Bottom Of Borehole Research Articles

Opracowanie konstrukcji świdra wiertniczego do zwiercania skał o różnych właściwościach mechanicznych

This paper presents a description of a bit design with a combined cutter layout, aimed at increasing the efficiency of breaking rocks with different mechanical properties. The results from industrial testing of the manufactured bits are analyzed, revealing the need to improve their hydraulic flushing system. Computer modeling was conducted using the Flow Simulation CAD/CAM package of the Solid Works system, where various models of the design options for the bit, the borehole bottom, and a segment of the drill string were created. For each variant, numerical calculations of the fluid motion were carried out using the finite element method. Based on the simulation results, optimal angles of inclination for the jet nozzles relative to the bit axis and their distance from this axis were determined. Key factors influencing the stability of the bit cutters, which destroy the rock by cutting with axial vibrations, were identified, and analytical dependencies for their predictive stability were derived. The wear rate of the bit cutters was determined by instantaneous values of such physical parameters as: the degree of wear, rock cutting speed, temperature, axial loading force on the cutter, and the friction coefficient at the contact between the cutter and rock. Temperature is especially impactful, reaching levels exceeding 1000°C in the cutting zone; it is often regarded as the primary factor influencing bit cutter stability. To maximize the efficiency of rock-breaking in the process of drilling wells, it is necessary to set the following vibration parameters: frequency, amplitude, and vibration mode, which can be determined from the results of mathematical modeling.

Investigation on rock damage associated with ice-filling borehole blasting

Rock excavation and ore extraction in cold regions (e.g., alpine and high-altitude regions) are often conducted using the drill and blasting method. Ice may be presented in boreholes drilled in cold regions due to the potential freezing of water (e.g., water in rock fractures and pores) flowing into boreholes from the surrounding ground. The performance of rock blasting is inevitably affected by the presence of ice and no study has examined the effect of ice in boreholes on rock blasting performance. The present study investigates rock damage induced by the ice-filling borehole blasting. The damage modes and mechanisms of rock mass under the ice-filling borehole blasting are analyzed. The differences of rock damage induced by the sole ice-filling borehole blasting and the ice-water and ice-air mixed filling borehole blasting are identified. The effects of ice volumes in boreholes on blast-induced rock damage are examined. It is found that blast-induced rock damage is greatly reduced as water in boreholes turns into ice. In addition, the blasting with the ice volume greater than 6.7 % filled at the bottom of borehole can induce less rock damage compared to full-coupled charge blasting. To improve the performance of rock blasting with ice-filling boreholes, the effects of two methods, i.e., changing ignition locations and using different types of explosives on rock damage induced by the ice-filling borehole blasting are investigated. An empirical formula of rock damage volume incorporating ice volume, explosive properties, and rock properties is finally proposed as the reference for the design of ice-filling borehole blasting in cold regions.

A novel solution for vertical borehole heat exchangers in multilayered ground with the Robin boundary condition

The ground surface condition is crucial in the thermal analysis of borehole heat exchange (BHE) systems, as it directly influences the thermal regime within the subsurface. However, most existing analytical solutions assume a constant temperature at the ground surface equal to the undisturbed ground temperature, overlooking the impact of various anthropogenic and environmental factors that alter ground surface conditions. This study addresses this gap by proposing a new semi-analytical solution that incorporates the Robin boundary condition for BHEs in multilayered ground. The solution, developed using the unsteady surface element method, balances computational efficiency with analytical precision. The proposed solution was verified with an exact solution in a homogeneous body, showing a maximum error of approximately 0.2 %. Compared with prescribing a constant temperature at the ground surface, using a Robin boundary condition better captures the heat exchange between the ground and the surrounding environment. The results show that variations in the heat transfer coefficient at the ground surface can cause differences in the mean borehole wall temperature change of up to 7.45 % over about 31.7 years (109 s) for a 70-metre borehole. Meanwhile, a unit heat flux at the ground surface can raise the mean borehole wall temperature by 0.56 °C for a heat transfer coefficient of 0.25 Wm−2K−1 over 31.7 years. Additionally, the circulating fluid can transmit the impact of the ground surface condition to greater depths. The results indicate that even at the bottom of a 70-metre borehole, using a fixed temperature can underestimate the temperature change by up to 6.11 % over 31.7 years compared with using the Robin boundary condition. These findings emphasize the indispensability of the proposed solution for accurately predicting the thermal performance of BHEs.

