Abstract:

The Outskirt area ofHua 152 well field is important oil producing region and major expansion well field, and Chang 3 reservoir is its principal producing formation. The research on the pore characteristics of Chang 3 reservoir is significant for the reservoir evaluation, the cognition of reservoir forming and reservoir distribution prediction. Based on thin section observation, scanning electronic microscope and pore throat image analysis, it is believed that residual primary intergranular pore is the main pore type in Chang 3 reservoir, followed by all kinds of secondary dissolution pores. Lamellar throat is the main type of throat, and secondly it is constriction pore and tubular throat. The pore features of the sandstone are related to the sedimentary environment. Medium to fine throat chiefly distributes in the sandstone reservoir of subaqueous distributary channel, and mediumthroat mainly distributes in the sandstone reservoir of river mouth bar. By means of mercury intrusion method, capillary pressure characteristics of Chang 3 reservoir are analyzed, and it is found out that there are complicated unimodal model and simply bimodal model of pore throat distribution. Capillary pressure curve can be approximately divided into typesⅠ, Ⅱ and Ⅲ. Pore throat sorting degree of Chang 3 reservoir is better on the whole, there is large difference among volume of pore throats. In brief, standstone pore structure and its distribution characteristics demonstrate that Chang 3 reservoir of the study area has fairly accumulation capability and is favorable for reservoir formation.

Key words: sedimentary facies, Shihezi Formation, Ordos Basin