Two Decades of Mangala Field Journey - Key Highlights, Learnings and Recommendations

Abstract

AbstractThe Mangala field in India was the first major oil discovery in the Barmer Basin having a STOIIP of nearly 1.3 billion barrels in multiple stacked fluvial reservoirs. It contains medium gravity (20-28 °API), waxy, viscous crude (9-17 cP) in high permeability (1-25 Darcy) clean sandstone reservoirs.The field was discovered in 2004 and brought online in 2009, one of the fastest from discovery to production phase. Hot water injection was started within few months of first production to sweep and maintain pressure. The hot water was essential considering wax appearance temperature (59 degC) close to reservoir temperature (65 degC). The hot water is also used as power fluid for jet pump (main lift system in field) and for annulus circulation in case of shutdown to avoid oil congealing. Jet pump application is the largest in the world with ~160 active wells lifting ~400,000 blpd reservoir liquid with ~500,000 bbls of power fluid.Plateau production of 125k bopd was achieved within 14 months from production start, which is one of the fastest among large onshore fields. The initial average oil rates in wells were ~2000-15000 bopd. Given the high well productivity, the field plateau rate was revised to 150k bopd within a year of achieving 125kbopd.Due to adverse mobility ratio with water, EOR screening and lab study was started right after discovery. Chemical EOR was identified as the most suited with polymer in the first phase followed by surfactant-based flood. Considering the EOR importance, a 5-spot polymer pilot was started almost simultaneously with the start of the field production. Basis pilot results, full-filed polymer flood was started from 2015 which is again one of the fastest EOR implementations. The polymer flood is one of the largest in world with 165 tons/day polymer consumption through ~500000 bwpd of polymerized water injection. Polymer flood reversed the production decline and is expected to give ~8% incremental recovery of STOIIP (~100 MMbbls) by 2030. Following polymer, a successful ASP pilot was conducted in the same wells/pattern which resulted in 20-25% incremental recovery of pilot STOIIP over polymer flood. Planning for large scale ASP implementation is underway.There have been several challenges and important learnings along the way including vertical conformance, areal VRR management, polymer development, degradation, viscosity and quality control over time, jet pump and ESP operations etc.Mangala field recovery has been quite fast with ~37% recovery within 13 years field life. Multiple infill campaigns have been conducted with ~280 wells drilled over 165 base development wells.The paper presents the development journey of Mangala from discovery to date with key achievements, many firsts, learnings and recommendations based on waterflood and polymer flood performance for other similar fields.