Day 2 Wed, March 06, 2019最新文献

{"title":"Well Control and Temperature Modelling Facilitates the Effective Delivery of Challenging Shallow Water HPHT Exploration Well","authors":"Mark P. Davis, Ivo Selent, Bertrand Duplessis, W. Janisch","doi":"10.2118/194175-MS","DOIUrl":"https://doi.org/10.2118/194175-MS","url":null,"abstract":"\u0000 Drilling operations in high-pressure/high-temperature (HP/HT) environments can be very challenging and costly. In an exploration well being drilled in a unique depositional environment, a rapid increase in pore pressure was anticipated, potentially reaching HP/HT conditions of up to 12,000 psi and over 180°C. The absence of close offset wells resulted in a large uncertainty in the magnitude of the pore pressure. This drove the planned casing design, which was limited by kick tolerance and potentially narrow margins between pore pressure and fracture gradient, resulting in planning for up to six casing strings.\u0000 To respond to this challenge, standard engineering practices were augmented with additional monitoring and predictive modelling solutions to improve well control and to predict and explain complex well behaviour and mitigate the associated drilling risks. The models were calibrated with measured mud properties and wellbore temperatures and pressures during operations. They were then used to simulate, explain, and predict variations in downhole pressures and surface mud volumes. Various innovative applications were used to guide safe operational decision-making. Where conventional practices would not have allowed, this modelling enabled total depth of the well to be reached while incurring minimal nonproductive time and no well control incidents.\u0000 By understanding wellbore conditions using advanced well control and temperature simulators, abnormalities normally failing the conventional practices could be detected and explained. This improved well control, safety, rig performance, and effective application of resources.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"173 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123269251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Mechanical Response of Concentric Cemented Casings Exposed to Arbitrary Transverse External Geomechanical and Salt Loads","authors":"U. B. Sathuvalli, S. Krishna, P. Suryanarayana","doi":"10.2118/194121-MS","DOIUrl":"https://doi.org/10.2118/194121-MS","url":null,"abstract":"\u0000 When wellbores are exposed to loads of geomechanical origin, the outer casings can become vulnerable to the transverse load components. These loads are usually non-uniform in character (Veeken et al. 1994). The collapse resistance of tubulars to non-uniform loads is substantially lower than their resistance to uniform loads. In the face of such reduced tubular strength, the well engineer uses thick walled high strength casings or a system of concentric cemented casings (Clegg 1971; Pattillo and Rankin 1981; Pattillo et al. 1995). In either case, the designer has to determine a quantitative measure of well integrity i.e., a safety factor (SF) of the casing for the non-uniform loading. In our industry, well designers have used finite element analyses (FEA) to assess the mechanical response of the casings subjected to such loads (Pattillo et al. 1995; Li et al. 2003).\u0000 The simplest stress analysis problem in such situations consists of at least three cylinders, the innermost casing, the cement sheath and the formation up to the farfield boundary. Depending on the numerical methods employed in the geomechanical analysis, the farfield geomechanical loads are presented as displacements or tractions. In this paper, we present an analytical procedure to determine the mechanical response of a system of nested concentric cylinders exposed to an arbitrary traction or displacement on the outer radius of the outermost cylinder. We use the solution to quantify the effect of the loads on the concentric casings and the intervening cement sheaths, and to assess the effect of the formation. To this end we use well-known methods employed in the theory of elasticity to derive our solution. The analytical solution presented in the mathematical appendices can be implemented in a programmable spreadsheet.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"52 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123414655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mitigation of Multi-Frequency Stick/Slip","authors":"Zhijie Sun, Qiuying Gu","doi":"10.2118/194120-MS","DOIUrl":"https://doi.org/10.2118/194120-MS","url":null,"abstract":"\u0000 Stick/slip-induced vibration has been recognized as a cause for bit wear, premature tool failure, and poor drilling performance, which represents a contribution of approximately 30% of drilling vibration dysfunction. Dynamic modeling of stick/slip phenomena in drillstrings shows that the vibrational waves travel back and forth along the drillstring between the bit and top drive, which typically leads to 15% fluctuation in surface torque. It is also found that stick/slip is much more likely to occur with certain drilling fluid types and in deviated holes with large dogleg severity. One method of stick/slip mitigation is through control of the top drive. In existing applications, the vibrational wave at a fundamental frequency is absorbed by tuning a proportional-integral (PI) controller.\u0000 Stick/slip-induced vibrations do not exist at a single frequency, and the simple PI controller cannot mitigate stick/slip occurrence at all vibration frequencies. Vibrations at frequencies other than the frequency chosen for mitigation can be amplified using existing tuning methods. In tests in which the method was applied, there were cases in which the vibration shifts to the second mode when the first torsional mode is mitigated. Therefore, the challenge is to target more than one vibration frequency.