ベトナム・ランドン油田の砂岩貯留層における随伴ガス攻法の掃攻率改善に対する取り組み

抄録

Immiscible hydrocarbon gas enhanced oil recovery（HCG-EOR）in full-field scale has been operated in Lower Miocene sandstone reservoir in Rang Dong Field offshore Vietnam since 2014. The EOR has been implemented in tertiary water-alternating-gas（WAG）scheme and certain incremental oil was observed; however, reduction of sweep efficiency and operation problems due to severe gas breakthrough were encountered in several wells due to difficulty of conformance control in heterogeneous layers. To address the issues, optimal field operation and new reservoir characterization methods were applied. In term of field operation, WAG ratio was increased and gas oil ratio was successfully reduced while maintaining oil production rate. To reproduce the actual gas breakthrough behavior and find more optimal WAG ratio by dynamic simulation approach, firstly inter-well connectivity in a certain area was investigated using capacitance resistance models（CRMs）. Being supported by the available tracer monitoring data, the result suggested strong one-to-one well connectivity and improved the predictability of reservoir simulation based on updated geological concepts. Then, with the updated model, opportunity of conformance control and WAG efficiency improvement was studied including the extension to a simulation scoping work of foam-assisted WAG application. In this paper, the efforts to tackle the issue of HCG-EOR in the mature oil field are comprehensively introduced.