RIASSUNTO
Abstract
The Piceance Creek field is a high pressure gas field located in the northwest corner of Colorado and production is from multiple zones at depths in the order of 12,000ft. Standard well construction in the field takes the form of monobore completions with several sets of perforations producing commingled. Typical exploitation techniques involve the perforating, fracturing and cleanup of the lowest zone followed by each successive zone being completed in the same manner by running a composite bridge plug and perforating guns on the same run in the well using electric line methods. In a recent well completion procedure the same techniques were used however, on one of the later runs, the composite bridge plug preset at a depth of 75ft while going in the hole resulting in a fish at surface straddling the lower part of the tree with the perforating guns still attached to the bridge plug and with high pressure at the wellhead. The only alternative available was to pull out of the e-line rope socket and attempt to fish the guns. Subsequent attempts to fish the guns with wireline techniques designed to shear out the plug setting tool resulted in two additional fish being left in the hole with the upper end straddling the tree and the swab valve. This presented a unique set of circumstances which required extremely careful handling in order to prevent a major well control problem.
In this paper the author will describe the subsequent operations which were performed to remedy the situation and bring the well back to a productive condition and all the challenges associated with it. This included freezing the wellhead to allow removal of the wireline lubricator and the upper part of the wireline fish followed by the installation of additional upper master/swab valves and a fishing operation using coiled tubing. Finally the plug was milled and full access to the well achieved, all without any HSE incident.
Introduction
The Piceance Creek field is a high pressure gas field located in Rio Blanco county in the north west of Colorado in the vicinity of Rangely at an elevation of approximately 6300ft. (see Fig. 1). This large area field is being developed by several operating groups using similar well completion techniques whereby a monobore casing string is set through the producing zones and each is in turn perforated, fractured and cleaned up in turn starting with the lowermost zone. Subsequent zones are then completed in similar fashion by running a composite bridge plug together with perforating guns on the same electric line run in the well. This enables the plug to be set and released using a standard wireline pressure setting assembly and the zone is then perforated on the same run in the well thus eliminating one run - the savings thus achieved can be considerable since the wells are typically completed in as many as eight separate zones. The zone is then fractured, cleaned up and subsequently isolated below the bridge plug when the next zone is similarly treated. In this same way the other zones are treated moving up hole and when all have been finished the bridge plugs are drilled up in one trip and the well completion finalized (see Fig. 2 for typical well schematic).