1、 本 科 毕 业 论 文（ 翻 译 ） 英文标题 Continuous circulation drillingsystem 学生姓名 学 号 教学院系 专业年级 指导教师 职 称 单 位 辅导教师 职 称 单 位 完成日期 2013 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
2、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 completing these formations was very costly and not always successful. Cycling the mud pumps off and on for
3、connections affects the pressure and is a major problem for MPD.Techniques and equipment have been developed to make a connection while continuing to circulate the drilling mud to maintain constant pressure. Since 2005, the Continuous Circulation System (CCS) has allowed continuous circulation durin
4、g connections with traditional jointed drill pipe, by using a chamber around the connection. Several companies 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 fro
5、m both an operational and safety standpoint. This paper describes the current MPD market and describes the philosophy adopted for a new side-entry sub. Introduction History was made in July of 2003, when the first continuous circulation chamber was tested in prototype form on a land rig. Jointed dri
6、ll 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 2005, many operators have begun using the co
7、ntinuous circulation chamber as a way to drill un-drillable wells, specifically those having “tight” pore pressure and fracture pressure windows. This means that the bottom-hole pressure must be very closely controlled at all times (even during connections) to avoid either fracturing the formation,
8、or allowing an influx. The system has worked reliably for the last six years.However, many operators cannot easily accommodate the dedicated crew required to operate the continuous circulation chamber.As operators weighed the benefits against the increase in drill crew, the obvious solution was to p
9、rovide 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 in-slips without flowing through the top 2 drive. Many o
10、f 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 ins
11、pectable before exposing the crew to a potential leak. The recently introduced continuous circulation subs have all introduced a non-replaceable, non-inspected barrier. The rig crew is also responsible for attaching high pressure connections to the sub during operation.With all these points in mind,
12、 existing continuous circulation subs have presented major safety concerns and reliability weaknesses.The new continuous circulation sub is focused on safety, reliability, and becoming part of the drilling process. The design does not place rig personnel near the high-pressure drilling ponent betwee
13、n the high-pressure drilling mud and atmosphere is easily removed and inspected between every connection. Each connection is checked for seal integrity before separation. This ensures reliability of the barrier, regardless of how long the sub has been in operation. The entire system is designed with
14、 the idea that the driller and existing crew will operate the equipment just as easily as existing floor equipment (ie, iron roughnecks, pipe rackers, etc). The solution aims to become a standard part of the drilling process； some key contributing features will be described. With the initial testing
15、 phase completed, the results will also be presented and discussed. The Concept The new continuous circulation sub has been designed with the same attention to detail as the original continuous circulation chamber. It has hands-free connection of the mud bypass, a replaceable barrier, automated conn
16、ection integrity checks, and integration into the drilling process with the rig crew. Hands free connection When using the continuous circulation chamber, the drill pipe was fed through several ram type Blow Out Preventer (BOP) style seals. This provided a sealed chamber around the connection. These
17、 seals were positioned at well center and were always in position, simply retracted when not in use. This posed a problem during operation, the floor was not clear for access. It is desired to improve the access to the well center when drilling ahead or otherwise not continually circulating. A metho
18、d of connecting the mud pumps to the side entry sub is no easy task. Some have tried using industry accepted hammer-unions, even though blunt force and subsequent sparks should be avoided with high pressure containment and in potentially explosive environments. Others have used threaded plugs, or cl
19、amp-on housings. All of these are potentially exposing the rig crew to increased danger. The new continuous circulation sub is a totally hands-free unit for this reason. The mud is transported from the standpipe using industry accepted swivel joints and piping, to allow movement. The sub is converted from drilling mode to side entry mode using very simple, easy to visually inspect, movements. The exact layout of the movement
