Challenges and Practical Aspects in Commingling Different Reservoirs: Theory and Case Study

Abstract

Abstract GS327 is a small field located 7 km east of southern Morgan field. It was discovered in May 1983 by well GS327-A1. An excellent sand quality was found in both Upper Rudeis ASL & KAREEM reservoirs (Lower Miocene). The field initial rate was about 6,000 BOPD, and after drilling 12 wells, the production hit 11,000 BOPD. After that production declined dramatically reaching 3,000 BOPD in 2011. Currently and after an extraordinary job, GUPCO succeeded to double the field rate by commingling the totally different isolated reservoirs (ASL & KAREEM) in the well EM327-1ST1 after intensive multidisciplinary study. This paper presents the methodology of that study and analysis done to commingle two different reservoirs safely highlighting challenges and uncertainties we had in both data and procedures. It shows how to estimate the new STOOIP and how to predict the new well/reservoir performance by using a combination of MBE, Well Modeling and DCA. The study covers three main sections of challenges; first one is Productivity of each reservoir in terms of Pressure and Fluid Mobility through different reservoirs to mitigate/evaluate cross-flow possibility, second section is Scaling Tendency issue since both reservoirs are expected to produce significant volume of water which may have different incompatible ions, third section is surface facility capacity to handle large amount of fluids expected to be produced from that multi-layer well. In this paper, you will find an integrated work processes at which different tools were combined; MDT's and Pressure Data interpretation, Geological and Petrophysical evaluation, Water compatibility analysis in Chemical Lab, use of different Models (Well, Reservoir & IPM basis), and finally verification of the result against actual data. Through this paper, you will know how to use every piece of data to answer uncertainty or overcome a challenge resulted in a doubled production.