摘要
文中将致密油藏定义为储层致密、只有经过大型压裂改造等特殊措施才可以获得经济产量的烃源岩外油藏,其绝对渗透率约小于2×10-3μm2,孔隙度约小于12%。以往普遍认为,致密油藏属于连续型油气聚集,为非常规油气之一类。研究表明,鄂尔多斯盆地伊陕斜坡三叠系延长组中、下组合主要为致密和近致密砂岩油藏,其成藏模式既非以往认为的典型的常规岩性油藏,又非典型的连续型非常规油藏,而是介于常规与非常规油藏或连续与不连续型油气聚集之间的一种过渡类型,文中称之为准连续型油藏或油气聚集。它主要具有以下成藏特征:①油藏大面积准连续分布,无明确边界;②大面积生烃,高强度充注;③储层物性差,非均质性强;④圈闭介于常规圈闭与无圈闭之间,为非常规圈闭;⑤油、水分异差,无明显边、底水;⑥油藏压力系统复杂,且多具负压异常;⑦油气运移聚集主要为非浮力驱动,近距离运移成藏;⑧油藏形成和分布主要受烃源和储层控制,构造影响小;⑨保存条件好,油藏变化小;⑩资源丰富,勘探开发潜力大。准连续型致密砂岩油藏成藏模式的提出,预示着这类油藏具有较大的勘探潜力,但传统的地质研究和勘探思路需要作出相应的调整。
Tight oil reservoirs are low-permeability oil accumulations in non-source rock reservoirs that can produce economic flow only through massive fracturing or other special measures.Their absolute permeability is less than 2×10-3 μm2 and porosity less than 12%.Tight oil reservoirs are widely accepted as the continuous-type accumulations of unconventional hydrocarbons.Based on our studies on the Ordos Basin in China,we found that oil reservoirs in the lower and middle plays of the Triassic Yanchang Formation on the Yi-Shan slope are mostly tight or near-tight sand oil accumulations.Their oil accumulation patterns are neither the conventional lithologic accumulations nor the continuous unconventional accumulations,instead a transitional type that we refer to as the quasi-continuous accumulation.The quasi-continuous hydrocarbon accumulation can be defined as extensive accumulations in tight reservoirs with neither defined boundaries nor water legs and controlled by unconventional trapping mechanisms.Studies indicate that the quasi-continuous tight sand oil accumulations in the Ordos Basin have the following characteristics：（1）oil distribution is extensive geographically in quasi-continuous form without a defined boundary;（2）the hydrocarbon generation covers vast area and the charging is highly intensive;（3）the reservoirs have unfavorable physical properties and are highly heterogeneous;（4）traps are unconventional that exist in the transition form between conventional shaped traps such as the structural and stratigraphic traps and the shapeless trap or no trap at all;（5）the oil-water contact is unclear and no obvious edge/bottom water present;（6）the formation pressure system is complex and underpressure is predominant;（7）the migration and accumulation of hydrocarbons are short-distanced and driven principally by non-buoyant forces;（8）the accumulation and distribution of oil pools are rarely controlled by local structures,but primarily by source rock and reservoir conditions;（9）the
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2012年第6期811-827,共17页
Oil & Gas Geology
基金
国家大型油气田与煤层气开发项目(2011ZX05007-004)
关键词
准连续型油藏
致密油
成藏模式
鄂尔多斯盆地
quasi-continuous accumulation
tight oil
accumulation pattern
Ordos Basin