Temperature Variations in Deep Thermal Well LZT-1 in Lądek-Zdrój (Bohemian Massif; SW Poland)—Evidence of Geothermal Anomaly and Paleoclimatic Changes

The thermal water deposit in Lądek-Zdrój (SW Poland) occurs in fractured reservoir rocks, and its hydrogeological regime is controlled by the features of the local geology and lithology of the hosting crystalline complexes, mainly impermeable high-grade metamorphosed mica schists and gneisses. The fractured thermal water aquifer is confined by a thrust fault-type aquitard that creates artesian pressure and, therefore, the water intakes and natural springs in Lądek Zdrój provide spontaneous outflow. Classical geothermometers yield an estimation of reservoir temperatures that ranges from 50 to 70 °C, with a maximum of 88 °C. The heat flux (HF) value of the Lądek-Zdrój region is 64 mW/m2. The new borehole, LZT-1, is in the border zone of a local thermal anomaly with a geothermal degree of 25–27 m/°C. The estimated temperature at the bottom of the LZT-1 borehole, under thermal equilibrium conditions, ranges between 70 °C and 80 °C. A stream of heated waters from the deep system flows from the recharge areas, shaping the local geothermal anomaly and thus influencing the thermal conditions in the Lądek-Zdrój area. The activation of this water circulation system occurred in the Pleistocene.

Evolution of Crack Source Mechanisms in Laboratory Hydraulic Fracturing on Harcourt Granite

Hydraulic fracturing has gained escalating significance in recovering unconventional reservoirs. However, the failure mechanism and its evolution with progressive fluid injection are not fully understood for granitic materials. To investigate, triaxial hydraulic fracturing on Harcourt granite and acoustic emission (AE) monitoring was performed by the self-developed multi-physical rock testing platform (MRTP). Source mechanism analysis suggests that tensile cracks account for the majority (62%) of all cracks throughout the hydraulic fracturing process. Tensile cracks with large energy are induced mainly around the borehole bottom, but their average energy is smaller than shear cracks. The entire hydraulic fracturing process is divided into three stages by injection measurements. In Stage 1, AE events are recorded with low energy emissions but high signal-to-noise ratios, revealing the initiation of hydraulic fractures before peak injection pressure. Tensile cracks are more dominant (78%) than other stages. In Stage 2, the number and magnitude of AE events increase exponentially along the trace formed in Stage 1. In Stage 3, hydraulic fractures have the largest magnitude among all stages. Shear cracks are nearly the same proportion as Stage 2, but more shear cracks with large magnitudes are observed following the trace formed by tensile cracks. A dense population of shear cracks can be found at the borehole bottom, and their distribution follows the average slip plunge of individual shear cracks induced by the injection fluid.

Using the methods to calculate parameters of drilling and +blasting operations for emulsion explosives

Mathematical modelling of rock mass breaking using blasting has been applied to obtain formulas for the calculation of crush zone radii, intensive fragmentation, and crack formation around the charging cavity in the structure, diameter of the charging cavity, diameter of the charge itself, detonation characteristics of an explosive, boundaries of the rock strength, rock mass jointing, and mineral compression under the effect of rock pressure. The methods have been developed to calculate parameters of drilling and blasting operations (DBOs) while driving the mine workings based upon the idea of the arrangement of blastholes in terms of areas they occupy in a fore-breast as well as upon their location relative to break-off outline. Stage one of the methods involves calculating and designing burn cuts where a distance between blastholes is determined with the help of a fragmentation zone radius. Stage two means calculation of both specific and total explosion consumption per borehole bottom, line of least resistance (LLR) for a borehole in terms of intensive fragmentation, areas of borehole groups, borehole number, analytical and actual distance between boreholes, actual charge amount per borehole, and actual specific and the total explosive (E) consumption per borehole bottom. The methods have been tested in the operating ore mine while driving a mine working. Emulsion explosive (EE) Ukrayinit-PP-2 (Україніт-ПП-2) has been applied. The developed methods have been used to calculate DBOs parameters for the explosive. Trial blasts demonstrated the good firing of a borehole bottom and uniform ore fragmentation; a high coefficient of borehole use has been supported.

