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Abstract Extending motor, bit, MWD, and BHA component life is of primary importance to the drilling process. Frequently downhole vibrations can cause anywhere from minor to catastrophic failure in any of the components of a typical BHA. Some types of vibrations are more detrimental to various components of the BHA. Most vibrations can be controlled with the alteration of surface parameters such as weight-on-bit and rotary speed in conjunction with downhole measurement tools such as downhole weight-on-bit and downhole torque as well as BHA alteration. The problem has always been knowing which parameters to alter without adversely affecting total drilling performance. Recent advances in MWD technology have provided a means of measuring downhole vibration in multiple axes. This information, provided in real-time, allows the driller to control the proper parameters to minimize specific vibration effects thereby maximizing BHA life and total drilling performance. Introduction Attempts to drill vertical holes with 30/60 pendulum assemblies (MWD and straight-hole mud motors) or 60/90 pendulums (in rotary mode with only MWD) had met with catastrophic failures in the past year. Mud motors had been "twisting off" and several MWD failures resulting in junked electronics were common. On the first case well, using a 30/60 pendulum assembly, the mud motor was twisted off at the AKO sub and the MWD failed. The MWD collar was even torn open. The MWD dump of the standard MWD shock counter revealed very high shocks. After this run, two rotary runs were made with only MWD and 60/90 pendulum assemblies. Both MWD tools failed. It was decided to employ the multi-axis vibration chassis to get a picture of what was happening downhole. The MVC data revealed violent episodes of mostly torsional and lateral vibrations characteristic of BHA whirl. These episodes occurred in hard, wet sands prevalent in this area. This MWD run failed as well. On run five, the MWD was stabilized top and bottom. Using the MVC, the drillers were able to "see" the sands and adjust their weight-on-bit and rotary speeds to reduce vibrations to acceptable levels and prevent the BHA from going into a whirling state. Parameters were returned to normal in shales. All failures ceased. On run six a record BHA run for this area was recorded with the application of a straight-hole motor with a sleeve stabilizer and the MWD and LWD tools correctly stabilized. On two subsequent wells the assemblies were modified using straight-hole motors with sleeve stabilizers. The drillers duplicated their drilling practices of the previous well and both wells were drilled without failure. Theory Drilling requires energy. In drilling, this energy is obtained with three basic drilling parameters, weight on bit, RPM, and mud flow. Vibrations are always present during drilling in varying magnitudes and these detract from and re-direct some of the energy used for the drilling process. The usual primary goal in vibration detection and prevention is to minimize these vibrations in order to maximize ROP. In this field case, this statement has become secondary. The primary goal in this case is to prevent the destruction of critical components of the BHA in order to extend drilling life downhole. To extend BHA life, it is critical to understand the mechanisms working against us and to be able to quantify their magnitude. With this knowledge, we can alter BHA construction as well as use surface drilling parameters to control these mechanisms. With a multi-axis vibration detection device we can identify the differing types of known mechanisms, measure their magnitude, and determine the effectiveness of our designs and efforts to control them. This case study will qualify these statements.
