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Collaborating Authors
Nile Delta
Abstract Scope of this paper is to show how the proper definition of reservoir rock types, based on core data and integrated with nuclear magnetic resonance (NMR) log results, is able to provide a reliable strategic estimation of permeability in un-cored wells where only conventional logs are available. The target is to optimize the perforated intervals by means of a robust discrimination between movable and un-movable fluids and consequent detection of the reservoir zones characterized by the best gas deliverability potential. Mercury injection capillary pressure measurements have been used to evaluate the core pore throat size distribution and to separate micro from macro porosity. The integration of these information with NMR, acquired on the same core, allows to calibrate the most efficient T2 cut-off, discriminating movable from the unmovable fluids. The final outcome is a robust link between reservoir properties (defined and directly measured on core data) and log classification, giving a key driver for the definition of a synthetic permeability profile, rock type dependent, and applied for perforated interval optimization in wells where no cores are available. The blind test was a comparison between estimated permeability from the well production performance and permeability derived from NMR logs, showing a good match. The work has greatly increased the value of NMR acquisition in Gas industry, showing how a proper T2 Cutoff core /log calibration is a vital factor to get the benefit of NMR in Gas reservoirs permeability prediction, providing a useful driver for perforated interval optimization. Introduction At present time, permeability estimation still remains a great challenge due to its not scalar nature: different correlations have been defined in literature to link this parameter to conventional downhole measurements and petrophysical properties, anyway none of the current available open hole logs can deliver directly an indication of the estimated permeability. Even the most advanced NMR tool will fails if applied in a standalone approach. The result is that the conventional log analysis approach, where core data are used mainly for outcome validation, still leave some uncertainties in the permeability profile definition and related reservoir effective deliverability.
- Africa > Middle East > Egypt > Nile Delta (1.00)
- Africa > Middle East > Egypt > Mediterranean Sea > Greater Nooros (0.30)
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.30)
- Asia > Middle East > Israel > Mediterranean Sea > Southern Levant Basin > Delta Field (0.99)
- Africa > Middle East > Egypt > Western Desert > Bahariya Formation (0.99)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > West Mediterranean Concession > Abu Qir Field (0.99)
- (9 more...)
Abstract Building an accurate static model is critical to understand the reservoir heterogeneity, maintain the production, and optimize new wells locations. The stochastic modelling approach proved significant efficiency as a new and accurate modelling tool. In this case study, we applied the stochastic modelling approach to Sequoia field. The Sequoia Field is a Pliocene gas field, offshore Nile Delta, Egypt. The field is a delta slope, multi-stacked canyon systems with complex turbidity channel-levee deposits. The reservoir architecture commonly is the first priority in a stochastic reservoir model and is usually described in terms of different facies to rock types. The geomodel grid layout was made considering the geological realism. It was constructed from the beginning not to be upscale at the end, on a scale grid design of increment 100×100×1.5m mean. This increment was selected in such a big field to preserve the heterogeneity of the field with respecting to run time and the maximum number of the cell could be run in a dynamic model. The new model built has been used to calculate in-place volumes for Sequoia Field. The integrated structural framework of the model was made using the time and depth converted seismic horizons which used to create horizon model in time and depth domain. And the fault sticks were used to create the fault model and eventually the fault surfaces within the reservoir. The facies volume fractions were calculated from wells and considering the gross rock volumes from magnitude maps and inversion volumes. The reservoir properties like porosity and water saturation volumes were modeled stochastically and co-simulated using correlation coefficients biasing to the facies property. The Stochastic geomodel optimizing on the grid resolution, provide better water predictions and planning of additional wells if needed. Introduction This study used the static modeling techniques to understand heterogeneity of sequoia channel in reservoir facies, porosity, permeability and water saturation. Tiab and Donaldson (1996) reported that petrophysics is the science concerned to study of the (physical and chemical) rock properties and interactions with fluids. A number of petrophysical properties; like, porosity, permeability, and saturation will be described. These properties depend on the distribution of other properties such as mineralogy, pore size, or sedimentary fabrics, and on the physical and chemical properties of the solids and fluids. Consequently, petrophysical properties may similar in a homogeneous reservoir or they may vary from one position to another, in a heterogeneous reservoir. Stochastic modeling techniques used to understand heterogeneity of sequoia channel in reservoir properties, and then gas volume can be estimated. AREA OF STUDY The Study Area (Sequoia Field) is located on the north-western margin of the Nile Delta, approximately 90km offshore of Alexandria., and approximately covering 90km2 (Fig 1). The field lies across the border between the West Delta Deep Marine Concession and the Rosetta concession.