New methodology for testing very coarse soils by “liquid plate loading”

Introduction. At present, the plate load testing is considered to be the most effective method for determining the deformation parameters of very coarse soils. However, the major challenge associated with such tests is the low accuracy of the results due to the inability to properly clean the borehole bottom.Aim. To develop a new methodology for plate load testing using an intermediate layer of a liquid, quick-setting material to ensure uniform load transfer to the very coarse soil.Materials and methods. The author conducted a number of laboratory and site investigations in order to select contact layer material, which meets requirements for plasticity, temperature, strengthening and setting time. Following that, the author recommended a liquid quick-setting composite material MasterFlow 928 for application. The study involved development of a technology for the material delivery to the borehole bottom and gathering data on the minimum required thickness of a contact layer depending on particle size of the tested soils. The methodology of using quick-setting composite materials was tested at three sites in different soil conditions and at two experimental plots where a set of parallel tests was made using 600 cm2 plate with and without quick-setting composite materials. The maximum discrepancy between the values of the deformation modulus obtained for the plates with application of quick-setting composite materials and the “reference” ones (screw and flat plate of 5000 cm2 ) did not exceed 14 %.Results. On the basis of the experimental investigations, the author developed a methodology and “Recommendations for plate loading tests to carry out using quick-setting materials at the plate-soil contact”.Conclusion. The suggested methodology for plate load testing tackles the issue of determining the deformation modulus for very coarse soils by using an intermediate layer of quick-setting liquid material that improves the contact between the plate and the soil for uniform load transfer, thus greatly increasing the accuracy of deformation parameters.

Theoretical and numerical simulation research about annular nozzle parameters influence on heat transfer in hot-water ice-coring drilling

Ice cores from polar zones could determine ice dating and biodiversity. Ice cores retrieved in hot-water ice-coring drilling partly melted owing to moderate drilling speed of annular drill head with many nozzles, which was largely depended on the heat transfer efficiency of jet to ice at borehole bottom. To obtain the higher drilling speed and ice cores of good quality, this paper explored the influence of nozzle parameters on the heat transfer efficiency of annular jet to bottom ice. Main nozzle parameters affecting the heat transfer efficiency were theoretically determined firstly. Then influence law of nozzle parameters on the heat transfer were estimated by theoretical calculation and numerical simulation. The result showed the heat transfer of annular jet to bottom ice was positively correlated with the nozzle flow and negatively relevant with the nozzle diameter, nozzle angle and nozzle quantity, which was further compared with the drilling speed value in experiment to confirm its correctness. The angle was proved to be the most influential parameter, when it increased from 0° to 30°, the drilling speed decreased 75%. The result can provided reference for designers on how to promote the drilling speed in hot-water ice-coring drilling and improve ice core quality.

Parameter Optimization of Constant Pressure Grouting Technology for Borehole Sealing with Inorganic Noncondensable Material in Tectonic Coalbed of South China

To solve the problem of a rapid attenuation of gas concentration along with drainage borehole collapse in the tectonic coalbeds of South China, a constant pressure grouting technology with inorganic, noncondensable material was proposed. Firstly, the slurry fluidity, water separation rate, and sealing performance of the inorganic sealing materials were tested under different water-cement ratios. The seepage model of slurry in a layer-through borehole was built with COMSOL Multiphysics simulation software, to explore the scopes of loose circles around drainage roadway and borehole, and to analyze the seepage capacity of the slurry under different grouting pressures. Eventually, the sealing performance of the slurry was investigated in the field. The results showed that the inorganic, noncondensable material with the water-cement ratio of 5 : 1 has a strong fluidity, low water retention, high permeability, and good sealing performance. After the excavations of No.2164 drainage roadway and layer-through borehole, there are obvious stress concentrations both at the shoulder corners of the roadway and at the borehole bottom, and the scope of the loose circle around the roadway is about 6.2 m. The effective seepage radius of the inorganic slurry gradually increases with a rising grouting pressure, and the slurry seepage range in the sandstone section is broader than that in the mudstone section. Adopting the constant pressure grouting technology with the slurry, the average drainage concentration of boreholes in Puxi coal mine is 51.5%, and the average gas flow rate is 0.005 m3/min, which are 1.35 times and 1.67 times than those with the cement grouting method.

