Determine the potential range of actual wellhead flowing conditions, design the cyclone geometry to suit, and predict separation performance and cyclone pressure drop.
The operator’s objective was to mill through the shallow cement plug installed in a well to mitigate the risk of gas trapped below the plug, displace the wellbore fluid with kill fluid, and then plug and abandon using drillpipe.
During the coiled tubing (CT) milling operations, it was necessary to separate cement debris at the surface from the fluid return before passing it into the production system. To achieve this, it was proposed that the operator use the new-generation AB model of WDC Series technology with its remotely actuated automated flushing system.
The cyclone unit consists of a cyclone housing containing a single desanding cyclonic insert mounted above a solids accumulator vessel. In operation, the solids are separated from the flow stream of water, oil, or gas in the desander vessel and spun down into the accumulator.
The new AB model’s remotely actuated flushing system enables solids flushing and collection for disposal from the accumulator during operation without the need to bypass or stop operations. It also features a solids weight measurement system for accurate measurement of the mass of produced solids in the accumulator.
CT was run into hole tagging the cement plug. The operator commenced milling the plug at a rate of 0.1m/min. During the milling operations, the debris was separated at the surface from the flow stream by using the AB model of WDC Series technology before passing the fluid to the process system. The technology is equipped with a solids weight measurement system and fully automated flushing system. This allowed the removal of separated and accumulated solids from the accumulator’s vessel automatically by actuating the flush sequences remotely from the lab cabinet. The solids weight was measured, recorded, and displayed on the control panel. It was also displayed on the screen of the acquisition flow computer making it visible to the field crew.
During the milling operations of the cement bridge, with the circulation rate of 39 m³/h, the total amount of 145.6 kg of cement debris was successfully separated from the flow stream using the new-generation, fully automated AB model of WDC Series technology. This increased the efficiency of the operation and reduced the crew size during the CT intervention work. It also proved to be highly efficient in automatically flushing the accumulator during ongoing operations. The information from the weight measurement system about solids production rate was acquired by the surface data acquisition system. It provided valuable information to the field crew.
Periodically, the accumulator needs to be isolated from the desander vessel, vented, and accumulated solids flushed. Holdup volume at the bottom of the desander vessel was necessary to collect the solids while the accumulator was being bypassed and flushed. The solids can be flushed to a pit, cuttings box, or another disposal site. Typically, the solids removal from the accumulator’s vessel is performed manually by bypassing the accumulator vessel and flushing content to the pit. The automated flushing system for accumulated solids removal eliminated the time and extra personnel required to remove the solids manually.