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81st EAGE Conference and Exhibition 2019
- Conference date: June 3-6, 2019
- Location: London, UK
- Published: 03 June 2019
81 - 100 of 1010 results
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The impact of Pore Typing on Saturation of Carbonate Reservoirs: Early Miocene Carbonates, Eastern Saudi Arabia
Authors A. Abdelkarim and M. MakkawiSummarySignificant pore system complexity occurs in carbonate lithofacies influencing its reservoir properties and efficiency. In this study, we attempted to disclose the response of carbonate pore system to the laboratory saturation procedures in gaseous and liquid phases by applying different experimental, spectral and imaging techniques. Thus, plug samples were obtained from two early Miocene, genetically-different carbonate lithofacies in eastern Saudi Arabia, namely; the skeletal oolitic peloidal grainstone and the stromatolitic boundstone. These lithofacies form prolific reservoirs in many petroleum fields in the Arabian Platforms. The skeletal oolitic peloidal grainstone was characterized by a laterally-extended uniform pore system, including fewer skeletal molds and dominant intergranular pores with significant pore bridging. In contrary, the stromatolitic boundstone revealed a complex pore system which varies laterally, with fewer interparicle, intraparticle, vuggy and moldic pores, and dominant isolated fenestral pores. This setting is believed to stand behind the under-saturation state as indicated by NMR porosimetry and visual analyses (SEM and micro-CT scan). The depositional and diagenetic settings of these lithofacies have contributed directly to the evolution of their respective pore types and geometries, which in turn influenced the gas flow, and to a higher degree; the liquid saturation procedures and its related properties derivations.
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Prediction of Cementation Factor: Empirical Correlations and Theoretical Approaches
Authors M.A. Shirzad, A. Soleymanzadeh and A. HelalizadehSummaryCementation factor (m) is one of the Archie's parameters which is used for estimation of fluid saturation in oil reservoirs. Many researchers have presented several correlations and classification methods for estimation of m. In this study, 16 carbonate rock samples were used for determination of m by different empirical correlations and several classification methods. Results revealed that using correlations generate large errors in prediction of cementation factor. Furthermore, it is concluded that Rezaee et al. and Soleymanzadeh et al. methods of classification are proper techniques to categorize electrical data, because these two methods consider physics of electricity transmission through rock samples.
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Classification of Formation Resistivity Factor Data Based on Electrical Tortuosity
Authors A. Soleymanzadeh, A. Helalizadeh, M. Jamialahmadi and B. Soltani SoulganiSummaryComplicated pore network of carbonate rocks and existence of different porosity types in them, generate many problems in petrophysical evaluation of carbonate reservoirs. Heterogeneous pore system of carbonate rocks causes unreliable estimation of Archie's parameters such as cementation factor (m) in calculation of water saturation. Traditional method for determination of m is log-log plot of formation resistivity factor (F) versus porosity. This technique gives undesirable results in carbonate rocks, because F data versus porosity significantly deviate from a straight line.
In this study, electrical tortuosity is introduced as a new classification parameter for categorizing F data to enhance the prediction accuracy of m value. In other words, rocks with similar values of electrical tortuosity constitute a distinct class which has its own linear equation of F versus porosity in log-log plot. Indeed, tortuosity is applied to divide F data into different electrical rock types. To verify this approach, an electrical dataset from one of the Middle East carbonate oilfield was used. Results showed that electrical tortuosity technique is a suitable approach for reduction of F data scattering and therefore improvement of estimation accuracy of m.
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Smart Waterflooding of Homogeneous and Heterogeneous Cores from Carbonaceous Reservoir
Authors J. Hao, S. Mohammadkhani, K. Louise Feilberg and A. ShapiroSummaryThe core scale heterogeneity is an important factor to account for enhanced oil recovery. The pore geometry and surface structure on the microscale were listed among the important factors, responsible for the different results from different rocks upon injection of low salinity brine. However, the core-scale heterogeneity has not drawn sufficient attention in the field of smart waterflooding, and its importance for the results of the flooding experiments has been overlooked. In this work we intend to find the evidence of the impact of heterogeneity on smart waterflooding under similar core flooding procedures. We have investigated smart waterflooding with homogeneous and heterogeneous carbonaceous cores from the North Sea reservoirs. Two processes have been tested: low salinity flooding with subsequent compression of a core, and injection of the brine containing bicarbonates. In both cases flooding of the heterogeneous cores resulted in a higher recovery than for the homogeneous cores.