Numerical Study of the Hydraulic Fracturing and Energy Production of a Geothermal Well in Northern Germany
Li, Mengting (Energy Research Center of TU Clausthal (EFZ)) | Hou, Michael Z. (Energy Research Center of Lower Saxony (EFZN)) | Zhou, Lei (Chongqing University) | Gou, Yang (Energy Research Center of Lower Saxony (EFZN))
ABSTRACT The hydraulic fracturing is an essential tool to increase the permeability of tight formations and to increase the petrogeothermal energy recovery. In this paper, a hydraulic fracturing model was developed based on the previous work and implemented in the coupled numerical simulator TOUGH2MP-FLAC3D. It considers the stress redistribution due to fracture opening and hydromechanical effects in full three dimensions. The cubic law was implemented, so that the fluid flow in both porous media and fractures can be simulated at the same time. With the advantages of TOUGH2MP, it is also capable to track the migration and distribution of injected fracturing fluid in the reservoir formation. The model has been used to study the hydraulic fracturing in the geothermal well Gross Buchholz Gtl in Hanover, Germany. The measured data during the hydraulic fracturing treatment has been matched. The simulated fracture geometry was comparable with that analyzed from the well test. The verifled model has been used to study the geothermal utilization in the Detfurth sandstone formation. 1 INTRODUCTION The development of renewable energy is of high priority due to the world's increasing energy consumption and climate change. As one of the most important members, the geothermal energy attracts a lot of attention because it is of huge amount, regenerable, and not dependent on weather. Especially in recent years, the development of deep geothermal energy is a hot topic (Kolditz et al. 2015). Currently, the development of deep geothermal energy is restricted by the current drilling technology, energy transition efficiency, environmental impacts etc. The deep geothermal energy is normally stored in tight sandstone or granite formations which has normally low or ultra-low permeability. This characteristic makes it difficult to produce the original fluid in place (for hydrothermal system) or injected fluid (for petrothermal system) in an economic rate. In order to increase the deep geothermal energy recovery, the hydraulic fracturing should be carried out to increase the permeability of tight formations. The hydraulic fracturing must be well designed and optimized, on one side, to maximize the productivity, and on the other side, to remove or minimize the related risks such as environment contaminations and induced micro earthquakes.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.73)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.53)
- Geology > Rock Type > Igneous Rock > Granite (0.53)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Non-Traditional Resources > Geothermal resources (1.00)
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (1.00)
Changes in the Time of the Properties of Rock Foundations of Large Hydraulic Structures According to Geophysical Monitoring Data
Savich, A. I. (Geodynamic Research Centre—Branch of the Hydroproject Institute) | Gorokhova, E. A. (Geodynamic Research Centre—Branch of the Hydroproject Institute) | Ilin, M. M. (Geodynamic Research Centre—Branch of the Hydroproject Institute)
ABSTRACT Operation of large hydraulic engineering structures such as the Sayano-Shushenskaya HPP (Eastern Siberia) and Inguri HPP (Western Georgia) and other high-pressure hydroelectric power plants causes significant changes in the initial rock properties, that is, the rock properties laid down in the project, as well as changes in the structure of the weakened zone and the discharge zone in comparison with the project. Long-term geophysical monitoring allow observe during significant time intervals, measured in tens of years, the changes in the properties and structure of the enclosing rock massif. Specified impacts are conditioned not only by rock excavation but also by the processes of their operation when due to periodical fluctuations of water level in the reservoir the significant changes of hydrogeological conditions and violent changes of force impacts transferred to the enclosing rock mass occur. At that, different natural and technogenic geodynamic processes development of which may cause hazard phenomena for the structures, such as damage of local parts of the foundation due to large cracks propagation, appearance of the zones of anomalously high seepage, collapse of separate blocks of the rock mass and others, are activated in the surrounding geological environment. Thus, geodynamic processes occurring during construction and operation of high dams result in significant changes of initial engineering and geological structure of enclosing rock mass. The operation of large hydraulic structures such as Inguri HPP (Georgia), Sayano-Shush-enskaya HPP (Eastern Siberia) and other high-head HPPs causes significant changes of initial, i.e. design properties of rock foundations (elastic, strain and strength indices), and changes in the structure of weak zone and zone of de-stressing in comparison with the design. Long-term geophysical investigations at monitoring allow observing the changes in properties of enclosing rock mass during the significant time intervals for the decades under the influence of seasonal fluctuations of the reservoir level and variations of stress-strain state of enclosing mass, water saturation, uplift pressure and factors that activate the modem natural and technogenic geodynamic processes in the near-surface parts of Earthโs crust at dam section, and thereby increase the geodynamic risk in the area of the project.
