Drilling Cycle Research Articles

Study on the Applicability of a New Type of Bit in Ordovician - Cambrian Dolomite Formation of Tarim Basin

The Ordovician-Cambrian reservoirs in Tarim basin are characterized by complex geological structure, deep reservoir, and thick dolomite strata in the middle and deep formation. The dolomite formation is characterized by large content of chert, high dense lithology, high uniaxial compressive strength, prominent impact and heterogeneity of the formation, it was difficult for conventional drill bits to form stable effective cutting depth and prone to vortex damage, which leads to short drill footage, low ROP and long drilling cycle, it seriously restricted the efficient exploration and development of Cambrian subsalt reservoirs in this block. Therefore, experimental analysis of rock mechanics in the Cambrian dolomite formation was carried out to quantitatively evaluate the rock mechanics properties in this area. A new type of PDC bit was designed to improve the impact resistance and eddy resistance of single teeth, and the impact fatigue test was carried out and successfully applied in the field. The research results show that compared with the adjacent wells in the same interval and lithology, the footage is increased by 39%, and the ROP is increased by 84%, which has achieved obvious acceleration effect, providing technical reference and support for the efficient exploration and development of Cambrian pre-salt reservoirs in the Tarim Basin.

Study and Application on ROP-Enhancing Technology of Ordovician-Cambrian Dolomite Strata in Tarim Basin

The Ordovician-Cambrian dolomite formation in Tarim basin has certain characteristics such as poor drillability, long drilling cycle, difficulty in selecting drill bit and accelerating tool. In order to meet the requirements of efficient exploration and development of Cambrian oil and gas reservoirs, there is an urgent need to design high ROP bit and acceleration tool suitable for dolomite formation, optimize drilling parameters and improve ROP to form the technical scheme of drilling acceleration in dolomite formation. Therefore, the drillability of the Cambrian dolomite strata was studied. The experimental analysis was carried out according to the geological characteristics and rock mechanical parameters. Dual index drillability analysis method was used to evaluate the formation compactness, abrasiveness and other formation drillability characteristics. A new type of PDC bit was designed to improve the impact resistance and eddy resistance of single tooth, a three-dimensional vibration acceleration tool was selected to reduce the vibration of the bit, and combined with the optimization of drilling parameters, the technical scheme for acceleration of the Ordovician -Cambrian dolomite formation in Tarim Basin was finally formed, which was successfully field tested in Well A of Tarim Basin. The research results show that compared with the adjacent well B section, the average footage and the average ROP are increased by 47.8% and 32.0% respectively. Compared with the adjacent well C section, the average footage and average ROP increased by 37.0% and 29.5% respectively. The results provide technical reference and support for the efficient exploration and development of Ordovician - Cambrian reservoirs in Tarim Basin.

Analysis and Application of Optimal and Fast Drilling Technology in Gaoshangpu Block of Jidong Oilfield

The Gaoshangpu block of Jidong Oilfield is a hot block for increasing production and storage in Jidong Oilfield. High-quality and efficient drilling and completion can shorten the operation time and have huge economic and social benefits. Aiming at the problems of large well depth, complex geological conditions, poor stratum drillability, low drilling machinery efficiency, and long drilling cycle in the Gaoshangpu block of Jidong Oilfield, this paper optimizes its drill bits, speed-up tools, drilling parameters, and drilling fluid performance. Through bit optimization, a PDC bit optimization template is formed. A single S1942 PDC and BTM159AR PDC bit can solve the problem of poor formation drillability, improve drilling efficiency, shorten completion time and optimize speed-up tools in the study area. For glutenite developed stratum (bottom of Guantao Formation), we use shock-absorbing thruster, and for gray mudstone (Shahejie Formation), we use shock-absorbing thruster + curved screw. 1% organic silicon polymer can be added to the three-open drilling fluid to improve the drilling fluid performance. The adding of the compound (PLH: KPAM: ammonium salt = 1: 1: 2) can inhibit mud making, and the 2% anti-collapse agent before drilling into basalt can solve the well wall collapse of Shahejie Formation and Guantao Formation. The liquid with density of 1.44-1.45 can prevent well overflow. The research results provide guidance for high-quality and efficient drilling in the Gaoshangpu block of Jidong Oilfield and ensure the safety of drilling operations.