- Geology > Geological Subdiscipline > Stratigraphy (0.48)
- Geology > Rock Type > Sedimentary Rock (0.32)
- Africa > Middle East > Egypt > Western Desert > Obaiyed Field (0.99)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > Sequoia Field (0.99)
- Africa > Middle East > Egypt > Mediterranean Sea > Rosetta Field (0.98)
ABSTRACT The Nile Delta province covers one of the world's great Tertiary deltas. The province encompasses approximately 250.000 km2 of the Eastern Mediterranean area. The Mesozoic-Cenozoic composite petroleum system for Nile Delta basin was defined to include the source rocks of Jurassic, Cretaceous, Oligocene, Miocene, Pliocene and Pleistocene ages. Many fields have been proved by PVT samples and production data, the presence of thermogenic gas and condensates in the Pre-Messinian reservoirs (Wakar, Sidi Salem, Qantara and Tinah Fms), while the Plio-Pleistocene section has been proved mainly as a biogenic gas potential. Thermogenic gases have been recorded also in some cases in the Plio-Pleistocene section; these gases being generated from the pre-salt section and migrated along faults and/or gas chimneys. Oil has been discovered in the eastern side of the Nile Delta basin in both onshore (Qantara oil discovery) and offshore (Tineh & Mango oil discoveries). Recently, oil has been discovered in the Pliocene reservoirs in the eastern offshore of the Nile Delta Basin. Bore hole samples indicate an oil gravity of 42 API degree with an gas oil ratio of 708.54 Scf/stb. This oil is likely to be originated from a deep source rocks and migrated along a fault planes which acts as a good conduit for hydrocarbon migration. According to geochemical analysis the Pliocene oil would appear to be evaporated oil, which opens the gate for oil exploration in the deeper intervals. INTRODUCTION Over the past 35 years more than 4.0 BBOE have been discovered in the Nile Delta, primarily as gas and condensate. Figure 1shows a location map of the area presented in this talk. With the discovery of Pliocene oil in the Eastern Nile Delta, given that such considerable amounts of oil are known, it is logical to ask "Where has it come from and when was it forms" the answer may provide clues to discovering yet more oil in less obvious places.
- Phanerozoic > Cenozoic > Quaternary > Pleistocene (1.00)
- Phanerozoic > Cenozoic > Neogene > Pliocene (1.00)
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Geological Subdiscipline > Geochemistry (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (1.00)
- Asia > Middle East > Israel > Southern District > Eastern Mediterranean Basin (0.99)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > Ras El Barr Concession > Seth Field (0.99)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > North El Amriya Concession > Kafr El Sheikh Formation (0.99)
- (4 more...)
ABSTRACT To drill and complete high efficiency and trouble free well is nowadays the most valuable way to carry out a development plan. Drilling progress and production rates monitored on a daily basis by the highest authority to ensure production schedule is uninterrupted or unhindered. With this in mind, it is critical to ensure that the Drilling fluid is engineered to address the drilling challenges and ensure minimum damage to the producing formation to maximize the production rates. The main target for the Drill-In fluid is to drill through the highly reactive interbedded Kafr el Sheikh shale and into the sand gas reservoir of the Egyptian concession with water base fluid while minimizing whole fluid losses to the formation and achieve zero skin factor. With known sand permeability and shale reactivity, the fluid is engineered to both effectively bridge the sand and at the same time provide the required inhibition. INTRODUCTION Shale samples and sand data were collected for comprehensive lab testing to ensure the right inhibition, encapsulation and lubrication as required. Shale reactivity required additional encapsulation and inhibition. After utilizing proprietary software to design the bridging package particle size distribution, the resulting outputs where tested and optimized in the lab. Furthermore, the final fluid formulation at 1.25 SG was tested in a core flood study whereby the reservoir downhole conditions such as overburden and differential pressures, flow regime and permeability were simulated. Therefore some efforts have been made in the lab to find out the best biopolymer to viscosify the KCl brine selected to achieve 1.05 kg/l and to optimise the particle size distribution of the calcium carbonate in order to promote the creation of a very thin and tight filter cake that would minimize differential sticking tendencies and be resistant to erosion during the gravel pack process. Through the use of core flooding tests, this drill-in fluid showed a very good recovery of the permeability and the formation of a filter cake with excellent fluid loss control performance. In the field, all drilling and completion phases proceeded as planned and no fluid losses were recorded while drilling and gravel packing, confirming the lab results on filter cake quality. No matrix stimulation treatments were performed for clean-up and expected gas production rate was soon exceeded on the well.
