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- Title
Analytical Prediction of Reservoir Fluids from Rock Physics Models: A Case Study of 'X'- Field Offshore Niger Delta.
- Authors
Ekom, Essien E.; Stanley, Eze U.; Saleh, Saleh A.
- Abstract
The significance of rock physics analysis in litho-fluid discrimination within a hydrocarbon reservoir using elastic rock properties can never be overstressed in reservoir characterization and hydrocarbon production. The aim of this study is to predict reservoir fluids within a hydrocarbon reservoir using elastic rock properties estimated from well log data from "X-Field" offshore Niger Delta. The reservoir intervals were identified from X-002 as HD1000 and HD2000 at depths of 5740-5780 ft and 5795-5935 ft respectively, which corresponds to the time gate 1345.00-1355.00 ms and 1355-1385 ms respectively on the seismic data. Elastic rock properties estimated within the reservoir window includes P-impedance (Ip), Vp/Vs ratio (velocity ratio), Poisson's ratio (σ), Lambda rho (λρ) and Mu rho (µρ). Cross plot indicators for these properties were colour coded with density and resistivity to give a 3D picture of the attribute response. The cluster pattern on the crossplot space gives a qualitative measure of the discriminative capacity of the attributes under consideration. Cross plot of P-impedance against λρ clearly delineated two zones, indicative of hydrocarbon sands and brine sands. Hydrocarbon zone (HC Sand) was identified by its low values on both Acoustic Impedance and λρ axis. Theoretically, hydrocarbon sands are characterized by low density and high resistivity values, while brine sands are characterized by high density and low resistivity values. Cross plot of µρ versus λρ, showed little or no separation of the reservoir fluids on the µρ axis, as low value of the attribute predominates. However, there is good separation in the λρ axis, making it a more fluid-sensitive attribute. Hydrocarbon zone delineated in this crossplot is suggestive of a gas filled zone based on density and resistivity values on the colour codes, as gas sand facies show lower values of λρ and higher values of µρ. All other attributes cross plots gave seemingly cluster pattern expected for hydrocarbon sands and brine sands at depths of 5758-5791 ft for brine sands, and 5904-5920 ft for hydrocarbon sands judging from the depth colour code in density versus λρ cross plot. These observations are possible because each lithology responds differently to rock properties, depending on the rock fluid content and mineral properties. The results obtained shows that for detailed lithofluid prediction during hydrocarbon exploration and production, it is absolutely necessary to characterize the hydrocarbon reservoir using cross plot indicators with heightened fluid sensitivity.
- Subjects
NIGER River Delta (Nigeria); HYDROCARBON reservoirs; POISSON'S ratio; PHYSICS; GAS condensate reservoirs; MINERAL properties; ROCK properties; ELASTICITY
- Publication
Petroleum & Coal, 2021, Vol 63, Issue 4, p1037
- ISSN
1335-3055
- Publication type
Article