TUNU is a gas condensate field situated in the swamp environment at the edge of the Mahakam Delta, East Kalimantan – Indonesia. Hydrocarbons are accumulated in multi-layer reservoirs deposited within a deltaic environment. The field can be divided into two intervals which are Tunu Shallow Zone (TSZ) (between 600 and 2,200 mSS – typically unconsolidated and strong aquifer support) and Tunu Main Zone (TMZ) (between 2,200 and 5,000 mSS).
Since the field start up in 1990, it has delivered 9 Tcf of gas production. At the beginning, the field's first development was focusing on TMZproduction, where the gas reservoir at TSZ was only considered as hazard for drilling. Through time, TMZ is more and more depleted; hence development of TSZ is the new focus.
TSZ dedicated development started in 2007 by drilling two horizontal wells, each targeting individual channel followed by drilling of four deviated twin wells. Given the excellent result, new campaign of TSZ development was kicked off. Since then, more than 185 TSZ wells have been drilled contributing to 40% of around 700 MMScfd of total field production. This is resulted from improvement on selection of new wells target, cost effective well architecture and efficient reservoir management.
The first seismic survey targeting TSZ was performed in 2009 and since then TSZ development relied on detailed interpretation of seismic anomalies. Performing detailed interpretation is a major challenge on designing economical wells. This difficulty has been accentuated by recent downturn of gas price; hence having full field geobody inventory is becoming crucial. A geomodel was therefore built to have an exhaustive view of TSZ resources.
Optimization in selecting well architecture is also deemed necessary. Tubing-less completion with Chemical Sand consolidation (SCON) was assessed and shown that it can give more cost effective completion compare to gravel pack completion. Drilling cost could be reduced up to 30 % by using tubing-less completion with SCON.
Production optimization can be achieved by carefully implement the efficient reservoir management technique, e.g. maximize the number of completed reservoir zones without risk to safety and production, selection of best reservoir zone for first production, and implementation of flowline debottlenecking to accommodate hepta-mingle wells.