Analysis on the controlling factors of reservoir property in Dongying formation of structure A2-1 in Bozhong Sag

On the basis of thin section analysis, electron microprobe scanning, physical properties and logging data, this paper studies on controlling factors of reservoir in Paleogene Dongying formation of structure A2-1 in Bozhong Sag and discusses the reasons for dif-ferent productions between the test sections. Through the analysis concerned, sandstone reservoir properties of Dongying formation in Bozhong Sag are mainly controlled by compaction, depositional environment, carbonate cementation, dissolution and clay transformation stage. In the minus-cement point diagram, most of the points are in the lower left corner, meaning compaction is the major factor of de-creasing porosity. Influence of depositional environment on reservoir properties reflected most outstandingly in respect of grain size and clay content. With decreasing of grain size and increasing of clay content, permeability is rapidly decreasing. Those are the major cau-ses of low yield. One of the reasons of low permeability and productivity of DST2 is that reservoirs generally contain carbonate cement. Dissolution which mainly reflected in the dissolution of feldspar generally exists in two test sections, DST2 test section is semi-closed system with strong overpressure, dissolving objects cant be effectively brought out from the system and deposit in pore and throat which destroyed reservoir properties a lot. Clay transformation stage has a good corresponding relationship with permeability, and permeability becomes worse when I/S(S%) is less than 15%.