Organic Inclusions as an Indicator of Oil/Gas Potential Assessment of Carbonate Reservoir Beds

Organic inclusions could be formed at the stages of either primary or secondary migration of hydrocarbonsso long as mineral crystallization or recrystallization takes place in the sediments,presenting a direct indicatorof oil/gas evolution,migration and abundance.Based on the study of organic inclusions in carbonate-type reser-voir beds of commercial importance from North China,Xingjing,North Jiangsu,Jianghan,Sichuan andGuizhou in China,many inclusion parameters for oil/gas potential assessment of carbonate reservoir beds aresummarized in this paper,including:1)Types of organic inclusion:Commercially important oil beds arecharacterized by inclusions consisting of either pure liquid hydrocarbons or liquid plus minor gaseoushydrocarbons,while commercially important gas reservoirs are characterized by inclusions consisting of eitherpure gaseous hydrocarbons or gas plus minor liquid hydrocarbons.2)Quantity of organic inclusions:The num-ber of organic inclusions in commercially important oil/gas reservoirs is over 60% of the total inclusion percen-tage.3)Temperature of saline inclusions:The homogenization temperatures of contemporaneous saline inclu-sions in oil reservoirs range from 91-161 ℃,while in gas reservoirs from 150-250℃).4)Inclusioncomposition:In commercially important oil reservoirs,C;/C;=2-10,C;/C;=2-4,C;/C;=2-21,（C;-C;）/（C;-C;）(%)>20,（CH;+CO+H;）/CO;（molecules/g）=0.5-1.0,and in C;-C;-nC;triangle diagramthere should be an upside-down triangle with the apex within the ellipse,while in commercial gas reservoirs,C;/C;=10-35,C;/C;=14-82,C;/C;=21-200,（C;-C;）/（C;-C;）(%)<20,（CH;+CO+H;）/CO;>1,and therewould be an upright triangle with the apex within the ellipse.The above-mentioned parameters have been used to evaluate a number of other unknown wells or regionsand the results are very satisfactory.It is valid to use organic inclusions as an indicator to assess the oil/gaspotential during oil/gas exploration and prospecting.This approach is effective,economic,rapid,and easy topopularize.