Reperforation of North Sea Electric Submersible Pump Wells Using AN ESP/Y-Tool/TCP System

Abstract

Abstract As a result of the increasing emphasis on reducing operating costs and minimizing deferred production, a new system was designed for the reperforation of wells lifted with Electric Submersible Pumps (ESP's). This paper describes an alternative method that can be used when a Tubing Conveyed Perforating (TCP) system is required for the underbalanced reperforation of an ESP well. The method employs a combined ESP/Y-tool/TCP assembly and can save approximately 24 hours in rig time over conventional methods. Use of the method can avoid substantial deferred or lost production, particularly when other wells requiring workovers are awaiting use of a rig at considerable cost. The system can also be used for the completion of new wells where an ESP is required from the outset. Introduction The Montrose Field is located in the North Sea, 130 miles (209 km) east of Aberdeen, Scotland (See Fig. 1). The field lies in blocks 22/17 and 22/18 and is operated by Amoco (U.K.) Exploration on behalf of Amoco, Enterprise Oil, Amerada Hess Ltd and Texas Eastern North Sea, Inc. Production is from a Paleocene sandstone with the reservoir located in a large anticline of low relief (Fig. 2). There are two distinct lobes of the field with slightly different fluid characteristics. There are currently 15 producing wells and 5 water injectors. One permanently installed rig handles all drilling and workover activities. Electric submersible pumps lift approximately 75% of the production from the field. Due to the number of workovers which ESP wells invariably suffer, the potential for formation damage is relatively high. A review of individual well performance during 1986 indicated significant skin damage in the majority of Montrose wells and a reperforation programme was undertaken to improve well productivity. Reperforation experience in the Montrose field clearly showed that tubing conveyed perforating (TCP) systems yielded the best results. The performance of TCP charges was necessary to achieve a depth of penetration beyond the near wellbore damage with underbalance conditions essential in preventing the plugging of the perforations with crushed material. An underbalance pressure of 1000 psi was targeted for each reperforation, which is consistent with data compiled by King, Anderson, and Bingham (Ref. l) for the perforation of oil zones in sandstone using tubing-conveyed systems (Fig.3).