埕北30区块潜山油气藏下古生界储层特征

CHARACTERISTICS OF LOWER PALEOZOIC BURIED HILL RESERVOIRS IN CHENGBEI-30 TRACT

通过岩心观察、薄片鉴定、阴极发光显微镜观察、岩心CT图像分析、测井解释等手段,以揭示山东埕岛油田埕北30区块潜山油气藏下古生界碳酸盐岩储层储集空间类型、裂缝发育特征、古岩溶等为目的开展工作,得到以下认识:储层具有裂缝-孔隙复合储集空间类型,发育溶孔、溶洞、晶簇孔洞、晶间孔隙、构造缝、风化破裂缝、缝合线等。下古生界发育5个裂缝频数高值带,风化壳以下150-250 m范围内为最有利的储集层段,地层总孔隙度可达15％以上,裂缝孔隙度一般大于0.5％。碳酸盐岩古岩溶作用是控制储层发育的主要因素,它分为加里东早期同生-近地表成岩早期溶蚀作用、加里东晚期-印支期风化壳溶蚀作用、燕山期浅埋藏溶蚀作用和喜山期深埋藏溶蚀作用等四期,受其影响储层具有强烈角砾化和非均质性严重等特点。应用该成果为油气田新增石油地质储量228×104t、溶解气地质储量4.31×108m3。

The reservoir type, fracture development features and palaeokarst of Lower Paleozoic buried hill carbonate reservoirs in Chengbei-30 tract of Chengdao oil field, Shandong Province,were revealed by these means as core observation, thin-section analysis, cathodoluminescence microscopic examination,core CT image analysis and log interpretation, etc. It was recognized that the reservoir belongs in fracture-pore compound reservoir type being composed of solution pores,karst cavities,drusy pores & cavities,intercrys-tal pores,structural fractures,weathering fractures and stylo-lites,etc;there are five high fracture frequency zones in Lower Paleozoic and the range of 150-250 m below the weathering crust is the most favourable reservoir interval,formation total porosity being up to over 15% and fracture porosity being more than 0. 5% in general; and the carbonate palaeokarst was the major factor of controlling reservoir development, there being four-stage corrosions,i. e. Early Caledonian syngenetic-near surface diagenesis early corrosion, LateCaledonian-Indosinian weathering crust corrosion, Yanshan epoch shallow burial corrosion and Himalayan epoch deep burial corrosion, by which the reservoirs affected are of the characters of strong brecciation and serious heterogeneity. By use of the research achievements,the oil reserves in place of 2280 ×103 t and dissolved gas reserves in place of 431×106 m3 have been increased in the field.