Rate of penetration

Purpose: The purpose of this paper is to study and analyse the possible impact of International Financial Reporting Standards on the level of earnings management. The paper includes a review of all such studies from around the world. Design/Methodology: Existing studies available on the topic are systematically reviewed. Different journals, periodicals and websites were used to gather the information. Time period considered for the study is from 2005 to 2019. Although most of the papers relate to foreign countries as not much research is available in the Indian context. Overall, 60 papers were considered, but out of them only 40 were found to be suitable for the present study. The review has been segregated into 3 parts. 30% of the paper focus on the meaning and determinants of earnings management, 20% of the studies relate to IFRS adoption around the world. Remaining research tries to analyse the connection between adoption of international standards and level of earnings management. Findings: The adoption of IFRS standards has no significant impact on the level of earnings management of any country. In fact, the level has increased in some countries after the compulsory adoption. However, if certain other factors are taken into account along with IFRS like audit quality, corporate governance practices, board management, R&D disclosure, enforcement mechanism, investor protection regime etc., the combined effect have yielded different results for different countries. Research Limitations and Implications: The study focuses only on one major area related to IFRS i.e., its impact on earnings management of a firm. Although there are many other determinants of earnings management and also IFRS had its impact on various other areas. But due to certain research limitations those are not considered Purpose: The purpose of this paper is to study and analyse the possible impact of International Financial Reporting Standards on the level of earnings management. The paper includes a review of all such studies from around the world. Design/Methodology: Existing studies available on the topic are systematically reviewed. Different journals, periodicals and websites were used to gather the information. Time period considered for the study is from 2005 to 2019. Although most of the papers relate to foreign countries as not much research is available in the Indian context. Overall, 60 papers were considered, but out of them only 40 were found to be suitable for the present study. The review has been segregated into 3 parts. 30% of the paper focus on the meaning and determinants of earnings management, 20% of the studies relate to IFRS adoption around the world. Remaining research tries to analyse the connection between adoption of international standards and level of earnings management. Findings: The adoption of IFRS standards has no significant impact on the level of earnings management of any country. In fact, the level has increased in some countries after the compulsory adoption. However, if certain other factors are taken into account along with IFRS like audit quality, corporate governance practices, board management, R&D disclosure, enforcement mechanism, investor protection regime etc., the combined effect have yielded different results for different countries. Research Limitations and Implications: The study focuses only on one major area related to IFRS i.e., its impact on earnings management of a firm. Although there are many other determinants of earnings management and also IFRS had its impact on various other areas. But due to certain research limitations those are not considered

High-frequency torsional vibration percussive drilling is considered a promising approach to improve drilling performance in deep hard formations, so studying its rock breaking mechanism and effect is the essential and basic issue. Compared with percussive-rotary drilling and high-pressure jet drilling, it can increase the service life of drilling tools and reduce drilling cost significantly. In this paper, based on elastic mechanics and principles of mechanical vibration, the cutting mechanism model of PDC (polycrystalline diamond compact) drill bit cutter and the amplitude-frequency characteristic model of steady-state vibration response of rock system are established, as well as the response characteristics of the rock system are also pointed out. Based on elastic-plastic mechanics and rock mechanics, Drucker-Prager criterion is adopted as the constitutive equation of rock, and plastic strain is used as the criterion of rock failure. Moreover, the model of rock damage failure is also established. The effect of exciting frequency on ROP (rate of penetration) has been studied by carrying out rock breaking test using high-frequency torsional vibration percussive drilling of PDC drill bit along with analyzing and handling test data. The study results show that when torsional vibration percussive frequency is approximately equal to inherent frequency of the rock, rock resonates with cutter, the plastic strain and ROP reach maximum, and drilling efficiency is the highest. The research results can help to deepen the understanding of the percussive drilling with high-frequency torsion vibration and provide useful insight into the design, application , and optimization of this new type of downhole tools in drilling engineering. ARTICLE HISTORY

With the increasing of drilling depth, the working conditions of the drilling engineering are becoming more complicated. When drilling in the complex well structure, there are many new problems or challenges such as low rate of penetration (ROP), serious stick-slip phenomenon, or high risk of downhole tools failure. The most critical factor in solving these new challenges is improving rock breaking efficiency. Considering this, this paper proposed a new oscillator based on the positive displacement motor. Combining with new complex drilling conditions, the new structure was designed. The mathematical models were presented, including the working mechanism of the new design with its structure parameters. Furthermore, the theoretical models of dynamics under new conditions were analyzed, including the new bottom hole assembly. Based on this, we can get the vibration displacement, velocity, and the system vibration spectrum at different drill string positions. Compared with the results of a numerical example, the lab test was carried out. The two important parameters of vibration frequency and impact forces were compared with the theoretical results, which verified the correctness of the theoretical model and the accuracy of the solution method. Moreover, field experiments were also tested to verify the results, and the field experimental data showed that the new design could increase ROP obviously. The method and conclusions of the research can provide a new reference for the new downhole technology of enhancing the ROP or improving the rock breaking efficiency in complex well structure.

