Specific Drilling Research Articles

Investigation of the specific charge variations in determining the optimal methods for drilling and blasting of tunnels

In this research, in order to compare and select the optimum patterns, two parameters of specific charge and specific drilling are used. Two explosive substances, including ammonium nitrate and fuel oil (ANFO) and Amulet, are used to charge the holes located on the cross-section of the tunnels in order to advance by 3 meters. Also, the cross-section of the selected tunnels was 19, 28, 32, 40, 48, 50, 65, and 76 square meters with horseshoe, circle and D-shaped. The diameter of the explosive hole is 48 mm for the Norwegian method and 51 mm for the two energy balance models and the Swedish method to compare them. A total of 160 designs are prepared for three types of limestone, sandstone and marl. The results obtained for two parameters of specific charge and special drilling for the selected rock material are completely opposite. Also, in the Swedish methods, according to the Amulet, the values of the calculated parameters are close to the energy balance model. Finally, according to the geomechanical parameters of the rock, for the Swedish method and the energy balance model in charging with amulet explosives, the energy balance model and the Holemberg-Persson method are proposed in the optimal design for the tunnel drilling and blasting pattern. In addition, for the Norwegian method and the energy balance model in charging the holes with ANFO, the energy balance model is prior to the Norwegian method. The amount of stemming of holes in different parts of the tunnel face is less for the Swedish method than the Norwegian and energy balance models.

Mathematical Model of Drilling Mud Movement along a Shale Shaker Screen

Introduction. When drilling oil or gas wells, rock from the bottomhole is brought to the surface by drilling mud, which is cleaned of sludge by shale shakers at the first stage. Shale shakers are equipped with such a screen and create such trajectories of vibration of the frame in order to solve a dual problem: on the one hand, to provide the cleaning of the drilling mud coming from the well mouth, and on the other hand — to maintain the proper degree of cleaning. To correctly select the nomenclature of screens, it is necessary to reliably determine the throughput capacity of a shale shaker in the real-time setting. This will allow you to pre-order the required number of screens with the required cell size. Previously, studies were conducted by sieving a mixture of calibrated granules on a standard shaker or by straining mineral oil through a fixed screen. However, this does not fully correspond to the actual conditions of drilling mud screening. The objective of this article was to simulate the throughput of a drilling shale shaker under real conditions by calculating the movement of drilling mud along a vibrating screen using its previously obtained specific throughput capacity.Materials and Methods. When creating a mathematical model of the full throughput capacity of a shale shaker, a previously known mathematical model of fluid flow in an open channel and a finite-dimensional approximation in the form of a sequence of sections of concentrated containers connected by hydraulic conductivities (by analogy with the approximation of long electrical lines and extended gas pipelines by the finite element method) were used. The fluid flow rate over the screen was determined according to Chézy law. In this case, the cross-sectional area of the flow above the screen for a specific section was specified as the arithmetic mean between the initial and final values of the drilling mud height in the corresponding section.Results. A chain calculation scheme for sieving drilling mud was compiled. Based on the material balance, mathematical models were developed for determining the throughput and height of drilling mud above the screen: for the first section of the screen and the first nodal point of the screen; for subsequent screen sections and subsequent screen nodal points; for the last section of the screen and the last nodal point of the screen.A mathematical model of the drilling mud movement along the shale shaker screen has been obtained, which, due to the finite-dimensional representation of this flow along n sections of the screen length, is a system of n integral equations describing concentrated tanks, and n – 1 algebraic equations describing the flow of drilling mud between tanks.Discussion and Conclusion. The movement of drilling mud along the length of the shale shaker screen corresponds to the movement of a steady uneven flow in an open channel. However, in the first case, the volume flow along the length is variable (decreasing to zero), and in the second case, it is constant along the length. Therefore, the use of only one differential equation for steady uneven flow in an open channel is not sufficient in this case. The resulting mathematical model of the drilling mud movement along the shale shaker screen is a mathematical basis for the development of a modeling program to determine the throughput of the shale shaker for real operating conditions, i.e., for a specific drilling mud, a given screen or a given drive system of the shale shaker.