\u0000 A new control system has been designed to observe stick/slip frequencies and then to dampen the stick/slip across a wide frequency range, while regulating the rotational speed of the drillstring at the desired set point. All control algorithms are implemented on a standard programmable logic controller (PLC). To eliminate the need to modify the existing top variable-frequency drives (VFD), this paper also proposes several methods to seamlessly implement the proposed controller.\u0000 Existing configurations and stick/slip mitigation tests based on PI controller-gained tuning have been achieved on a test rig. Field tests demonstrating the new control method have been performed, and the results are presented and analyzed in this paper.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125755700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Slide Drilling Guidance System for Directional Drilling Path Optimization","authors":"Can Pehlivantürk, J. D'Angelo, Dingzhou Cao, Dongmei Chen, P. Ashok, E. Oort","doi":"10.2118/194096-MS","DOIUrl":"https://doi.org/10.2118/194096-MS","url":null,"abstract":"\u0000 The amount of uncertainty related to directional drilling makes it challenging to accurately model and predict the results of drilling actions, leaving much to human know-how and interpretation. Additionally, few path planning methods in the literature consider the directional steering tool being used which results in a loss of optimality when sliding and rotating instructions are fitted on a geometric optimal path. The formulation of the optimization problem varies greatly between rotary steerable systems (RSS) and mud-motor configurations. Additional cost functions and constraints are present for mud-motor use, which significantly increases the problem complexity. A slide drilling guidance system is proposed to combat this issue and to help automate directional drilling. The guidance system leverages three main modules. The first is a computationally efficient, non-linear wellbore propagation model. The second is a set of cost functions that aims to quantitatively represent the actual value of the well, representing production loss, drilling time, completion cost, and wellbore quality. The last module is a Genetic Algorithm (GA) solver that generates sets of optimal drilling instructions. The guidance system is built into a software package that utilizes an intuitive, easily-accessible Graphical User Interface (GUI) to be an effective advisory tool for the directional driller. The software is currently being implemented into the Real Time Drilling (RTD) system by an operator.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134273979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intelligent Wellbore Path Estimation Using Multiple Integrated MEMS Sensors","authors":"Huan-xin Liu, R. Shor, Simon S. Park","doi":"10.2118/194127-MS","DOIUrl":"https://doi.org/10.2118/194127-MS","url":null,"abstract":"\u0000 To improve magnetic disturbance rejection and robustness of wellbore survey measurements, an adaptive neuro network-based fuzzy inference system (ANFIS) filter for wellbore position calculation is presented. This technique significantly improves magnetic disturbance rejection and reduces sensor error influence for borehole survey measurements. The new approach for the ANFIS filter is based on two redundant sets of IMUs which are located in different positions in the BHA at a known, constant distance. The distance between these two sets of IMUs will physically fade the effect of the magnetic disturbances. Each IMU set outputs position estimation based on the splines method which is then input into an ANFIS filter. The inputs of the splines calculation are azimuth, inclination angles and measurement depth, and the outputs are moving distance in three directions (Northing, Easting and True Vertical Depth). However, the accuracy of the splines method highly depends on the accuracy of the inputs, which are difficult to obtain during the measurement while drilling process even under pure clean environments (without any magnetic disturbances). Furthermore, the distorted azimuth caused by magnetic interference affects the borehole position accuracy. In order to deal with those problems, the designed ANFIS filter has a two-level structure. First a local level position estimation (splines method or well trained local ANFIS based on the sensor accuracy) for two sensor sets is used. If the sensor measurement accuracy is low, this local ANFIS will correct the position estimation. Then the outputs of the local modules were input into ANFIS for second level filtering (global filter) to remove the error which caused by unknown magnetic disturbances. According to the judgement of the ANFIS, the IMU set with the smaller magnetic disturbance is given greater weight to reduce the interference effect on the borehole position estimation. This two-level filter is compared to the traditional splines method under different tests situations. First, we evaluate this method by comparing with GPS positioning, from this test we know that the ANFIS filter shows a good performance when the magnitude of magnetic disturbance is within the training magnitude range. Even when the magnitude of magnetic disturbance is above the training range, the ANFIS filter shows a higher robustness than the traditional splines method. Also, this method was applied to borehole data with two IMU containing accelerometers and one magnetometer measurements. In order to apply our method, we duplicated one more magnetometer measurement data under magnetic interference for assessment. The results proved its magnetic disturbance robustness in borehole position estimation. Finally, we demonstrate the full potential using a laboratory experimental setup.