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EAGE/ALNAFT Geoscience Workshop
- Conference date: January 28-29, 2019
- Location: Algiers, Africa
- Published: 28 January 2019
1 - 20 of 42 results
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A New Ten-Step Integrated Petrophysical Rock Type Verification Process
Authors G.W.G. Gunter and M.Y.S. SaharSummaryOur ten-step workflow process couples deterministic with neural networks using the following steps:
- The number of PRTs is selected using common statistical analysis approaches (CDF, histograms or probability plots).
- The best PRT grouping is determined from the shape of log computed Sw and Swirr compared to the shape of PRT and PTRi in depth space.
- Further validation of PRT includes comparing results to geological facies, mercury injection capillary pressure, special core analysis results & Core and Log based thickness-weighted averages.
- Select a limited number of DPRT training points 1-3 for each of the PRTs as determined previously.
- Run an IPSOM neural network and compare predicted PRT-IPSOM to DPRT in depth space and cross plot space and repeat until the best statistical results are obtained.
- Repeat the IPSOM neural network analysis using “no training points” and evaluate the results.
- Individual wells can be further verified using the Multi-Component Advanced Flow Unit Plots and confirm that PRT and reservoir capacities (flow and storage) change slope simultaneously.
- Completing a final verification of identifying the “best PRT” includes inputting PRT results into a saturation height model comparing predicted Sw from the SHM to a baseline Sw
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Oil Production Optimization using Data Analytics Approach, Algeria
By B. HammadiSummaryThis paper presents an approach, that uses predictive Data Analytics models as an advanced problemsolving algorithm to evaluate gas injection and enhance oil production of hydrocarbon fields. The gas injection process incorporates the measured injection pressure and injected gas volumes assessment to better manage gas sweep and control gas breakthrough in the oil producing wells. Reservoir and production parameters are only known within a certain range, not all the possible parameters combinations can be covered by simulation models to obtain a probability distribution of possible outcomes. To illustrate the use of this technique, a real study has been conducted on a field under miscible gas injection. Gas injection and oil production data from various injection patterns are used to set up series of input parameters; Neural Network (NN) models are then generated. Subsequently, by training a NN on the injection and production patterns, a model which can interpolate between the individual gas injectors and the oil producers is created for each injection cell. This way, a large variety of different prediction scenarios can be represented with a limited amount of model runs within a short time frame. The Neural Networks which are a pattern-recognition with their abilities to learn, to associate, and to be error-tolerant can unravel the sensitivity of the input data (Injected gas volumes) on the output (oil production) with a range of limited uncertainties using an iterative process.
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70 years of oil production: Emlichheim long living example of full field EOR, Germany
Authors M. Ibrahim and U. StreckerSummaryEmlichheim field was discovered in 1943 and started production in 1944. It represents an extraordinary long production plateau for more than 70 years in particular when considering the oil viscosity range of 170–200 cP and a reservoir temperature of 37°C. In fact, the oil acts as a “glue” for the host unconsolidated sands of lower Cretaceous and sand control is needed. The field development phases proceeded in time with the technology which permitted the current recovery factor of 30%. The high RF is achieved thanks to the close-loop steam injection at temperature >300°C (to increase oil mobility) which is coupled with cold water injection to maintain reservoir pressure. The latest drilling campaign confirmed the presence of bypassed and attic oil still to recover. The new 3D seismic survey (2017) aim is to better nterpret the faults sealing capacity and to identify the steam paths in order to plan the next wells (producers & injectors). Additionally, the steam injection capacity joined with debottlenecking are planned to be increased and optimized respectively. Horizontal steam injectors are also designed. All is planned to achieve a field recovery factor of 50% and postpone the field abandonment date for decades.
