【正文】 me or less time will be taken when removing the ball. With a predicted five minute or less connection time, MPD is being much more efficient. This is a very significant leap forward for MPD. Initial Testing Certain elements of the design have been developed based on the results of testing. The replaceable barrier has been tested using a flow fixture with various arrangments of valves to simulate the rig’s stand pipe manifold. The flow fixture was transparent where the ball enters the sub and seals. Water is flowed through the setup to simulate very thin drilling mud. The timing of the valves opening and closing plays a role in how efficiently the ball is shifted into the circulation sub. It was a challenge to reduce the number of valves to a minimum, but also provide doublevalveprotection at all times. Figure 1 shows the typical valve schematic for the new continuous circulation sub. During testing it was found that the ball can be shifted with very little pressure differential and that velocity appears to be the largest influence on the operation. Once seated the pressure differential required to generate a seal is also negligible. Another development was the position and shape of the internal geometry, such that the ball is encouraged to travel “up” into the sub, even at very low transition speeds. A pressure gage on the downstream side of the sub registered almost no pressure changes during shifting of the ball. This is primarily due to the flow area never being restricted throughout the shifting sequence. The ball material was also experiemented with, and the initial testing was done with a rubber coated steel core. The significant weight of the ball posed no issue with being transferred using almost no pressure differential. Another area of interest was the clearance between the internals of the continuous circulation sub and the associated plumbing with respect to the ball. This ball must be transported efficiently within these pipes for a short distance, so the leakage cannot be excessive. The clearance didn’t prove to be as much concern as expected, even when using low viscosity fluids and much larger than practical clearances. The system is also very intuitive。 本 科 畢 業(yè) 論 文（ 翻 譯 ） 英文標(biāo)題 Continuous circulation drillingsystem 學(xué)生姓名 學(xué) 號(hào) 教學(xué)院系 專業(yè)年級(jí) 指導(dǎo)教師 職 稱 單 位 輔導(dǎo)教師 職 稱 單 位 完成日期 2022 年 04 月 1 Continuous Circulation Drill String Sub Abstract There is an increasing need to drill difficult reservoirs in a cost effective way. Over the past few years Managed Pressure Drilling (MPD) has made it possible to drill reservoirs which have a narrow window between pore and fracture pressure gradients. Before the introduction of MPD techniques, safely drilling and pleting these formations was very costly and not always successful. Cycling the mud pumps off and on for connections affects the pressure and is a major problem for and equipment have been developed to make a connection while continuing to circulate the drilling mud to maintain constant pressure. Since 2022, the Continuous Circulation System (CCS) has allowed continuous circulation during connections with traditional jointed drill pipe, by using a chamber around the connection. Several panies have developed continuous circulation subs which are threaded between tool joints to achieve continuous circulation without a pressure chamber. These have had varying degrees of success from both an operational and safety standpoint. This paper describes the current MPD market and describes the philosophy adopted for a new sideentry sub. Introduction History was made in July of 2022, when the first continuous circulation chamber was tested in prototype form on a land rig. Jointed drill pipe was separated inside a sealed chamber, which was filled with drilling fluids provided by the mud pumps. The drill string was separated, another joint added, and drilling continued without ever shutting down the mud pumps. After its introduction in 2022, many operators have begun using the continuous circulation chamber as a way to drill undrillable wells, specifically those having “tight” pore pressure and fracture pressure windows. This means that the bottomhole pressure must be very closely controlled at all times (even during connections) to avoid either fracturing the formation, or allowing an influx. The system has worked reliably for the last six , many operators cannot easily acmodate the dedicated crew required to operate the continuous circulation operators weighed the benefits against the increase in drill crew, the obvious solution was to provide the same continuous circulation functionality, with a streamlined package that reduced the footprint on the rig operations. There have been many attempts to create a continuous circulation sub which allows the mud flow into pipe sitting inslips without flowing through the top 2 drive. Many of these attempts have been successful, but have introduced a major safety concern. When looking at continuous circulation chambers, the barrier to prevent fluid from erupting out of the separated connection is typically a gate valve, with replaceable rubber seals. This barrier is replaceable and inspectable before exposing the crew to a potential leak. The recently introduced continuous circulation subs have all introduced a nonreplaceable, noninspected barrier. The rig crew is also responsible for attaching high pressure connections to the sub during all these points in mind, existing continuous circulation subs have presented major safety concerns and reliability new continuous circulation sub is focused on safety, reliability, and being part of the drilling process. The design does not place rig personnel near the highpressure drilling