For improving the rock-breaking efficiency of oil and gas drill bits, a new drill bit is presented with tornado-like bottomhole model (named swirling cutting bit). The new drill bit cutter breaks rock with shocking and cutting effect during the drilling process, and the elements on largest ring cross the borehole center with high speed. It can effectively improve the center rock-breaking efficiency. Meanwhile , for all cutters on different rings breaking rock at the same time, it can optimize the rock-breaking volume of each element and improve the bit service life. To analyze the interaction features between cutters and rock, the position equations are established by the cylindrical coordinates and complex movement principles, and then the velocity and acceleration equations can be obtained. Based on the numerical example results, this paper analyzes the bottomhole model, the contact section, and the distribution features of velocities and accelerations on different rings. By analyzing the acceleration results, we can study the failure mechanism of cutters. At the same time, lab experiments test the bottomhole model and rock-breaking features, and it verifies the accuracy of calculation method and equations. Moreover, the analysis method and models are also applicable to other types of bits or composite bits, and the inputting parameters need corresponding adjustment for different type of bits.

Rate of Penetration (ROP) prediction is an important aspect of drilling in the Oil & Gas Industry. Several studies have been carried out to predict ROP. Primarily, Artificial Neural Networks (ANN) has been used. In this paper, the objective is to explore a new approach to predict ROP using K-means and Ensemble of Gradient Boosting Model (GBM) technique. Nine input parameters are used for ROP prediction-True vertical depth, weight on bit, standpipe pressure, flow-rate, torque, equivalent circulating density and RPM. The model is evaluated on the basis of accuracy, R^2 and Root-mean square error (RMSE)

For improving the rate of penetration of the complex well structure and performance of the coring drill bit, this paper is to investigate a new type of coring drill bit that generates small-diameter core samples during the drilling process. A special jet channel is designed inside the drill bit body, and the high-pressure drilling fluid flows through the special jet channel to the coring channel, then the cored rock is taken out of the downhole from the drill bit under the negative pressure. Based on the hydrodynamics theory, rock breaking mechanics and actual drilling conditions, the rock breaking mechanism model of the coring drill bit is established. The difference of rock breaking performance between the new drill bit and the existing drill bit is analyzed based on the analysis of numerical example, laboratory and field test. The research results indicate that the special structure design in the new drill bit has the effect of 'absorbing the bottom rock cuttings and pushing the upper rock cuttings' during the process of rock breaking. The effect can reduce the repeated cutting of cores at the bottom hole and improve the ROP(rate of penetration). Field tests show that when the flow rate of drill pump is 25L/s, the result of ROP can be increased by 15%-40%. The new design drill bit can present innovative ideas for improving the efficiency of coring and the quality of geological logging during the drilling process. Moreover, the analysis models can provide references for the new research of improving ROP and drilling efficiency, especially under the conditions of complex structure or large displacement wells.

For the low rock-breaking efficiency at borehole centre of the current drill bit, this paper presents a new bit with swirling bottom-hole model (swirling-cutting bit) and analyses its kinematics and rock-breaking features. Using the cylindrical coordinate, the bit revolution and cone rotation motion behaviour are analysed. With the position and velocities equations establishment of cutting element, the contact section between different cutting elements ring and rock are given, including the velocities distribution results on the section. With the numerical calculation and experimental test, the results show that the elements on maximum elements ring pass through the borehole centre, and broke the rock with compression and cutting effect. With the start point at the bottom-hole and end point at the borehole wall, the contact force of element acting on rock contains effect of 'digging' from the inside out and from the bottom up. The conclusions provide reference for improving the bit rock-breaking efficiency, cutting element distribution and bit structure optimisation. Pang, X. (2015) 'Kinematic and rock-breaking characteristics of new drill bit with swirling bottom-hole model', Int.

It is of great importance that the drilling program required for the newly drilled wells is estimated by using the drilling data of the previously drilled wells in a field or basin to complete the drilling under economic and optimum conditions within the estimated time. In this study, in the Southeastern Anatolia and Thrace basins of Turkey, where both oil and gas exploration and production are performed, a new approach has been presented for the estimation of drilling time before drilling, using the rate of penetrations (ROPs), weights on bit (WOB), rotation speeds, and actual (net) drilling times of the previously drilled wells as well as based on the formation thicknesses predicted by the geological and geophysical data provided from any field. For the formations in both basins, equations for the actual drilling time estimation and drillability factors have been determined depending on them. The results of the new approach show that the actual drilling times can be estimated with high accuracy according to the formation thickness to be drilled before drilling. Moreover, ROPs can be forecasted based on the estimated actual drilling times.
Keywords: oilwell drilling, drilling time, rate of penetration, drillability factor, drillability of rocks

Abrasive jet machining is a metal removal process involving erosion of work surface on account of impingement of stream of high speed abrasive particles through a nozzle by high pressure air or gas. The small bits of work surface material get loosened due to repeated impacts and get loosened thereby being carried away by jet of abrasive particles. This paper reviews various parameters of abrasive jet machining and their respective effect on different materials

In new drilling conditions such as extended reach drilling or long horizontal well, to avoid large friction between drill string and wellbore or weigh on bit decreasing, a new drilling vibration tool (called antifriction oscillator) is presented in this article. For discussing its working mechanism and performance, first, the kinematics models are established based on the structure design parameter, and then the horizontal vibration models are presented according to drilling conditions. With the numerical example results, it can be concluded that the frequency of the flow area between the static and dynamic valve plates is proportional to the flow rate. Moreover, with the increasing size of static valve plate, the flow area is increasing while the total axial force is decreasing. Furthermore, according to the experiment test results with static valve plate hole diameter 35.56 mm, the vibration results are discussed by comparing with numerical example results, and it can verify the analysis models' rationality and the calculation formulas' correctness. The research results provide basis for theoretical research and field applications of drilling oscillator. Furthermore, by changing corresponding parameters, the research methods and models can also provide reference for the design of new methods or tools of drilling friction reduction or rate of penetration increasing technologies.