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Design of New Model (ANNSVM) Compensator for Saturation calculation Based on Logging Curves for Low Resistivity Phenomenon
Authors M.Z. Doghmane and B. BelahceneSummaryThe objective of this study is to design a new model for saturation calculation based on resistivity curves in case of low resistivity phenomenon. This model is constructed using support vector machine technique; it has been proved to be an efficient tool for modeling complex phenomenon in different engineering fields. Low resistivity phenomenon had appeared in specific field in Algeria, for which many studies have been realized to correct the under estimation of hydrocarbons volume calculated using petrophysical curves, precisely resistivity variables. It has been proven through these studies that the presence of heavy minerals is the major cause of the underestimated results, moreover some of the researchers have proposed compensator terms in different studies in literatures, however these terms are generally added empirically and have no mathematical development background, and thus it is so difficult to be generalized for the whole region. Our study aims to design a compensator model based on artificial neural network and support vector machine (ANNSVM), based on field data, the model gives representation that can be more trustable and the compensation match with results given by modular dynamic tool (MDT) sampling.
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Deterministic Seismic Inversion in a Tight Sandstone Reservoir and Integration in the Geological Model of the Irharen Gas Field (Timimoun Basin, SW Algeria)
Authors G. Rodrigo, P. Alonso, GY. Brenner, R. Faro and L. SerraSummaryExtended abstract with main figures have been uploaded below:
The Irharen field forms part of the Timimoun natural gas project, located in the Timimoun basin in southwest Algeria ( Figure 1 ). Dry gas is there produced from several tight reservoirs of Early Devonian age. The Irharen gas field, discovered in 1993, is currently producing from a very low poro-perm sandstone reservoir of Praguian age, which shows laterally better petrophysical properties more favorable for gas production
Porosity prediction is the main challenge for the Praguian reservoir in the Irharen field. Good porosity areas are mainly controlled by local diagenesis and their distribution is very difficult to predict.
This paper describes the process and findings of the deterministic inversion carried out on the reprocessed pre-stack Irharen 3D seismic and its input for reservoir geological modelling.
Well log data showed a correlation between reservoir petrophysical parameters and rock elastic properties for the Praguian reservoir. Cross plotting between P-impedance and Vp/Vs ratio at log scale showed a correlation, which allowed discriminating gas saturated, and high porosity sandstones. Based on seismic partial stacks, wavelets and low frequency model, a model based pre-stack seismic inversion was carried-out. First result of the inversion was used to define a gradient volume obtained from the correlation between P impedance and VP/VS Ratio and is therefore related with porosity. Areas showing high gradient values correspond to low P-impedance and low VP/VS ratio zones, which may be associated to high porosity sand areas.
Prior to modeling, a statistical analysis of the gradient volume versus well data was carried-out. Frequency diagrams by rock type enable to discretize the gradient cube in probability classes and optimized a minimum threshold for high productivity intervals identification. An improvement of the well to seismic relationship was achieved by crossing the gradient cube with a 3D Vclay model. These cubes were used to locally guide the porosity model giving satisfactory results in the history match and open up additional development well location in the Irharen structure.
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Understanding exploration risk using critical time and maturation modelling in Hodna, NEC and SEC area, Algeria
More LessSummaryExploration focus in this basin has been Jurassic to Tertiary, however, primary focus has been Cretaceous and Tertiary due to limited data for deeper stratigraphy (Jurassic). Main reservoirs in Cretaceous are Aptian L.St/Dolomite, Lower Albian sandstone, Cenomanian-Turonian carbonate, Eocene carbonate and Miocene sandstone whereas main source rocks include upper Albian- Vraconian shale, Cenomanian-Turonian marl/Shale and Eocene- Ypresian marl/shale.
Wells for thermal maturation modeling in this study are selected to cover tectono-stratigraphic domains across the basin (Pre-Atlas, Sharan Atlas, Miocene Foredeep and Aures).
Input for model building (Age, and lithology and source rock data) is based on actual well data which is given appropriate regional perspective based on published literature review. Erosion is estimated based on well correlation and synthesis of published literature. Boundary conditions (PWD, heat flow) are assessed based on regional information. Few key wells are calibrated using Tmax converted to VRE data wherever reliable Tmax data available.
Based on thermal maturation modelling of main source rocks (Eocene, Cenomanian-Turonian and Vraconian), evaluation of critical time is primary focus besides subsidence and thermal maturation. The critical time shall be discussed in the context of structuration of main reservoirs using regional understanding to assess the timing for charge risk.