Experimental investigation on high voltage electric pulse rock breaking under drilling mud conditions

High voltage electric pulse rock breaking technology is a novel and promising rock breaking technique that is environmentally friendly, efficient, and nearing industrial application. However, the drilling performance of electrode bits under varied drilling muds and the mechanism of high voltage electric pulse rock breaking remain unclear. This study entails real drilling experiments conducted on red sandstone using electrical pulse drilling (EPD) under different initial voltage peaks, electrode bits, and drilling muds to investigate the impact and mechanism of EPD. A laboratory experimental system for high voltage pulse rock breaking is established based on a 0–80 kV EPD pulse generator. Three types of electrode bits are devised, namely, petal-structural, four-point-structural, and circular-ring-structural electrode bits. The EPD experiments on red sandstone are executed under seven different drilling muds at initial peak voltages ranging from 13 to 17 kV. And the efficiency of EPD rock breaking is assessed using five quantitative indexes: rate of penetration, breaking volume, specific energy of rock breaking, and the proportion of electrical fragmentation and hydraulic-electric rock fragmentation. Furthermore, the physical parameters, i.e., density, conductivity, Zeta potential, PH, and apparent viscosity, of the seven drilling muds are measured, shedding light on the rock breaking mechanism of EPD under specific drilling mud conditions. Subsequently, the designed electrode bit is evaluated, and based on experimental phenomenon, structural optimizations of the electrode bit and EPD drilling recommendations under various drilling mud conditions in real drilling scenarios are proposed. This research is poised to offer valuable insights into the design of EPD electrode bits and the selection of drilling mud for enhancing drilling efficiency.

Combining Bourgoyne and Young Equations by Bagging Tree Regression to Predict Rate of Penetration in a Southern Iraqi Field, Case Study

Abstract Achieving an accurate and optimal rate of penetration (ROP) is critical for a cost-effective and safe drilling operation. While different techniques have been used to achieve this goal, each approach has limitations, prompting researchers to seek solutions. This study’s objective is to conduct the strategy of combining the Bourgoyne and Young (BYM) ROP equations with Bagging Tree regression in a southern Iraqi field. Although BYM equations are commonly used and widespread to estimate drilling rates, they need more specific drilling parameters to capture different ROP complexities. The Bagging Tree algorithm, a random forest variant, addresses these limitations by blending domain knowledge and capturing non-linear relationships. Its ensemble nature also mitigates the impact of outliers. This approach combines physics-based equations with machine learning to enable more accurate ROP predictions in drilling operations. It enhances drilling efficiency, reduces expenses, and improves decision-making in the oil and gas sector. Extensive testing on actual drilling datasets has demonstrated outstanding performance compared to the multiple linear regression (MLR) method. With the increased R2 and zero P-value. positive findings show that this tool can benefit precise future ROP prediction in southern Iraqi oil well drilling.

Enhancing rock fragmentation assessment in mine blasting through machine learning algorithms: a practical approach

The optimization of blasting operations greatly benefits from the prediction of rock fragmentation. The main factors that affect fragmentation are rock mass characteristics, blast geometry, and explosive properties. This paper is a step towards the implementation of machine learning and deep learning algorithms for predicting the extent of fragmentation (in percentage) in open pit mining. While various parameters can affect rock fragmentation, this study considers ten among them (i.e., spacing, drill hole diameter, burden, average bench height, powder factor, number of holes, charge per delay, uniaxial compressive strength, specific drilling, and stemming) to train and test the models. However, due to a weak correlation with rock fragmentation, drill diameter, average bench height, compressive strength, stemming, and charge per delay are eliminated to reduce model complexity. A total of 219 data sets having five input features including the number of holes, spacing, burden, specific drilling, and powder factor are used to develop the models. Machine learning models (random forest regression, support vector regression, and XG boost), as well as a deep learning model (neural network regression), are applied to develop a practical way that can optimize the prediction of fragmentation. This study employs performance measures such as R-squared, RMSE, MSE, MAPE, and MAE. The optimization of the model revealed promising results, indicating that the architecture 5-64-32-16-1 exhibits strong performance. Specifically, the model achieved mean squared error (MSE) values of 41.32 and 28.59 on the training and test datasets, respectively. The R2 value for both training and test is 0.83. RFR is also performing well compared to SVR and XG boost with MSE values of 12.37 and 9.89 on training and testing data, respectively.in both sets, the R2 value is 94%. Based on permutation importance and shapely plot values, it is observed that the powder factor has the highest impact, while the burden has the lowest impact on fragmentation.