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Polymer Throughput Effects on Injectivity and Retention
More LessSummaryIn this work, we investigate the effects of throughput (volume of polymer solution injected) on injectivity and retention. High throughput is representative of the near-wellbore area. It is important to investigate throughput effects to safeguard against excessive polymer retention and/or injectivity losses. Single-phase displacement experiments were performed at reservoir conditions using polyacrylamide polymers and representative reservoir brines and core samples. Tests were conducted at high flowrates to mimic the near-wellbore conditions. One test with extended polymer injection was performed to investigate throughput effects. The effluent polymer concentrations were analyzed by total organic carbon (TOC) measurements for determining polymer retentions. Pressure measurments were used to infer residual resistance factors (hence injectivity losses).
Results showed that the polymer dynamic retention results were generally very close, ranging from 0.128 to 0.204 mg/g-rock. Higher throughput yielded only a slight increase in retention. Furthermore, residual resistance factor (RRF) was relatively low, ranging from 1.20 to 1.39. There was no appreciable increase in RRF even after injection of around 100 PV of polymer solution. These results indicate that injection of large pore volumes within the near wellbore region do not have significant impact on water injectivities at least for the studied system.
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Disappearance and Appearance of Cations during Modified Low Salinity Waterflooding by Ammonium Ion in Shaly-Sandstone Formation
Authors H. Vu Quoc and F. SrisuriyachaiSummarySeveral previous studies have shown that low salinity waterflooding involves three main mechanisms which are fine migration, pH rising and Multi-component Ion Exchange (MIE). MIE was mentioned as a major technique in enhance oil recovery by using monovalent ion to expel divalent ions, as a bridge between oil droplets and rock surface. Ammonium ion is a positively charged polyatomic cation and it has several properties in common with potassium ion such as hydrated number and ionic diameter. These properties may favor MIE mechanism during low salinity waterflooding. This study is performed to evaluate abiity of ammonium ion in replacing divalent ions in shaly-sandstone. Comparison of effectiveness of ammonium ion and potassium ion was also made. The results show that ammonium ion can displace both calcium and magnesium ions from shaly-sandstone. Moreover, combination of ammonium ion and calcium ion in injected water can also favors dissolution of magnesium ion. It can be concluded that hydrated properties of ammonium ion have a decent influence on the MIE mechanism. It can also be noted that potassium ion, as a monovalent ion, is more complicated than ammonium ion as it can be found in both injected water and mineral surface.
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Modeling Wettability Alteration in Low Salinity Water Flooding
Authors A. Jahanbani Ghahfarokhi and O. TorsaeterSummaryThe mechanisms of Low Salinity Water Flooding (LSWF), as a cost-effective technique for improved oil recovery, have been investigated during the last years. Although the mechanisms are still subject of research, wettability alteration from oil wet to water wet as a result of multi-component ion exchange (MIE) is considered as a feasible mechanism. Modeling wettability alteration is a challenging task due to the complex interactions among ions in the injected brine and crude oil on the solid surface. Effect of geochemical reactions on the performance of LSWF was previously investigated using numerical models with parameters identical to those used in the experiments considering aqueous reactions, ion exchange, and mineral dissolution and precipitation. The approach was used in this study to further address the modeling of LSWF performance at field scale. Injections are performed in secondary and tertiary modes, to predict oil recovery in a variety of conditions. Simulation results show that transport of the phases is related to the desorption of the divalent ions from the clay surface. The release of cations and hence oil recovery depend on several factors like connate water and brine compositions, and clay content.
