Underbalance Perforation in Long Horizontal Wells in the Andrew Field

Abstract

Summary Andrew field in the U.K. Continental Shelf, which is operated by British Petroleum (BP) Exploration, is being developed using horizontal oil producers and completed with cemented liners. The main challenges of perforating these wells are maximizing well productivity by avoiding formation damage, minimizing the possibility of sanding, maximizing ultimate hydrocarbon recovery, perforating long horizontal sections safely and efficiently, optimizing the economic value of perforating, and minimizing perforating debris. In general, to avoid impairing well productivity, it is best to perforate the underbalance. However, the advantage is compromised, because of the fluid invasion and loss-control material, if a well will be killed when the tubing-conveyed perforating (TCP) guns are removed. Existing deployment methods with coiled tubing (CT) enable perforation and subsequent gun removal in an underbalance condition. Unfortunately, various limitations would require multiple runs with CT for perforating each horizontal well in the Andrew field, which would result in significant time and on balance perforation for each subsequent run. The combination of the newly developed mechanical ball valve and the deployment of TCP guns with hydraulic workover units enables long horizontal wells to be perforated in one run in underbalance, and enables the guns to be removed without killing the well. Specially engineered guns and perforating charges are used to minimize sanding and gun debris. This paper describes how these new technologies, used for perforating operations, meet many challenges. The same technologies can be used readily for perforating other long horizontal wells with similar problems. To date, three horizontal wells in Andrew field were perforated successfully with the method described in this paper. The initial results indicate that the combination of the cemented liner completion, the engineered perforation systems, and the correct TCP gun deployment method using the mechanical deployment valve have contributed to improve well performance, to reduce cost, and to improve operability and safety in long horizontal wells.

A Successful Completion/Perforation by Use of a Downhole Lubricator Valve: A Case Study from the Siri Field, Danish Sector, North Sea

“…The idea of a downhole lubricator valve was not entirely new in itself, a version having previously been run on Andrew Field, as a result of plans to perforate long intervals without killing the well 1 .…”

Productivity of Selectively Perforated Horizontal Wells

“…Selective perforating has been implemented in horizontal wells drilled in many fields such as Andrew (Kusaka 1998), Oseberg (Sognesand et al 1994), Statfjord (Kostøl and Østvang 1995), Elk Hills (Gangle 1995), and others (Benavides et al 2003;Stenhaug et al 2003;Sulbaran et al 1999;Eriksen et al 2001;Tronvoll et al 2004;Hillestad et al 2004).…”

“…The theory, field applications, equipment, and operational procedures for oriented perforating are all described in Kusaka et al (1998), Benavides et al (2003), Stenhaug et al (2003), Sulbaran et al (1999), Eriksen et al (2001), Tronvoll et al (2004), and Hillestad et al (2004). Oriented perforating has been successfully implemented in an unidentified field in the North Sea (Benavides et al 2003), the Visumd field (Stenhaug et al 2003), Eocene C reservoir in Lake Maracaibo (Sulbaran et al 1999), the Varg field (Eriksen et al 2001;Tronvol et al 2004), and the Norne field (Hillestad et al 2004).…”

Inflow Performance Relationship for Perforated Horizontal Wells

“…However, in some fields, horizontal wells may need to be cased and perforated. Selective perforating has been implemented in the horizontal wells drilled in many fields such as Bongkot, 1 Joanne, 2 Andrew, 3 Oseberg, 4,5 Wytch Farm, 6 Statfjord, 7 Elk Hills, 8 Beryl, 9 Dan, 10 Alba, 11 Yowlumne, 12 and Prudhoe Bay. 13 King 14 pointed out the significance of gun clearance and positioning in perforating and gravel packing the horizontal wells.…”