A Data-Driven Approach to Predict the ROP of Deep Wells in Fukang Sag

In the deep well drilling process in the Fukang Depression of the Eastern Junggar Basin, rock fracturing issues and low rate of penetration (ROP) have posed significant challenges to drilling efficiency. Accurate predictions of ROP prior to drilling are of considerable value in this context. Precise predictions enable on-site engineering teams to proactively identify drilling difficulties and anticipate potential complex scenarios, facilitating them in designing preventive measures in advance, such as selecting appropriate drill bits, adjusting drilling parameters, or employing specific drilling techniques to address these issues. This, in turn, enhances drilling efficiency and greatly reduces drilling risks. Traditional mechanical-specific energy drilling rate models, despite their widespread use, exhibit significant disparities with actual results when predicting ROP. These models only consider the influence of drill bits, drilling tools, and some drilling parameters on ROP, failing to adequately account for the variations caused by engineering factors and failing to capture the interrelationships between various parameters, especially when dealing with complex subsurface formations in the Fukang Depression. Random forest is a non-parametric algorithm in the field of machine learning that is suitable for analyzing and predicting ROP affected by various complex and non-linear drilling parameters. This paper establishes a Random forest model based on a dataset containing multiple variables of logging parameters and the actual ROP. The model ranks and assesses the important feature parameters of ROP to reveal their impact. Additionally, the model uses bootstrap sampling and feature random selection to construct multiple decision trees, reducing the risk of overfitting and endowing the model with a high generalization capability. Evaluation metrics indicate that the model exhibits a high prediction accuracy and performs well, significantly improving the accuracy of mechanical drilling rate predictions in the deep wells of the Fukang Depression. This model provides robust support and serves as a positive demonstration for addressing mechanical drilling rate issues in complex subsurface formations in the future.

Simulation of induced flyrock due to open-pit blasting using the PCA-CART hybrid modeling

The primary objective of open-pit blasting is to achieve optimal rock fragmentation while minimizing undesirable side effects such as flyrock, backbreak, and vibrations. Accurate prediction of these blasting side effects plays a pivotal role in preventing accidents and enhancing overall mine safety and productivity. This paper introduces a simulation model that integrates Classification and Regression Tree (CART) analysis and Principal Component Analysis (PCA) to simulate and predict flyrock occurrences during mine blasting operations. The research focuses on the Sangan iron ore mine as a case study, collecting a dataset of 96 observations from various mine locations during blasting operations. The dataset includes controllable parameters such as burden (B), spacing (S), hole length (L), sub-drilling (U), specific drilling (SD), stemming (T), specific charge (P), and average charge per blast hole (Q). PCA is employed to assess correlations among these input variables. Notably, strong correlations are identified between variables S and B, T and L, and SD and P, leading to the selection of S, L, and P as representative variables. Consequently, S, L, U, P, and Q are chosen as uncorrelated inputs for the CART-based flyrock modeling. Of the 96 datasets, 81 are employed to train the CART model, while the remaining datasets are reserved for testing its performance. The determination coefficients achieved during the training and testing phases are 0.924 and 0.945, respectively, indicating a high level of accuracy in the CART modeling. Additionally, performance indices, including performance index (PI), variance accounted for (VAF), and normalized root mean square error (NRMSE), are calculated, yielding values of 1.423, 92.351 %, and 0.095, respectively. Based on the CART modeling, 21 key guidelines for designing blasting patterns are proposed. Furthermore, sensitivity analysis conducted to highlight the varying importance of input variables in flyrock prediction, wherein variables P and S identified as having the highest and lowest impact, respectively. Finally, the study's findings are applied to recommend and implement a modified blasting pattern in the Sangan iron mine, resulting in a substantial reduction in both vertical and horizontal flyrock incidents.