Simulation and experimental investigations of ultrasonic-assisted drilling with Micro-PDC bit

Ultrasonic-assisted drilling (UAD) technology is a new drilling technology, which combines polycrystalline diamond compact (PDC) bits and performs better than conventional PDC drilling in improving the rock-breaking efficiency during deep hard formations. In this study, a series of simulations and laboratory tests were conducted to explore the dynamic rock-breaking mechanism of UAD with a PDC bit and the influence of different input parameters on the force and energy distribution. First, the UAD process was analyzed using a simplified drilling system model, and the relationship between the axial and tangential forces was investigated using a single PDC cutter cutting model. Then, a finite element analysis model that considers rock heterogeneity was used for the analysis. The drilling process, element damage situation, and broken form of the borehole bottom of conventional drilling (CD) and UAD were compared, and the impact of amplitude, frequency, and rotary speed on the weight on bit (WOB), torque, cutting force, and energy consumption were evaluated. Finally, laboratory experiments on PDC micro-drilling for different drilling conditions were conducted to verify the effectiveness of UAD. The results indicate that during rock-breaking using UAD, the PDC cutter periodically penetrated and broke away from the rock with ultra-high frequency, causing a large amount of damage to the rock. The frequency and amplitude significantly influenced the UAD: when the vibration frequency was between 25 and 35 kHz, the force state of the PDC cutter greatly improved compared with that of CD, and the effect of ultrasonic load reached the maximum at 33 kHz; when the amplitude was between 10 and 50 μm, WOB and torque decreased significantly and the effect of ultrasonic load improved with increase in amplitude, but the rotary speed had little effect on the torque and WOB of UAD. During the laboratory experiments, the drilling efficiency and rate of penetration (ROP) improved on using UAD. When the WOB was 100–200 N and the rotary speed was 300–400 rpm, the efficiency of ultrasonic rotary drilling to improve the ROP increased by 14.7–23.4%.

Improvement of the current methodology for calculating the parameters of drilling and blasting on the explosive force

Purpose. Improvement of the current methodology for calculating the parameters of drilling and blasting (D&B) by determining the explosive force by the degree of realization of the detonation velocity for all types of industrial explosives (IE). The methodology of research. To solve the problem, a systematic approach was used, including an analysis of the current industry methodology for calculating the parameters of D&B in underground ore mining using IE, improvement of the power-law dependence of the calculation of the line of least resistance (LLR) of charges by determining the coefficient of explosive force of the IE, taking into account the degree of implementation of the burning rate, as well as approbation of the improved technique in the conditions of the operating iron ore mine. Findings. According to the methodology for determining the coefficient of explosive force of explosives (EX) according to the degree of implementation of the burning rate and according to the results of experimental studies of the change in the burning rate of the bulk emulsion explosive (EE) Ukrainit-PP-2, an improvement is proposed for the current industry methodology for calculating the parameters of D&B for the mines of the Kriviy Rig basin and the Private Joint Stock Society "Zaporozhye iron ore plant" (PJSS "ZIOP"). This made it possible, in the conditions of the experimental block of the mine "Yubileinaya" of the PJSS "Sukhaya Balka", using the bulk EE Ukrainit-PP-2, to increase the LLR and the distance between the borehole bottom up to 17%, and to obtain good results of ore reduction. The originality. The well-known power-law dependence of the determination of the LLR of borehole for rock breaking has been improved through the refinement of the coefficient of explosive force of the IE, which takes into account the degree of realization of the burning rate EX. Practical implications. The results of the research have improved the power-law dependence of the calculation of the LLR on the explosive force, taking into account the degree of implementation of the burning rate, the use of which will allow rationalizing the parameters of the D&B when breaking the ore mass using all types of IE.

