Time-Lapse Simultaneous AVO Inversion of the Widuri Field, Offshore Southeast Sumatra

Reservoir characterization in Windri field is complicated by complex lithology and difficulties in predicting changes in fluid distribution. 33-4 Sand body is interpreted as complex compartmentalized channel and part of water flood project associated with distributary channels, mouth bars and delta front shoals. Seismic amplitude mapping at the Base Upper Gita horizon reveals a system of meandering channels. In 2000 and 2004, 4D seismic data set was acquired and processed to take advantage of seismic AVO effects. The base line 1991 seismic data set was reprocessed in parallel. The primary reason for the monitor data set was to observe the reservoir pressure depletion state around a water-flooding project. Detection of 33-4 sandstone reservoir is feasible based on interpretation of AVO P, G, P*G, P(30°) attributes. Fluid replacement model created into three scenarios (oil, water, gas) to predict the hydrocarbon saturation. Integrated time lapse 4D seismic by using map differences in seismic response has been conducted for monitoring pressure decrease and subsequent water flooding sweep patterns. Windri area divided into 6 sweep patterns area to make improved connectivity analysis.AVO attributes using intercept (P), gradient (G), P*G, and P(30°) has been done to determine of 33-4 sand. Feasibility study on AVO analysis has been applied by using fluid replacement model on the well data. A more advanced interpretation of the expanded AVO analysis for 33-4 sand has been done by using simultaneous inversion and 4D time lapse seismic. Practically, this method is used to map differences in seismic response over time attributable to production related processes, especially amplitude response which directly interpreted as replacement of oil by dissolved gas, and also suggest re-pressurizing the reservoir. Reservoir characterization using 4D simultaneous inversion enhances interpretative resolution and reduces uncertainty sand and fluid prediction. Integrated analysis of time lapse 4D seismic has been well implemented for increasing infill and injector success ratio, as well as predominating pressure degradation in Windri field. This comprehensive study is essential for understanding of complex lithology, monitoring pressure decrease and subsequent water flooding sweep patterns in 33-4 sandstones reservoir. Knowing the concept of depositional setting, facies and reservoir behavior to be applied in the waterflood project is crucial to optimize the production.

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Integrated Waterflood Connectivity Analysis in Compartmentalised Reservoir of Windri Area, Asri Basin, Indonesia

Widiatmo¹,

Gunawan²,

Afi³

et al. 2017

SPE/IATMI Asia Pacific Oil &Amp; Gas Conference and Exhibition

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This paper describes an efficient approach to evaluate waterflood connectivity performance in complex compartmentalized reservoir, the objectives are to increase the oil production performance and manage mature fields effectively, and also to enhance ultimate recovery in the long run. It is also very useful to get better understanding of detail reservoir characterization, reservoir internal architecture, reservoir distribution, pressure monitoring and subsequent water flood sweep pattern efficiency. Multi-disciplinary methods applied to maximizing all of data and create strong analysis. The first phase is deep sub-surface analysis in property distribution, simultaneous inversion, 4D time lapse seismic and sweep pattern analysis, those analysis have been done to get comprehensive interpretation of reservoir characterization and waterflood monitoring. The second phase is tracer injection, we implement tracer in several wells to ensure connectivity from injector to several producers are efficient and optimal. These methods were performed for several regions of this area which contains a large number of well, nearly 200 wells consist of vertical, deviated and horizontal wells. Reservoir distribution in Windri area interpreted as stacking channel with high sinuosity geometry. This reservoir consists of predominantly of marginal marine claystone interbedded with deltaic sandstones, thin limestone and coal. Bio-stratigraphic analysis from cores shows that the reservoir was deposited in estuarine setting, interrupted by a brief shallow marine incursion. Seismic amplitude mapping at the upper base Gita horizon reveals a system of meandering channels. Compartmentalised reservoir in Windri area divided into 5 sweep pattern to make analysis more detail and accurate. Each of compartment have different characteristic, this is the challenging part in Windri area. East of windri area channel divided into 4 channels and it shows the evolution and movement of the channel that can control the property distribution and reservoir connectivity. Group two shows good result from tracer injection and it is supporting the interpretation of reservoir distribution and characterization within the area. Integrated 4D time lapse seismic generate pressure monitoring movement from each of waterflood phase. The results of this integrated study implementation are excellent, the ineffective water injection pattern now become effective, there is no unavailing injection well, every pattern is connected and link to each other, so that we can achieve our goal to enhanced recovery factor from 16% to 20%. Reservoir characterization using multi-discipline method reduce uncertainty of heteroginity sand and fluid prediction. Integrated waterflood analysis has been implemented for prospect generation, production optimization and overcome pressure degredation in this area.

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Time-Lapse Simultaneous AVO Inversion of the Widuri Field, Offshore Southeast Sumatra

Cited by 5 publications

References 8 publications

Seismic Reservoir Monitoring

Seismic Reservoir Monitoring

Waterflood Sweep Pattern Monitoring Using 4D Seismic in Windri Area, Asri Basin, Southeast Sumatra, Indonesia

Integrated Waterflood Connectivity Analysis in Compartmentalised Reservoir of Windri Area, Asri Basin, Indonesia

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