Płuczki wiertnicze w skomplikowanych warunkach: przegląd

The review in this article focuses on various aspects of drilling extended reach (ERD) wells. Reaching extreme depths and setting world records for deviation illustrates the importance of well design and operating strategies. Studies of articles describing various locations, including Sakhalin Island in Russia and offshore Vietnam, provide insight into ERD operations. Furthermore, the challenges of drilling in specific geological conditions, such as layered sandstones and reactive clay, are considered. Particular attention is paid to issues related to wellbore instability and drilling fluid optimization. The results of technical studies highlight the key role of maintaining wellbore stability in achieving successful ERD results. The articles emphasize the importance of understanding geomechanical factors, employing optimal mud weight, lubrication, and specialized drilling fluids to counteract instability. It demonstrates that maintaining appropriate mud weights and employing specific drilling techniques are crucial for mitigating instability-related issues. The integration of mechanical and chemical approaches is advocated for effectively managing shale-related instability. The utilization of innovative materials and fluid systems is central to the successful resolution of stability-related problems. The incorporation of micronized sealing polymers in conjunction with conventional plugging materials is detailed as an effective approach to counter wellbore instability. The synergistic combination of materials, additives and mud salinity is showcased to achieve effective shale stabilization and optimize drilling time. The authors emphasize the importance of selecting the optimal composition for each well based on experience and laboratory testing and present laboratory-tested solutions that have been successfully applied in field operations. In summary, these articles collectively offer insights into a range of strategies to combat wellbore instability. They cover the use of advanced materials, innovative fluid systems, and chemical approaches to maintain wellbore stability, improve drilling efficiency, and reduce nonproductive time.

A newly developed blasting cut in tunnels; application of “combined method” in small to medium-sized tunnels

Drilling and blasting method have been widely used for driving tunnels in hard rock. When designing a blast operation especially in case of long tunnels, the primary objective of contractors is to ensure optimized blast parameters for achieving the most economical and time-saving technique of excavation. Choosing a proper blasting cut has a crucial role in the successfulness of the whole blast round in terms of quality, time and cost. The first aim of cut is to break and throw rocks and create a cavity for the upcoming production detonators. An attempt has been made here to test and develop an innovative cutting system for small to medium-scale tunnels where classical wedge cut is physically difficult to execute; what is called in this paper “combined or quasi-wedge method”. Proposed drilling and blasting patterns have been first put in computerized drilling machines and then tested in the tunnels located in Rishikesh-Karnaprayag Railway Project, Package 2, driven in sedimentary rock mass. After thorough investigation of trial-and-error blasts economically and technically, necessary changes have been made to guarantee optimization and find proper design configurations. In comparison to conventional parallel cut, the newly developed cut leads not only to the betterment of cycle time for excavation but also improvement of specific drilling and specific charge, the two main performance indicators of blast operations. Vibration, fragmentation, pull length, fly rock and profile quality, as pro-blast parameters, were also found highly satisfactory.