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Methodology to Review and Optimize the Waterflooding Segments in Mature Fields
Authors K. Slimani, J. Orjuela, R. Balcazar and M. JamalSummaryWaterflooding optimization aims at expanding volume sweep to recover bypassed oil in undrained areas or remaining oil in poorly swept areas. For that, the multi-disciplinary SIS consulting team in Kuwait has introduced a methodology to improve oil recovery from mature fields under waterflooding by segments analysis and optimization. It consists of understanding the connectivity between injector and producer wells within a segment by combining the analysis of the available static and dynamic data without using the numerical simulation. The static data involves the fault systems, sand thickness, porosity-permeability maps and well correlations. In the other hand, the dynamic data involves production rates, tracer, PLT, ILT, salinities and different types of pressures (SBHP, WHP and PIP). In addition to that, allocation factor, instantaneous VRR, Hall plot and diagnostic plots were calculated and used in this methodology.
At the end of each segment review, recommendations were provided to optimize the existing waterflooding segments and improve the oil recovery such as: definition of new injection rates, change of lifting system (NF to ESP), water shut-off (WSO), re-perforation, increase the size of ESP, stimulation and change of reservoir target. Within 2 years of consulting, more than 35 waterflooding segments in UB and MA reservoirs from SA field were reviewed, analyzed and presented to KOC generating more than 10,000 BOPD of oil gain resulting directly from execution of the recommendations.
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Engineered Completion and Well Spacing Optimization Using a 3D Planar Frac Simulator and Fast Marching Method: Application to Eagle Ford
Authors A. Bachir, M. Paryani, R Khandelwal, S. OZA and D. BOUKHELFSummaryOptimizing a well’s hydraulic fracture design within a pad development environment is a multi-disciplinary effort and requires a 4-dimensional understanding of the reservoir.
The workflow described here uses an integrated workflow that combines geology, and geomechanics. The reservoir model can be interrogated and updated with a geologically and geomechanically constrained grid-based 3D planar frac model and production simulation using a fast marching method. In this case, as applied to an Eagle Ford well to address concerns of completion optimization, production and depletion forecasting, well spacing and well interference.
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3D advanced seismic and its impact on reservoir characterisation in mature fields: case studies.
Authors L. Michel and P BertrandSummaryOptimizing hydrocarbon recovery from mature basins requires a detailed and intimate knowledge of the reservoirs (compartmentalization, fluid circulation, etc.) enabling engineers to design the most effective field development plans. It relies on the capacity to identify subtle features of reservoir intervals and characterize their properties. We first show that in cases where vertical resolution is not sufficient, geostatistical inversion is the most effective way to go beyond the limitations of the data. However, acquiring high quality data and applying new G&G technologies and workflows is generally the only way to deliver the information conventional technologies have not been able to deliver so far, even by applying the latest data processing and reservoir characterization workflows. It is now broadly recognized that the key acquisition related parameters to produce seismic data suitable for reservoir characterization applications - commonly designated as “high fidelity seismic data” - are seismic bandwidth and data density. The three case studies shown in this presentation illustrate the benefits of advanced workflows to identify and characterise reservoir intervals, and the step change made possible by high-fidelity seismic data.
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Increasing Chance of Success for Hydraulic Fracturing in Low Permeability and Multi-Layer Oil Reservoirs using Quantitative Subsurface Criteria
Authors M. Wantawin and M. RongdechprateepSummaryThis paper summarizes the main takeaway from past hydraulic fracturing campaigns, which have been continually performed in multi-layered mature oilfield of Thailand. In addition, it presents the candidate selection methodology which was built from real-field hydraulic fracturing implementation and experience. The developed technique help to overcome the challenge of selecting appropriate targets in complex reservoirs using quantifiable subsurface quality, thus mitigating risk of well stimulation outcome.
