Worldwide, seventy-five percent of the increased oil reserves comes from existing oil fields. It is important to understand the residual hydrocarbon saturation distributions and how to develop the old oilfields efficiently and economically. This paper presents a method of using MRIL data to evaluate the residual oil distribution of the old oilfields and reservoir preponderant channels formed by injection flange entry after injection recovery, i.e. ? high-capacity channel?. This method is significant to understand residual oil saturation at the stage of high water-cut, control the low efficient and inefficient circulation of the injected water, and reduce the recovery cost. After water injection recovery, the existence of reservoir preponderant channels, i.e. ? high porosity channel?, which are formed due to the very big change in formation pore structure and clay distribution in the pores, seriously affects the recovery efficiency of mature oilfields. The common approach of describing reservoir pore structure by the correlations between mercury penetration distribution and NMR T2 spectrum obtained from laboratory NMR studies is only suitable fluid saturation cases, which the actual reservoir situation of multiphase fluid saturation. We found that by comparison of fast relaxing components with respect to all relaxation components, NMR logs can be useful for characterizing reservoir heterogeneity, reservoir pore structure and for identifying high porosity channels. The case studies in the old oilfields verified the significance of this method in controlling low efficient and inefficient circulation of the injected water situations and in reducing the recovery cost. Unlike resistivity based saturation analysis, NMR based saturation estimates are independent of formation water salinity and reservoir pore structure. It was found that conventional logging data interpretation for water flooded layer identification was problematic; this paper presents a method of using MRIL data to qualitatively identify water flooded layers. Laboratory core NMR analysis and MRIL logging responses are quite different due to different fluid phase saturations and different experimental parameters (such as gradient and TE. To consolidate the difference, we developed a spectrum shift method so that the T2 spectra from core measurements and logs are comparable. We applied this method to identify water-flooded layers and obtain oil saturations in many oil blocks in Daqing Oil Field. The results satisfactorily demonstrated the effectiveness of this method.
The Distribution Study Of Reservoir High-Capacity Channel And Residual Oil Saturation By Using Mril Data
Yan, Wang, Guolixin, _, Wanghongjian, _, and _ Liqingfeng. "The Distribution Study Of Reservoir High-Capacity Channel And Residual Oil Saturation By Using Mril Data." Paper presented at the SPWLA 46th Annual Logging Symposium, New Orleans, Louisiana, June 2005.
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