Depositional Environments and Reservoir Evaluation of Otuma Oil Field, Niger - Delta basin, Nigeria

This study was carried out by using well logs to evaluate the depositional environments and hydrocarbon reservoirs in the Otuma oil field, Niger Delta basin. The gamma motif/model within- study interval in the drilled well shows blocky, symmetrical, and serrated shapes which suggest a deltaic front with mouth bar to a regressive - transgressive shoreface delta respectively. A correlation was done on the well logs across the wells and the ten well logs were used to evaluate the petrophysical characteristics of the reservoirs. The reservoirs showed highly porous and permeable channels where the wells were used for the characterization. The ten reservoirs were mapped at a depth range of 2395 m to 2919 m with thicknesses varying from 4m to 135m. The petrophysical results of the field showed that the porosity of the reservoirs ranges between 0.10 to 0.30, and permeability from 48 md to 290 md; the water saturation ranges from 0.39 to 0.52, and hydrocarbon saturation from the field 0.48 to 0.61. The By-passed hydrocarbons identified in low resistivity pay sands D4 and D3 at depth 2649 m to 2919 m, respectively were also evaluated and will be put to production in the field.

Geotechnical Characteristics of Benin Formation, Owerri Imo State, Nigeria

A good road network consists of a constant stretch of asphalt laid down for a smooth ride. The spot in the smooth ride on the pavement is commonly referred to as "pavement failure." Soil type, load bearing capacity of materials, zone of vulnerability, resistance to permeation, compressibility, shrinkage limit, and other details are frequently required in order to construct a very good and solid foundation for the planned bridge site. In Nigeria, numerous factors contribute to the failure of road construction projects. They are primarily insufficient research on subgrade and other pavement materials (sub-base and base courses) prior to the start of road projects; flawed engineering, including a poor drainage system and supervision throughout road construction; and shoddy workmanship that was superimposed with asphaltic concrete to improve strength. Within the Niger Delta basin, the study area is located between latitude 5.485°N and longitude 7.035°E. The Benin Formation underpins the study area. It is composed primarily of friable sands, conglomerates, very coarse sandstone, and isolated gravel units, as well as intercalation of Pliocene to Miocene shale/clay lenses. Natural Moisture Content (NMC), Linear Shrinkage (LS), Particle Size Distribution, and California Bearing Ratio were among the laboratory tests performed on samples collected at failed and stable sections of some selected road segments (CBR). When compared to the stable sections, the NMC along the failed sections was on the high side (ranging from 13.11 percent to 26.89 percent) (ranging from 11.11 percent to 16.40 percent). The majority of the tested soils passed the 0.075mm sieve with a percentage greater than the Federal Ministry of Works and Housing's maximum of 35% for subgrade materials. The maximum dry density (MDD) for the samples at failed and stable sections was 1550 kg/m3 to 1860 kg/m3; 1650 kg/m3 to 1980 kg/m3; and the Optimum Moisture Content (OMC) was 8.30% to 20.30%. The soaked CBR values ranged from 2 to 17 percent, while the unsoaked values ranged from 4 to 25 percent.

3-D Seismic Structural Interpretation of High Field Offshore Western Niger Delta

Seismic Structural interpretation of subsurface system is a vital tool in mapping source rocks and good trapping system which enhances good understanding of the subsurface system for productive drilling operation. This study is geared towards mapping the structural traps available within the hydrocarbon bearing zones of the “High field” with the use of well log and 3D seismic data. Seven horizons (H1, H2, H3, H4, H5, H6 and H7) were identified on well logs using gamma ray log and resistivity logs. Nine (9) faults were mapped on seismic sections across the field, two (2) of which are major growth faults (F1 and F2), two (2) synthetic faults (F3 and F7) and five (5) antithetic faults (F4, F5, F6, F8 and F9). Rollover anticlines which are structural closure and displayed on the depth structural maps suggest probable hydrocarbon accumulation at the down throw side of the fault F1. Structural interpretation of high field has revealed a highly fault assisted reservoir which depicts the tectonic setting of Niger Delta basin.

Chemical Classification of Sediments in JVX -Well, Greater Ughelli Depobelt Niger Delta Basin, Nigeria

This study evaluate the Chemical classification of sediments in JVX well, Greater Ughelli Depo belt Niger Delta Basin. Samples collected from different intervals were analyzed using geochemical proxies. Agbada Formation was suggested for the sampled intervals due to the presence of shaleand sand intercalations. lithofacies units gotten from sampled intervals are Sand, Shale and Shaly sand facies . The sands are milky in colour, translucent to opaque, medium to coarse grain, subangular to subrounded and are moderately sorted while the shales are Grey in colour,fissile with the presence of lignite streak and calcareous materials.The geochemical studies of the sediments revealed that SiO2 is the dominant oxide followed by Al2O3 and Fe2O3 which constitutes over 90% while others like CaO, K2O, TiO2, Na2O and MgO constitute 10%. The sediments were classified as Fe-shale, Fe-sand and Quartz arenite. Samples that plotted in the quartz arenites region suggests an intense degree of weathering and reworking. The SiO2/Al2O3 ratios for the sediments in the well are appreciably high indicating that the samples have been heavily weathered, evidenced from the enrichment of quartz and depletion of feldspars. Also, the relatively high concentrations of Fe2O3 and TiO2 is an indication of iron-titanium minerals such as haematite and anatase retiles.

