بررسي كانيهاي رسي سازند پابده در برش تيپ و داده هاي NGS اين سازند در ميدان نفتي كوپال (چاههاي شماره 12 و 38 )

Clay Mineral Study of Pabdeh Formation in Type Section and its Comparison with NGS Data from Kupal Oil Field (Well No. 12 & 38)

The calcimeteric analysis of samples from Pabdeh Formation, in type section (north of Dezful embayment subzone), represent a marl and shaly marl lithology. SEM images from these samples represent chlorite flakes with diagenetic origin (transformation of illite to chlorite) and imply the possible existence of other detrital clay minerals (include chlorite). However, XRD analysis of select­ed samples indicates the existence of montmorillonite, illite and chlorite showing a descending trend for clay percent and montmo- rillonite and ascending one for illite and chlorite from bottom to top of these deposits. Based on these evidences, we introduced the possibility for cooling in climate condition and shoaling in depth of deposition, from bottom to top of the Pabdeh Formation. Study of Th, K & Th/K peaks of NGS log represents the existence of montmorillonite and illite, as common clay mineral. Calculat­ing clay mineral percent, shale percent and uranium trend imply an anomaly at the uppermost part of the Pabdeh Formation which could be related to fault activity in Central Dezful embayment subzone and sediment supply probably due to Pyrrenean orogeny. Therefore, investigation of clay mineral represent difference in sedimentary framework between northern Dezful em­bayment subzone and central Dezful embayment subzone and their different response to change in geological condition.