IMPROVING THE METHOD OF SELECTING BUFFER TO IMPROVE THE QUALITY OF WELL ANCHORING WITH THE USE HYDROCARBON-BASED DRILLING FLUID

Currently, when cementing casing strings, various formulations of buffer fluids are used, the choice of which is based on laboratory testing of its compatibility with specific drilling and grouting solutions. The development of market relations evolutionarily pushed manufacturers to obtain and use the most efficient, durable materials and technologies that meet the requirements of ISO 13500:2008 [11], ISO 10426-2:2003(R) [12].In foreign and Russian practice, leading oil and gas companies use integrated quality management systems. However, due to the influence of a number of socio-economic factors, there has been a sharp rise in the cost and reduction in the production of components, along with a continuous increase in the need for efficient materials in many industries. The use of components produced by domestic enterprises in industrial volumes makes them deficit-free, and in terms of price quite affordable and competitive raw materials [6].«RN-BashNIPIneft» LLC together with the «USPTU has developed a methodology to establish uniform requirements for the evaluation of buffer fluids for hydrocarbon-based drilling fluids when cementing casing strings. The methodological basis for achieving this goal is the concept of a systematic approach in the quality management of buffer fluids [8].

Research on Interdependence between Specific Rock Cutting Energy and Specific Drilling Energy

A method based on extensive laboratory and field measurements was developed to determine the dependence of specific rock cutting energy (SEc) on specific drilling energy (SEd) for machines with different operating and design characteristics and similar breaking mechanics. Laboratory measurements were performed on a linear rock cutting device and a laboratory drill, using a measurement system to measure electrical power and cutting forces using force/torque transducers. Field power consumption measurements were performed on a chainsaw cutting machine and a hydraulic rotary drill under real working conditions in the dimension stone quarries. The analysis of the measured results confirmed the strong dependence of the specific rock cutting energy on the specific drilling energy and confirmed that laboratory devices can be used to simulate actual rock cutting and drilling process. In addition, the results are applicable in the dimension stone exploration and exploitation phase in order to assess and reduce energy consumption by optimizing the operating parameters of the chain cutter and/or the hydraulic rotary drill.

Die Bohr‐ und Injektionsarbeiten des Bauloses SBT 1.1 – Tunnel Gloggnitz

AbstractThe Semmering Base Tunnel (SBT), which has a total length of 27.3 km, is one of the most important construction projects in the Baltic‐Adriatic railway corridor. The base tunnel crosses the foothills of the Eastern Alps and connects the two federal states of Lower Austria and Styria. Due to the complex rock conditions, extensive and novel grouting systems are used. The primary target of the grouting is to reduce the permeability of the rocks and reduce the water entry (peak water ingress in the tunnelling area up to 300 l/s), as well as to improve the rock mass strength in some parts.Based on the grouting design, specific drilling and grouting procedures with various grouting materials were developed for sealing and tempering the water‐bearing areas of Grassberg and Otterstock. Innovations include the development of a standpipe packer and a cased grouting‐pipe system with grouting valves to prevent erosion along the drilling line for use in unstable borehole conditions. The combined cement/polyurethane suspension (hybrid grout) allows an extended economical use of cement suspensions.

Drilling and Grouting Works for Pressurised Groundwater Conditions of the Semmering Base Tunnel

The Semmering Base Tunnel (SBT), with a total length of 27.3 km, is one of the leading construction projects of the Baltic-Adriatic Railway Network. The tunnel connects the two federal provinces of Lower Austria and Styria and cuts through the eastern part of the Alps. The construction lot SBT 1.1-Tunnel Gloggnitz is characterized by a complex geological- and hydro-geological architecture containing alternating competent geological structures, major fault zones, and corresponding geological transition zones. There are three main water-bearing formations at the construction lot SBT 1.1: (a) Karst-prone blocky limestone with an initial water pressure of 10 bar. The discontinuities form a highly permeable interconnected joint network with a significant storage coefficient of the groundwater table. (b) Massive to blocky dolomite with an initial water pressure of 25 bar. The systematic discontinuities and disturbed zones of subsidiary structures with karst form a permeable, interconnected joint network. (c) The transition zone of the limestone to base structure marks the most challenging area for consolidation- and sealing grouting. Weak fault rocks characterize transition zones with intense fracturing. However, as subjected to high groundwater pressure of 10 bar, these zones are associated with the potential of flowing ground conditions. Based on the overall project requirements, specific drilling- and grouting methods and materials for pre-excavation grouting have been established and successfully implemented in the construction process. The innovations include a Standpipe-Packer substituting a conventional steel standpipe, a specifically cased drilling system with grouting inserts to prevent erosion within the borehole and allow for defined grouting. In addition, this Grouting-Pipe system replaces standard tube-à-manchettes and controls the flushing while drilling with preventers. Finally, a combined cement-polyurethane grout mix (Hybrid Grout) was implemented to stabilize the grout. The implementation of these measures will be discussed in detail, and their benefits to the construction process will be highlighted.

