非常规油气有关概念、分类及资源潜力

Conception,Classification and Resource Potential of Unconventional Hydrocarbons

尽管非常规油气的勘探开发已引起广泛重视,但对其概念的理解目前还存在一定差异,对其分类也未见有系统讨论。根据对非常规油气地质及开采特征的分析,将非常规油气定义为在油气藏特征与成藏机理方面有别于常规油气藏、采用传统开采技术通常不能获得经济产量的油气矿藏。非常规油气的内涵比连续油气聚集的含义广,后者是非常规油气资源中重要的组成部分,但不是全部。系统的分类研究表明,非常规油气可按其赋存相态分为气、液、固3类;按储层类型分为致密油气、页岩油气和煤层气;按油气分布特点或圈闭特征分为连续型、准连续型和不连续型;按源—储关系分为源内型和源外型;按成因分为原生型和次生型。初步分析认为,我国非常规石油原地资源量估计在720×108t左右,可采资源量约为210×108t(不包括致密油和页岩油),与常规石油资源量大体相当;非常规天然气原地资源量可能在320×1012 m3左右,其中仅致密气、煤层气和页岩气3种主要非常规天然气的原地资源量可能高达175×1012 m3左右,可采资源量估计在70×1012 m3左右,相当于常规天然气可采资源量的3～4倍。另外,根据油气资源形成条件与成藏特征,提出了新的资源三角图的概念,将油气资源分为不连续的常规油气、准连续的致密油气和连续型聚集的源内油气3级,据此预测在致密储层发育的含油气盆地,致密油气的资源量虽可能小于页岩油气和煤层气等烃源岩层内聚集的油气资源数量,但可能大于常规油气的资源量。由于致密油气资源潜力大,储层条件相对好于其他非常规油气,因此建议我国非常规油气的勘探开发首先应以致密油气为主攻目标,其次应加强煤层气的勘探开发,同时积极开展页岩气资源潜力评价与先导试验研究。

Despite of the wide attention that the exploration and development of unconventional hydrocarbons has attracted,neither a distinct and consistent definition nor a systematic classification of the unconventional hydrocarbons can be found in the literature.Based on a comprehensive investigation and analysis,this paper defines the unconventional hydrocarbons as such a kind of hydrocarbon resources that is distinguished from conventional hydrocarbons by reservoir features and accumulation mechanism,and cannot produce economically with traditional measures of exploitation.Comparison between unconventional hydrocarbons and continuous accumulation shows that the former is broader than the latter in connotation,notwithstanding the continuous accumulation is a dominant part of the unconventional resources.Unconventional hydrocarbons can be divided into（1） gaseous,liquid,and solid types according to the state of hydrocarbon phases;（2） tight reservoired oil/gas,shale oil/gas,and coalbed methane in terms of the reservoir types;（3） continuous,quasi-continuous,and discontinuous types based on the characteristics of petroleum distribution or trapping;（4） self-sourced and outer-sourced types according to the source-reservoir relationship;and（5） the primary and secondary types in terms of the genesis of accumulation.Investigation of resource assessment in China indicates that the original in-place resource of unconventional oil is roughly 720×108t,and recoverable resource is about 210×108t（excluding tight oil and shale oil）;the original in-place resource of unconventional gas is some 320×1012m3,of which the sum of tight gas,coalbed methane,and shale gas resources is possibly 175×1012m3,and their recoverable resource is about 70×1012m3,approximately 3 to 4 times that of conventional gas.Based on the analyses of the condition and characteristics of hydrocarbon accumulation,we suggest a new resource triangle concept that petroleum resources are divided into three grades,namely the discontinuous（conventional）,quasi-continuous（tight）,and continuous（self-sourced unconventional） accumulations,respectively.From this concept,we forecast that in petroleum basins where tight reservoirs are developed the amount of petroleum resources from the tight reservoirs is presumably in between that of the conventional accumulation and that of continuous unconventional accumulation from the source rocks.Because tight hydrocarbons are of better quality of reservoirs than coalbed methane and shale gas and are predicted to be of greater resource potential than assumed previously,they should be given top priority in the exploration of unconventional resources in China.