西藏地区伦坡拉盆地牛堡组原油稠化地质成因  

Geological origin of crude oil thickening in the reservoir of Niubao Formation in Lunpola basin,Tibet

作　　者：李宇平[1] 范小军[1] 

机构地区：[1]中国石化勘探分公司,四川成都610041

出　　处：《油气地质与采收率》2015年第6期32-35,46,共5页Petroleum Geology and Recovery Efficiency

基　　金：国土资源部油气中心和中国石化战略合作项目"伦坡拉盆地油气资源选区调查"(1211302108021-1)

摘　　要：伦坡拉盆地是西藏地区惟一发现工业油流的古近系陆相残留盆地。早期勘探已揭示,油藏埋藏深度超过1 500 m为稀油,然而新完钻的W1井在1 800 m钻遇的原油仍偏稠,可见该盆地原油纵向分带性复杂。为明确原油稠化地质成因及有利稀油富集带,采用地质与物探相结合的分析手段,对原油性质、原油分布规律、原油稠化地质成因等方面进行综合研究。结果表明,该盆地古近系牛堡组原油稠化主要受次生改造作用控制,并非低熟油所致;W1井油藏位于牛堡组顶部不整合面以下800 m油气氧化界面以内,由于该井位于盆地中央凹陷带中部断裂带,构造解释和岩心观察均显示断裂及高陡裂缝发育,导致原油轻组分散失,故油质偏稠,从而明确了该盆地原油纵向分带性。Lunpola basin is a Paleogene continental residual one and the only basin in Tibet with industrial oil discovery.Early exploration revealed that the thin oil distributed in the reservoirs with their buried depth more than1 500 m. However,the crude oil in new Well W1 at the depth of 1 800 m is still heavy,which indicates the complicated vertical zoning of crude oil in this basin. In order to clarify the geological origin of crude oil thickening and the favorable thin oil-enriched zone,physical properties,distribution rule and geological factors of crude oil thickening were studied comprehensively based on geological and geophysical data. The results show that the crude oil thickening in reservoirs of the Niubao Formation in Lunpola basin was mainly controlled by secondary alteration instead of low-mature oil. The reservoir of Well W1 locates under the oil-gas oxygenation level,which is 800 m below the unconformity surface. Structural interpretation and core observation show that the fractures and high-steep cracks of Well W1 are widely developed,for it locates in central fault region of central depression zone of the basin. This can lead to the loss of light components of the crude oil,so it is easy to be thickened. Thus the vertical zoning of the crude oil is clear.

关 键 词：稠化地质成因 次生改造作用 油气氧化界面 稀油富集带 牛堡组 伦坡拉盆地 

分 类 号：TE124.1[石油与天然气工程—油气勘探]