Classified Evaluation of Sand-Conglomerate Reservoir of the Upper Section of the Fourth Member of Shahejie Formation in Yanjia Area, Dongying Depression

Key words: 
• sand-conglomerate /
• reservoir classification /
• reservoir characteristics /
• reservoir evaluation

Abstract: Based on the core observation, thin-section identification, physical property test and other technical methods, with porosity, reservoir space characteristics, diagenesis characteristics, reservoir pore throat size distribution characteristics and lubricity characteristics for comprehensive classification basis, the sand-conglomerate reservoir in the near-shore subaqueous fan of the fourth member of Shahejie Formation (Es₄) in Yanjia area Dongying depression have been divided into three categories and seven small classes. Ⅰ-1 type reservoir is characterized by medium-weak compaction and weak cementation, with primary pores relative development; Ⅰ-2 type reservoir is characterized by medium compaction and strong dissolution, feldspar and debris dissolution pores and intragranular pores are relatively growing; Ⅰ-3 type reservoir is characterized by medium cementation and strong dissolution, with dissolved pores of carbonate and feldspar relative development; Ⅱ-1 type is characterized by medium-strong compaction and medium dissolution, feldspar and lithic dissolved pores are relatively developing; Ⅱ-2 type is characterized by medium-strong cementation and medium dissolution, with carbonate and feldspar dissolved pores relative development; pores do not develop in Ⅲ type reservoir, Ⅲ-1 type reservoir is characterized by strong compaction and Ⅲ-2 type reservoir is characterized by strong cementation. FromⅠ-1 type reservoir to Ⅲ-2 type reservoir, porosity reduces, pore throat structure becomes worse, the fluorescence intensity becomes low, and oil and gas shows in core become weaker. Combined testing and production test data, reservoir combinations in different sedimentary subfacies have been evaluated. The results show that reservoir combination type in different sedimentary facies and its productivity have big differences. Reservoir combination in the middle fan is relatively superior and single-layer thickness of reservoir combination is various, corresponding to the medium-high daily liquid production per unit thickness. Reservoir combination in root fan comes the second and have a larger single-layer, corresponding to the relative lower daily liquid production per unit thickness. Reservoir combination in fan edge is the worst and single-layer thickness of reservoir combination is very thin, corresponding to the lower daily liquid production per unit thickness.