Sirikit Oil Field Interwell Tracer: Listen To Reservoir Rhythms

Abstract

Waterflooding has been successfully implemented throughout the S1 field with the mature areas including TRT_W and EFR_E blocks. Beyond waterflooding, the enhanced oil recovery (EOR) techniques had been evaluated and EOR screening together with detailed laboratory study confirmed that chemical EOR is the most suitable method to maintain field production. To carefully design an EOR pilot project, interwell tracer program was designed and executed to provide the critical information of injector-producer connectivity and sweep efficiency. Interwell tracer is a well-known technique to enable the tracking of flow paths along reservoirs. The successful tracer program was designed by Uzma Tracer and PTTEP personnel based on the integration of geological and production data. Field visit and kick-off meeting prior to tracer injection had been effectively conducted to ensure smooth operations. After tracer injection at five injectors in TRT_W and EFR_E blocks, the water samples from 18 producers have been collected as planned for 16 months. With contribution from operation team, the 100% of planned samples have been collected so that the insightful tracer analysis could be accomplished. The collected samples were systematically selected for chromatography test to measure the tracer concentration. The tracer analysis was conducted both qualitatively and quantitatively. For the qualitative method, the tracer breakthrough time could be obtained directly from analysis results. The early breakthrough time of 13 and 32 days was observed indicating the presence of high permeability path between producers and injectors in both areas. For the quantitative method, the calculation of tracer recovery and sweep volume by various analytical correlations was studied in the constructed automatic interpretation worksheet. The tracer recovery ranges from 1.1% to 47.3%, while the sweep volume ranges from 4,000 to 119,000 BBL. The low tracer recovery (1.1%) suggests that water injection from the injector has not flowed to nearby producers due to the presence of several small faults blocking the flow path. Overall, sweep volume appears to be less than the static volume, which signifies large unswept area. Therefore, the additional injectors and pattern re-orientation were proposed to improve waterflood efficiency. In addition, the interpretation has been incorporated in the simulation model to enhance the pilot EOR injection strategy. The successful tracer project requires multi-disciplinary collaboration from the project design, field execution, sample collection, to data interpretation. This technology benefits not only mature but also newly implemented waterflood areas and allows us to listen to our complicated reservoirs.

AAPG Datapages/Search and Discovery Article #90331©2018 AAPG Asia Pacific Region GTW, Back to the Future – The Past and Future of Oil and Gas Production in the Asia Pacific Region, Bangkok, Thailand, September 26-27, 2018