鏡煤素反射率(vitrinite reflectance)常作為有機物成熟度的指標，當此指標出現抑制(suppression)現象時，則不易正確地反映有機物成熟度的真實情況，進而影響油氣潛能評估的可靠性。本研究即探討鏡煤素反射率受抑制的可能問題，即利用單一樣品(臺灣三峽地區，中新世石底層煤樣)透過ZnCl2比重離心分離的過程，而達到富集膜煤素(exinite)等煤素質(maceral)材料，並比較分離前、後樣品的熱裂分析(Rock-Eval Pyrolysis)、鏡煤素反射率之結果。 在ZnCl2分離液對煤樣的熱裂分析的影響上，樣品分成原始樣、浸泡ZnCl2分離液及洗除ZnCl2分離液後之樣品。結果顯示：ZnCl2分離液對Tmax(熱解烴峰值溫度)、S1(游離烴)、S2(熱解烴)、TOC(總有機碳)及HI(氫指數)等之測定均有明顯下降的影響，但對IP(產率指數)並沒有產生影響。洗除ZnCl2分離液後，除IP有明顯下降外，其它熱裂參數幾乎可恢復如原始樣的情況。 在鏡煤素反射率受抑制的機制上，一種可能的原因是來自於量測的機率與垂直方向的透光問題；即在膜煤素高含量的情況下，拋光後所出現的鏡煤素薄層，當其達到透光的程度時，可以造成垂直方向的疊加透光效應，使得低值反射率被量測到的次數頻率增加，而平均反射率則向低值偏移。 The influence of ZnCl2, a centrifuge-separation liquid, to Rock-Eval pyrolysis was studied. Coal sample was collected from Yu-Feng mine in San-Hsia area, northern Taiwan. The sample was crushed and then divided into three parts namely P1, P2 and P3 respectively. P1 is the original coal sample; P2 had been immersed in ZnCl2 liquid and then dried up in room temperature; P3 is similar to P2, but had been water-washed before drying up. Preliminary results show that both S1(volatile hydrocarbons) and S2(hydrocarbons derived from coal pyrolysis) were evenly distributed in coal particles. Significant differences in S1 , S2, Tmax(temperature at which the S2 peak reaches its maximum), TOC (total organic carbon) and HI (hyrogen index) was observed for P2 sample, but not Ip (production index) value. After cleaning ZnCl2 by water-washed, P3 show that the previous pyrolysis parameters, can be recovered to those of P1 , although Ip still drops. Exinite-riched macerals were separated from coal samples by using density centrifugation of ZnCl2 solution. The frequency distributions of vitrinite reflectance were compared among original coal sample, washed coal sample and the separated exinite-riched sample, the probable reason for suppression of vitrinite reflectance can then be discussed. The suppression of vitrinite reflectance may be resulted from exinite underneath the measuring surface of thin-layered vitrinite.
