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Valve and Actuator Technology for the Offshore Industry
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
A subsea well is drilled down through the seafloor to reach the oil. After drilling the well in the seabed and placing tubing inside it for oil production, the well should be completed. Well completion is the process of making the well ready for production after the drilling has been completed. As part of this process, casings should be installed inside the well to prevent it from collapsing. The area between the casing and tubing is sealed by a tubing packer. Packers are used to prevent the pressure of the well fluid from entering the production casing. A wellhead is installed on top of the well on the seabed; it serves multiple purposes, such as providing a pressure barrier, providing access to the well bore and production tubing, ensuring pressure and structural integrity for the well casing and tubing, etc. The upper part of the wellhead, which is located on the subsea bed, contains valves, piping, actuators, fittings and the structures necessary to control the flow and pressure inside the well; this is called a “Christmas tree” or simply a “tree.” It is called a wet tree (see Figure 5.9) if it is installed subsea and a dry tree if it is installed on land. In addition to the valves and actuators that are installed on the trees, some valves are installed on the subsea manifolds and in the well. A subsurface safety valve is installed in the well on the upper wellbore to provide emergency stoppage of well production in the event of a high-pressure scenario inside the well. This type of valve is excluded from the scope of this book.
Background
Published in Jie Zhang, Chuanjun Han, Rubber Structures in Oil and Gas Equipment, 2022
A blowout preventer (BOP) is one of the core equipment for the well control operation, which can ensure the safe and normal operation of oil and gas drilling engineering. In drilling operation, when the liquid column pressure in the well is less than the formation pressure, blowout may occurs. The blowout preventer can quickly close the wellhead to prevent blowout accidents. While, the blowout preventer also plays an important role in underbalanced drilling, pressure operation and other processes [20]. The blowout preventer failure causes serious environment pollution and life threatening. The rubber core is one of the key components of the blowout preventer. The rubber core performance determines the sealing performance of the blowout preventer and the oil and gas exploitation progress.
Learning from Experience: Incident Management Team Leader Training
Published in Schraagen Jan Maarten, Laura G. Militello, Tom Ormerod, Lipshitz Raanan, Naturalistic Decision Making and Macrocognition, 2017
Schraagen Jan Maarten, Laura G. Militello, Tom Ormerod, Lipshitz Raanan
At 3:59 a.m. on 21 May 2003, the 6,000-ft drilling riser suddenly parted at a depth of 3,200 feet sub-sea (see Figure 6.1). The drilling riser is a large-diameter pipe that connects the wellhead equipment on the seabed to the rig at the sea surface and which returns drilling chemical “mud” to the surface (see Figure 6.2a). Without the drilling riser, the chemical mud used for drilling purposes could spill and contaminate the seabed. The riser was under 2.1 million pounds of top tension and the parting produced not only a loud bang but everyone on board the drill ship felt the subsequent sudden jarring (Kirton, Wulf, and Henderson, 2004). Inspection by a Remote Operated Vehicle (ROV) showed that the drill pipe (which is internal to the drilling riser) was intact, and was actually supporting the broken riser. Wellhead equipment is the part of the oilwell where it reaches the surface (whether on land or sub-sea) and comprises valves and spools that contain the pressure and the oil within the well. The wellhead equipment on the seabed (see Figure 6.2b) functioned properly, preventing substantial leakage from the sub-sea reservoir into the Gulf.
Survey on reliability analysis of dynamic positioning systems
Published in Ships and Offshore Structures, 2023
Fang Wang, Liang Zhao, Yong Bai
Position loss may occur on DP MODUs while connected to a subsea well (Figure 3). In normal operations, a MODU should be positioned within a green zone inside the yellow limit. When the vessel loses the capability to maintain position by means of thruster force, she may have an excursion beyond the yellow or even the red limit. This condition is denoted drive-off or drift-off event, which is generic to all DP vessels. If the vessel passes the yellow limit, the drilling operation must be stopped and the driller starts to prepare for disconnection. If the vessel passes the red limit, emergency disconnection must be initiated in order to disconnect the riser/LMRP (lower marine riser package) and shut in the well. Failure of disconnection may result in damage of the riser, wellhead, or BOP (blowout preventer). This could cause significant financial losses and vessel downtime, and in the worst case could escalate into a subsea blowout.
An improved coupled model for axial dynamic analysis of deepwater drilling risers under a soft hang-off mode
Published in Ships and Offshore Structures, 2023
Nan Zhang, Yuanjiang Chang, Lei Xu, Guoming Chen, Xiuquan Liu, Zhi Zhao, Weiguo Zhang, Yongguo Dai
The drilling riser system is critical and vulnerable offshore equipment during drilling operations (Wang et al. 2015; Mao et al. 2016; Meng et al. 2018; Chang et al. 2019; Chen et al. 2021a, 2021b; Liu et al. 2022). Normally, the drilling riser system connects the submarine wellhead system and the floating drilling platform to form a circulation path for the drilling fluid. However, the drilling riser should be disconnected from the BOPs and suspended on the platform to secure the drilling riser system and the wellhead in harsh environments, such as typhoons or storms (Mao et al. 2019; Li et al. 2021; Zhao et al. 2022; Zhang et al. 2023a, 2023b). Hang-off modes for the riser are divided into hard hang-off modes and soft hang-off modes according to the different upper boundary conditions of the riser, as shown in Figure 1(a,b) (Liu et al. 2018; Mao et al. 2020). In hard hang-off mode, the top end of the riser is connected to the platform directly and rigidly (Wu et al. 2014). While in soft hang-off mode, the top end of the riser is suspended on the platform through the tensioner.
The effect of decomposition of natural gas hydrate on deep-water drilling
Published in Petroleum Science and Technology, 2022
Zhi Zhang, Yuan-jin Zhao, Nan Cai, He-xing Liu, Chuan-hua Ma, Ji-wen Liang
Changes in BHP can be divided into two parts: the decreasing in BHP brought on by the annulus mixed fluid density decreasing as a result of gas invasion, and the increase in BHP brought on by drilling fluid flowing into the annulus from the bit. As shown in Figure 8, the gas influx caused by hydrate decomposition is small and still near the bottom of the well when the bit has just drilled into the hydrate formation. Gas occupies little space in the annulus, and the decrease in fluid mixing density in the annulus is slight. Therefore, the BHP considering gas invasion is slightly lower than regular drilling. With the gradual decomposition of hydrate, the gas influx into the wellbore increases, as does the volume of gas along the annulus, and as the fluid mixing density in the annulus increases, so does the BHP. The gas reaches the wellhead and begins to be discharged 1.9 hours later, while the drilling fluid continues to flow into the annulus to supplement. BHP's decline range narrows slightly.