Tectono-Stratigraphy and Reservoir Facies of Serravallian-Tortonian Succession and Its Impact on the Explorative Potential in Northeastern Offshore Nile Delta Basin, Egypt
Adel, M. (Belayim Petroleum Company) | Zaki, A. (Belayim Petroleum Company) | Nasser, M. (Belayim Petroleum Company) | Abrar, M. (Belayim Petroleum Company)
ABSTRACT The study area covers Temsah concession in the eastern Mediterranean sub-basin, Nile Delta, Egypt. Over 25 wells have been drilled within the area, targeting channelized flow deposits that covering a part of the four-way dip closure Akhen-Temsah anticline. Despite the Serravallian hydrocarbon system within this area is proved, the interpretation of the recently acquired seismic data suggests that its potentiality might be significantly larger than initially evaluated. The tectono-stratigraphic approach has been applied to delineate the Serravallian reservoir bodies in the down-flank of Akhen-Temsah anticline. The application of this approach has been proved by a gas discovery. This will open a new opportunity to explore other anomaly trends. The studied interval shows a fining upwards gamma ray log pattern with a sub-parallel thinning up-dip seismic reflectivity. Seismic interpretation was performed within Serravallian-Tortonian succession in the study area, including characterization of seismic signatures based on acoustic impedance contrast, continuity and stacking pattern. Amplitude map analysis through this interval shows SW-NE anomaly trends. New hydrocarbon potential arises under the assumption that the new identified reservoir bodies is related to the anomaly trends mapped on the over-laying levels, from those under-laying producing levels in the main field area. Reservoir rock distribution was primarily controlled by tectonics and relative sea level change, meanwhile its architecture prevents communication between permeable up-dip producing levels to down-dip younger overlying levels. Based on the mentioned assumption; the future exploration activity should be carried out over the turbiditic reservoir bodies, which located in the southeastern flank of Akhen-Temsah anticline. 1. INTRODUCTION The study area is located offshore Nile Delta, Egypt about 65 km away from Port Said city. It covers the Temsah concession (Fig. 1) with an area 1155 km2. Such area was discovered by MOBIL in 1977-1981 with the drilling of the first two wells, Temsah-1 and Temsah-2, in the southern part of the structure. The reservoir is hosted in terrigenous sandy rocks of Middle-Late Miocene (Serravallian-Tortonian) ascribed to Sidi Salim Formation. The present study addresses the tectono-stratigraphic framework of Serravallian-Tortonian succession and sheds light on the events that controlled the sedimentary processes of the studied interval in addition to distinguish the vertical and lateral facies variations of Temsah reservoirs. Also, it devotes to demonstrate the impact of tectono-stratigraphy and reservoir facies on the explorative potential in this area.
- Africa > Middle East > Egypt > Nile Delta (1.00)
- Africa > Middle East > Egypt > Port Said Governorate > Port Said (0.24)
- Phanerozoic > Cenozoic > Neogene > Miocene > Middle Miocene > Serravallian (1.00)
- Phanerozoic > Cenozoic > Neogene > Miocene > Late Miocene > Tortonian (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (1.00)
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.78)
- Asia > Middle East > Israel > Southern District > Eastern Mediterranean Basin (0.99)
- Africa > Middle East > Egypt > Port-Said > Nile Delta Basin > Temsah Field > Wakar Formation (0.99)
- Africa > Middle East > Egypt > Port-Said > Nile Delta Basin > Temsah Field > Sidi Salem Formation (0.99)
- (6 more...)
ABSTRACT Estimates of hydrocarbon reserves and the optimal scenario of their future recovery directly determine the profitability of the field development plan. The uncertainty in reservoir recovery predictions has been always considered as a major concern. Studying reservoir uncertainties should provide us with information about how "incorrect" a proposed scenario is. One effective approach to quantify reservoir uncertainties is to apply the concept of Experimental Design. As the name implies, experimental design is the technique used to guide the choice of the experiments to be conducted in an efficient way. Samples are chosen in the design space of the uncertain parameter in order to get the maximum amount of information through the lower number of experiments. Several experimental design techniques are introduced in literature, some are useful and effective and some are not. The objective of this paper is to introduce an efficient experimental design technique called Sobol sequence to the arena of petroleum reservoir uncertainty quantification. Sobol sequence technique is a space filling experimental design technique that uses one base Van Der Corput sequence for all design space dimensions and a different permutation of the vector elements for each dimension. To show the potentiality and efficiency of Sobol sequence technique, different reservoir analytical models are used as testing problems to compare between Sobol sequence performance in solving assisted history matching problems and the performance of the most popular experimental design technique, Latin hypercube. A performance indicator is developed to quantify how each response surface model created using the two different techniques approaches the correct solution of the testing problems. The results of this work indicate that the Sobol sequence technique is superior to the Latin hypercube method and hence provide improved reservoir uncertainty quantification.
