【正文】 ave 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。 one provides pressure and flow from the mud pumps,and the other is primarily a vent line. By having two high pressure access points to the connection, it is possible to have a “safe” pressure differential. If a leak is detected, the process can be reversed and attempted again. In the new continuous circulation sub, the ball can be returned to the valve system and reinserted, or simply replaced. Because the ball is a selfaligning seal mechanism, it is very difficult to see a nonsealing situation. If difficulty is seen when seating the ball, the dynamics of the pressure differential can be tuned to provide a more positive “hammer” when it seats, or a stronger application of pressure differential. Additionally, the low cost of the ball encourages the precautionary measure of changing it for each connection. Many material choices are available which can cope with the specific mud conditions experienced。 some key contributing features will be described. With the initial testing phase pleted, 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 handsfree connection of the mud bypass, a replaceable barrier, automated connection 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 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 method of connecting the mud pumps to the side entry sub is no easy task. Some have tried using industry accepted hammerunions, 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 clampon housings. All of these are potentially exposing the rig crew to increased danger. The new continuous circulation sub is a totally handsfree 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 3 will be customer specific. The current proof of concept is an extending arm arrangement. Potential alternate versions are track mounted or pedestal mounted with an arm system, or even adapted to the existing iron roughneck. The final articulation method will depend largely on the customer and their requirements to either be part of the rig floor, or as a temporary installation. Replaceable barrier The novelty of the sub design is based on the barrier, which is a round ball, with sealing characteristics (ie, “soft” pared to the seat). This presents a perfect sealing surface, which can be reused multiple times. The ball is inserted through the side of the sub and shifted “up”, much like a shuttle valve, using differential pressure. Minimal amounts of pressure differential will be sufficient to shift the ball (a small test fixture was used to prove this theory). With the ball in the sub, and “seated” against the topdrive side of the connection, mud is pumped “down” the string, through the same hole from which the ball was ntroduced. While in this condition, the connection directly above the sub is still made up and sealed. The barrier is then tested for leakage before the control system gives the “green light” to pr