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Learning from Polymer Flooding in Offshore Viscous Oil Reservoirs
Authors D. Puckett, J. Faroppa and X. LuSummaryPolymer flood applications in offshore fields face more challenges than that of onshore fields. These challenges include limited platform space, costs to transfer polymer chemical, short service life, large well spacing, and high salinity formation water and reduced polymer viscosity when mixed with sea water. The above challenges make it's hard to directly applied the onshore polymer flood technologies and experiences proved successful. Also, there are seldom practical polymer flood projects that had been implemented in offshore conditions as analogs. Taking five offshore viscous oil polymer flood projects as examples, this paper summarizes their implementation, production performance, reservoir management and lessons learned during pilot or field-wide polymer flood process.
Key lessons learned are: (1) early polymer flood combing secondary and EOR could be a key strategy for offshore field, which recovers oil in short time, saves the cost of production fluid processing due to reduced water handling requirements and achieve relative high recovery factor; (2) Mechanic degradation at the near wellbore is the main source of polymer degradation due to permeability impairment caused by poor quality produced water injection. Rather than the most popular HPAM, the salinity and shearing resistance polymer such as hydrophobic associated polymers work better.
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Potential of the Eastern Jeanne d’Arc Basin, NL, Canada
Authors E. Le Guerroué, P. Filleaudeau, D. Thomas, A. Prelat, T. Pichot, P. Chenet, D. Norris, V. Mitchell, E. Gillis and R. WrightSummaryThe underexplored Eastern Jeanne d’Arc appears prospective for oil and gas, after new regional seismic data validates the extension of know plays in the area.
The objective was to provide petroleum resource estimates for the area using 2D/3D basin modelling for play risk analysis and volume estimates.
Regional sequence stratigraphy and geodynamic work coupled to a Forward Stratigraphic Model (DionisosFlow™) helped to map the extension of reservoirs, carrier beds and seals. Source rock potential was assessed using the FSM model to estimate deposition and degradation of organic matter during early burial.
After calibration of the thermal and fluid flow regime temperature, maturity and pressure, an integrated 3D model was built using TemisFlow™ to estimate the oil and gas charge in the potential traps (stratigraphic and structural) in the various plays.
The resource assessment of the Eastern Jeanne d’Arc area demonstrates a potentially prolific petroleum system. The uncertainty on HC volumes is given by the distribution of unrisked volumes in place. The range varies from 2.1 BOE to 9.8 BOE. The Probability of Geological Success is estimated to 11%.
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Seismic Input for Prospect Maturation and Trap Risking
Authors A. Laake and M. FrancisSummary3D seismic data are routinely used in the exploration process. We study the input 3D seismic which may reduce the uncertainty for geological elements considered in the risking and volumetric estimation process. We use an established procedure for prospectivity assessment using the probability concept in this study. We show that structural and stratigraphic horizons can be extracted from input 3D seismic data. The geologic soundness of structural horizons can be obtained from studying depositional environments along these horizons. The detailed composition of faults from fault segments and individual fault stress assessment is possible, which becomes an important input to the trap delineation risking processing. Lithologic and stratigraphic aspects can be obtained from a joint interpretation of the texture and the colour processed depositional environment image along structural horizons.
This methodology may be impacted by poor quality seismic data, for example when surface noise and multiples have not been removed efficiently. The impact of this limitation however, will be mainly on the depositional environment mapping. Structural aspects are less impacted due to the vertical extent of the structural feature and therefore makes the interpretation for structural features less dependent on the data quality.
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The Integration of Geoscience Disciplines to Reduce the Risk - A Case Study from Niger Delta
Authors S. Dabeer, I. Samaila, A. Shehu, H. Mansouri, U. Ngala, A. Ogbechie and R. NazarianSummaryThe focus of this paper is a cluster of prospects (Prospect-N, Prospect-S and Prospect-W) in the offshore Niger Delta. Two commercial fields with multiple reservoirs and one dry well have been drilled in the study area. The amplitude anomalies were identified in each prospect but similar amplitude anomaly was also located where the dry well was drilled. The reservoir rock at the regional scale and the trap were identified as the major risks for these prospects. The main objectives of this study were to understand the regional reservoir presence and effectiveness, the nature of seismic amplitude anomalies and reduction of the trap risk.
