PALYNOFACIES ANALYSIS AND THERMAL MATURATION STUDY OF SEDIMENTS OF IDM 4 AND IDM 5 WELLS OF NIGER DELTA BASIN, NIGERIA

Abstract

Palynofacies analysis and thermal maturation study was carried out on IDM-4 and IDM-5 wells of the Niger Delta Basin. The location of the studied area lies within Latitude 04⁰ 08’ 02’’ N and longitude 06⁰ 08’ 06’’ E for IDM-4 and latitude 04⁰ 08’ 0’’ N and longitude 06⁰ 07’ 06’’ E for IDM-5. The studied depth of the well is 10030 ft– 11700 ft at 30 ft interval. Palynological processing, analysis and interpretations were carried out on forty-nine and forty-seven ditch cutting samples from the IDM-4 and IDM-5 wells, respectively. Kerogen analysis was also carried out on the part samples. Simple acid method of sample preparation was used during the palynofacies analysis. Physical observation and Gamma Ray log were used in determining the lithology of the sedimentary succession. The lithology consists of the fine to medium sized sandstones and sandy mudstones. Abundant species of palynomorphs and palynomacerals were recovered. Some of which are biomarkers such as Zonocostites ramonae, Pachydermites diederixii, Sapotaceodaepollenites sp., Psilatricolporites cassus. Crassoretitriletes vanraadshooveni, Laevigatasporites sp. This is correlatable to early-Miocene to middle-Miocene stratigraphic ages. Two zones were established in IDM-4well. They are Pachydermites diederixizone which falls within the 7000 ft and 7990 ft and Crassoretitrites vanraadshooveniZone which falls within the interval 6030 ft and 7000 ft. Three zones were established in IDM-5 well. They are Polypodiaceoisporites sp. Zone, Magnastriatites howardi Zone and Pachydermites diederixi Zone. The palynofacies associations show the depositional environment of Pachydermites diederixii to be mangrove swamp while Crassoretitrites vanraadshooveni Zone indicates mangrove- shoreface depositional environment for IDM-4 while the depositional environment of the studied interval is interpreted to predominantly range between Mangrove and Channel depositional environments for IDM-5. For IDM-4 well, the intervals such as 6050 ft, 6150 ft, 6400- 6600 ft, 6900- 6950 ft are the intervals that show the mature phase of liquid oil while intervals 6100 ft, 6200- 6400 ft, 6600- 6900 ft, 6950- 7950 ft are the phase of dry gas. For IDM-5 well, intervals 10000 -10950 ft are the phases of dry gas while intervals 10950- 11025 ft and 11450-11700 ft are the phases of mature liquid oil.