Установление дистанции выстрела по дробовой осыпи при отстреле патронов, снаряженных пыжами-контейнерами

Introduction. Most often, in cases of crimes related to the use of firearms, in addition to establishing that an object belongs to a firearm and resolving the issue of its serviceability and suitability for shooting, it is necessary to solve other non-identification tasks, such as establishing the direction and distance of the shot. As a rule, these two tasks are set together and the identification of such significant data as the distance of the shot and the angle at which the gunshot damage was inflicted allows us to give a correct criminal-legal assessment of the events that occurred. In this work, the results obtained by the A. F. Lisitsyn nomogram were compared with the real data obtained when shooting cartridges, factory equipment with wad containers. Experimental part. The experiment was conducted in a closed shooting range, targets made of 1 mm thick metal sheets, chipboard and wallpaper were selected. The shooting was carried out from three distances: 5, 10, 15 meters; half of the targets were located at an angle of 90 degrees, the second half was placed at an angle of 75 degrees. A total of 54 shots were fired: 18 shots at targets made of wallpaper, 18 shots at metal sheets and 18 shots at chipboard. The weapon used in the experiment was a copy of the IZH-27M 12-caliber hunting rifle. The shooting was carried out from the upper barrel with a muzzle narrowing “choke” with cartridges of the Russian company “NPF “AZOT” the model “Azot Russian Hunter B/K”. Discussion of results. The obtained results of the scattering diameters of shot spread were used to determine the distance of the shot using the A. F. Lisitsyn nomogram. The calculated intervals of distances were compared with the actual shooting distances. The results of the comparison show that the values of the intervals of the shot distance obtained by the A. F. Lisitsyn nomogram give a significant error – the actual values of the shot distance are about a third greater than the upper limit of the interval of the shot distance determined by the A. F. Lisitsyn nomogram. According to the results of the study, a proprietary nomogram was derived to determine the shot distance from the traces of shot spread. Conclusions. If there is a trace of the wad container, to determine the distance of the shot, it is better not to use the Lisitsyn nomogram, but to build an experimental dependence of the maximum and minimum values of the diameters of the shot spread at specific distances for a gun from the scene of the incident or a similar model of weapon. There is a need to improve and update currently existing methodological research, since the use of outdated information hinders the rational implementation of the tasks assigned to forensic ballistics. It is necessary to conduct research to establish the firing distance of a poly projectile when using a weapon with a specific drilling of the Lancaster barrel bore. The latest developments in the weapons industry – such models as the TR 366 TKM with a “Paradox” type barrel drill, in which a 366 TKM shotgun cartridge with an oval capsule for a police squad can be used, require further improvement of methods for establishing the distance of the shot.

Machine Learning Model for Monitoring Rheological Properties of Synthetic Oil-Based Mud.

The drilling fluid rheology is a critical parameter during the oil and gas drilling operation to achieve optimum drilling performance without nonproductive time or extra remedial operation cost. The close monitoring for rheological properties will help the drilling fluid crew to take quick actions to maintain the designed profiles for the drilling fluid rheology, especially when it comes to the flat rheology drilling fluid system, which is a new generation for harsh and specific drilling conditions that require flat profiles for the mud rheology regarding the temperature condition changes. The current study introduces a machine learning application toward predicting the rheology of synthetic oil-based mud (flat rheology type) for the full automation system of monitoring the mud rheological properties. Four models are developed, for the first time, to determine the rheological characteristics of flat rheology synthetic oil-based system using artificial neural networks. The developed models are capable of predicting the plastic and apparent viscosities, yield point, and flow behavior index from only the mud density and Marsh funnel as model inputs. The proposed models were trained and optimized from a real field dataset (369 measurements) with further testing the models using an unseen dataset of 153 data points. The predicted rheological properties achieved a high degree of accuracy versus the actual measurements and showed a coefficient of correlation range from 0.91 to 0.97 with an average absolute percentage error of less than 9.66% during the training and testing phases. Besides, machine learning-based correlations are proposed for estimating the rheological properties on the rig site without running the machine learning system for easy field applications.

