Summary The most important contributor to improved oil recovery on mature fields is drilling of infill wells. Managed–pressure drilling (MPD) and continuous–circulation–system (CCS) techniques can be used for improved control of bottomhole pressure when drilling wells in depleted fields with narrow pressure windows, but rig heave is a challenge when drilling from floating drilling units. Rig heave, caused by sea waves, induces downhole pressure oscillations that could exceed the operational pressure window. These oscillations are called “surge and swab,” and occur during tripping in and tripping out of the borehole, as well as during drillpipe connections, while the drillstring is suspended in the slips. Downhole choking was introduced as a method to reduce downhole pressure oscillations induced by the rig heave, and the concept was tested at laboratory scale and using computer simulations (Kvernland et al. 2018). The simulations were performed using a purpose–developed software that uses such input variables as wave height, pump flow, drillpipe movements, rig characteristics, and drilling–fluid properties, along with well design, drillpipe, and bottomhole–assembly (BHA) data, to simulate downhole pressure induced by rig heave. The simulator is designed to model dynamic interactions between the drilling fluid and the drillstring in a rigorous manner, which gives it the ability to accurately predict rapid downhole changes, such as those induced by ocean waves. In this paper, we provide an overview of the surge–and–swab simulator, describing its capabilities and limitations. Data from drilling a North Sea well are then used to validate the simulations performed using the software. The well used as an example in this paper was drilled conventionally from a floating rig. The downhole pressure variations recorded during three different drillpipe connections are compared with simulated downhole pressure. The simulations are performed on the basis of the recorded rig heave as well as the actual drilling–fluid, well–design, and drillpipe data. Results show that there is a good correlation between simulated and actual measured downhole pressure. The surge–and–swab simulation software is then used to simulate the same drillpipe connections using three different techniques and combinations of techniques used for improved downhole pressure control: (1) MPD, (2) MPD combined with CCS, and (3) MPD combined with CCS and a downhole choke. Results show that rig heave–induced downhole pressure variations are reduced to a level that is considered acceptable for drilling a well with a narrow pressure window for the last two cases, whereas use of backpressure MPD alone is not sufficient. The combination of MPD and CCS reduced surge and swab for two out of three drillpipe connections. For the third and deepest connection, the surge–and–swab pressure increased. The largest reduction in significant downhole pressure variations occurs when MPD and CCS are combined with downhole choking. Future work will consist of further developing the surge–and–swab simulator so that it will be possible to use it in well planning and as real–time decision support during drilling operations. The simulator will also be developed to include the possibility of simulating various well completion operations such as running casing and liners. The next hardware development phase consists of designing and building a complete downhole tool for testing in a well.
Human fatigue is one of the main causes of accidents in maritime domain. How to use physiological data to estimate degree of human fatigue without medical domain knowledge is significant to the safety of tasks in maritime operations. In this paper, a decentralized sensor fusion approach is proposed. Various sensor data used to monitor brain wave, heart rate, muscle tension, body temperature, visual focus and head movement, together with subjective measurement of Karolinska Sleepiness Scale (KSS) values are selected as the data source for this study. Convolutional neural networks are adopted in the approach to extract local features of each individual data channel. The local features are further fused into a 5-layer fuzzy neural network for classification of the KSS values. A case study of fatigue monitoring test of ship maneuvering in simulator has been carried out. Through a comparative study with a centralized fusion approach, the proposed method is verified to be able to provide high accuracy up to 96.08% for fatigue level classification, and in particular, robust enough to maintain the accuracy to 88.42% in case of sensor failure.
The most important contributer to Improved Oil Recovery (IOR) on mature fields is drilling of infill wells. Managed Pressure Drilling (MPD) and Continuous Circulation System (CCS) techniques can be used for improved control of bottomhole pressure when drilling wells in depleted fields with narrow pressure windows, but rig heave is a challenge when drilling from floating drilling units. Rig heave, caused by sea waves, induces pressure oscillations downhole that may exceed the operational pressure window. These oscillations are called "surge & swab" and occur both during tripping in and out of hole as well as during drill pipe connections, when the topside heave compensation system used during drilling is disabled because the drill pipe is put in slips. Downhole choking was introduced as a method to reduce downhole pressure oscillations induced by the rig heave and the concept was tested in laboratory scale and using computer simulations (Kvernland et al., 2018). The simulations were perfomed using a purpose-developed software which utilizes such input variables as wave height, pump flow, drill pipe movements, rig characteristic (RAO), drilling fluid properties as well as well design, drill pipe and Bottom Hole Assembly (BHA) data to simulate downhole pressure, induced by rig heave. The simulator is designed to model dynamic interactions between the drilling fluid and the drill string in a rigorous manner, which gives it ability to accurately predict fast downhole changes, such as ones induced by ocean waves. This paper gives an overview of the surge & swab simulator, describing its capabilities and limitations. Data from drilling of a North Sea well is then used to validate the simulations made using the software. The well, used as example in this paper, was drilled conventionally from a floating rig. The downhole pressure variations recorded during three different drill pipe connections are compared with simulated downhole pressure. The simulations are based on the recorded rig heave as well as the actual drilling fluid, well design and drill pipe data. Results show that there is a good correlation between simulated and actual measured downhole pressure. The surge & swab simulation software is then used to simulate the same drilling pipe connections using three different techniques and combinations of techniques utilized for improved downhole pressure control: (1) Managed Pressure Drilling (MPD) (2) Managed Pressure Drilling combined with Continuous Circulation System (CCS) and (3) MPD combined with CCS and a downhole choke. Results show that rig heave-induced downhole pressure variations are reduced to a level which is considered acceptable for drilling a well with narrow pressure window for the last two cases, while utilization of backpressure MPD alone is not sufficient. The combination of MPD and CCS reduced surge & swab for two out of three connections. For the third and deepest connection, the surge & swab increased. The largest reduction in significant downhole pressure variations (43-68 % vs. conventional drilling for the three connections) occurs when MPD and CCS are combined with downhole choking. Future work will consist of further developing the surge & swab simulator so that it will be possible to utilize it in well planning and as real-time decision support during drilling operations. The simulator will also be developed to include possibility of simulating various well completion operations such as running casings and liners. A prototype of the downhole choke is currently being tested at the mud loop of the Ullrigg test rig facility in Stavanger, Norway, and the next development phase consists of designing and building a complete downhole tool for testing in a well.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.