Exploration Insights February 2020

6 | Halliburton Landmark Exploration Insights | 7 calcareous shales and syn-rift Miocene marine shales (e.g. Duwi and Rudeis formations), analogous to the Gemsa and Ras Fanar fields in the Gulf of Suez Three frontier fairways with proven analogue success in the neighboring Gulf of Suez were considered: » Pre-rift Early Cretaceous (Nubian) sandstones charged by pre-rift Late Cretaceous marls and calcareous shales (e.g. Duwi Formation), analogous to the October Field in the Gulf of Suez A variety of data was extracted and interpreted (Figure 1), including: lithostratigraphic, biostratigraphic, temperature, and heat flow datasets from exploration wells in the Egyptian Red Sea; organic geochemical and vitrinite reflectance data; and basement relief inferred from free-air gravity, magnetic, and limited seismic data. » Syn-rift sandstones (Rudeis and Kareem formations) charged by both pre-rift Late Cretaceous marls and calcareous shales and syn-rift Miocene marine shales (e.g. Duwi and Rudeis formations), analogous to the Belayim Marine Field in the Gulf of Suez TECTONOSTRATIGRAPHY The Northern Red Sea Basin is a hyperextended rift margin in a state of incipient break-up. It is divided, politically, into the Egyptian Red Sea (west) and the Saudi Arabian Red Sea (east). » Syn-rift carbonates (Upper Rudeis, Kareem, and Belayim formations) charged by both pre-rift Late Cretaceous marls and EPOCH Quaternary Pliocene FORM- ATION STRATIGRAPHY PSE Shagara R Wardan R Zeit C South Gharib Oligocene TMS4 Belayim Miocene Eocene Paleocene Late Cretaceous C R S R v v Oblique rifting, hyperextension GoS structural isolation — basin restriction Volcanism and dykes TMS3 Thebes Orthogonal rifting Marine incursion from Tethys to north RIFT ONSET TMS2 v Pre-rift volcanics Seal-level lowstand regional unconformity S Esna Duwi/ Dakhla S C Matulla Raha Early Cretaceous TMS1 R PALEOZOIC Najd Shear Faulting Sandstone v CHARGE ANALYSIS Modeling Strategy and Construction Complex salt stratigraphy, variable burial thicknesses, and high and variable heat flow in this very recently active rift system are likely to have had a significant influence on charge in the Egyptian Red Sea. Basin modeling and sensitivity analysis were carried out in Permedia petroleum modeling software to investigate and test the impact of these variables on maturity windows, and to spatially analyze charge and phase risk. Six 1D basin models were constructed in a transect across the Egyptian Red Sea (Figure 3), available to Neftex Advanced Insights subscribers through the Webmapper. These models were based on wells and the Neftex Northern Red Sea Play Cross Section, which were interpreted using the Neftex Sequence Stratigraphic Model. Two models are of exploration wells, Quseir A-1X and Quseir B-1X, and four models are of predicted pseudo sections representing variations in salt thickness, overall burial thickness, and heat flow across the transect. Data inputs were assessed for uncertainty, and the impact of possible local variation in the ratio of salt, sandstone, and mudstone in the pseudo model zones was tested using sensitivity analysis. Key Source Rocks TETHYS PASSIVE MARGIN Basement Legend Neo-Tethyan upwelling — source rocks Syrian Arc Inversion R Nubian Group NEOPROTEROZOIC Marine incursion from Indian Ocean to south AQUABA TRANSFORM ONSET Kareem Tayiba Continued rifting, oceanic accretion to south Mantle exhumation S Rudeis TMS5 TECTONIC EVENTS Salt mobilisation Nukhul TMS The stratigraphy of the Egyptian Red Sea comprises five main tectonostratigraphic mega sequences that lie unconformably over Precambrian basement (Figure 2). For a detailed review of the main tectonic events of the Northern Red Sea Basin, refer to the Neftex Northern Red Sea Play Cross Section (available to Core subscribers of the North Africa and Middle East regions). Volcanics © 2020 Halliburton R Clastic reservoir Unconformity Argillaceous evaporites Basement R Carbonate reservoir Limestone Evaporites Organic-rich sediments C Seal Carbonate mudstone and marl Mixed continental clastics Shale S Source rock Figure 2> Tectonostratigraphy of the Egyptian Red Sea margin, summarizing the stratigraphy subdivided into five main tectonostratigraphic mega sequences (TMS), the key petroleum system elements (PSE), and the major tectonic events through time (adapted from Gordon et al., 2010; Ball et al., 2017; Stockli and Bosworth, 2019). Three main potential source rock intervals were modeled, as shown in the table below. Source Rock Interval Formation(s) Primary Lithology Depositional Environment Kerogen Type Cretaceous pre-rift Duwi, Dakhla and Sudr Mixed siliciclastics and carbonates Open marine Type II Early Miocene syn-rift (pre-salt) Rudeis Mixed siliciclastics and marls Restricted deep marine Type II Middle–Late Miocene syn-rift (intra-salt) Kareem, Belayim, and South Gharib Mixed siliciclastics and evaporites Restricted marginal marine Type II/ Type III © 2020 Halliburton Miocene source rocks are proven in wells that have been drilled in the Egyptian Red Sea (e.g. the RSO_Z_95_1 well). Although no Cretaceous source rocks have been drilled offshore, several oil and gas shows in the Egyptian Red Sea have been typed to both penetrated syn-rift strata and Cretaceous outcrop samples (Gordon et al., 2010), supporting their occurrence in the offshore. Thermal Calibration The evolution of heat flow through time is a crucial factor in the assessment of phase and charge risk when basin modeling at rifted margins. Rifted continental lithosphere follows predictable trends in heat flow and subsidence during and after rifting, which can be inferred using a pure-shear 1D model (after McKenzie, 1978), as applied by White (1994), and calibrated at a particular location using measured thermal data. The RSO B 95-1 well, for which there are publicly available vitrinite reflectance, heat flow, and geothermal gradient data, was used to calibrate a paleo heat flow trend for all models in the study transect. This trend was adjusted at each model location to calibrate with the local, present-day heat flow data. Model Results Modeling results demonstrate the influence of recent heat flow history, burial history, and salt thickness on maturity, phase, and generation in the Egyptian Red Sea (Figure 3). Closest to the rift axis, the effects of relatively thin overburden are canceled out by high heat flows, resulting in an oil window of a similar stratigraphic level to that further from the axis, where overburden is higher and heat flow is lower. At Quseir B-1X, where the salt is up to 2 km thick, maturity windows are relatively depressed compared with adjacent locations, where rift structuration has led to marginal or non-existent salt. Sensitivity analysis further illustrates the impact of salt on the timing of generation. In one pseudo model, switching between the two end members of 100% salt and 0% salt in the Middle to Late Miocene stratigraphy results in a difference in the onset of oil generation of coeval source rocks of 5 million years.

Exploration Insights February 2020 | Page 6