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (1.00)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > Sabriyah Field > Marrat Formation > Upper Marrat Formation (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > Sabriyah Field > Marrat Formation > Sargelu Formation (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > Sabriyah Field > Marrat Formation > Sabiriyah Mauddud (SAMA) Formation (0.99)
- (6 more...)
ABSTRACT Mediterranean Sea offshore concessions are located about 30 – 60 km off the Northern Egyptian coast. More than 25 gas prospects have been identified. These accumulations are often characterized by several hydraulically independent reservoirs. Three gas-condensate fields were discovered by three exploratory wells in 1982, 1983 & 1995, finding several gas bearing intervals inside Wakar and Abu Madi Formations (Miocene age). Following, further 9 gas fields have been discovered identifying several lean gas bearing intervals inside Kafr El Sheikh Formation (Pliocene age). In 2002, a lot of wells started to produce sand causing severe problems to the surface facilities and reducing the concessions production potential. In 2003, a sand control campaign was undertaken in Mediterranean Gas fields to recover the full fields' capacity using both Gravel Pack Completions (first time in Egypt in well PFM–7) and Expandable Sand Screen Completions (first time in Egypt in well PFM–8). By time, Expandable Sand Screen Completions proved its failure in many cases and are minimized to very limited cases. The aim of this poster is to highlight the advantage of Gravel Pack Completion technique used in North Port Said, Temsah & Baltim concessions over Expandable Sand Screen Completion technique focusing on successful case histories and its positive impact on production and reservoir potential. INTRODUCTION Most of the gas wells are producing from sandstone formations deposited in marine or delta environments. In the case of older and deep formations, sand grains are cemented by limestone or silica minerals, and in general the consolidation process is at a mature stage. More recent deposits, (starting approximately from the Miocene) are partially consolidated and their degree of cementation is non-existent or extremely low. In such reservoir, the sand production risk is extremely high. In most cases, sand production leads to serious operative problems affecting production and safety. This factor is one of the most important constraints in developing reservoirs in weak sandstone formations and, consequently, one of the main factors that determine the profitability of the investments.
- Africa > Middle East > Egypt > Nile Delta (0.54)
- North America > United States > Texas > Wharton County (0.40)
- Africa > Middle East > Egypt > Port Said Governorate > Port Said (0.24)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > North El Amriya Concession > Kafr El Sheikh Formation (0.99)
- Africa > Middle East > Egypt > Port-Said > Nile Delta Basin > Temsah Field > Wakar Formation (0.98)
- Africa > Middle East > Egypt > Port-Said > Nile Delta Basin > Temsah Field > Sidi Salem Formation (0.98)
- (4 more...)
- Well Completion > Sand Control > Screen selection (1.00)
- Well Completion > Sand Control > Gravel pack design & evaluation (1.00)
INTRODUCTION DGE plans to drill wells in Pliocene reservoirs which are represented by Kafr El Sheikh (KES) and El Wastani formations of Nile Delta (geographical location Fig-1). Fig-2 shows these aforesaid formations and relevant mega sequences on a seismic section. Kafr El Sheikh is subdivided into three Mega-Sequences of this massive marine transgressive-regressive series of sequences and the sequence boundaries correlate with changes in the relative sea level and consistent with Global Eustatic Curve Changes (El Haq et al., 1989). The thickness of these formations increase toward the north. Kafr el Sheikh Unit rests conformably over the Abu Madi Formation and underlies the El Wastani Formation. It mainly consists of shales and clays which are generally intercalated with fine sand beds. El Wastani Formation consists of thick sand beds interbedded with a thin clay beds. The depositional environment of KES rocks range from inner to outer neritic with fluvio-marine conditions, especially in the southern mid-delta area. Onshore Nile Delta Pliocene age/KES formation gas reservoirs are dominated by slope-channel systems. Also, it is worth mentioning that the fluid content within KES FM is usually dry gas with in situ biogenic source to wet gas on the lower part from deeper thermal source rock. Objectives: DGE recently carried out the prospectivity analyses of its Pliocene portfolio (mainly Kafr El Sheikh Formation) to identify the well locations and meet the business goals. The key objectives of the study were two-fold:Identify remaining commercial gas pools Enhance the rate of success of the futurewells DGE have been drilling Pliocene sands since many years but only with a mixed rate of success. The study focused to identify the causes of well failures and define the way forward to improve the success rate. It is worth highlighting that until 2010, most of the wells were chosen for drilling mainly based on the negative high amplitudes (Normal SEG polarity) on full stack seismic data.