Research and Development of Drilling Operation Data Benchmarking Management System

Benchmarking management, as a measure for the continuous improvement of scientific management of enterprises, provides advanced ideas for enterprises to analyze the problem of insufficient production capacity, and through data modeling can provide solutions for the improvement of deficiencies, which is conducive to the improvement of the overall management level and competitiveness of enterprises. Changqing Drilling Corporation has a large difference in the speed of drilling among the drilling crew, and has not formed an overall drilling speed-up plan. This paper uses an integrated data platform to establish a drilling operation benchmarking management system model, through the comparative analysis in different regions, different operation conditions of ROP and drilling cycle. Using machine learning to establish a benchmark optimization model for ROP and drilling cycle, in order to lay a foundation for drilling operations to improve operating efficiency and reduce operating costs.

Tool wear analysis in high-frequency vibration-assisted drilling of additive manufactured Ti6Al4V alloy

Drilling of Additive Manufactured (AM) Ti6Al4V alloy parts represents a necessary operation in the prosthetics manufacturing to guarantee tight tolerances and acceptable surface finishing. However, due to the AM process, the parts are characterized by a different microstructure if compare to the wrought material of the same chemical compositions and thus a different machinability. In this research, an innovative system of high-frequency Vibration-Assisted Drilling (VAD) was implemented to investigate the tool wear and holes quality in drilling of Ti6Al4V parts fabricated through Laser Powder Bed Fusion (LPBF). AM cylindrical samples were manufactured and holes with a diameter of 1.6 mm were produced using both Conventional Drilling (CD) and VAD for which the values of frequency and amplitude were determined by analytical modelling. Tool wear was evaluated during subsequent drilling cycles and related to the hole quality. The results showed that VAD not only preserved tool life, but it also improved the overall holes quality. The reasons for these improvements were ascribed to the VAD kinematics, characterized by an interrupted cut mechanism favoring the chip removal and evacuation. In summary, the impulsive separation between the drill bit and hole surface in VAD was proved to favour the machinability of AM alloys.

Study on wellbore instability mechanism and drilling fluid optimization of Yingsha block in southwest Tarim Basin

The southwest area of Tarim has good potential for exploration and development, but the geological conditions of Yingsha block are complicated and complex conditions occurred frequently in drilling operations. There were 11 times lost circulation, which ranged from N2a to E1a and the lithology ranged from mudstone and sand-mudstone interbeds to gypsum rock, and the drilling cycle is up to 719 days, which seriously restricts the exploration and development of oil and gas resources. In this paper, the rock mineral composition and physical and chemical characteristic profiles of the whole well have been established for the well drilled in this area. The characteristic profiles show that quartz (21.4%~57.4%) and clay minerals (17%~44.9%) are the main layers in the lower strata (5069 m-7015 m) drilled in Yingsha. The clay minerals are dominated by illite (58%~85.75%) without smectite. The highest proportion of illite/smectite formation is 25%, the highest expansion rate is 23.87%, and the lowest recovery rate is 3%. Therefore, the stratum has strong hydration and dispersion characteristics. The average porosity of 4064 m-6666.5 m is 1.86%-6%, and the formation cracks are well developed. The wellbore instability mechanism in Yingsha is the good physical property of the sandstone, the development of cracks and micro-cracks in the lower strata, the broken strata, and the strong hydration and dispersion ability. The performance evaluation of KCL-Polysulfonate drilling fluid used in Yingsha shows that the recovery rate increases to more than 80% when the amount of KCL is 7–10%. With the introduction of paraffin nano-emulsion, the filtration loss is reduced by 30%, and the inhibition and plugging performance of drilling fluid is further improved.