RTA-Assisted Type Well Construction in Montney Tight Gas Reservoir from Western Canada Sedimentary Basin

Tight gas reservoirs are mainly developed by multistage hydraulic fracturing horizontal wells (MSHFHWs). A type well provides average production profiles based on real well data and can be constructed from multiple wells to investigate the behavior of the reservoir. For unconventional reservoirs, type wells are the key to reserve calculations and medium- and long-term field development planning. Both geological and completion parameters are key factors affecting single well performance of MSHFHWs. Based on the drilling, hydraulic fracturing, and production data for over 1,800 MSHFHWs in the Montney tight gas reservoir in the Groundbirch region of the Western Canada Sedimentary Basin (WCSB), the main hydraulic fracturing factors affecting the production performance of MSHFHWs were investigated. A rate transient analysis- (RTA-) assisted workflow for type well construction is proposed based on existing production data and considering the geological and engineering factors. Based on the field data, the main hydraulic fracturing factors that affect the production performance of the MSHFHWs in Montney are lateral length, proppant tonnage, and the number of stages. Base type wells are predicted from the P50 wells, which are selected from the wells with normalized lateral length and the same fracturing technique and proppant tonnage. The base type well represents the well performance for a specific drilling and completion background. RTA was introduced to scale up the base type well to predict the type well of new completion design. The new workflow predicts both the base type well with a specific drilling and completion background and the upgraded type well, which uses new completion design. It is highly meaningful and provides a valuable reference to practical studies involving type well prediction in unconventional gas reservoirs.

A risk prediction method of pipe sticking accidents due to wellbore uncleanness for long horizontal section wells

The prediction of pipe sticking accidents due to wellbore uncleanness is significant for safe drilling, while existing qualitative prediction methods result in inaccuracy and lateness. To cover the shortages, a novel quantitative pipe sticking prediction method is established to achieve pipe sticking prediction early in drilling preparatory stage. First, the additional axial forces and torques on the drill string exerted by accumulated cuttings are calculated in tripping out, tripping in, back reaming and reaming processes based on granular mechanics. Second, the torque and drag model is modified considering additional axial forces and torques to calculate the hook load and the top drive torque. Finally, the pipe sticking prediction is conducted according to the critical hook load and the critical top drive torque in a specific drilling process. A case study including comparison with the classical model and sensitivity analysis is conducted. Under the given condition, pipe sticking risk is predicted with the new mothed by anticipating hook loads (5524.67 and −667.71 kN) and top drive torques (60.87 and 66.36 kN m) exceeding the critical values. The hook load and the top drive torque change exponentially with the travelling distance. In tripping out and back reaming processes from 4350 to 4250 m, the hook load and the top drive torque respectively increase for 1894.36 kN and 53.99 kN m. In tripping in and reaming processes from 3450 to 3550 m, the hook load decreases for 29925.66 kN and the top drive torque increases for 157.3 kN m. According to the sensitivity analysis, low frictional coefficients, initial cutting volume fractions, torque and drag frictional factors and high junk slot ratios are required to reduce the risk of pipe sticking. This study provides a timely and quantitative prediction method for pipe sticking accidents due to wellbore uncleanness in long horizontal drilling.

