which limits their application. In this article, we present a ømm robotic steerable surgical drill offering high stiffness, strength, and dexterity, simultaneously. Contrary to existing flexible-transmission-based approaches, we use nonflexible transmissions (tendon-driven articulated joints and universal joints) to provide two distal degrees of freedom. To evaluate its performance, we integrated it with a customized tendon actuation platform for mechanical performance tests and the da Vinci Research Kit, as an exchangeable instrument, for robotic steerable drilling tests. The results of these tests showed that our drill had high strength, stiffness, accuracy, and drilling stability while preserving high steerability and was sufficient to complete hole drilling in confined space in MISF.

Relationship between Residual Stress and Net Strain in Low-Temperature Transformation Weldments Considering Microstructure

Weldments inevitably shrink during cooling from the melt pool. Residual stresses then occur owing to surrounding constraints. Tensile residual stresses in weldments cause various problems, such as deformation and reduction of fatigue strength. Low-temperature transformation (LTT) welding consumables can reduce the tensile residual stress through volume expansion, which accompanies a phase transformation from austenite to martensite. In this study, the relationship between residual stress and net strain was examined, mainly by controlling the martensite start (Ms) temperature, and the result was related to the weld’s microstructure. The Ms temperature and the expansion accompanying the phase transformation were analyzed by the dilatometric method. A hole drilling test was carried out to measure the residual stress in the weldments. The highest compressive stress was observed in the most expanded weldment at room temperature, and a linear relationship between the net strain and residual stress was derived. This linear relationship was analyzed with a microstructural approach.

Influence of a Novel Drill Design on Heat Generation During Conventional and Guided Implant Osteotomy.

The aim of this in vitro study was to evaluate the temperature development of a novel, electropolished drill design during conventional and guided implant osteotomy in comparison to conventional drills under standardized conditions. Single and sequential 12-mm-deep drilling protocols (guided and unguided) with a conventional (control groups) and novel drill (test groups) were performed in artificial bone blocks under external irrigation. Each drilling protocol was repeated 30 times with drill diameters of 2.2, 2.8, 3.5, and 4.2 mm. Temperature changes were recorded by an infrared camera, and the accumulated thermal energy was calculated. For group comparison, a one-way analysis of variance (ANOVA) and Tukey post hoc test were used with a level of significance set to = .05. The highest temperatures were measured up to 77.9°C for small-diameter drills in the control and test groups. The 3.5-mm and 4.2-mm novel drills showed significantly lower heat generation during guided and unguided osteotomy preparation for single and sequential drilling. The accumulated thermal energy during guided osteotomy preparation was significantly lower with the electropolished drills. The drill design has an important impact on heat development during osteotomy, which was most pronounced for guided osteotomy with conventional drills and for small-diameter osteotomies.

Evaluation of Rock Abrasiveness Based on a Digital Drilling Test

Abstract The accurate evaluation of rock abrasiveness is the basis for the cutting tool design of tunnel boring machines and efficient tunneling. However, the conventional test method is complicated and costly, and in situ measurement cannot be obtained easily. A new digital drilling test system was developed to assess rock abrasiveness in which drilling parameters, including the thrust on bit, rotational speed, torque, and drilling displacement, can be simultaneously collected. Based on the force analysis of the drill bit and the energy conservation law, the energy dissipation per unit volume of drilling or modified specific energy was proposed as an evaluation index, and the quantitative relationship between the index and rock abrasiveness was explored and verified. The results showed that the average difference rate between the Cerchar abrasiveness indexes obtained from the digital drilling test and Cerchar test was less than 15 %, thus proving the effectiveness and feasibility of this method for evaluating rock abrasiveness. The method is easy to implement and has few requirements for sample preparation. It can also be used for the in situ testing of rock abrasiveness in engineering sites.

Condition monitoring of deep-hole drilling process based on improved empirical wavelet de-noising and high multiple frequency components of rotation frequency

The machining condition monitoring is an important task to improve product quality and avoid economic losses in deep-hole drilling. Out-of-roundness-tolerance is one of major defects in deep-hole drilling process. In this work, the spindle vibration signals generated in deep-hole drilling process are studied to seek the characteristics which can reveal the roundness error change. Considering the influence of background noise on monitoring effect and the sensitivity of high multiple frequency components of spindle vibration signal towards the roundness error change, an improved empirical wavelet de-noising method is proposed to remove the noise of the spindle vibration signal. The high multiple frequency components of the rotation frequency are extracted from the de-noised spindle vibration signal. Firstly, the spindle vibration signal is decomposed by empirical wavelet transform into a set of wavelet coefficients, and then an improved thresholding function is proposed to process the Fourier spectrum of wavelet coefficients for removing the noise from the wavelet coefficients. Secondly, the wavelet coefficients are reconstructed based on the de-noised wavelet coefficients, and the wavelet coefficients which contain high multiple components of rotation frequency are selected. Finally, the energy entropy of the selected wavelet coefficients is calculated as a roundness error monitoring indicator to detect the roundness error of deep hole. The proposed method is verified with well-designed deep-hole drilling tests. The test results show that the monitoring indicator can effectively reflect the roundness error change in deep-hole drilling process.