Capacity Limitations of brine Contamination on High Density Oil-Based Drilling Fluid

Aimed on the problem that the Drilling fluids were easily intruded by the saline water in high-pressure salt-gypsum formations, and the properties of the drilling fluid were damaged and accidents easily occur. The mechanism of drilling fluid contamination by the formation brine was analyzed and the capacity limits of the contamination were found out. The results show that small amount of brine invasion causes emulsification while large amount of brine invasion lead to demulsification. Two capacity limitations were proposed. The first limitation is 10% of saline water concentration, below which the performance of the drilling fluid remains relatively good. The second limitation is 30% of saline water concentration, below which the drilling fluid needs to be systematically maintained, and after which the fluid has no potential for maintenance. This proposal has been successfully used in 8 wells in Kuqa foreland area, and the drilling cycle was saved by 35 days on average.

The effect of cutting parameter changeover position on interface borehole quality in drilling of aerospace CFRP/Al stacks

Drilling multi-material aerospace stacks (e.g. CFRP/Aluminum) at the interface region represents the most challenging phase of the drilling cycle due to bi-material engagement of the cutting edges. This research investigates the impact of several drilling strategies on interface borehole quality, to allow for a fundamental understanding of the machining process taking place at the stack interface. In the experiments, cutting parameters were changed over from one workpiece material layer to the next at different positions relative to the interface, and the resultant impact on interface borehole quality was assessed based on borehole diameter, composite surface damage and interlayer burr height.

Study and application of wellbore trajectory optimization for dense cluster wells

In the middle and late stage of oilfield exploration and development, the difficulties such as land acquisition on the surface, high density of underground well pattern and high development cost are serious. Dense cluster Wells are mainly way to development mode transformation and quality and efficiency improvement. Combined with the practice of dense cluster well in Dagang Oilfield, the paper detailed analyzes the difficulties faced by the design of dense cluster well drilling engineering, which including well pattern arrangement, wellbore trajectory optimization, wells anti-collision, all of those are beneficial to realize benefit drilling development. The applications show that this technology has a significant effect on improving wellsite utilization rate, shortening drilling cycle and reducing drilling cost in Dagang oilfield, and has a very important reference and popularization significance in similar oilfield development.

Diffcult Point & Solution of Zhengan Shale Gas High Effective Horizontal Well Drilling

This article aims to provide technical support for the high-efficiency and high-quality horizontal drilling construction in Zhengan shale gas field. Based the analysis of the formation characteristics and drilling conditions in the Zhengan area, the technical issues of horizontal drilling improving in this area are explained, and based on speed-up and efficiency-increasing technologies such as the resigned high-efficiency PDC bit, high-torque&long-life motor, drilling parameter optimization, friction&torque monitoring, friction-reducing and torsion-reducing tools, near-bit geology steering technology, rotary steerable drilling technology and loss control and anti-collapse mud etc., solutions for the issues have been proposed. Through the application of related technologies, it is expected that improvements for the ROP of horizontal wells in the area and the drilling cycle will be made.

Process Monitoring in Heavy Duty Drilling Rigs—Data Acquisition System and Cycle Identification Algorithms

The monitoring of drilling processes is a well-known topic in the mining industry. It is widely used for rock mass characterization, bit wear monitoring and drilling process assessment. However on-board monitoring systems used for this purpose are installed only on a limited number of machines, and breakdowns are possible. There is a need for a data acquisition system that can be used on different drilling rigs and for an automatic data analysis procedure. In this paper, we focused on the automatic detection of drilling cycles, presenting a simple yet reliable system to be universally installed on drilling rigs. The proposed solution covers hardware and software. It is based on the measurement of electric current and acoustic signals. The signal processing methods include threshold-based segmentation, a short-time envelope spectrum and a spectrum for the representation of results. The results of the research have been verified on a real drilling rig within the testing site of its manufacturer by comparing the results with the data of the on-board monitoring system installed on the machine. Novel aspects of our approach include the detection of the pre-boring stage, which has an intermediate amplitude that masks the real drilling cycles, and the use of the percussion instantaneous frequency, which is estimated by acoustic recordings.