Assessing the explosion effect on rock mass pre-destruction

Introduction. Theoretical and empirical research into rock blasting proved that detonation wave propagation results in the development of destruction and pre-destruction zones around the explosive cavity. In the destruction zone, rock crushes. In the pre-destruction zone, stresses set up by the detonation wave are concentrated on rock mass structure defects, giving rise to new micro defects and the development of the existing ones. Rock fracturing and cavitation increase, lowering its strength properties; this is called rock pre-destruction. There are works devoted to the qualitative analysis of rock in the pre-destruction zone, but the problem requires elaboration to offer possibilities for practical application. Research aims to quantify rock mass pre-destruction to use the parameters of rock blasting by borehole charges under opencast mining in engineering calculations. Methods of research. To assess the degree of rock mass pre-destruction at a distance from the charge axis, a pre-destruction intensity coefficient is used. The destruction zone radius is determined by a well-known method. In the destruction zone, the value of the pre-destruction intensity coefficient is higher than one, i. e. there is discontinuity of the rock mass. Beyond the destruction zone, there is a pre-destruction zone where the value of the pre-destruction intensity coefficient is less than one. The pre-destruction zone boundary is at distances of the order of 200–250 charge radii. The pre-destruction intensity coefficient of a particular zone attained after all charges have been fired is determined by summing the pre-destruction intensity coefficient from every charge. According to the energy approach, rock strength can be assessed by the value of the specific drilling energy intensity. In order to determine the reduction value of the specific drilling energy intensity in a particular zone, it is essential to know the drilling specific energy capacity of this zone in the natural state, the pre-destruction intensity coefficient attained after a large-scale blast of borehole charges, and specific drilling energy intensity of completely disintegrated rock. The effect made by another borehole charge explosion on the rock mass is weaker due to its pre-destruction by previous blasts. So we propose the impact multiplicity coefficient that reflects the accumulation of pre-destruction in a particular zone under the sequence blasting of borehole charges. Results. The expected value of the specific drilling energy intensity has been calculated for the individual arbitrarily spaced wells within the pre-destruction zone of a particular rock mass zone. The calculation results were compared with the practical values measured during blasting preparation in the preset rock mass zone. Conclusions. The findings of this study have made it possible to quantify the impact of explosions on rock mass pre-destruction. The developed technique makes it possible to predict the value of drilling energy intensity in the pre-destruction zone and, as a result, establish the required specific energy intensity of detonation and hence the consumption of explosives. Thus, it becomes possible to reduce the consumption of explosives under the existing blasting scheme at the enterprise and model other charge initiation types to select the least expensive one.

Drill bit state-oriented drilling process classification with time-series data for wheeled drilling rigs

This paper represents an analysis of the wheeled drilling rig’s drilling process. Thanks to data from the onboard measurement unit of the machine, the characteristics of the drilling process regarding state of the drill bit are identified and calculated. The aim of the work is to provide a comparison between different drill qualities and process classification using Threshold-based segmentation with feed pressure levels and duration of single hole drilling. Second methodology is hierarchical clustering to create cluster analysis. Thanks to these approaches, it is possible to detect the time when the drill bit should be changed. The obtained results state that the average drill time for a new drill bit is shorter approximately by 50% than for the worn-out bit in terms of average drilling duration. Moreover, these changes are visible in the subsystem pressure level of the machine under specific drilling regimes.

Drilling optimization of petroleum wells

The petroleum industry is already demanding lowering exploration costs, which reflects in needs of reducing drilling operational costs, which can be achieved through implementation of more efficiency in operations. Researches have shown that scientist and companies are already experiencing different approaches aiming at boosting drillability. One method not well implemented is variation of flow-rate as a mechanical specific drilling parameter, given its complexity and relation to well integrity. This paper details the influence in flow-rate and related parameters in rate of penetration, showing how DHAP, ECD, Flow-rate and ROP are related to each other. It can be seen that by increasing a flow-rate, an increase in ROP is possible, but that flow-rate changes also influence the down-hole pressure and ECD, what imply in possible downhole differential pressure variation. The higher the down-hole differential pressure, the less will be the implied ROP. All these have influence on drilling efficiency.