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Reservoir rock attributes such as porosity, permeability, pore-size geometry and net-to-gross ratio can grossly be affected by inaccurate delineation of the sand intervals. It is therefore pertinent that well log cross-plot is utilized to accurately delineate the sand body and correctly evaluate the petrophysical properties of the mapped sandstone...
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High-resolution image data is instrumental in quantifying the rapid variation of rock fabric in formation evaluation that conventional well logs fail to capture. However, acquiring high-resolution image data for all wells of an entire formation is expensive and time-consuming. Therefore, extrapolation of rock fabric information of expert-derived fa...
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... In contrast, sands A and C exhibit more modest thicknesses of 7.25 m each. Furthermore, a salient trait emerges in the form of uniform lateral thickness, in consonance with the tenets expounded by 27 . ...
This study focuses on the comprehensive reservoir characterization of the ‘Kukih’ Field within the onshore northeastern Niger Delta region, Nigeria. The absence of its detailed description with delineated reservoir properties, lateral continuity, and their use to identify potential reservoir quality and heterogeneity necessitated this study. Integrating well log and 3D seismic data, the investigation aims to elucidate reservoir properties, lithofacies, and depositional environments to unravel hydrocarbon potential. The geological setting, encompassing the Agbada Formation of Early and Middle Miocene age, is scrutinized through detailed geologic analysis. Petrophysical evaluation of four well logs (Kukih-1, Kukih-2, Kukih-3, and Kukih-4) facilitated the determination of key parameters such as shale volume, effective porosity, and water saturation. Seismic interpretation further enriched the structural characterization of the field. Results showcase three predominant reservoir sands (A, B, and C) with distinct lithofacies and thickness variations. Effective porosity ranges from Fair to Excellent, with permeability exhibiting high values for hydrocarbon reservoir potential. Water saturation trends, lithofacies distributions, and structural features were illuminated through iso-parametric maps and seismic analyses. Depositional environments were inferred through facies analysis, revealing the presence of funnel-, cylinder-, and bell-shaped successions that hint at intricate marine sedimentary processes. Challenges owing to limited core data were acknowledged, and the integration of methodologies emerged as a pivotal strategy for enhanced reservoir understanding. This study underscores the ‘Kukih’ Field's hydrocarbon potential, accentuating the significance of multidisciplinary approaches in deciphering complex reservoir systems. In light of the petrophysical analysis derived from the well logs and the identification of structural highs through the structural maps, this study recommends the drilling of unexplored zones exhibiting promising structural characteristics.
... Crossplots of the attributes from logs (Ip, Is, , µ and µ ) were generated. The well log analysis method employed is efficient and less expensive in prospecting for hydrocarbons and is reliable when combined with other geophysical methods such as seismic and core analysis(Ohakwere-Eze et al., 2018) ...
Here we demonstrate the separation of gas sand from surrounding shale using Lamé petrophysical parameters; , µ and µ where other rock attribute fails to give such clear distinction. Gather stacks (near and far) were generated to improve fidelity of pre-stack seismic. AVO models were generated then combined and inverted with the Seismic gathers to generate Impedance volumes (Zp and Zs) which were transformed to volumes of the Lamé attributes. Results of this method on the logs and pre-stack seismic gathers show significant improvement in DHI detectability over the conventional analysis based on Vp/Vs or Zp, Zs, variations. The results show that moderate to high values of µρ were indicative of clean sands and lower values of λρ and µ (<1) are indicative of high porosity and therefore high reserves in place, in this case gas. The good correlation of the results of the λρ and µ inversion volumes with those of rock physics analysis observed at the well provided confidence in our interpretation of a prospect away from the well thereby leading to discovery of another potential field in the region.
Adequate reservoir information is needed for accurate reservoir characterization towards enhancement of hydrocarbon recovery. The reservoir petrophysical parameters and elastic (seismic) properties are related to the quantity of reservoir rock fluids as well as the interaction of fluid types in the reservoirs’ pore space. Apart from the usually study of the petrophysical properties, the elastic properties are also vital because they are affected by the pore fluids interchange during hydrocarbon production or extraction. This study is aimed at examining and predicting those elastic properties that are most responsive and sensitive to changes during the fluid substitution. Information from three well logs from the ‘Royal G’ field’ situated in Niger Delta (onshore) were used for the petrophysical analysis and rock physics interpretation. The 3D crossplot outcomes were established by utilising Gassmann's fluid replacement or substitution modelling evident considering 0% oil and 80% brine (full) saturations in the reservoirs. Reservoir A and B have porosity, permeability and hydrocarbon saturation of 10-29%, 285-670 mD and 62-90% respectively. The 3D crossplot of the pseudo elastic logs give descriptive and distinct lithology and definite fluid content separation. Rock properties identified and noted to be extremely sensitive/reactive for lithology as well as fluid differentiation in the probed reservoirs are Acoustic Impedance, Density, Poisson ratio and Lambda-Rho. The outcome will generally enhance production and recovery of hydrocarbon.
The Taranaki Basin has an area of 100,000km2 and is the main source of petroleum in New Zealand, with most of its well located offshore. The reservoir of Kupe Field is located within the Farewell Formation, which is mainly composed by sandstones, siltstones and interbedded with claystones in some locations. This produces a high variability in the sedimentary composition, affecting gamma ray readings, neutron porosity and density logs in the area related to the reservoir sandstones.
Feasibility studies were applied to identify which rock property or petrophysical parameters would mostly discern the lithologies and fluids comprising the Farewell Formation. It was verified that these parameters are acoustic impedance correlated with density and 𝑉𝑝/𝑉𝑠ratio. Cross-plots of these properties were made in order to recognize clusters of sandstones, siltstones and claystones and further to verify the occurrence of probable gas bearing sands. This procedure was performed in all the gas-producing wells available for this study: Kupe South-1, Kupe South-4 and Kupe-1.
Pre-stack inversion was applied to produce inverted volumes of density, acoustic impedance and 𝑉𝑝/𝑉𝑠, aiming to extrapolate the results obtained with the well log cross-plots in the seismic cube. The obtained results showed a very good correlation between well cemented regions with high densities and higher impedances and also 𝑉𝑝/𝑉𝑠 values associated to the most clean, hydrocarbon-bearing and permeable sandstones. Probable gas-producing zones could then be identified what can facilitate future prospection projects in the region.
Keywords: Feasibility studies, Pre-stack Inversion, Impedance, 𝑉𝑝/𝑉𝑠, Taranaki Basin, Farewell Formation.
