In the context of this work, the well-studied is located in the Abidjan margin (Figure 1). It is the LEO-3X well, with geographic coordinates 4˚05'58.84"N and 3˚43'06.52"W.

Ninety-six (96) cuttings from the HIPPO-1X well were used for this geochemical and sedimentological study.

After the lithological description, twenty grams (20 g) of sediment from each sample were soaked in soapy water for 45 minutes. Before air-drying at room temperature and homogenization using a porcelain pestle and mortar, the sediments were treated with water on a column of two sieves (100 and 63 μm). The prepared samples were subjected to Rock-Eval 6 analysis for the determination of four (4) geochemical parameters:

· Maximum pyrolysis temperature (Tmax), which quantifies the thermal maturation of organic matter;

· petroleum potential (S2), which indicates the quantity of “potential” or residual

hydrocarbons that could be produced if burial and maturation continue;

· Total Organic Carbon (TOC), is used to assess the petroleum potential of organic matter (OM);

· Hydrogen Index (HI): the proportion of hydrocarbon effluents emitted during pyrolysis in relation to TOC. It is used to assess the type and origin of organic matter present in sedimentary rocks.

The geochemical data were interpreted in parallel with the S2/TOC and HI/TOC diagrams. They are associated with stratigraphic stages to better assess the presence or absence of bedrock and the type of kerogen it contains.

The formations studied range from 2498 m to 1372 m and have been subdivided into three lithological intervals, each comprising two units. From base to summit, we distinguish three intervals named 1, 2 and 3.

Interval 1

This interval, with a height of 136 m, lies between elevations 2498 m and 2362 m. It is characterized mainly by marl, limestone and argillite. Two lithological units can be distinguished in this interval (Figure 2).

Unit 1 (2498 m - 2426 m) is predominantly calcareous with argillite intercalations. The limestone is light brown, sometimes light gray, hard with a microcrystalline texture, clayey, with oligosteginides. The argillite is dark gray, firm, massive, slightly calcareous, micromicaceous, with traces of pyrite and carbonaceous micro-debris.

Unit 2 (2426 m - 2362 m) is characterized by alternating marl and argillite, with marl predominating. The marl is brownish-grey and subfissile. The argillite is dark gray, firm to crumbly, massive, sometimes subfissile, slightly calcareous, micromicaceous. Carbonaceous debris can be observed in this interval, with the percentage gradually decreasing from base to top. Glauconite is virtually absent and pyrite is present. This suggests deposition in a reductive environment with

continental influences. The sediments contain high levels of calcium carbonate, ranging from 10% to 50%. This is explained by the lithology, which consists of marl and limestone rich in foraminifera.

Interval 2

This interval (2362 m - 1908 m) is characterized by alternating sand, sandstone, argillite and kaolinite. It is subdivided into two units (Figure 3).

Unit 1 (2362 m - 2073 m), 289 m high, is characterized by a predominance of argillite and fine sand. The argillite is brownish-gray to dark gray, firm, friable, massive, sometimes subfissile, slightly calcareous, micromicaceous, with traces of pyrite and carbonaceous micro-debris. The sand, mainly between coasts 2332 m and 2362 m, is translucent, fine to coarse, subrounded and moderately sorted.

Unit 2 (2073 m - 1908 m) is characterized by a series of sand, sandstone, kaolinite and argillite of varying proportions. The sand is translucent, sometimes transparent, fine to coarse, subangular to rounded, and poorly sorted. Sandstones are light gray, friable to firm, very fine to fine-grained, subrounded to rounded, moderately to well sorted, with siliceous cement and limestone in places, micromicaceous. Kaolonite is white, friable, slightly sandy and micro micaceous. Clayite is dark gray, firm, massive to subfissile, non-calcareous, and silty, with calcareous fossil debris. Pyrite is present, glauconite is abundant in places and carbonaceous debris is virtually absent, suggesting an anoxic marine environment with little continental influence. The calcium carbonate content of the sediments is relatively low, peaking at around 15% at elevation 2207 m. This is due to the presence of alternating thick layers of dark-gray, non-calcareous to slightly calcareous argillite and thin banks of calcareous-cemented sandstone, with few foraminifera.

