Case Study: An Offshore Malaysian Production Well Requires a Unique Solution to Maximize Production Using Minimal Dynamic Underbalance (dub) for Clean-Up in Low Compressive Strength Sand-Producing Formation Via Tubing Conveyed Perforating (tcp)
Authors: Daly K. G. , Ibrahim A. A. 
Published: February 2025

This case study focuses on the successful application of Tubing Conveyed Perforating (TCP) in a challenging offshore well in Malaysia. The client aimed to enhance the connection between the wellbore and the reservoir, which is critical for production in cased wells. However, the well posed unique challenges due to the low compressive strength and the targeted sand-producing formation. These complications required innovative solutions in selecting specialized equipment and processes. Pre-job models were used to design an optimal bottom-hole assembly (BHA), and post-job data validated the accuracy of these models, demonstrating a successful outcome.

The well's conditions, precisely the low compressive strength of the formation, called for the use of TCP with very low Dynamic Underbalance (DUB) to avoid damaging the formation. Comprehensive pre-job planning ensured that each operational component, including the gun system and BHA, was optimized. Downhole gauges measured real-time conditions, helping to validate the accuracy of pre-job models and ensuring that the client's production objectives were met. The Perforating System Comparison (PSC) model identified the optimal gun system for maximizing production. In contrast, the Shock and Dynamic Underbalance (SDU) model determined the best BHA and DUB for ensuring effective cleaning of the perforations without causing formation collapse. Post-job data from fast gauges were compared to these models to confirm their accuracy.

Several key factors contributed to the operation's success. First, the pre-job modeling helped to select the largest possible TCP gun that could fit within the casing, maximizing perforation tunnels while considering the formation's compressive strength and other variables. Second, the TCP method allowed for a single firing of perforating guns along the target formation. This process relied on both Static Underbalance (SUB), which surge-cleaned the interval immediately upon firing, and Dynamic Underbalance (DUB), which further manipulated the well's surge effect to clean the perforations without collapsing the weak formation. Overuse of DUB in such formations could have led to tunnel collapse, so precise modeling was essential.

This case's novelty lay in using low DUB in a low-compressive strength sand-producing formation, a non-typical and innovative approach. Zinc-cased charges, known for extending the pressure pulse of the perforating event, were also used, despite not being typically associated with DUB applications. Zinc debris has been shown to plug certain formations. In this context, if the formation is not adequately cleaned using DUB, the zinc debris could lead to formation damage and reduced production, particularly in gravel pack applications.

This case illustrates the importance of meticulous planning, innovative equipment selection, and precise modeling to overcome the challenges posed by complex well conditions, ensuring successful completion and optimal production outcomes.