مطالعه ژيوشيميايي و تاثير تغييرات محيط رسوبي بر پتانسيل هيدروكربني سازند پابده در ميدان نفتي منصوري

Geochemical Investigation and Effect of Sedimentary

ارزﻳﺎﺑﻲ ﺳﺎزﻧﺪ ﭘﺎﺑﺪه ﺑﻪ ﻋﻨﻮان ﻳﻜﻲ از ﻣﻬﻢﺗﺮﻳﻦ ﺳﻨﮓﻫﺎي ﻣﻨﺸﺎء اﺣﺘﻤﺎﻟﻲ در ﻣﻴﺪانﻧﻔﺘﻲ ﻣﻨﺼﻮري ﺣﺎﺋﺰ اﻫﻤﻴﺖ اﺳﺖ. در اﻳﻦ ﻧﻮﺷﺘﺎر، ﻋﻼوه ﺑﺮ ارزﻳﺎﺑﻲ ﭘﺘﺎﻧﺴﻴﻞ ﻫﻴﺪروﻛﺮﺑﻨﻲ، ﺗﺄﺛﻴﺮ ﻣﺤﻴﻂ رﺳﻮﺑﻲ ﺑﺮ ﺗﻐﻴﻴﺮ ﭘﺘﺎﻧﺴﻴﻞ ﻫﻴﺪروﻛﺮﺑﻨﻲ و ژﺋﻮﺷﻴﻤﻴﺎﻳﻲ ﺳﺎزﻧﺪ ﭘﺎﺑﺪه در ﻣﻴﺪ ان ﻧﻔﺘﻲ ﻣﻨﺼﻮري ﻧﻴﺰ ﻣﻄﺎﻟﻌﻪ ﺷﺪه اﺳﺖ. ﺑﺪﻳﻦ ﻣﻨﻈﻮر، از ﭘﺎراﻣﺘﺮﻫﺎي ژﺋﻮﺷﻴﻤﻴﺎﻳﻲ آﻟﻲ ﺳﺎزﻧﺪ ﭘﺎﺑﺪه ﺣﺎﺻﻞ از ﻧﺘﺎﻳﺞ آﻧﺎﻟﻴﺰﻫﺎي راكاﻳﻮل (Rock Eval) ، ﻛﺮوﻣﺎﺗﻮﮔﺮاﻓﻲﮔﺎزي(GC) ، ﻛﺮوﻣﺎﺗﻮﮔﺮاﻓﻲﮔﺎزي ـ ﻃﻴﻒﺳﻨﺞ ﺟﺮﻣﻲ (GC-MS) و ﻣﺪلﺳﺎزي ﺗﺎرﻳﺨﭽﻪ ﺣﺮارﺗﻲ اﺳﺘﻔﺎده ﺷﺪ. ﻧﺘﺎﻳﺞ ﻧﺸﺎن داد، در زﻣﺎن اﺋﻮﺳﻦ ﭘﺴﻴﻦ ﺑﻪ ﻃﻮر ﻧﺴﺒﻲ، ﺳﻄﺢ آب ﺑﺎﻻ رﻓﺘﻪ و در زﻣﺎن اﻟﻴﮕﻮﺳﻦ ﺳﻄﺢ آب ﻛﺎﻫﺶ ﻳﺎﻓﺘﻪ اﺳﺖ. ﺗﻐﻴﻴﺮات ﻧﺴﺒﻲ ﺳﻄﺢ آب ﺳﺒﺐ ﺷﺪه ﻛﻪ ﺳﺎزﻧﺪ ﭘﺎﺑﺪه از ﻧﻈﺮ ﭘﺘﺎﻧﺴﻴﻞ ﻫﻴﺪروﻛﺮﺑﻨﻲ ﻳﻜﻨﻮاﺧﺖ ﻧﺒﺎﺷﺪ. ﺳﺎزﻧﺪ ﭘﺎﺑﺪه در ﻣﻴﺪان ﻧ ﻔﺘﻲ ﻣﻨﺼﻮري ﺑﻪ ﺳﻪ ﺑﺨﺶ ﺗﻘﺴﻴﻢ ﺷﺪ؛ ﺑﺨﺶ زﻳﺮﻳﻦ و ﻓﻮﻗﺎﻧﻲ در ﺳﺎزﻧﺪ ﭘﺎﺑﺪه ، ﭘﺘﺎﻧﺴ ﻴﻞ ﺳﻨﮓﻣﻨﺸﺎء ﻣﻨﺎﺳﺐ ( 1-5/0 TOC% ﺗﺎ) ﺧﻮب ( 2-1 TOC% را) داﺷﺘﻪ و ﺣﺎوي ﻛﺮوژن ﻧﻮع III ﻲﻣ ﺑﺎﺷﻨﺪ. ا ﻳﻦ ﺑﺨﺶ ﻫﺎ، ﭘﺘﺎﻧﺴ ﻴﻞ ﺗﻮﻟ ﻴﺪ ﮔﺎز را دارﻧﺪ. اﻣﺎ ﺑﺨﺶ ﻣﻴﺎﻧﻲ، ﭘﺘﺎﻧﺴ ﻴﻞ ﺳﻨﮓﻣﻨﺸﺎء ﺑﺴﻴﺎرﺧﻮب (4-2 TOC% ﺗﺎ) ﻋﺎﻟﻲ TOC > )%4 ) را داﺷﺘﻪ و ﺣﺎو ي ﻛﺮوژن ﻧﻮع II و ﻣﺨﻠﻮط ﻧﻮع II و III ﻲﻣ ﺑﺎﺷﺪ. ﻳﻦا ﺑﺨﺶ از ﺳﺎزﻧﺪ ﭘﺎﺑﺪه ﭘﺘﺎﻧﺴ ﻴﻞ ﺗﻮﻟ ﻴﺪ ﻧﻔﺖ را دارد. ﺑﺮرﺳﻲ ﻧﺘﺎﻳﺞ راكاﻳﻮل و ﻣﺪلﺳﺎزي ﺗﺎرﻳﺨﭽﻪ ﺣﺮارﺗﻲ ﻧﻴﺰ ﻧﺸﺎن داد، ﺳﺎزﻧﺪ ﭘﺎﺑﺪه در ﻣﺮﺣﻠﻪ اﺑﺘﺪاي ﭘﻨﺠﺮه ﻧﻔﺖزاﻳﻲ ﻗﺮار داﺷﺘﻪ و ﭘﻨﺠﺮه ﻧﻔﺖزاﻳﻲ ﺣﺪوداً از 6-5 ﻣﻴﻠﻴﻮن ﺳﺎل ﻗﺒﻞ در ﺳﺎزﻧﺪ ﭘﺎﺑﺪه آﻏﺎز ﺷﺪه و ﺗﺎ ﺑﻪ اﻣﺮوز اداﻣﻪ دارد.

Pabdeh Formation is one of the most important probable source rocks in Mansuri oilfield being under investigation. In this study, hydrocarbon potential of Pabdeh Formation is evaluated. Also effect of sedimentary environment changes on geochemical and hydrocarbon potential variation is studied. To achieve this, hydrocarbon potential of Pabdeh Formation with Rock Eval pyrolysis was investigated. Besides that, gas chromatography and gas chromatography- mass spectrometry data were utilized. Based on this study, in the Late Eocene age, relative sea level had raised, while in the Oligocene age, falling in sea level was occurred. Variation in sea level caused Pabdeh Formation to be heterogeneous in hydrocarbon potential. Pabdeh Formation in Mansuri oilfield from geochemical aspects is divided into three divisions. Lower and Upper zones in this formation, have fair (0.5-1% TOC) to good (1-2% TOC) hydrocarbon potential and contain kerogen type III. These zones have gas production potential. Middle zone, has very good (2-4% TOC) to excellent ( > 4% TOC) potential and contains kerogen type II and mixed type II and III. Middle zone has oil production potential. Rock Eval data as well as thermal history modeling demonstrate that; Pabdeh Formation is in early oil window, started yielding petroleum since 5-6 million years ag