Pores Type and Diagenesis in the Chang 4+5 Sandstone Reservoirs of the Jiyuan Oilfield
XU Bo1,2,SUN Wei11.State Key Laboratory of Continental Dynamics/Department of Geology,Northwest University,Xi'an 710069,China2.College of Petroleum Engineering,Xi'an Petroleum University,Xi'an 710065,China
The petrologic characteristics,diagenesis and pore types in Chang 4+5 reservoir of the Jiyuan oilfield in Ordos Basin are studied by varied methods,including examination of the normal physical properties,thin-section casting thin-section,heavy minerals,X-ray diffraction and SEM analysis.The dominating pore type of Chang 4+5 reservoirs is intergranular pore and feldspar-dissolved pore,the subordinate is the dissolved intergranular pore.Assembly of the pore types is usually intergranular pore and dissolved pore-granular pore.The constructive diagenesis in Chang 4+5 reservoir is compaction,secondary enlargement of quartz and feldspar,cementation of carbonate mineral,etc.It is the compaction that reduces the primary pore space in Chang 4+5 reservoirs.The destructive diagenesis that keeps or enlarges pore space is dissolution,clay membrane of chlorite.It is insufficient for dissolution to improve the pore space.
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