The geological model was used to understand the regional reservoir presence and effectiveness. The 3D seismic interpretation and fault seal analysis helped reduce the uncertainty around the structure and the trap. The Extended Elastic Impedance was used to further dig into the relationship between lithology, fluid and amplitude anomalies. The integration of various geoscience disciplines and data types resulted in substantial reduction in overall prospect risk. The study concluded that Prospect-N has the lowest overall risk and presents a promising location for the next exploration well in the block.
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The Underexplored Shelf-Edge Plays of the West Africa Transform Margin Through Togo, Benin & Western Nigeria
Authors M. Tyrrell and B. BiaouSummaryShelf edge plays which are prevalent in North West Africa Atlantic Margin are shown to continue through the Transform Margin of West Africa in Togo, Benin and Northwest Nigeria. Advanced interpretation work conducted on merged 3D seismic and well datasets across these three countries has identified considerable overlooked shelf edge prospectivity in open acreage. Wells drilled to date have proved the presence of good quality reservoirs and the potential of the play landwards of the shelf edge. The opportunity now presents itself for oil companies to explore the play through the three countries and to map and derisk the numerous leads identified. Where the shelf edge is targeted, explorers might expect to find the best reservoir qualities and future drilling of this play is expected to lead to success.
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A New Integrated Pseudo-3D Petroleum System Model of Central Italy and Adriatic Sea:Insights and Exploration Potential
Authors A. D’Ambrosio, L. Lipparini, T. Cassola and J.F. DerksSummaryThe Central Adriatic foreland and its adjacent on and off-shore foredeep area has been a target of great interest for hydrocarbon exploration since the past century and were a widespread occurrence of small/medium oil accumulations, is the clear proof of an active petroleum system. Our geological and modelling work, allowed a better regional understanding of the processes and key factors at the base of the activation of the petroleum system, reducing the overall geological risk and representing a good base for future exploration efforts in the region (both on-shore and off-shore).
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HiRes GravMag Data Reveal New Insights of Black Sea Crustal and Basement Configuration
Authors L. Cascone, S. Subias Rodriguez, H. Matias, I. Munteanu, G. Tari and L. Calle-BenavidesSummaryIn late 70s, hydrocarbon exploration in Blach Sea concentrated on the shallow water shelf area. The exploration focus has change for the frontier deep water settings in the last decade, with the discovery of Domino gas field. The hydrocarbon exploration brought significant amount of new data, both with local and regional character. These include 2D and 3D seismic, Gravimetric and Magnetic data, with a reasonable amount of well data, essential for models calibration and validation. The integration of these new data brings new insights over the basin architecture and evolution. One of the key aspects for basin kinematics and petroleum system modeling is the continental oceanic boundary (COB) definition, especially helpful to assess the paleo heat flow in the Black Sea. The exploration also requires a better constrain over the basin evolution and architecture with the continental oceanic limit being one of the most important feature for the basin modelling of the petroleum system.
Our work focuses on the definition of the COB offshore Bulgaria and identification of crustal domains, by integrating the seismic interpretation of the 3D and a dense grid of 2D data both PSTM and PSDM with interpretation and inversion of GravMag data.
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Geological Implications of High Resolution Gravity and Magnetics in the Zambezi Delta
Authors M. Parsons, J. Martin and G. DuvalSummaryThe integration and modeling of a recent high resolution 3D seismic, gravity and magnetic survey offshore Mozambique has provided new insight into the nature of the crust and the tectonic evolution of the Zambezi Basin and Beira high.
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The Application of High Frequency Bright Spot Based on T-K Energy Wavelet Transform in Hydrocarbon Detection
Authors D.J. Hou, D.H. Zhou, P.P. Zhang, C. Li and H.G. ZhangSummaryStrong seismic reflection often represents the oil and gas reservoir, or the tuning caused by thin layer. It is very important to accurately and effectively identify the true and false bright spots. In this paper, we propose a new hydrocarbon detection method based on the TK energy wavelet transform to detect the hydrocarbon reservoir with “high frequency bright spot” characteristic. Firstly, using the wavelet transform based on the TK energy, we can get different frequency divisions. The comparative analysis can identify the spectral characteristics of the thick water layer caused by the low frequency tuning, while the thin oil layer still has strong energy at high frequency. Then the frequency components are extracted, which is sensitive to the difference of oil and water layers. After weighted by the power index and merged of these selected frequency band seismic information, we can obtain the fluid indicator factor. Finally, the hydrocarbon detection result is obtained by multiplying the fluid factor by the -90 degree phase shift result. The result effectively identifies the false bright spots caused by thick water layer and enhances the recognition ability of thin reservoirs. Thereby the model test and actual application show this method is feasible and effective.