Geochemical Maturity and Paleo-Weathering Indices of Sedimentary Succession in JV Field Greater Ughelli Depo-Belt Niger Delta Basin

This study evaluates the geochemical maturity and paleo weathering indices of X well JV-Field, Greater UghelliDepo belt Niger Delta Basin, using reflected light microscope and geochemical proxies. The data obtained identified three lithofacies units as Sand, Shale, and Shaly sand facies .The application of source area weathering using Chemical index of alteration (CIA) and Chemical index of weathering (CIW) values for the sampled intervals ranges from (48.6-94.9%) and (60.6-96.7%), and have median values of (83.2 and 90.3) % respectively which is an indication of high weathering at the source. The values are variable and it may be as a result of multiple provenances of the sediments which have variable proportions of source area weathering and related processes or may be due to low concentrations of the alkalis and alkaline earth elements. However, all the samples excluding one with depth (12430ft) show CIA and CIW values greater than 70% indicating high (intensive) weathering either at the source or during transportation before deposition .From the high alteration indices value recorded from the sampled intervals, it can be inferred that the sediments are geochemically and texturally mature.

Modeling the Chance of Commerciality of Petroleum Assets for Economic Development

The chance to discover hydrocarbon volumes of economic quantity diminishes with progressive discovery in explored basins. Given the preponderance of smaller deposits in extensively explored basins and the cost implications of discovering deposits less than the required Minimum Economic Reserves (MER), explorationists and investors in exploration activities need a framework to evaluate the chance of a successful petroleum resources discovery to minimize the risk of unsuccessful exploration. This study develops a new framework to evaluate the chance of discovery of at least a minimum economic reserves volume in an extensively explored basin. It leverages on the postulation for the determination of probability of hydrocarbon economic success as a building block for the new framework. The model combines the concepts of Minimum Economic Reserves, Discovery Efficiency and Probability to derive an explicit analytical function for discovery efficiency and hydrocarbon probability for a commercial discovery. It digitalizes existing Risk Table to ease the complexity to obtain geological chance of success and hydrocarbon asset evaluation for commerciality. Nine Case studies from the prolific Niger Delta basin of Nigeria are used to validate the model. The result of the semi-digital solution of the model shows that three of the studied cases are commercial whereas the remaining six cases are sub-commercial. The study recommends the application of the new framework for hydrocarbon asset evaluation for chance of commerciality to complement models like the cream off curve to predict chance of commercial discovery of hydrocarbon assets.

Characterization of reservoir sands using 3D seismic attributes in the coastal swamp area of Niger Delta Basin

Hydrocarbon accumulation and production within the Niger Delta Basin are controlled by varieties of geologic features guided by the depositional environment and tectonic history across the basin. In this study, multiple seismic attribute transforms were applied to three-dimensional (3D) seismic data obtained from “Reigh” Field, Onshore Niger Delta to delineate and characterize geologic features capable of harboring hydrocarbon and identifying hydrocarbon productivity areas within the field. Two (2) sand units were delineated from borehole log data and their corresponding horizons were mapped on seismic data, using appropriate check-shot data of the boreholes. Petrophysical summary of the sand units revealed that the area is characterized by high sand/shale ratio, effective porosity ranged from 16 to 36% and hydrocarbon saturation between 72 and 92%. By extracting attribute maps of coherence, instantaneous frequency, instantaneous amplitude and RMS amplitude, characterization of the sand units in terms of reservoir geomorphological features, facies distribution and hydrocarbon potential was achieved. Seismic attribute results revealed (1) characteristic patterns of varying frequency and amplitude areas, (2) major control of hydrocarbon accumulation being structural, in terms of fault, (3) prospective stratigraphic pinch-out, lenticular thick hydrocarbon sand, mounded sand deposit and barrier bar deposit. Seismic Attributes analysis together with seismic structural interpretation revealed prospective structurally high zones with high sand percentage, moderate thickness and high porosity anomaly at the center of the field. The integration of different seismic attribute transforms and results from the study has improved our understanding of mapped sand units and enhanced the delineation of drillable locations which are not recognized on conventional seismic interpretations.