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114469039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Slim Well Casing Design for a Deepwater Application Using a Fast and Flexible Finite Element Engine","authors":"Murat Panayirci, O. Houette, S. Brands, M. Paraschiv, S. French","doi":"10.2118/194056-MS","DOIUrl":"https://doi.org/10.2118/194056-MS","url":null,"abstract":"\u0000 In the exploration and production (E&P) industry attempts at reducing the cost of the well construction by applying various well architecture slim designs has attracted attention from operators for decades. The recent industry downturn has further contributed to a renewed focus on this strategy. In this study we present a slim well design application within the FortunaCo project (a Joint Venture between OneLNG and Ophir), which aims at developing the Fortuna and Viscata fields in Deepwater offshore Equatorial Guinea. An advanced static nonlinear Finite Element engine is used in this process, which considers contact and friction; can handle large deformations and is therefore suitable to carry out buckling analysis. The top hole structural robustness is analyzed using this engine in the event of a worst case axial load, which for this study is assumed to be:The Conductor Pipe (CP) able to take its own weight only,The upper section of the surface casing (inside the CP) free of cement,The full buoyant weight of the Horizontal Christmas tree and Subsea Blowout Preventer applied onto the well.\u0000 This paper demonstrates that the selected numerical model is suitable to estimate critical buckling loads and identify post-buckled modes exerted on surface structural casings. Furthermore, it is shown that the visualization capabilities and speed of the engine allow the operator to optimize the design iteratively in an efficient manner. We conclude that the selected methodology is suitable for the operator to validate a slim well design for a Deepwater development application at concept phase for minimal cost with the necessary level of confidence.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124877156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Novel Microbially Induced Self-Healing Cement/Concrete for Underwater Concrete Offshore Structures","authors":"C. Noshi, J. Schubert","doi":"10.2118/194173-MS","DOIUrl":"https://doi.org/10.2118/194173-MS","url":null,"abstract":"\u0000 Techniques for offshore structure concrete remediation have received minimal consideration in the oil and gas industry in spite of its potential. Emerging \"bio-concrete\" to plug micro-cracks have shown concrete results in various lab experimentations. Recently, MICP technology has garnered world-wide attention and popularity for various multi-disciplinary applications where smart synthesis of calcium carbonate minerals generate at ambient conditions contributing to bio-cemented self-healing agents by mixing bacteria into the cement slurry. Concrete fails to self-heal and repair cracks greater than 0.2 micron.\u0000 The technique comprises of mixing the preparatory material with operative quantities of urease producing spores and a calcium ions under standard conditions of hydrolyzed urea. Scientists found that microbes extensively multiply when nutrients comprising of cheap carbon sources like molasses/glycerol is added to the mixture. Live microbes propagate via cracks channels and micro-voids and smartly cement the cracks by calcifying the matrix structure.\u0000 Bacteria can then act as a autogenous self- healing agent. The precipitating bacterial strains generate urease enzyme which metabolically precipitate calcium minerals in the neighboring environment as calcium carbonate. The degradation of urea via bacterial metabolism locally rises the surrounding pH allowing the carbonate microbial calcification. These precipitates can autogenously plug the cracks and improve concrete robustness. The calcifying bacteria can be secluded from cement matrix or various natural sources. The purified spores can cultivate for limited time periods and then supplemented to the concrete matrix for application. The spores remained viable after prolonged periods. After short curing times, the healing capability of micro-cracks, durability, and tensile strength showed significant improvement.\u0000 This novel approach of crack plugging is highlighted to save substantial costs associated with crack restoration and repair of underwater concrete offshore structures and platforms.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124887263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Micro-Sonde Well Logging System; a Novel Method for Along-Well Measurements","authors":"Gunnstein Saelevik, H. J. Skadsem, S. Kragset, D. Gardner, E. Randeberg, M. Hjelstuen","doi":"10.2118/194153-MS","DOIUrl":"https://doi.org/10.2118/194153-MS","url":null,"abstract":"\u0000 The micro-sonde well logging system is a concept for obtaining along-well measurements of temperature, changes in fluid velocity and pressure while drilling. The micro-sondes are encapsulated, self-contained measurement devices designed to follow the flow from the bottom hole assembly to surface. Once retrieved at surface, the measurements can provide information about well conditions such as the presence of cuttings beds, washed out zones and gain/loss zones. Post-processing of the data requires knowledge of the forces acting on the micro-sonde and the resulting trajectories from the release point at the bottom hole assembly and to surface. The main objectives of the studies presented in this work are to understand the micro-sonde motion in the mud flow and to design and construct a demonstration device.\u0000 We have performed a literature study, CFD-modelling and experiments to better understand the behavior of a micro-sonde in a typical annular flow domain. The trajectory of a single micro-sonde has been investigated as it passes tool-joints under the influence of inner string rotation. Further, the experiments investigated the likelihood of transporting the micro-sonde intact to surface for a drilling application. For the experimental studies, two annular flow loops, one vertical without rotation of the drill-string and one horizontal with a rotating drill-string, including tool-joints and a model bottom hole assembly have been constructed and utilized.