Investigation on the cuttings carrying capacity of a novel retractable drill bit used in casing while drilling with air reverse circulation

An orthogonal experimental design method is employed to investigate the effect of the structural parameters of the drill bit used in the Casing-while-Drilling (CwD) technology on its rock cuttings carrying capacity and reverse circulation performance. The results of the range analysis indicate that diameter of inner jet nozzle has the most significant impact on the cuttings carrying capacity of the drill bit, followed by the diameter of flushing nozzle. While for the reverse circulation ability, the diameters of the flushing nozzles have a dominant impact, followed by the diameters of the inner jet nozzles. In addition, the cuttings carrying capacity and the reverse circulation effect of the drill bit can be improved by shrinking the inner jet nozzle or appropriately enlarging the flushing nozzle. Accordingly, the optimal structural parameters of the drill bit are determined. Through further experiments, the cuttings carrying efficiency and the entrainment ratio of the optimal drill bit are 99.57% and 20.36%, respectively. Moreover, the rotation speed of drill bit has a trivial effect on its performance. At any tested rotation speed, the entrainment ratio is greater than 20%, and all the rock cuttings can be carried out of the borehole bottom using the proposed drill bit with the optimal structure. To test its real performance, a large-diameter retractable drill bit with a diameter of 600 mm was manufactured and tested in field. The results demonstrated that this retractable drill bit had excellent cuttings carrying and reverse circulation ability. The average penetration rate of the drill bit reached about 1.7 m/h in the formation of weathered sandstone with argillaceous composition, which was 1.7 times greater than conventional mud drilling in the same area.

Intelligent boring automatic machine for optimal control drilling of oil and gas wells

The main methods of ensuring optimal conditions for drilling oil and gas wells are considered. The method concern the optimal control of the drilling process and an adaptive method of automatic control of the axial load on the bit by using a boring automatic machine, in which rock at the borehole bottom is recognized, the calculation of the optimal axial load and the borehole bottom is drilled according to the optimization criterion «maximum mechanical speed». Keywords well drilling, adaptive optimal control, drilling model, boring automatic machinewell drilling, adaptive optimal control, drilling model, boring automatic machine

Directional fracture behavior and stress evolution process of the multi-slit charge blasting

The multi-slit charge developed from the traditional double-slit charge has more and more engineering applications in roadway blasting and excavation. In this paper, numerical simulation and model experiments are used to compare the dynamic behaviors of double-slit/three-slit charge blasting in crack propagation, stress evolution and blasting vibration. The research results show that the directional fracture effect at the borehole middle and borehole bottom in the slit charge blasting is the best, followed by the directional fracture effect at the borehole orifice, and the length of the directional crack formed along the slit direction at the borehole middle is the largest. Compared with the double-slit charge blasting, the dynamic stress intensity factor of the directional crack at initiation stage and early propagation stage in the three-slit charge blasting is smaller, and the directional cracks formed are shorter. In addition, the effective stress evolution and blasting vibration attenuation of the gauging points along the slit direction are affected by slit number and cross-section position. The effective stress and blasting vibration of gauging points at the borehole bottom in the slit charge blasting are significantly larger than those of gauging points at the borehole orifice. For the three-slit charge blasting, the model experiment finds that the directional crack deflected to the side of protected rock mass during the propagation process. The occurrence of such deflection phenomenon is likely to cause overbreak of rock mass, which is not conducive to the formation of a straight profile surface in the rock roadway excavation.

Modeling for gas dissolution and diffusion in water-intrusion coal seam and its potential applications

In order to determine the gas pressure for water-intrusion borehole, a new method of gas pressure measurement in water-intrusion borehole based on gas solubility was proposed. A mathematical model of gas migration in water-intrusion borehole considering the effective diffusion coefficient was established. The influencing factors, such as water-intrusion radius, diffusion coefficient and solution convection, on the dissolution equilibrium of gas in borehole water were investigated. Finally, the feasibility of the new gas pressure measurement method was discussed. Results showed that the gas diffusion coefficient and water-intrusion radius of coal seam are the key factors influencing the equilibrium duration of gas dissolution. During the accumulation stage of formation water in borehole, the gas is able to quickly dissolve and diffuse in borehole water. The amount of dissolved gas can reach more than 90% of solubility in three days. After the formation water enters the coal seam, the equilibrium time grows sharply because the effective diffusion coefficient of gas in water-saturated coal is much lower than that in pure water. In addition, the water convection causes a higher amount of gas dissolved at the borehole bottom. Finally, the field applicability for the new method of pressure measurement were analyzed by combining the data from previous works. This work provided a new idea for the gas pressure measurement of water-intrusion borehole.

