Multi-lateral Wells With Cemented Junctions

Abstract Multi-lateral drilling and completion technology is advancing rapidly in the petroleum industry. It is currently being applied or considered for applications in most operating areas of the world. This paper covers the procedures involved in drilling, casing and completing a multi-lateral well featuring the first commercially cemented lateral in North America. The drilling system utilized. Sperry-Sun's LTBS ™ (Lateral Tie-Back System) is described in detail as it pertains to this well. The procedures employed to drill a main bore lateral, lined with 5 ½ " wire wrapped screens, and a 6 ½ " lateral lined with 4 ½ " wire wrapped screens are presented. Procedures are also outlined for the re-entry of the lateral and subsequent inflation of an external casing packer and cementing of the lateral junction. Problems which occurred during the various operations are presented along with their solutions. This part of the discussion demonstrates how a systematic analysis of operational difficulties results in sound solutions, thereby allowing the technology to be enhanced for future applications. Introduction The application of multi-lateral technology was identified by Mobil Canada as an economic means of increasing reservoir exposure, and hence improving the productivity of the well bore. The objective being to place a horizontal lateral in each of two separate producing zones (the Upper and Lower Roseray Sands) with production being co-mingled. The well in question is situated in the Battrum field in Saskatchewan (Figure 1). The multi-lateral system selected for this application was the 9 5/8 "Lateral Tie-Back System ™ (LTBS ™) supplied by Sperry-Sun Drilling Services of Canada. This system features the ability to drill any number of laterals (in any desired sequence) from a primary cased well-bore, and to line and tie-back the laterals to that primary casing. In order to provide enhanced lateral junction integrity for this application (and to prove the viability of the technique for future applications) a contingency plan was instigated to cement a short section of the lateral liner back to the main bore casing utilizing a stage cementing method in conjunction with an external casing packer. BACKGROUND Prior to this application several multi-lateral wells had been drilled which feature cemented lateral liners. However, these involve the use of wash over technology, whereby the liner is cemented in place (predominantly using stage cementing techniques to cement the upper curve section of the lateral), and then the protruding part of the liner is removed by washing over, leaving the liner flush with the i.d. of the primary casing at the lateral junction. The application at Battrum was to be the first utilization of stage cementing techniques with a system featuring a mechanically tied back lateral liner. SYSTEM DESCRIPTION The multi-lateral drilling system selected for this application was the 9 5/8 "LTBS. This system consists of six main components:pre-milled casing window jointdrilling whipstocklateral liner hanger assemblylateral liner running toolcementing whipstockre-entry whipstock Casing Window Joint The window joint is fabricated from a standard joint of 79.6 kg/m 9 5/8 "L-80 casing (Figure 2).