A sequence-based method for dynamic reliability assessment of MPD systems

Managed Pressure Drilling (MPD) system is widely used in the deepwater drilling operation. Reliability assessment plays a critical role in the MPD system in the management of drilling operation risk and the prevention of blowouts. However, the reliability assessment of the MPD system is challenged due to its sequential operations and multiple processes. Consequently, the present work proposes a sequence-based dynamic reliability assessment method, which focuses on the dynamic modeling of sequential operations for the MPD system by integrating GO-FLOW and dynamic Bayesian Network (DBN). GO-FLOW models are firstly used to define the time interaction between multiple phases for complex systems. A sequence-based mapping method is also proposed for the DBN to construct the reliability model of the MPD system throughout the entire drilling cycle. In the end, the case study analyzed by the proposed framework indicates that the reliability of the MPD system decreases with increasing drilling depth, and the reliability of “tripping in” is highest among four different phases, while the “drilling process” is the lowest. The method provides an important technique that can be implemented with online condition monitoring tools to assess and monitor the reliability of the MPD operation in real-time.

E&P Notes (December 2020)

E&P Notes (December 2020)

Study on the mechanism of drilling speed increase considering the axial vibration of drill string

Based on the existing research and combining with downhole conditions, this paper proposes a new type of downhole vibration tool to increase the rate of penetration (ROP), shorten the drilling and completion cycle and achieve more productive operations. As a whole, the axial vibration of the drill string is analyzed uniformly and the ROP is increased. A dynamic analysis model of the axial vibration of the drill string in the horizontal well is established. Based on the research on the working mechanism of the tool, this paper analyzes the flow area, pressure drop and axial force of the core valve system and determines the change law of the axial force. The field experiments verified the correctness of the established dynamic model method and the rationality of the tool and showed that the tool has a significant effect of increasing the ROP. The theoretical model established in this paper can improve the understanding of drill string dynamics. The proposed design method can provide ideas for the development of new drag reduction and speedup tools, and the calculation results can provide a reference for the determination and optimization of key parameters for drilling speedup.

Feasibility of tool configuration and the effect of tool material, and tool geometry in multi-hole simultaneous drilling of Al2024

The use of the multi-spindle head in drilling technology can reduce the drilling cycle time by simultaneously producing multiple holes in one go. However, selecting the appropriate drill material and geometry is critical to overcoming the challenges of multi-hole drilling to ensure high-quality holes. This study investigates the use of the multi-spindle head with different tool configuration, tool materials and tool geometry during multi-hole simultaneous drilling of Al2024. A comparison is made among the high-speed steel drills (diameter: 6 mm; point angle: 118°) and two different carbide drills (diameter: 6 mm and 10 mm; point angle: 140°) as well as the maximum and minimum possible centre to centre tool distances of the multi-spindle head. The experiments are based on measuring the thrust force, evaluating the hole quality in terms of surface roughness and burrs, the formation of chips and post-drilling tool conditions. The results showed that carbide drills with high point angle and smaller diameter generated less thrust force, produced higher quality holes, and formed less built-up edge due to short chips. Besides, tools of the multi-spindle head can be adjusted in any position without affecting the hole quality which is useful for increasing productivity at a higher rate in manufacturing industries.

Well Factory Practice in Bailu Lake Cluster Wells

It is very difficult to economically develop Bailu Lake low permeability reservoir, facing severe anti-collision challenge, as well as trajectory controlling and cuttings carrying of high difficulty, beyond that the reservoir located in the scenic area, where the well site area was limited and the environmental protection requirements were very strict. On the basis of learning the foreign companies’ successful experience on cluster well factory, the authors analyzed the situation and difficulties of Bailu Lake well factory project initially, thus proposing Bailu Lake well factory overall optimized scheme, including slot drilling sequence and trajectory optimization. Through fast rig moving technique, PDC bit and motor optimization and high inhibitive and environment friendly CaCl2 mud system, the rig moving time was shorten by 2 days averagely and one run safe drilling in the second spud. Finally, the total 43 wells were successfully completed, and the average well drilling cycle was shorten by 15.49 days, which had achieved good effects.

