Diagenesis of Yingcheng and Shahezi reservoirs in Shiwu Oil Field, Lishu Fault Depression, Songliao Basin

Analyses such as casting thin slice,SEM,mercury penetration,cathodeluminescence,X-ray diffraction and inclusion were made with core samples from the Shahezi and Yingcheng reservoirs in the Shiwu Oil Field,the Lishu Fault Depression,the Songliao Basin,by means of which the diagenesis,diagenetic sequence and pore evolution of the two reservoirs were studied.The diagenetic effects in the study area were mainly compaction,cementation,denudation and structural fragmentation,among which denudation and structural fragmentation were contributive for reservoir physical property while compaction and cementation were destructive.The major pore style of sandstone reservoir was the combination of primary intergranular pore,intergranular erosion expand pore (accounting for the largest part) and a few fractures.The diagenetic sequence of sandstone reservoir was established as followed:mechanical compression→overgrowth of quartz and feldspar→structural fragmentation→erosion of aluminosilicate such as feldspar→cementation of grainy calcite→oil injection in the early stage→fragmentation→the second period of erosion→cementation of intergrowth calcite→late hydrocarbon injection.In the study area,the main controlling factors for reservoir property were sedimentary environment,diagenetic effect,structural effect and petroleum charging.