Magnetic Properties of Late Cenozoic Sediments in the Subei Basin: Implications for the Yangtze River Run-through Time

Shu, Q.; Zhao, Z.; Zhao, Y.; Chen, Y., and Zhang, M., 2021. Magnetic properties of late Cenozoic sediments in the Subei Basin: Implications for the Yangtze River run-through time. Journal of Coastal Research, 37(1), 122–131. Coconut Creek (Florida), ISSN 0749-0208.The Subei Basin is situated in the lower reaches of the Yangtze and Huai Rivers. In this study, samples were selected from the XH-2 borehole near the subsidence center of the Subei Basin, and modern sediments from the lower reaches of the Yangtze and Huai Rivers. The aim of this study is to decipher the evolution of the regional river system and the formation of the Yangtze River's Three Gorges through the analyses of paleomagnetism, mass susceptibility, and magnetic minerals. The results show that the river system in the Subei Basin experienced several major upheavals. (1) During 4.76–4.2 million years before present (Ma BP), the Yangtze River flowed through the study area in the vicinity of the XH-2 location; (2) During 4.2–2.2 Ma BP, the Yangtze River had migrated from the study area, and the Huai River flowed through the area; (3) During 2.2–0.55 Ma BP, the Yangtze River flowed through the area again; (4) During 0.55–0.12 Ma BP, the Yangtze River and Huai River alternatively influenced the study area; and (5) Since 0.12 Ma BP, the Yangtze River withdrew from the Subei Basin entirely, and the Huai River flows through the XH-2 position again. The Yangtze River sediment in the bottom of the XH-2 borehole indicates that the time of formation of the Three Gorges of the Yangtze River is probably greater than or equal to 4.76 Ma BP. This estimated time is earlier than the previous conclusions of an Early Pleistocene run-through time for the Yangtze River.

Evaluation methods and standards for rock drillability in oil and gas drilling engineering in China: A review

In western China, 70% of the oil, gas, and geothermal resources are buried in deep formations (more than 3000 m), but the low rate of penetration has become a key factor restricting the development of these resources. Rock drillability evaluation is a basic task for oil, gas, and geothermal drilling engineering design that includes bit design, bit selection, and drilling parameter optimization. Different tests and standards to evaluate rock drillability have been developed worldwide. Against this backdrop, the evaluation methods and standards for rock drillability are reviewed. Various rock drillability tests and classification standards are compared and analyzed. Results show that these methods and standards are inaccurate and fail to meet the design requirements of drilling technology and bit selection in deep and ultradeep drilling wells. In China, micro-drilling test is commonly used to evaluate rock drillability in oil and gas drilling engineering. This method was developed as an oil and gas industry standard and has been used for more than 40 years. However, its results do not reflect the significant effects of high temperature and pressure at the bottom hole on rock drillability and breaking; thus, the results cannot be used in drilling designs. Testing methods and classification standards for rock drillability require innovative developments. This review highlights the following: (1) the classification standards for rock drillability must be refined in the future to meet the requirements of drilling designs in deep and ultradeep wells; (2) efficient and fast rock drillability tests are required to deal with complex and difficult formations; (3) the influence of the real physical environment of the borehole bottom on rock drillability must be further clarified.

Geo-resistivity data set for groundwater aquifer exploration in the basement complex terrain of Nigeria, West Africa.

