scholarly journals Lithology and fluid discrimination using rock physics-based modified upper Hashin–Shtrikman bound: an example from onshore Niger Delta Basin

2021 ◽  
Vol 11 (2) ◽  
pp. 569-578
Author(s):  
C. G. Okeugo ◽  
K. M. Onuoha ◽  
A. C. Ekwe
Keyword(s):  
Upper Bound ◽  
Acoustic Impedance ◽  
Niger Delta ◽  
Rock Physics ◽  
Time Lapse ◽  
Successful Prediction ◽  
Niger Delta Basin ◽  
Reservoir Connectivity ◽  
4D Seismic ◽  
Gas Bearing

AbstractThe Ozifa reservoir is proven reservoir that cuts across the Northern and Greater Ughelli depo-belts of the Niger Delta Basin. This reservoir possesses heterogenous character southward of the field, making elastic properties, lithologies and fluid types difficult to describe accurately. In this study, rock physics template was applied to porosity and acoustic impedance (AI) crossplot clusters to illustrate rock–fluid relationships using modified Hashin–Shtrikman upper bound, Voigt upper bound and Reuss lower bound, as an input in the template. Values of acoustic impedance and porosity were used as lithofacies classification parameters for discrimination of lithofacies and fluid types. Our result showed that modified Hashin–Shtrikman upper bound line when applied in acoustic impedance (AI) and porosities (φ) crossplot domain discriminated gas-filled reservoirs from brine filled reservoirs and shale effectively. Similarly, results from crossplot showed clear separation of shale, heteroliths filled with brine and gas bearing sand, which was not plausible using conventional petrophysical analysis. This approach was successfully applied in analysing lithofacies and fluid relationship in different well locations and serves as a model for successful prediction of different lithology and fluid types, a major requirement for determining effects of geological variables such as sorting, clay distributions on the reservoir connectivity and optimum production using time-lapse (4D) seismic interpretation.

scholarly journals Time-Lapse Seismic Monitoring of Onshore Reservoirs in Niger Delta, Field ‘K’ as a Case Study

2017 ◽  
Vol 1 (1) ◽  
pp. 23-27 ◽  
Author(s):  
A. Ogbamikhumi ◽  
T. Tralagba ◽  
E. E. Osagiede
Keyword(s):  
Seismic Data ◽  
Acoustic Impedance ◽  
Niger Delta ◽  
Rock Physics ◽  
Time Lapse ◽  
Seismic Survey ◽  
Impedance Change ◽  
Data Set ◽  
Reservoir Fluid ◽  
4D Seismic

Field ‘K’ is a mature field in the coastal swamp onshore Niger delta, which has been producing since 1960. As a huge producing field with some potential for further sustainable production, field monitoring is therefore important in the identification of areas of unproduced hydrocarbon. This can be achieved by comparing production data with the corresponding changes in acoustic impedance observed in the maps generated from base survey (initial 3D seismic) and monitor seismic survey (4D seismic) across the field. This will enable the 4D seismic data set to be used for mapping reservoir details such as advancing water front and un-swept zones. The availability of good quality onshore time-lapse seismic data for Field ‘K’ acquired in 1987 and 2002 provided the opportunity to evaluate the effect of changes in reservoir fluid saturations on time-lapse amplitudes. Rock physics modelling and fluid substitution studies on well logs were carried out, and acoustic impedance change in the reservoir was estimated to be in the range of 0.25% to about 8%. Changes in reservoir fluid saturations were confirmed with time-lapse amplitudes within the crest area of the reservoir structure where reservoir porosity is 0.25%. In this paper, we demonstrated the use of repeat Seismic to delineate swept zones and areas hit with water override in a producing onshore reservoir.

Time-Lapse Seismic for Reservoir Management: Case Studies From Offshore Niger Delta, Nigeria

2016 ◽  
Vol 19 (03) ◽  
pp. 391-402
Author(s):  
Sunday Amoyedo ◽  
Emmanuel Ekut ◽  
Rasaki Salami ◽  
Liliana Goncalves-Ferreira ◽  
Pascal Desegaulx
Keyword(s):  
Case Studies ◽  
Niger Delta ◽  
Reservoir Management ◽  
Time Lapse ◽  
Seismic Survey ◽  
Elastic Model ◽  
Field Development ◽  
4D Seismic ◽  
The Impact

