Abstract:

The microcosmic characteristics of the Siegenian Formation reservoir in X block are analyzed by studying the effect of lithology, diagenesis, pore types and clay minerals on pore structure based on cores, welllogs, and formation test data including the rock thin sections and cast thin sections, the observation of scanning electron microscopy, pressuredmercury testing and X-ray diffraction analysis of clay minerals. Reservoir lithology is mainly quartz fine sandstone with high compositional maturity. Six pore types including primary intergranular pores, intragranular dissolved pores, intergranular dissolved pores, moldic pores, cement dissolved pores and microfractures, are identified in the Siegenian Formation reservoir. The quartz intergranular dissolved pores and the quartz overgrowth cement dissolved pores are found for the first time in this area. The secondary dissolution pore is the main pore type in X block. Pore structure is mainly micropore with thin to microthroat association, beside a few medium pores with thin throat and micropores with microthroat. The diagenesis types are various. Compaction and cementation is the main reasons for the pores and pore throats decreasing. In the opposite, dissolution is important in improving the quality of reservoir. This study of the reservoir will guide the future exploration of this area.

Key words: Algeria, Devonian, Siegenian Formation, pore type, pore structure, diagenesis