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Contribution of the seismic anisotropy in shale gas reservoirs exploration, a case study from the Barnett shale (USA)
Authors S.A. Ouadfeul and L. AliouaneSummaryHere, we show the contribution of the seismic anisotropy in the characterization of natural and hydraulic fractures of the Lower Barnett shale gas reservoir. Data of the sonic scanner tool recorded in a horizontal well drilled in the Lower Barnett shale gas reservoir located in the Fort Worth Basin (USA) are used. Results interpretation show that the seismic anisotropy is able to detect only some natural and induced fractures azimuths.
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The Best Practice to Combine IOR / EOR Project and valorization of rich gas
Authors R.L. Lamali and O.S. SalmiSummaryThis abstract presents the subsurface feasibility of a liquids stripping scheme in an Algeria`s onshore asset: Rhourde Ouled Djemma (ROD) field. The ROD Development is comprised of six fields within the Berkine Basin. The fields produce a light oil, from TAGI reservoirs, that are routed to the BRN processing facilities operated by Groupement Sonatrach-Agip (GSA).
The liquids stripping development by Natural Gas Liquid (NGL) plant is strictly connected to the reservoir management topic since Enhanced Oil Recovery (EOR) technique is currently applying injecting miscible gas into the reservoir. With the aim of maximizing oil production, a significant technical concern is that injecting lean gas will negatively impact oil recovery, due to the loss of miscible displacement in reservoir. A preliminary slim tube simulation has been performed to analyze the impact of the new injection stream on the miscibility. Using the compositional model of ROD changing the gas injection stream for rate and composition, the iteration between NGL plant and reservoir was modelled.
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Case study of EOR modelling in brown field in the Algeria off shore
Authors M. Moumene, M. Rametta and M. BotteonSummaryGravity segregation and viscous fingering may produce anticipated gas breakthrough in WAG applications; thus gas control is a major challenge to improve the efficiency of WAG injection. Several advanced technologies are being researched in the oil industry: Foam Assisted WAG (FAWAG) is one of the most effective EOR techniques in terms of gas production control.
In general, foam is defined as a large gas volume dispersed as bubbles in a continuous water phase; it is generated when gas contacts a foaming agent (i.e. surfactant). At field scale, surfactant is injected in water phase before gas, to generate foam directly in-situ and mitigate gas production issues.
The most significant impact of foam propagation in porous media is the reduction of gas mobility. At field scale, this leads to delayed gas breakthrough, decreased GOR, improved macroscopic sweep efficiency and thus a general improvement in terms of oil recovery,
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Effect of Gas Cycling on Condensate Baheviour in Gas Condensate Reservoirs
Authors B. Meghdouri and H. IkeneSummaryNo summary provided
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Emerging unconventional plays in western Algerian Saharan platform: tectono-stratigraphic approach of Cambrian to Devonian units
Authors J. Allard, S. Roussé, D. Savva, B. Murat, F. Saint-Ange, M. Djidjeli, C. Basuyau and A. LounesSummaryIntegrated G&G analysis of the whole Western Algerian Paleozoic basins allows to obtain new insights on both the Cambrian to Devonian unconventional potential plays.
The Cambro-Ordovician Tigh plays display a voluminous sandstone-gross-volume, bounded by syn-sedimentary tectonic lineaments and inferred facies belt.
The Devonian Tight plays display a more complex facies partitionning linked to both intrinsic facies variations and Caledonian tectonic activities.
Thus the remaining prospectivity for the Paleozoic Tight Plays, relies on our ability to address major off-structures trapping mechanism as well as subtle mixed traps (structural and stratigraphic).
Meanwhile the Silurian Shale Play displays various potential source rocks levels; the lowermost hot shale unit (Llandovery) shows the highest potential for exploration despite a discontinuous geographical distribution along the WASB.
The Frasnian-Famennian Shale Play appears as a sandwich-layered system (organic-rich vs organic-poor levels) with high potential. This study has revealed that organic-rich deposits are frequent but highly laterally discontinuous and directly associated with platform clinoform bottom-set prograding northward. Thus, such Shale Play cannot be evaluate as Silurian Shale Play and needs to be considered with seismic-stratigraphic approach.
