Study Of The Effective Reservoir Control Factors In The 8^th Member Of Shihezi Formation In The Southeast Of Sulige Gas Field

With the increasing demand of oil and gas rapid development, low porosity and permeability reservoirs have becoming the key area and new growth point of oil exploration and development. The low porosity and permeability reservoirs have various types and complicated structure, of which theirs' genetic types are also different in different field. The genetic types are classified into three types:sedimentary type, diagenetic type and tectonic type. The various types and complicated structure of low porosity and permeability reservoirs seriously restrict the recognition and tracking of the effective reservoirs, as well as the oil-gas exploration and development.Southeast Sulige area lies in the north central part of Ordos Basin, where the gas field is typical low porosity, low pressure and low abundance with large-area distribution. Upper palaeozoic in the 8^th Member of shihezi Formation is the main gas bearing interval, of which the effective reservoirs control factor analysis is the essential point and problem. This thesis focuses on the study of effective reservoir control factor in the 8^th Member of shihezi Formation in southeast Sulige gas field. To clear the genetic types and physical property low limit, evaluate the effectiveness and describe the distribution feature of effective reservoir, the thesis does comprehensive relationship research between sedimentary system, sedimentary microfacies, reservoir geological characteristics and reservoir. The conclusions and recognition are as following:?1? The provenance of western in the 8^th Member of shihezi Formation area mainly comes from middle YinShan Paleo-land, where the quartz content in mother rock is high,the sandstone are mainly lithic quartz sandstone and sand stone,the ingredients is with high maturity and the reservoir physical property is good. While the provenance of eastern area comes from eastern Yinshan Paleo-land, the quartz content in mother rock relatively low,the sandstone mainly lithic quartz sandstone, the ingredient maturity and physical property is relatively poor.?2? The analysis of the rock types and combination and sedimentary structure data reaches the conclusion that the 8^th Member of shihezi Formation belongs to braided stream delta plain sediment. Sedimentary microfacies are mainly channel bar, distributary channel and flood plain. The sand body superimposed relationship is classified into three types: river-type, scour truncation and isolated type. The effective reservoir mainly distributes on channel bar and distributary channel. On channel bar sediment, the sand body and effective reservoir are with great thickness and distributes continuously; while on distributary channel, the effective reservoir is in the bottom of river, and the thickness and continuity is poor.?3? The reservoir, with various types, experiences strong diagenesis, enters into middle diagenesis phase B now. The physical property is generally poor. The porosity type and structure is complex and changeable. It indicates that compaction and cementation, which have bad effects for reservoir, are the main reasons for low porosity and low permeability reservoir densification. While, the effects of corrosion has good influence on improving reservoir physical property, it is the key for the formation of effective reservoir.?4? The empirical approach, mercury intrusion method and logging parameter cross-plot method jointly determined the low limit of effective reservoir:porosity=5%, permeability =0.1�10^-3?m².