Abstract:

JOURNAL OF SOUTHWEST PETROLEUM UNIVERSITY(SCIENCE & TECHNOLOGY EDITION)，VOL.32，NO.5,65-69,2010（ISSN 1674-5086，in Chinese）
Abstract：Medium-fine arkose-lithic and lithic-arkose are mainly sandstones of 2nd Member，Xujiahe Formation in Baojie Area.The roundness which is subround/subangle is medium.There are line and point-line and concave-convex contact forms which are pore-contact and overgrow-pore cementation among rock grains.The Xujiahe reservoir is characterized by low component maturity and textural maturity.The main pore types are granular pore and secondary feldspar-dissolution pore.The Xujiahe reservoirs are super low permeability with mean permeability of 1.2733mD.The sedimentary facies，mineral composition and grain diameter of the sandstones are the key factors influencing the reservoir formation and evolution.Furthermore，the strong compaction and cementation are the main factors resulting in the low porosity and low permeability of the reservoir，while dissolution and tectonic action are the main factor improving the physical property.

Key words: North Longchang, Xujiahe formation, tight sandstone, reservoir characteristic, reservoir physical property, control factor