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3D-sedimentary model of a Late Ordovician glacial cycles: fully-integrated subsurface approach (Illizi Basin, Algeria)
Authors S. Roussé, J. Allard, T. Chrest, L. Drab, L. Kuhfuss-Monval, M. Benseradj, K. Hachour and A. ZemmoukSummaryBased on a detailed sedimentological analysis of the glaciogenic sediments, integrated with seismic and petrophysical characterization, this paper aims to address the nature, complexity and prediction of sedimentary tunnel-valley infill as well as the related potential petroleum reservoir occurrences.
In the particular Late Ordovician glaciogenic context, accurate reservoir prediction and source rock distribution relies on: (1) preservation of synglacial reservoirs units from secondary glacial incisions; (2) precise definition of superimposed tunnel valley pathways/networks for sandy reservoir distribution; (3) spatial distribution on postglacial sediments themselves dependent on inherited glacial topography.
The best potential glaciogenic reservoir have been recognized within inverted 3D seismic volume, as relatively thin subglacial sandstones veneers lying scattered on glacial erosive surface and as more voluminous sand-prone outwash deposits generally limited by glacial valley envelop. These facies presents important both lateral and vertical heterogeneity with rapid change in facies (clean-sandstone to diamictites) implying a strong decrease in reservoir prospectivity.
Such presented approach appears as suitable to map, with precision, sedimentary geobodies in an exploration assessment context.
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Predicting Reservoir Quality in Exhumed Basins: Insights from Burial History Modelling of the Illizi Basin, Algeria
Authors J. Redfern, K.L. English, D. V. Corcoran, J. M. English and R. Y. CherifSummaryNo summary provided
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Dielectric Scanner Technology added-value in tight reservoirs characterization
Authors R. Lamali, RL LAMALI and NA Bendali AmorSummaryOne of the main challenges in tight gas reservoir characterization is the evaluation of water saturation, due to the effect of tightness on the resistivity logs which can no longer help discriminate between hydrocarbon and water bearing intervals.
The Dielectric scanner technology offers a direct measurement of the water volume, when combined with porosity measurement, it will derive a resistivity-independent water saturation.
The multifrequency Dielectric Scanner (ADT) has been run in several wells in the South West of Algeria, mainly in the Ahnet tight Ordovician Play and the results have proven the robustness of the new measurement and its efficiency in the determination of gas-water contact, which is of high value especially that most of those wells are future candidate for hydraulic fracturation.
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Integrated approach of sedimentology, diagenesis and log response for the characterization and the prediction of Devono-Carboniferous Reservoirs in the Berkine Basin, Algeria
Authors G. Musial, F. Fournier, L. Cuilhé, M. Médaouri, A. Bellahcene, N. Filali, J. Pitz, A. Prélat, A. Le Saos and V. MachaultSummaryAn integrated study based on sedimentology, stratigraphy, diagenesis and electrofacies has been performed on Devono-Carboniferous intervals in the central part of the Berkine Basin to better constraint the origin of the compartmentation of hydrocarbon targets accumulations, the processes and their impacts on fluid distribution in reservoirs.
Devonian reservoirs are strongly degraded by quartz overgrowths. Hydrocarbon accumulations are preferentially located in chloritic zones where the grain coating has preserved the pore space. This diagenetic process is directly related to the depositional environment where tidal actions are present. Same observation has been made in Lower Carboniferous reservoirs where the distribution of chlorite sandstones takes an important part in hydrocarbon prospecting. However, Strunian reservoirs are them degraded by chlorite in fill, probably alimented by underlying Devonian deposits eroded and reworked during the Ahara high reactivation at this period of time.
This tectonic reactivation and changes of sedimentary supplies are corroborated by the diagenetic analysis of the Carboniferous which highlights that feldspar rate is decreasing upward. This progressive decreasing though the time is related to the sedimentary source migration. The sediment sourcing was initially located in the metamorphic Hoggar High to the South and has moved at the end of Strunian period until dominant northward supplies.
Upper Carboniferous reservoirs of Visean are by the way less affected by the diagenesis and strongly controlled by stratigraphic architecture which is characterized by an important stack of sandy bars interfingerred with shale. In this vertical segmentation context, the least one of fault movement could have an impact on hydrocarbon distribution.
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