Alkali-Surfactant-Polymer Pilot Implementation in South Oman: Establishing Waterflood Baseline

Abstract

Abstract A field in Southern Oman has been identified as a potential target for Alkali-Surfactant-Polymer (ASP) flooding. Experimental investigations showed that ASP flood recovers more than 90% of waterflood remaining oil saturation. Simulation study showed that ASP increases the field recovery factor by more than 20% over waterflood or 12% over polymer flood. The potential size of the prize by ASP in this field alone is significant. The successful ASP single well chemical tracer test (SWCCT) and micro-pilot in this field validated the lab experimental results and demonstrated the significant desaturation by ASP and the extremely low oil residual after ASP. The ASP pilot was designed and initiated to de-risk and underpin the financial investment decision for a full-field implementation. The ASP pilot is designed as a small 1.4 acres (75m × 75m) inverted 5-spot pattern. It ensures completion of the field trial within one year of ASP flood. The pilot was commissioned in Q1 2014 with water pre-flush and the first ASP injection is anticipated for Q1 2016. A dynamic model was constructed and simulation was carried out. A comprehensive surveillance program was included in the pilot design and is being executed successfully. Surveillance data provide critical information to understand pattern communication, fluid flow path and reservoir characteristics. This paper will describe the results and analysis of some waterflood surveillance data and the integrated workflow of history matching. During the ASP pilot drilling campaign in 2013, an unexpected fault was encountered crossing the well pattern. This introduced an element of uncertainty regarding pattern communication. Pressure data and a passive tracer test confirmed the connectivity between the injector to 4 producers and that the fault is non-sealing. Initially the sector model was built with one fault across the pilot area, but the fluid communication in the pattern revealed by analysis of tracer suggested possible different geological realizations than the initial model. Therefore several static geological models were generated to reduce the uncertainties on history match. Well conformances were determined by PLT and DTS/DAS and were incorporated in the dynamic model. The time-lapse NMR log in the observation well provides insights on sweep, desaturation and micro displacement efficiency. Establishing and building a waterflood baseline is the foundation for the next phase of ASP implementation. This paper will share the analysis, learnings and practical implications of the pilot to date.