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Methodology of Detecting Bright-Spot Gas-Bearing Reservoirs Using Amplitudes in Different Frequency Components Extracted From Seismic Data
More LessSummaryA large amount of gas-bearing reservoirs, with a thickness of 2–8m, are developed in the shallow layer of BX oilfield. These gas-bearing reservoirs exhibit relatively strong seismic reflections called ‘bright-spot’. The water-bearing reservoirs with the tuning thickness have the same large reflection amplitudes, and interfere with the detection of thin gas layers. In order to solve the problem, this paper analyzes the characteristics of amplitudes of the water layers and gas layers in different frequency components extracted from seismic data, and use the amplitudes to detect gas layers with different thicknesses. The method is successfully applied on the prediction of the distribution of gas-bearing reservoirs in BX oilfield.
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Permeability Evaluation in Low Permeability Reservoirs Based on Multifractal Characteristics of NMR Logs
More LessSummaryPermeability is an important parameter to evaluate the reservoir quality and estimate the resource potential. Especially in low permeability formation, there is strong heterogeneity of formation. It is particularly critical to accurately evaluate permeability for reservoir development and exploration of remaining oil. Multifractal method is a popular method to describe the self-similar characteristics of irregular geometric figures. In this paper, the multifractal analysis based on the NMR logs was applied to evaluate permeability of low permeability water layers. Firstly, a multifractal method for Nuclear magnetic resonance (NMR) T2 spectrum logging data is established. Then, after multifractal processing and analysis, fmin and Dmax have been proved to be effective multifractal parameters for evaluating permeability of water layers. Last, a method for evaluating permeability using multifractal parameters is established. In addition, the application and prospect of this method are analyzed.
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The Inversion Method of Thin Interbedded Reservoir Based on Spectrum Expansion Seismic Data
More LessSummaryThin interbed refer to a layer combination of different lithology less than tuning thickness. Due to the tunable interference of seismic waves between thin layers, the seismic wave field is complex, and it is difficult to effectively characterize the development and transverse distribution of thin interbeds. In this paper, to solve the problem, based on the framework of Bayesian theory, firstly the logging information was converted to the geological statistics prior information in the spectral inversion, the spectrum of seismic data was expanded, then wave impedance inversion data was obtained from the spectrum expanded data using Bayesian wave impedance inversion method so as to achieve effective characterization of thin interbeds. The method was applied to thin interbedded sandstone oil reservoirs developed in Guantao formation in Miaoxi area of Bohai oilfield, a lot of thin sand bodies which can not be described by conventional data with thickness of 5m were successfully characterized by this method, providing a high-precision data support for exploration and development in this region.
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A Combined Method for Gas-Bearing Identification on Complex Sandstone Reservoir
More LessSummaryLanggu Depression is a matured oil and gas exploration area with complicated lithology and physical property, its greatly changeful formation fluid, low-resistivity hydrocarbon reservoirs and non-uniform logging series make it hard to identify gas reservoirs. According to sensitivity analysis of gas in this area, a new combined gas-bearing identification method is proposed based on the various well logging series. The result shows that the new gas identification chart, based on neutron gamma logging, turns out effectively eliminate the influence of physical properties and formation water salinity, works well in the identification of gas reservoirs in the old wells. And the fluid factor based on array acoustic logging is sensitive to the development of gas reservoirs, can be used for the gas reservoirs identification in the new wells with array acoustic logging. Concrete field examples show that the new combined method greatly enhances the identification ability and prediction accuracy towards gas-bearing layers.
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