Hydrocarbon inventory of the eastern part of the Rio Del Rey Basin using seismic attributes

Journal of Petroleum Exploration and Production Technology https://doi.org/10.1007/s13202-017-0412-5 ORIGINAL PAPER - EXPLORATION GEOPHYSICS Hydrocarbon inventory of the eastern part of the Rio Del Rey Basin using seismic attributes K. F. Fozao1 · L. Fotso2 · A. Djieto‑Lordon1 · M. Mbeleg3 Received: 24 June 2017 / Accepted: 26 November 2017 © The Author(s) 2017. This article is an open access publication Abstract The use of seismic attributes for understanding reservoir complexity has been proven to work in several fields. Thus, we demonstrate applications of seismic attributes for evaluating the oil and gas reservoirs in the eastern portion of the Rio del Rey (RDR) Basin. The presence of these fluids in twenty-six (26) reservoirs of the study area was confirmed with the help of Larson VizEx Pro software using well and seismic data. The 3D merged seismic data reprocessed in 2011 were used to extract the root-mean-square (RMS) and maximum amplitude attributes for each of the reservoirs. Forty-seven (47) RMS and maximum surface attributes were generated using Petrel E&P 2014 software. Seven (7) of these attributes have been presented. Quality control using Interactive Petrophysics (IP) software was applied on the reservoir fluid type found in each well. These fluid types were later superposed on each of the amplitude maps to match the corresponding amplitude responses. A good match could be observed between some well tops and their corresponding amplitude values. The results obtained indicate that GH and WX concessions could be the best concessions in the eastern part of the RDR Basin since most of their reservoirs, especially WX S6.3 maximum amplitude map, matched with their well fluid contents. The results obtained have been used to propose potential areas for further drilling. Keywords RDR Basin · Reservoirs · Well data · Software · Seismic attributes Introduction Cameroon’s geology has revealed that the country has many sedimentary basins belonging to the active petroleum system in Central Africa (Abolo 2008). These basins are subdivided into two categories; coastal basins which include: Rio Del Rey (RDR) and Douala/Kribi Campo (DKC) Basins; and the intra-continental basins which include: the Mamfe and the Logon Birni Basins. The coastal basins are known to host hydrocarbons, and no petroleum is known to occur in the inland basins so far. Taking this into account, the government of Cameroon has decided to subdivide these basins into blocks or concessions to put them at the disposal of * K. F. Fozao 1 Petroleum Research Group, University of Buea, P.O. Box 063, Buea, Cameroon 2 Department of Earth Science, University of Douala, P.O. Box 24157, Douala, Cameroon 3 Perenco, Douala, P.O. Box 2214, Douala, Cameroon the private petroleum companies. Presently, the Cameroon mining domain has about thirty concessions mainly located in the RDR and Douala Basins which are managed by the National Hydrocarbons Cooperation (NHC). Seismic attributes have been applied differently in reservoir studies. So far, in the RDR Basin, this has not been done. The primary objective of this work is to identify and select the attributes that work best in predicting hydrocarbon presence in a reservoir. These will then be used to make an inventory of the hydrocarbon reservoirs of the eastern portion of the RDR Basin. However, care must be taken when choosing the seismic attributes, because it is not unusual to find spurious or false correlations that do not reflect any physical basis for the relationship. Geologic setting Geographical location of the RDR Basin The RDR Basin is a divergent passive margin basin found in the southwest of Cameroon (Longmore and Lee 2010) 13 Vol.:(0123456789) Journal of Petroleum Exploration and Production Technology and represents the southeastern extension of the Niger Delta in the Gulf of Guinea (Coughlin et al. 1993). It is located between 4° and 5° of latitude north and between 8°20′ and 9°10′ of longitude east (Fig. 1). This Basin is further limited in the north and northeast by the Tertiary and Cretaceous outcrops; in the northwest, it is limited by the Niger River; in the south, it is limited by the Equatorial Guinea boundary and finally in the southeast by the Cameroon Volcanic Line (CVL). This line also separates the RDR Basin from the DKC Basin (Ntamak-Nida et al. 2010). The RDR Basin is a coastal basin and has a surface area of about 7000 km2 offshore. It is one of the basins from which hydrocarbons are produced in Cameroon with about 90% of the country’s production (SNH 2010). Tarreserence 1990); Sync-rift stage (Late Jurassic to Early Cretaceous, with the deposition of thick sequences of fluvial and lacustrine rocks); and Post-rift stage (Late Cretaceous to Holocene, which is made up of younger rocks and deposited as transgressive units consisting of shelf clastic and carbonate rocks followed by progradational units along the continental margins and as open-ocean water units (Brownfield and Charpentier 2006). The RDR Basin is made up of four structural provinces showing different features (SNH 2015) (Fig. 2). These include the Cretaceous onshore province, the growth fault province in the north, the shale ridge province in the southwest, and the Delta Toe-thrust in the south central area. Structural setting Regional petroleum system The RDR Basin is one of the Equatorial Atlantic marginal basins of the Gulf of Guinea of the Atlantic Ocean formed by the separation of the South American block from the African continent block (Tuttle et al. 1999). The RDR Basin has a geologic history that can be divided into three (3) stages of basin development: Pre-rift stage (late Proterozoic to Late Jurassic, with the deposition of about 600 m2 of continental clastic rocks of Carboniferous to Jurassic age (Villemin and This is a combination of certain elements capable of accumulating and producing potential hydrocarbons. These elements are the source rock and migration path, the reservoir rock, and the trapping mechanism. The source rocks are made up of upper prodeltaic marine shale of the Paleocene Akata Formation (Evamy and Haremboure 1978). We may also have interfingering shales belonging to the base of the Eocene Agbada Formation. Type III/II Fig. 1  Location map of the entire Rio Del Rey (RDR) Basin 13 Journal of Petroleum Exploration and Production Technology Fig. 2  Regional structural setting of the RDR Basin showing the four provinces (Kumar 2012) kerogens (humic to mixed type) have mostly been documented, indicating a predominantly terrestrial origin for the organic matter (Stacher 1995). The reservoir rocks in the RDR Basin are made up of sandstones and paralic non-consolidated sand from the Agbada Formation. The characteristics of these reservoirs are controlled by depositional environments and depth of burial. Oil is produced from the sand facies of the Agbada Formation (Short and Stauble 1967). Nevertheless, turbiditic sands from (...truncated)