Technology Update: System Cuts P&A Cost by Creating Rock-to-Rock Barrier in One Trip

Abstract

Technology Update Traditional well plugging and abandonment (P&A) methods are not efficient. For example, section milling is time-consuming and expensive because of the number of rig days required. The milling produces cuttings, which have to be handled. Contamination of the milling fluid with oil-based mud (OBM) requires separation before disposal. Cutting casing requires pulling it from the hole. Handling tubulars has numerous inherent risks, and removing old tubulars, especially, could bring up naturally occurring radioactive material from the subsurface. Decommissioning a well must always achieve permanent integrity, and central to this is the successful placement of a rock-to-rock cement barrier. Creating such a barrier, without section-milling or retrieving and pulling the casing, offers a major cost advantage over traditional methods. Developed by Archer, the Strong-hold Barricade system (Fig. 1) leaves the casing in situ. The system perforates, washes, and cements the annulus, creating a rock-to-rock barrier in one trip (Fig. 2). In addition, the system reduces personnel risk, in part by reducing the number of individuals required. For example, not having to pull casing eliminates the casing crew and tong operations. The system only requires a single tool operator and the cementer, who would normally be present on the rig to pump the cement. Specialized Technologies Two features are central to this system. First are the firing heads. Most conventional firing heads are operated by annular pressure. For this system, the company developed a firing head that is operated by tubing pressure. A contingency system with multiple sets of guns can also be used. If the first set of guns fails to create the required injection ports, the second set can be fired by annular pressure without pulling out of the hole. The second feature is the creation of a cement base to contain the cement plug above. The cement base is effectively an integrated bridge plug. Situated immediately above an auto-gun release, the cement base is activated after the guns are released and the tool is run to below the perforated interval to provide a secure base for the cementing operation. The cement base is set by pressuring up on a dropped ball. A pull test and further pressure then releases the base from the string. The dropped ball is retained in the base, leaving the pipe with no restriction.