| Popis: |
This paper describes a new procedure/technique which was used to control wells with high upward crossflow. The procedure was successfully deployed in four wells at different occasions. The subject wells, located in brown fields, are tubingless water injectors identified with shallow casing leaks. The shallow leaks were located above an existing liner hanger. The casing leaks prompted upward crossflow of high magnitude in all four wells. The downhole dynamic upward crossflow took place between two formations at shut-in conditions. Water was flowing from a deep high pressure zone to a shallow low pressure zone through the casing leak in all wells. The crossflows were confirmed inside the wellbore and their flowrates were determined using electric line flowmeter measurement. Conventional methods such as surface bullheading, downhole dynamic kill, and mechanical plugs installation had previously been used, and proven costly and ineffective atsuch high rates. This new procedure repurposes several oilfield workover equipment items to achieve well control in cases of dynamic upward crossflow. The procedure deploys a drill string that comprises a modified liner tie-back stem, casing joints, liner top packer without slips, float sub with float valve, and all associated running equipment. This drill string is then stung into an existing liner tie-back area. This tie-back area was already existent in all four wells and is fundamental to implementing the proposed procedure. The modified liner tie-back stem (which is the bottom component of the drill string) forms a metal to metal contact with the existing tie-back area. Although the contact may not entirely form a pressure seal, it will decrease the crossflow rate entering the leak area. The liner top packer is then set without slips to allow for future retrieval after killing the well to cure the casing leak. After setting the liner top packer, a normal kill fluid bullheading is performed using the appropriate mud weight through the drill string to achieve the required well control. The field deployment of this new technique resulted in safe, successful, and cost-effective well control in all four case studies. In addition, costly remedial actions such as drilling relief wells and premature well plug and abandonment were avoided. The paper will describe in details the new procedure, equipment used, conveyance method, and related engineering calculations. |
