Abstract:

Based on the observation and analysis of rock thin sections, cast thin sections,physical properties and intrusive mercury curves of cores derived from sandstone reservoirs(E₂s₄) in the west slope of west depression of Liaohe oilfield, the lithology, diagenesis and physical properties of E₂s₄ were analyzed. The results show that the main lithological types are feldspathic lithic sandstone and lithic sandstone in the study area, and the common diagenesis types are compaction, cementation, metasomatism, dissolution and alteration; pore types mainly include primary intergranular pore, intergranular dissolved pore and intragranular dissolved pore, among which the expanded intergranular pore is the most common type; pore structure types are mainly fine-medium pores with fine throat and the physical property of reservoirs is good with mediumlow porosity and medium permeability. The influence of diagenesis on reservoir development shows that compaction and cementation have destructive effect while dissolution plays a constructive role in improving reservoir property. This study indicates that intergranular dissolved pore, intragranular dissolved pore, expanded intergranular pore and oversize macropore formed by dissolution make the greatest contribution to the reservoir, resulting in the formation of high quality reservoirs with medium-high porosity and medium-high permeability. Two abnormal high porosity-permeability intervals in which dissolution widely develops are identified in depths of 900-1,900 meters and 2,300-2,900  meters, and these two intervals should be the focus of next exploration targets to find favorable reservoirs.

Key words: diagenesis, reservoir physical property, pore structure, the west slope of west depression, Liaohe oilfield