Summary This paper presents case studies focused on the interpretation and integration of seismic reservoir monitoring from several fields in conventional offshore and deepwater Niger Delta. The fields are characterized by different geological settings and development-maturity stages. We show different applications varying from qualitative to quantitative use of time-lapse (4D) seismic information. In the first case study, which is in shallow water, the field has specific reservoir-development challenges, simple geology, and is in phased development. On this field, 4D seismic, which was acquired several years ago, is characterized by poor seismic repeatability. Nevertheless, we show that because of improvements from seismic reprocessing, 4D seismic makes qualitative contributions to the ongoing field development. In the second case study, the field is characterized by complex geological settings. The 4D seismic is affected by overburden with strong lateral variations in velocity and steeply dipping structure (up to 40°). Prestack-depth-imaging (PSDM) 4D seismic is used in a more-qualitative manner to monitor gas injection, validate the geologic/reservoir models, optimize infill injector placement, and consequently, enhance field-development economics. The third case study presents a deep offshore field characterized by a complex depositional system for some reservoirs. In this example, good 4D-seismic repeatability (sum of source- and receiver-placement differences between surveys, dS+dR) is achieved, leading to an increased quantitative use of 4D monitoring for the assessment of sand/sand communication, mapping of oil/water (OWC) front, pressure evolution, and dynamic calibration of petro-elastic model (PEM), and also as a seismic-based production-logging tool. In addition, 4D seismic is used to update seismic interpretation, provide a better understanding of internal architecture of the reservoirs units, and, thereby, yield a more-robust reservoir model. The 4D seismic in this field is a key tool for field-development optimization and reservoir management. The last case study illustrates the need for seismic-feasibility studies to detect 4D responses related to production. In addition to assessing the impact of the field environment on the 4D- seismic signal, these studies also help in choosing the optimum seismic-survey type, design, and acquisition parameters. These studies would possibly lead to the adoption of new technologies such as broad-band streamer or nodes acquisition in the near future.

Time-lapse seismic monitoring methodologies applied to the Pyrenees Field, offshore Western Australia

2015 ◽  
Vol 55 (2) ◽  
pp. 412 ◽  
Author(s):  
Ramses Meza ◽  
Guy Duncan ◽  
Konstantinos Kostas ◽  
Stanislav Kuzmin ◽  
Mauricio Florez ◽  
...  
Keyword(s):  
Seismic Response ◽  
Coming Out ◽  
Rock Physics ◽  
Time Lapse ◽  
Reservoir Rock ◽  
Gas Field ◽  
Field Development ◽  
Fluid Saturation ◽  
Band Limited ◽  
4D Seismic

Time-lapse dedicated 3D seismic surveys were acquired across the Pyrenees oil and gas field, Exmouth Sub-basin to map production-induced changes in the reservoir. Rock-physics 4D modelling showed that changes in pore pressure and fluid saturation would produce a time-lapse seismic response of sufficient magnitude, in both amplitude and velocity, to overcome time-lapse noise. The dominant observed effect is associated with gas coming out of solution. The reservoir simulation model forecasted that reservoir depletion would cause gas breakout that would impact the elastic properties of the reservoir. The effect of gas breakout can be clearly observed on the 4D seismic data as a change in both amplitude and velocity. The analysis of the seismic datasets was proven to be enhanced significantly by using inversion methodologies. These included a band-limited extended-elastic impedance (EEI) approach, as well as simultaneous 4D elastic inversion. These datasets, combined with rock physics modelling, enabled quantitative interpretation of the change in 4D seismic response which was a key tool for assisting with the infill well placement and field development strategy.

scholarly journals Rock physics attribute analysis for hydrocarbon prospectivity in the Eva field onshore Niger Delta Basin

2020 ◽  
Vol 10 (8) ◽  
pp. 3127-3138
Author(s):  
Alexander Ogbamikhumi ◽  
Nosa Samuel Igbinigie
Keyword(s):  
Feasibility Study ◽  
Niger Delta ◽  
Poisson Ratio ◽  
Rock Physics ◽  
Plot Analysis ◽  
Attribute Analysis ◽  
Geological Conditions ◽  
Niger Delta Basin ◽  
Ratio Versus

Abstract Direct hydrocarbon indicator (DHI) expressions observed on seismic could arise due to various geological conditions. Such expression could lead to misinterpretation as hydrocarbon presence if not properly analyzed. This study employs rock physics attributes analysis to evaluate an identified prospect in the undrilled area of the studied reservoir. Prospect identification was actualized by analyzing structural and amplitude maps of the reservoir, which revealed a possible roll over anticline at both the exploited and prospective zone, with a very good amplitude support that conforms to structure. Well-based cross-plot analysis adopted four cross-plot techniques for feasibility study to test the applicability of rock physics for prospect evaluation in the field; Lambda-Rho versus Lambda-Rho/Mu-Rho ratio; Mu-Rho versus Lambda-Rho; and Poisson Ratio versus P-impedance. The result presented Poisson ratio, Lambda-Rho and Lambda/Mu-Rho ratio as good fluid indicator and Mu-Rho as a viable lithology indicator. As such, they were selected for seismic-based attribute and cross-plot analysis to validate the identified prospect. The results from seismic-based analysis showed consistency in the expression of the analyzed attribute at both the exploited and prospective zone. The seismic-based cross-plot analysis result was similar to the well-based analysis and was able to confirm that the observed amplitude expression in the exploited zone is an indication of hydrocarbon-bearing sand.