To delineate prolific groundwater aquifers in the basement complex terrain of Ilorin, Nigeria, West Africa, a carefully designed Electrical Resistivity Surveys were undertaken at eighty-five (85) stations using Vertical Electrical Sounding (VES) technique with Schlumberger array. Data acquisition system comprised SAS 3000 ABEM Resistivity Meter, a D. C. battery, four metallic electrodes, electrical cables, portable Geographic Positioning System (GPS), hammers, measuring tapes, and other accessories. In addition to the resistivity data, the geographic coordinates of the survey points were measured for ease of geo-referencing of the exact points where the data were collected and for secondary use of the data. The data acquired were processed, analysed and interpreted using auxiliary curve matching techniques and computer iteration method. The results were used to: evaluate the subsurface in terms of the different geo-electric layers, their thicknesses, depths, and resistivities; evaluate the groundwater potential of the aquifer; identify suitable sites for locating boreholes for groundwater exploitation; and recommend depths to borehole bottom in the different parts of the study area. The data presented can be reused to determine the protective capacity of the overburden material against groundwater contamination; to determine the engineering-geophysics and geotechnical properties of the rocks for Civil Engineering applications; for predicting groundwater flow models; and for mineral exploration within the area. The data presented can be used with other geophysical and geological data acquired from the same area for a better evaluation of the subsurface for multipurpose applications.

Evaluation of drilling hydraulic calculation to the ability of bottom hole cleaning

In drilling operation there are two important matters that must be considered, which are the pumps and drilling fluid rheology that are influencing hydraulics drilling system. The major function of drilling fluid is to lift the drill cutting to the surface and still maintain the drilling hole to avoid an encounter. Evaluation of hydraulics drilling for bottom hole cleaning will count the parameter success which influence in removal of cutting to the surface for bottom hole cleaning and optimization drilling calculation hydraulics. The velocity of drilling fluid in annular, the flow that is formed and the ability of bottom hole cleaning are highly influenced by specifications of mud pump as a resource power for mud to flow that also will determine how the value of flow rate can be circulated. Mud rheology, PV, YP and MW will influence the performance of mud to carry cutting on drilling operation. The penetration to formation rock will make the broken bits of solid material removed from a borehole drilled by bit and resulting the drill cuttings. These cuttings could settle on the bottom of borehole so the main purpose of drilling fluid is to carry the cuttings to the surface, besides the drilling fluid also protecting borehole condition from any drilling problems. This evaluation is using Power Law Model for calculate pressure losses, drilling hydraulic optimization and also observe the parameter of Cutting Transport Ratio (Ft), Cutting Concentration (Ca), Cutting Carrying Index (CCI) and Particle Bed Index (PBI). The optimization results from Bit Hydraulic Horse Power (BHHP) method produce significant changes which are percentage horse power delivered to bit (%HHP) increasing to 53.17 – 54.79 % from actual condition which only ranges 5 – 51 %. Q optimum is very influential on the value of bit hydraulic horse power (BHHP) and surface horse power (HPS) that provide more optimized power to pump the mud with minimize the effect of pressure loss.

Analysis of Implementation Effectiveness of Two Working Fluids Characterized by Different Viscoelastic Characteristics at Hydrodynamic Impact on the Borehole Bottom Zone

Combination of hydrodynamic impact on the formation with acid treatment may be seen as a promising direction in the field of well development and repair in complex geological conditions. With multiple repetition of hydraulic shocks in conjunction with the injection of acid solution, the depth and opening of cracks gradually increases, which contributes to a deeper penetration of the acid solution into the reservoir. The article presents analytical studies, which are aimed at determining the effectiveness of applying the technology of hydrodynamic impact on the bottomhole zone of an oil reservoir when using two fluids with different viscoelastic characteristics as a working fluid. They are devoted to determining the pressure drop at the borehole bottom depending on the initial applied pressure at the wellhead, the velocity of the shock wave, the viscosity of the working and well fluid, and their quantity. These studies were based on the well-known models of Thomson – Tаt and Maxwell, considering viscous liquid flow. The dependence obtained proves that with an increase in the pressure pulse generated at the wellhead, the development of pressure pulses at the borehole bottom is a power-law dependence, and with significant volumes of fluid in contact with the bottomhole formation zone, the pressure drop generated at the borehole bottom does not depend only on pressure pulses generated at the wellhead, but also on the dynamic viscosity of this fluid. Conducted studies have shown the effectiveness of hydrodynamic impact technology application when using two liquids with different viscoelastic characteristics and obtaining a synergistic effect during the development and repair of wells in low-permeable reservoirs. Analytical studies were based on data from previously conducted experimental industrial tests on the operating injection well.