GEOCHEMICAL INVESTIGATION OF THE MIDDLE AND THE UPPER JURASSIC ROCKS, WELL HF35/1, ABU SENNAN AREA, NORTH WESTERN DESERT, EGYPT

Abstract

The Abu Sennan area is located at the southern rim of the Abu Gharadig basin east of Qattara topographic depression. The whole lithostratigraphic units throughout the well HF35/1 of the study area are mentioned in the present study. The deepest sedimentary succession of both the Middle Jurassic (Khatatba Fm.) and the Upper Jurassic (Masajid Fm.) was chosen to evaluate their capability for hydrocarbon production and their sedimentary setting in the studied well. Twenty-seven cutting samples from the present Formations were subjected to organic geochemical analysis using Rock-Eval pyrolysis technique. A twenty-four samples represented the Middle Jurassic and three samples of the Upper Jurassic were examined. The TOC values of the present succession reveal that the Masajid Formation has extremely fair quantity (average; 0.52 wt%), whereas the Khatatba Formation contains favorable hydrocarbon of good to very good quantity (average; 1.53 wt, %). However, the freely released hydrocarbons during pyrolysis indicates the domain of poor and fair petroleum potential for both formations. The plotting samples of the studied formations on the production yield (Py) versus TOC diagram confirms that the Masajid Formation is poor where the Khtatba Formation is dominant of fair petroleum potential. The kerogen type of the Masajid is Type III of hydrogen index (HI) values between 60.38 and 76 (mg HC/g TOC) and an S2/S3 ratio is around 3. The Khatatba is the same as the Masajid of the majority of type III with a little sample of type II/III did not exceed 12 % of the total examined samples. The latter type II/III represents the lowermost part of the Khatatba Formation. The dominance of kerogen III in the studied formations may relate to the proximity of sedimentation processes to the shore of the basin and/or the flourish of the terrestrial land plant during this period. The maturity parameters of Tmax, PI (production index), and Ro (vitrinite reflectance) of the studied formations show a late stage of maturity within a condensate wet gas (gas window) of the low conversion. Statistical analysis of the studied samples shows that the mature zone is considered to be within depth intervals of 2700m to 4150m.