Horizontal Lateral Drilling and Completion with Openhole Gravel Pack through a Unique TAML Level-4 Multilateral Junction System: The Installation Case Study from South China Sea
Authors: Zhang Wei Guo , Rao Zhi Hua , Lei Hong , He Yue , Zhang Leimin , Huo Ying , Revheim Kjell , Shafiq Umer , Zhao Geng , Yu Hua Jing , Cao Peng , Zhang Dong , Bian Jin Wei 
Published: February 2023

A Technology Advancement of Multi-Laterals (TAML) level-4 completion was installed in the South China Sea in 2022. The unique design of this multilateral completion system increased efficiency and reliability in drilling and completing the well and enabled selective production from the main bore, the laterals, or both. It also incorporated a safe way of combining an openhole gravel pack job with a multilateral application.

The main bore was completed with 9.625-in. casing. An 8.5-in. sidetrack was drilled and completed by the TAML level-4 junction and 7-in. liner was cemented in place. The key components of this multilateral completion system are an anchor packer system to temporarily isolate the main bore; a sidetrack whipstock and milling system to drill through 9.625-in. casing for 8.5-in. lateral bore; a robust 9.625 in. × 7 in. TAML level-4 junction system that combines a main bore production tieback assembly, main bore junction assembly, lateral bore junction assembly, and a junction drilling diverter isolation system. A 6-in. horizontal lateral bore was drilled through junction. An anti-swab openhole gravel pack system was installed in the 6-in. horizontal section to prevent sand production. For selective production from target zones in each lateral, a 3.5-in. intermediate string was installed. A specially designed multilateral well shrouded shearable tieback seal assembly was run back into the lateral bore. A standard sliding sleeve (SSD) and landing nipple were installed above the tieback assembly. Comingled production is achieved by leaving the SSD open, and selective production is achieved from the lateral bore by closing the SSD. Selective production from the main bore is achieved by leaving the SSD open and setting an intervention plug into the landing nipple. The upper production string was completed with an electrical submersible pump system.

In early 2022, the full system was successfully installed for the first time in the region with zero health, safety, or environmental incidents and zero non-productive time. The lateral bore 7-in. liner and TAML level-4 multilateral junction were installed in a single trip, and the 7-in. liner cementing operation and excess cement cleanout were completed efficiently in that same trip. The 6-in. slim-hole drilling tool and openhole gravel pack sand control system both passed the multilateral junction with no hang up issues. The intermediate tieback string was successfully run back into lateral bore. The successful installation of entire well completion verified the high reliability and efficiency of this robust 9.625-in. ×7-in. multilateral well completion system.

A traditional multilateral junction only hangs one 7-in. liner inside the 9.625-in. main bore casing. In contrast, this robust new TAML level-4 junction system enables designing the main bore junction assembly and the lateral bore junction assembly separately; the two assemblies can be installed in the same single trip together with cementing operation. The openhole gravel pack operation was then performed in a conventional way through the 7in cemented lateral liner. This drastically reduced the overall operational risk, by separating the operational risk of installing the multilateral junction and the open hole gravel pack job. This newly designed junction system and separate gravel pack operation were key enablers to complete this well smoothly and safely.