Robotic drilling tests in simulated lunar regolith environment

AbstractA deep extraterrestrial drilling mission potentially adds a new level of complexity, and it is crucial to understand the associated challenges. To cope with China's Chang'E 5 mission to return subsurface regolith samples from the Moon, a series of laboratory tests were performed to validate the lunar robotic drilling from 2015 to 2018. The tests took place in a simulated thermal‐vacuum regolith environment, a highly relevant lunar analog site. Force and temperature sensors were integrated into a 2‐m class dry auger coring drill to assess the mechanical and thermophysical status of the sampling process. The operation of the entire testing system was automated, covering regolith penetration and data collection and storage. The science team used sensing data to characterize the subsurface geologic strata, assess the conditions of the drilling robot, and direct the sampling strategy. This experiment represents an essential first step in understanding the technology and operational requirements for lunar drilling and sampling mission. Many laboratory tests have helped guide the design and implementation of the highly successful lunar regolith‐sampling task in the Chang'E 5 mission. This paper documents the experimental system design, highlighting some critical design criteria and design tradeoffs. It also discusses the results of laboratory testing and lists some of the key technological lessons learned.

Challenges for In-Situ Stress Measurement in Rock Caverns by Hydraulic Fracturing and HTPF Tests-Case Study: Azad Hydropower Project

Hydraulic fracturing (HF) and hydraulic testing of pre-existing fractures (HTPF) are efficient hydraulic methods in order to determine the in-situ stress of rock mass. Generally, the minimum (Sh) and maximum (SH) horizontal principal stresses are measured by hydraulic methods; the vertical stress (SV) is calculated by the weight of the overburden layers. In this work, 37 HF and HTPF tests are conducted in a meta-sandstone, which has about 10% inter-layer phyllite. The artesian circumstance, considerable gap between the drilling and hydraulic tests in the long borehole, no underground access tunnel to rock cavern at the early stages of projects, and a simplified hypothesis theory of HF are the main challenges and limitations of the HF/HTPF measurements. Due to the instability in the long borehole, the drill rig type and borehole length are revised; also TV logger is added to the process of selection of the test’s deep. The HF/HTPF data is sequentially analyzed by the classic and inversion methods in order to achieve an optimum number of hydraulic tests. Besides, The SH magnitude in the inversion method is lower than the classic method; the relevant geological data and the faulting plan analysis lead to validate the SH and Sh magnitudes and the azimuths obtained by the classic method. The measured SH and Sh magnitudes are 7-17 MPa and 4-11 MPa, respectively; the calculated vertical stress magnitude is 6-14 MPa at the test locations. Indeed, the stress state is (SH > SV > Sh), and SH azimuth range is 56-93 degrees.

Evaluation of geotechnical parameters of reclaimed land from near-surface seismic refraction method

Correct execution of civil engineering structures depends largely on the adequate and detailed mapping of the subsurface. This can be achieved by the application of appropriate geophysical or geotechnical methods in association with a detailed information on the geological sequence of the subsurface structure. In this study, a combination of near surface seismic refraction method, cone penetration test and borehole logs were used to obtain 2-dimensional (2D) information of the subsurface geological features. These methods were used to characterize the subsurface condition of a reclaimed land in Ajah area of Lagos for the purpose of construction. The seismic refraction method revealed three geologic layers with seismic velocities ranging between 258 and 3544 m/s. Additionally, the cone penetration test revealed that the geologic formation from the topsoil to a depth of 6 m was an alluvium of soft and highly compressible property. Furthermore, the percussion drilling test also confirmed the geologic formation from the topsoil to a depth of about 6 m to be highly compressible. However, a geologic formation with good geotechnical characteristics, such as a low compressibility potential, was encountered at a depth between 7 and 16 m, which coincides with the third layer of the seismic refraction method. The results of the three methods confirmed that the depth to most competent layer must be located before the foundations of engineering constructions are sited.

Development and experimental validation of a macroscopic analytical model aiming to generate metal-FRP stacks drilling cutting force and torque

Composites materials and especially FRP are increasingly employed in many fields of applications (transport, aerospace, …) due to the current trend of improving global energy performances of new designs notably by mass saving. However the use of metallic materials such as aluminum and titanium alloys is still necessary in many cases and a lot of structures are made of a dual technology called stacks (panels composed of different layers of FRP and metal bounded together). Combining the different properties of these materials offers many advantages regarding the mechanical and structural aspects. This is nevertheless for the same reason that machining and especially drilling stacks is a laborious task: the tools and cutting conditions are way too divergent to avoid vibrations, problems of dimensional tolerances and delamination of the composite. The knowledge and characterization of the drilling cutting forces is a first step to solve these issues. The purpose of this article is to provide an accurate macroscopic analytical model fitted for stacks and compare it quantitatively with experimental tests. The given model is divided in two parts (i.e. respectively adapted for the two materials) and is based on the discretization of the cutting edge. The proposed algorithm is able to predict accurately drilling force and torque along time in function of the cutting conditions, the tool and material configurations. A reverse least squared method is used to obtain the empirical input parameters, allowing to minimize the number of experimental drilling tests to obtain the empirical input parameters.