Time Lapse (4D) Seismic for Reservoir Management: Case Studies from Offshore Niger Delta, Nigeria

2014 ◽  
Author(s):  
Sunday Oluleye Amoyedo ◽  
Emmanuel Ekut ◽  
Rasaki Salami ◽  
Liliana Goncalves-Ferreira ◽  
Pascal Desegaulx
Keyword(s):  
Case Studies ◽  
Niger Delta ◽  
Reservoir Management ◽  
Time Lapse ◽  
4D Seismic

Enhancement of dynamic reservoir interpretation by correlating multiple 4D seismic monitors to well behavior

2015 ◽  
Vol 3 (2) ◽  
pp. SP35-SP52 ◽  
Author(s):  
Zhen Yin ◽  
Milana Ayzenberg ◽  
Colin MacBeth ◽  
Tao Feng ◽  
Romain Chassagne
Keyword(s):  
History Matching ◽  
Time Lapse ◽  
Quantitative Information ◽  
Matching Efficiency ◽  
Reservoir Simulation Model ◽  
Seismic Amplitudes ◽  
Reservoir Description ◽  
Major Factors ◽  
Reservoir Connectivity ◽  
4D Seismic

We have found that dynamic reservoir interpretation can be enhanced by directly correlating the seismic amplitudes from many repeated 4D seismic monitors to the field production and injection history from wells. This “well2seis” crosscorrelation was achieved by defining a linear relationship between the 4D seismic signals and changes in the cumulative fluid volumes at the wells. We also found that the distribution of the well2seis correlation attribute can reveal key reservoir connectivity features, such as the seal of faults, fluid pathways, and communication between neighboring compartments. It can therefore enhance dynamic reservoir description. Based on this enhanced interpretation, we have developed a workflow to close the loop between 4D seismic and reservoir engineering data. First, the reservoir model was directly updated using quantitative information extracted from multiple surveys, by positioning and placing known barriers or conduits to flow. After this process, a seismic-assisted history matching was applied using the well2seis attribute to honor data from the seismic and engineering domains, while remaining consistent with the fault interpretation. Compared to traditional history matching, that attempts to match individual seismic time-lapse amplitudes and production data, our approach used an attribute that condensed available data to effectively enhance the signal. In addition, the approach was observed to improve the history-matching efficiency as well as model predictability. The proposed methodology was applied to a North Sea-field, the production of which was controlled by fault compartmentalization. It successfully detected the communication pathways and sealing property of key faults that are known to be major factors in influencing reservoir development. After history matching, the desired loops were closed by efficiently updating the reservoir simulation model, and this was indicated by a 90% reduction in the misfit errors and 89% lowering of the corresponding uncertainty bounds.

scholarly journals Correction to: Lithology and fluid discrimination using rock physics-based modified upper Hashin–Shtrikman bound: an example from onshore Niger Delta Basin

2021 ◽  
Author(s):  
C. G. Okeugo ◽  
K. M. Onuoha ◽  
A. C. Ekwe
Keyword(s):  
Niger Delta ◽  
Rock Physics ◽  
Original Publication ◽  
Niger Delta Basin

In the original publication of the article, table 2 and some of the figures were incorrectly published.

scholarly journals Cross plot Analysis of Rock Properties from Well Log Data for gas detection in Soku Field, Coastal Swamp Depobelt, Niger Delta Basin

2018 ◽  
Vol 3 (4) ◽  
pp. 180
Author(s):  
Okoli Emeka Austin ◽  
Okechukwu Ebuka Agbasi ◽  
Onyekuru Samuel ◽  
Sunday Edet Etuk
Keyword(s):  
Acoustic Impedance ◽  
Niger Delta ◽  
Gamma Ray ◽  
Rock Physics ◽  
Oil Field ◽  
Rock Properties ◽  
High Resistivity ◽  
S Wave ◽  
Lithology Identification ◽  
Well Data

The cross plotting of rock properties for fluid and lithology discrimination was carried out in a Niger Delta oil field using well data X-26 from a given oil field in the coastal swamp depobelt. The data used for the analysis consisted of suites of logs, including gamma ray, resistivity, sonic and density logs only. The reservoir of interest Horizon 1, was identified using the available suite of logs on the interval where we have low gamma ray, high resistivity and low acoustic impedance specifically at depths 10,424ft (3177.24m) to 10 724ft (3268m). We first obtained other rock attributes from the available logs before cross plotting. The inverse of the interval transit times of the sonic logs were used to generate the compressional velocities and the S-wave data was generated from Castagna´s relation. Employing rock physics algorithm on Hampson Russell software (HRS), rock attributes including Vp/Vs ratio, Lambda-Rho and Mu-Rho were also extracted from the well data. Cross plotting was carried out and Lambda Rho (λρ) versus MuRho (μρ) crossplots proved to be more robust for lithology identification than Vp versus Vs crossplots, while λρ Versus Poisson impedance was more robust than Vp/Vs versus Acoustic impedance for fluid discrimination, as well as identification of gas sands. The crossplots were consistent with Rock Physics Templates (RPTs). This implies the possibility of further using the technique on data points of inverted sections of various AVO attributes within the field in areas not penetrated by wells within the area covered by the seismic.

Sign in / Sign up

Export Citation Format

Share Document