Interval 3

This interval extends from 1908 m to 1372 m. It is clay-dominated and subdivided

into two units (Figure 25). Unit 1 (1908 m - 1631 m), 277 m high, is characterized by argillite and traces of sandstone. The argillite is dark gray to brownish gray, firm, massive, subfissile, very slightly calcareous, very glauconitic and containing fragments of calcareous fossils. Sandstones are light gray, hard, very fine-grained, well sorted and siliceous-cemented. Unit 2 (1631 m - 1372 m) is characterized by a dominant argillite series and fine limestone beds. The argillite is dark gray to brownish gray, firm, massive, subfissile, very slightly calcareous, glauconitic and containing calcareous fossil debris. Limestone is light brown, hard, microcrystalline in texture and slightly clayey. Pyrite is present in small quantities. Glauconia is also abundant in places, and carbonaceous debris is virtually absent, suggesting an anoxic marine environment with little continental influence. The calcium carbonate content of the sediments is relatively low, with two peaks of around 15% at elevations 1885 m and 1630 m, and 30% at elevation 1510 m. This is due to the presence of alternating thick layers of dark-gray, non-calcareous to slightly calcareous argillite and thin banks of calcareous-cemented sandstone with few foraminifera. The sediments encountered are argillites with fine sandy and sandstone layers corresponding in places to weak carbonate peaks. The drop in content is explained by the absence of marl and limestone in this interval and the drop in foraminiferal content. These formations have been replaced by mudstones and sandstones. On the other hand, the peaks observed are due to calcitic cement sandstones. The LEO-3X well formations were sedimented in an anoxic marine environment with variable continental influence. The lithological section shows three (3) facies grouped into

lithological intervals were delineated in the direction of sedimentation. Interval 1 consists of alternating argillite, limestone and marl. Sediments in this interval were deposited by settling. Interval 2: alternating argillite, sand and sandstone. This interval is dominated by sand. The sediments of this interval were deposited in an intermittent environment. Interval 3 consists of argillite. The sediments of this interval were deposited by settling in a fairly calm, deep environment.

Albian (2498 m - 2380 m)

The sediments of the 118 m-high Abien contain a good deal of organic matter (1.72% by weight on average). With an S2 of 6.47 mgHC/g rock. We therefore have the presence of source rock and type II kerogen. This source rock is capable of generating oil given these parameters of HI 373 mg HC/g TOC (Figure 5).

Cenomanian (2371 m - 2225 m)

These sediments, with a total height of 137 m, and only 18 m contain an average amount of organic matter (0.77% by weight on average). With an S2 of 2.79 mgHC/g rock. This indicates the presence of source rock and type II kerogen. This source rock is capable of generating oil with an HI of 360 mg HC/g TOC. 119 m of sediment is free of source rock (Figure 6).

Turonian (2216 m - 2198 m)

These 18 m-high sediments contain an average amount of organic matter (0.77% by weight on average). With an S2 of 2.22 mgHC/g rock, these sediments do not constitute a source rock (Figure 7).

Late Senonian (2188 m - 2097 m)

These sediments, with a total height of 91 m, contain a good quantity of organic matter (1.25% by weight on average). With an S2 of 3.12 mgHC/g rock, we can see the presence of bedrock and type II-III kerogen. This source rock is capable of generating a mixture of oil and gas with HI parameters of 249 mg HC/g TOC (Figure 8).

Campanian (2079 m-1786 m)

These sediments have a total height of 293 m.

· 2079 m - 2060 m: These sediments, 19 m high, contain an average amount of organic matter (0.793% by weight on average) and have an S2 equal to 2.42 mgHC/g rock. They do not constitute a source rock (Figure 9).

· 2051 m - 2015 m: With a height of 36m, these sediments contain a good

quantity of organic matter (1.73% average weight). With an S2 of 6.53 mgHC/g rock. We therefore have the presence of source rock and type II-III kerogen. This source rock is capable of generating a mixture of oil and gas with HI parameters of 239 mg HC/g TOC (Figure 9).

· 2006 m - 1914 m: These sediments, 92 m high, contain an average amount of organic matter (0.66% by weight on average). S2 is 2.20 mgHC/g rock. They do not represent a source rock.

· 1905 m - 1881 m: 24 m high, these sediments contain a good quantity of organic matter (1.92% average weight). They have an S2 equal to 7.67 mgHC/g rock. We therefore have the presence of source rock and type II kerogen. This source rock is capable of generating oil with HI parameters of 400.67 mg HC/g TOC (Figure 9).

· 1868 m - 1786 m: These sediments, 82 m high, contain a good deal of organic matter (1.6% by weight on average), with an estimated S2 of 3.45 mg HC/g rock. These data are characteristic of the presence of source rock and type II-III kerogen. This source rock is capable of generating a mixture of oil and gas with HI parameters of 237.77 mg HC/g TOC.

Maastrichtian (1777 m - 1402 m)

These sediments have a total height of 375 m.

· 1777 m - 1676 m: These sediments, 101 m high, contain very high levels of organic matter (2.02% by weight on average). With an S2 of 3.33 mgHC/g rock. We therefore have the presence of source rock and type II-III kerogen. This source rock is capable of generating a mixture of oil and gas with HI parameters of 255.62 mg HC/g TOC (Figure 10).

· 1667 m - 1494 m

173 m high, these sediments contain a very high level of organic matter

(3.19% by weight on average). With an S2 of 14.46 mgHC/g rock. We therefore have the presence of source rock and type II kerogen. This source rock is capable of generating oil with HI parameters of 452 mg HC/g TOC (Figure 10).

· 1475 m - 1402 m

With a height of 73 m, these sediments contain a good quantity of organic matter (1.80% by weight on average). With an S2 of 6.55 mgHC/g rock. We therefore have the presence of bedrock and type II kerogen. This source rock is capable of generating oil with HI parameters of 452 mg HC/g TOC (Figure 10).