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"128 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132760839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Active Return Flowline Sensor for Onshore Drilling Rigs","authors":"Patrick M Lambie, J. Sampaio","doi":"10.2118/194087-MS","DOIUrl":"https://doi.org/10.2118/194087-MS","url":null,"abstract":"\u0000 This paper presents the concept, construction, and test of a small scale volumetric flow rate sensor using the simple principle of mass conservation with the purpose of accurately measure the flow return in onshore drilling operations. The results demonstrate that the solution is accurate, extremely sensitive to flow variations, and capable of identifying and measuring flow variations caused by influx or loss of fluids in the wellbore.\u0000 The solution uses the principle of mass conservation and is limited to low compressibility fluids which corresponds to the larger portion of onshore operations in US and abroad. Under this assumption, the principle of mass conservation is replaced by volume conservation, which allows the appropriate measure of the return flow rate. The principle is realized using off-the-shelf equipment. The solution is installed as a bypass of the regular flowline on conventional drilling rigs and does not require the use of special equipment like rotating head and expensive Coriolis systems.\u0000 The small-scale sensor system constructed and tested is capable of handling up to 40 gpm with a footprint of about 4 ft2. Considering the scale to handle typical flow rates up to 1,000 gpm the size of the equipment in real scale is roughly in the linear ratio of three, which corresponds to a footprint of 36 ft2 (3’x12’), compatible with the available area between the rig structure and the mud pits. Several tests indicate that the system can sense changes in flow rate in the range of ±1% of the maximum nominal flow rate in few seconds after a flow perturbation/variation occurs and obtain accurate readings of the actual flow rate in less than 30 s (5 s to identify, 10 s to measure, 15 s to stabilize). This means that the time to identify influx of gases or loss of fluid is reduced substantially compared to traditional differential methods used in onshore rigs, and are comparable to solutions using Coriolis methods, at a fraction of the cost. The system can also provide a real-time measurement of the return fluid density. The use of this system in onshore rigs brings to these scenarios the same level of safety as the case of offshore operations using Coriolis systems.\u0000 This new measuring system uses sound principles and is implemented using off-the-shelf equipment, although for higher efficiency and optimized reliability the use of a design-for-fit equipment is advisable. The invaluable benefit is to bring the same level of safety as the case of more expensive systems usually affordable only in offshore scenarios. By reducing substantially the influx volume of kicks or the volume of fluid lost before appropriate actions are taken makes this system economically and environmentally attractive.","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121783464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Well Control Incident in the North Sea as Interpreted with Advanced Gas Influx Modelling","authors":"J. O. Skogestad, K. Bjørkevoll, J. Frøyen, H. Linga, Eivind Lenning, S. T. Havardstein","doi":"10.2118/194145-MS","DOIUrl":"https://doi.org/10.2118/194145-MS","url":null,"abstract":"\u0000 \u0000 \u0000 Handling well control incidents during drilling operations safely and efficiently is of crucial importance, due to the potential danger to crew, rig and environment, as well as the economic aspects. In this paper, we study an actual incident from a North Sea drilling operation, using recent advances in gas influx modelling, which allows for improved understanding of the underlying physical processes, hence enabling more accurate well control simulations.\u0000 \u0000 \u0000 \u0000 Data has been gathered from a drilling operation where a well control incident occurred, and put into a hydraulic drilling model. This model is enhanced with compositional modelling of PVT properties of the gas/fluid system, allowing for better description of the gas absorption capability of the drilling fluid. Furthermore, effects of non-instantaneous gas loading are handled by a novel kinetic model. Multiple simulations with varying model parameters are run in order to understand how different physical processes can explain the behavior observed in the dataset.\u0000 \u0000 \u0000 \u0000 Simulations of the case have been compared to the operational data, showing how the different modeling parameters of gas influx impact the simulation prediction performance. A key to safe handling of well control incidents is early detection, but relying only on recordings for topside process conditions limits accuracy and reliability as compared to using the topside data in combination with real-time downhole data and/or advanced mathematical interpretation software. The results show how, by using a combination of downhole modelling and observations, it is possible to obtain a more complete picture of the well conditions throughout the operation. The results also give an indication on early signs that may allow for faster reaction and more confident handling of a gas influx.\u0000 \u0000 \u0000 \u0000 This case-study of a gas influx scenario with sophisticated gas absorption modelling is the first of its kind, providing useful insights relevant for well control handling and illustrating the benefit of digitalization of drilling operations. By implementing the technology for real-time surveillance, safer and more efficient handling of well control incidents is allowed for, thus reducing the risk of dangerous situations on the rig.\u0000","PeriodicalId":441797,"journal":{"name":"Day 2 Wed, March 06, 2019","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127631275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}