A novel methodology of Combined Compromise Solution and Principal Component Analysis (CoCoSo-PCA) for machinability investigation of graphene nanocomposites

The interest in the application of Graphene oxide/polymer nanocomposites is recently rising in various industries such as drug delivery, bioimaging, aircraft structures, sensors, battery application, etc., due to the improved features of Graphene oxide. The machining behavior of polymers is remarkably different from metallic alloys due to anisotropic and high synergistic effects. This article investigates the machinability aspect and machining response optimization of the developed hybrid nanocomposites. The drilling responses, namely, average surface roughness (Ra), Mean roughness depth (Rz), and Circularity error (Ce), were optimized by using the integrated approach of Combined Compromise Solution and Principal Component Analysis (CoCoSo-PCA). Response Surface Methodology (RSM) array is utilized to execute the drilling tests. The optimal setting is obtained as drill speed 2400rpm, feed 80mm/min, 1 weight% of Graphene oxide (G%). The feed rate shows a primary role in controlling both the surface roughness indices and Circularity error. The high feed value affects the development of the drilling-induced defect and cracks. The SEM analysis of the machined samples was performed to check the machined hole quality and surface finishing. ANOVA estimates the model adequacy of the proposed hybrid model. The obtained results have been validated by a confirmatory test, which proves the proposed hybrid module practicality in the manufacturing environment. Besides, the proposed approach is compared with the recently developed optimization modules to evaluate the application potential.

Friction drilling of AA7075-T6 and AZ31B alloys under dry and oil containing ceramic particulates

This study investigates the friction drilling behaviors of AA7075-T6 aluminum and AZ31B magnesium alloys containing ceramic powders of B4C, SiC, and Al2O3 under dry and minimum quantity lubrication (MQL). The aim is to create a composite structure while applying the pressure of a drilling tool on the hole surface when adding ceramic powders into the cutting oil during frictional drilling. Friction drilling tests are performed at a constant spindle speed and feed speed, and the effects of dry and cutting oil mixtures containing ceramic particulates on the thrust force, temperature, hole surface quality, bushing profile, and thread stripping strength of the specimens are investigated. The results revealed that ceramic particles penetrated through the hole and created a composite structure on the surface. The dry friction drilling of AA7075-T6 and AZ31B yielded acceptable surface quality. However, the surface quality worsened considerably during the friction drilling of AA7075-T6 using the oil mixture, whereas the surface roughness and hole bushing of AZ31B magnesium alloys are not negatively affected by the ceramic containing oil mixtures. Petal formation and cracks appeared in the hole profiles of the AA7075-T6 aluminum alloy. Thread stripping tests indicate that the ceramic-particle- containing oil mixtures enhanced the thread shear strength of AA7075-T6 by 19.2 %, and the highest shear strength of 56.78 kN is achieved using the Al2O3 containing an oil mixture. The oil mixture-containing B4C ceramic particles improved the thread shear strength of AZ31B by 7.7 %.

Thermal exposure of implant osteotomies and its impact on osseointegration-A preclinical in vivo study.

Thermal and mechanical stresses during osteotomy preparation can impair implant osseointegration. This study investigated implant osseointegration following the measurement of temperature exposure during osteotomy drilling, varying drill design, sequence, and drill wear. 36 tapered implants were placed in a mandibular minipig model after guided drilling of implant osteotomies using 4 different groups: (1) control drills with a conservative, sequential drilling sequence, (2) control drills using a shortened drill sequence (PF), (3) novel test drill displaying an optimized drill design and surface treatment, PF, and (4) aged test drill, PF. Intraosseous temperatures during drilling were measured using a temperature probe. BIC, fBIC, and tissue reactions were histomorphometrically derived after 2 and 8weeks of healing. Compared to control drills (1) or (2), test drills (3) resulted in significantly lower maximum temperatures ((35.4 (CI 30.2-40.5)°C vs. (46.5 (CI 41.0-52.0)°C, p=.0021)) and shorter drill times ((4.5 (CI 1.6-7.3)sec vs. 10.3 (7.3-13.4)sec). Lower osteotomy temperature values and shorter drill times corroborated with significantly higher BIC after 2 and 8weeks healing for the test (3) compared to control groups (2) (2weeks: (44.9 (CI 34.1-55. 7)% vs. (31.3 (CI 20.5-42.2)%, p=<.0001 and 8weeks: (73.7 ( CI 64.2-83.2)% vs. (66.2 (CI 57.0-75.4)%, p=<.0455). The improved osseointegration of implants placed after osteotomy preparation with novel test drills using a shortened drill sequence compared to standard drills and conventional drill protocols might be attributed to more favorable thermal profiles and less mechanical stress exerted on the bone surrounding the implant osteotomy.