Monitoring of hole surface integrity in drilling of bi-directional woven carbon fiber reinforced plastic composites

Fiber-reinforced plastic is one of the top priorities lightweight materials with excellent mechanical properties for the aerospace industries in recent years. However, it is difficult to machine despite having unique properties due to its non-homogeneous and abrasive nature in alternate fiber and matrix layers. Thus, it is found to be a challenging task to drill hole on such hard-to-machine materials, which is highly essential for the development of most of the engineering structural components. The present work addresses various drilling-induced defects such as delamination, circularity error, and roughness variations in the hole surface during drilling of quasi-isotropic cross-fiber oriented bi-directional woven-type carbon fiber reinforced plastic laminate using a full factorial design of experiments for different drill geometry. The response surface methodology was considered for the regression model development, which was found to be highly significant. The machining forces with associated torque have also been acquired during drilling, which was divided and further analyzed in time domain to correlate with drilling flaws. The drilling-induced delamination was found to be higher at a high feed rate using a higher drill point angle due to substantial thrust force generation at the initial stages in the drilling cycle. However, the internal surface finish with associated circularity error was reduced for higher spindle speed with less feed rate using a low drill point angle because of low torque fluctuation at the final drilling phases. The axial thrust force was found to be a prime indicator of drilled hole surface delamination, whereas drilling torque precisely indicated internal surface roughness as well as circularity error. The global root mean square, along with a local peak of thrust and torque, both were highly essential to completely characterize the drilled hole quality.

Process signals characterisation to enable adaptive drilling of aerospace stacks

When drilling multi-material stacked structures, carrying out adaptive drilling would allow for the utilisation of optimal parameters throughout the drilling cycle. This research work focuses on establishing relationships between process incidences and signals recorded from different sensors when drilling aerospace stacks, as well as the effects of tool wear on these relationships. Drilling tests were carried out while recording cutting forces, acceleration and acoustic emission, at different stages of tool wear. All signals were found to strongly correlate with process incidences, suggesting that they could be used as sources of information for decision-making in a process monitoring system.

Influence of oil injection parameters on the performance of diesel powered screw air compressor for water well application

In this paper, a study has been carried out to find the influence of oil injection parameters on the performance of diesel powered screw air compressor which is used in water well application. Oil injection parameters considered in this study are oil injection orifice size, engine speed and oil injection pressure. Performance of the screw compressor is evaluated by measuring the fuel consumption, discharge oil temperature and free air delivery. An experimental design is created using Central Composite Design (CCD). The lower and upper bound of input parameters were fixed based on the application requirement and theoretical estimation. The experiments were performed as per the experimental design and output responses were recorded. The significance of the input parameters on output responses was studied using Analysis of Variance (ANOVA). Response Surface Methodology (RSM) is employed to study the optimum range of parameters to obtain the best performance of the compressor in drilling and idling cycles. The best performance is achieved by setting engine speed value of 1490 rpm, injection orifice diameter of 9.5 mm and an oil injection pressure of 135 psi(g) in the drilling cycle. For idling cycle, an engine speed of 1260 rpm, oil injection orifice diameter of 8.5 mm and an oil injection pressure of 150 psi(g) result in the best performance of compressor in idling cycle. The optimized parameters are validated by conducting confirmatory tests. The water well screw compressor operated with optimum parameters results in considerable savings in the fuel consumption. A lubrication circuit is designed incorporating the optimum nozzle size obtained in this study.

Cuttings Transport Using Pulsed Drilling Fluid in the Horizontal Section of the Slim-Hole: An Experimental and Numerical Simulation Study

Poor transport of cuttings in horizontal sections of small-bore well holes leads to high torque and increases the risk of the drill becoming stuck, reducing its service life and posing a threat to safe operation. Because the conventional cuttings transport method cannot effectively remove the cuttings bed, a transport method using pulsed drilling fluid based on a shunt relay mechanism is proposed. A three-layer numerical simulation model of cuttings transport in horizontal small-bore wells is established. Using both experiments and numerical simulations, the cuttings transport is studied in terms of the moving cuttings velocity, cuttings concentration, and distance of movement of the cuttings bed. By varying the pulsed drilling fluid velocity cycle, amplitude, and duty cycle at the annulus inlet, their effects on cuttings transport are analyzed, and the optimal pulse parameters are determined. The results show that the use of pulsed drilling fluid can effectively enhance the moving cutting velocity and transport distance of the cuttings bed, reduce the cuttings concentration, and improve wellbore cleaning.