Summary Vibration measurements have traditionally targeted the improvement of downhole-tool reliability. This paper targets the effects of vibration on the complete drillstring. Failures associated with drillstring vibration continue to happen despite the sophistication of today's measurements. These failures represent a very significant amount of lost time, which we target to improve. The industry has a very limited database for evaluating indices to manage or quantify risks of vibration to the complete drillstring. This fact makes the use of the methods in the field heavily depend on the past experience of the drillers and on the rig types. Operators are faced with an unknown quantification of the risk severity when attempting to mitigate vibration. By quantifying the risk, this work demonstrates how the prevention of incidents can be achieved. These incidents include but are not limited to, twistoffs, backoffs, and bottomhole-assembly (BHA) component failures. The proposed solution is based on real-time measurements of drillstring vibration to estimate an ongoing drillstring-integrity risk, which is used as a guideline to improve decisions while drilling the well. This solution has been developed through use of advanced vibration sensors to discriminate between different types of vibration. This was critical to estimating realistic cumulative damage to the drillstring, which is highly dependent on the type of vibration suffered by the assembly and the onset of vibration-mode coupling. This paper shows that approximately 80% of drillstring-integrity failures analyzed can be identified and prevented through use of the proposed risk-quantification solution. This result has been obtained despite unknown fatigue or wear of drillstring components before a run, and vibration sensors were located at a single position in the drillstring. This indicates that the primary contributor to drillstring failures is the drilling conditions for any given run.
- Asia (0.68)
- North America > United States (0.28)
- South America > Brazil > Brazil > South Atlantic Ocean (0.89)
- North America > United States > Montana > Andes Field (0.89)
- Well Drilling > Drillstring Design > Drill pipe selection (1.00)
- Well Drilling > Drilling Equipment (1.00)
Abstract Failures associated with drillstring vibration continue to occur, despite the use of risk quantification techniques based on vibration intensities and root mean square (RMS) accelerations. This paper introduces the concept of modified vibration stability plot as a practical tool to minimize and predict vibration. It integrates the modified vibration stability plot with a feature modeling data analysis tool to predict drillstring failures caused by torsional and lateral vibration. The modified stability plot provides optimum operating parameters, including weight on bit (WOB), revolutions per minute (RPM), and rate of penetration (ROP), to minimize vibration. However, actual real-time drilling parameters are not always optimum. Consequently, the deviation of real-time parameters from the optimum values are used to calculate "deviation vectors" using statistical tools. These are then used to generate operating stability clusters to detect outliers in the drilling data that signify potential vibration events. Safe operating limits and operating times have been proposed by integrating the clustering technique with vibration risk index and cumulative vibration intensity plots to mitigate failures. The workflow has been applied to cases in which severe and moderate vibrations were encountered downhole and at the surface, respectively. Extensive simulations were performed to compare the data from downhole vibration sensors. The results show that the workflow closely predicts the occurrence of sustained vibrations before an actual downhole string failure event. Prolonged operations outside of the stability circle can cause failures, depending on the fatigue strength of the material. The occurrence of outliers outside of the stability clusters are calibrated with actual drillstring failures to correlate cumulative vibration intensity plots with the time duration of a vibration event. This calculation helps to define a vibration risk index that can trigger decisions to stop drilling or to change operating parameters before a failure occurs. The workflow also simultaneously predicts the dominant type of vibration in the system and in causing failures. The study concludes by providing guidelines to integrate the vibration stability chart with data analytics and explicates the significance of a statistics-based risk index to initiate real-time procedures to prevent drillstring integrity failure. The workflow proposed and validated with case histories strives toward cost-effectiveness and increased productivity. This paper also implements data-driven techniques for risk quantification. The results and the method for determining a risk index and operational limits are robust, and can be applied as a starting point for other string configurations in similar downhole environments.
- Europe (0.95)
- North America > United States > Texas (0.47)
- Research Report > Experimental Study (0.68)
- Research Report > New Finding (0.66)
- Data Science & Engineering Analytics > Information Management and Systems > Data mining (1.00)
- Management > Professionalism, Training, and Education > Communities of practice (0.70)
- Data Science & Engineering Analytics > Information Management and Systems > Knowledge management (0.70)
- Well Drilling > Drillstring Design > Drillstring dynamics (0.67)