- Geology > Rock Type > Sedimentary Rock (0.76)
- Geology > Mineral > Silicate > Phyllosilicate (0.71)
- Geology > Geological Subdiscipline > Stratigraphy (0.50)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > North El Amriya Concession > Kafr El Sheikh Formation (0.99)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > El Wastani Formation (0.89)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > Abu Madi Formation (0.89)
ABSTRACT The offshore Nile Delta basin is considered as one of the most promising province in Egypt with an excellent potential gas and condensate reserves for future exploration. Most of the discoveries in Nile Delta were driven by the detection of direct hydrocarbon indicator (DHI), where depend on AVO class (III), such as the reservoirs in the Upper Miocene and Middle to Upper Pliocene. The exploration in our concessions from many decades depend on traditional AVO class (III), we urgently need to add more reserves in the area specially there are some gas potential in Lower Pliocene without DHI supported that have been successfully tested; Lower Pliocene sand did not show any response in all the seismic volumes (full, near and far). The AVO analysis of this sand reservoir referred as AVO class (II-p). Other case of subtle Lower Pliocene reservoir shows AVO class (I) which was tested by three wells. Using the Enhance AVO Pseudogradient equation to create new attribute cube could be extract all the anomalies and identify AVO classes for each anomaly. In this cube the AVO class (I) appears as negative, while the other classes are positive. The difference between class (III) and classes (II, II-p) is done by high positive response compare with week response for classes (II, II-p). After knowing the AVO class we can use new equation to create new attribute cube (new model) which can be used to differentiate between the gas and water anomalies for all AVO anomalies. This method (new model) was successfully proven in Petrobel's concessions, where it helps us to discover subtle anomalies and open the gate for further exploration activities in the area. INTRODUCTION Baltim Concession is the study area, where it is a large exploration license located in the present day in the Nile Delta, offshore Egypt with water depth ranging between 20 and 300 meters. The concession covers about 435 Km2 of the central portion of the Nile delta cone. In 1996, IEOC and the partner PETROBEL acquired a high quality 3D seismic survey to discover more new reservoirs then reprocessed in 2004 and apply Near angle stack with (3:18) degree, Mid angle stack with (15:30) degree and Far angle stack with (24:42) degree. The Pliocene section is considered a prolific hydrocarbon-bearing interval in the Nile Delta and Mediterranean Sea. In the past decade's, most of the exploration companies activities concentrated in the Messinian reservoirs. In the last few years, the Pliocene play took attention as a result of the widespread use of high quality seismic data and seismic attributes.
- Phanerozoic > Cenozoic > Neogene > Pliocene > Lower Pliocene (0.67)
- Phanerozoic > Cenozoic > Neogene > Miocene > Upper Miocene > Messinian (0.35)
- Geology > Sedimentary Geology > Depositional Environment (1.00)
- Geology > Geological Subdiscipline (0.83)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.49)
- Asia > Middle East > Israel > Southern District > Eastern Mediterranean Basin (0.99)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > North El Amriya Concession > Kafr El Sheikh Formation (0.99)
- Africa > Middle East > Egypt > Nile Delta > Nile Delta Basin > El Wastani Formation (0.99)
- (4 more...)
Bayesian Petrophysical-Seismic Inversion Techniques for Key Reservoir Parameter Estimation: A Case Study From the Offshore Abu Qir Field
Aleardi, M. (University of Pisa) | Calabrò, R. A. (Edison R,D&I) | Ciabarri, F. (Edison R,D&I) | Garcea, B. (Edison E&P) | Giussani, M. (Edison E&P) | Peruzzo, F. (Edison E&P) | Terdich, P. (Edison E&P) | Mazzotti, A. (University of Pisa)
ABSTRACT Recent advances in seismic-constrained reservoir characterization combine statistical rock-physics and amplitude versus offset/angle (AVO/AVA) inversion in order to directly estimate petrophysical properties such as porosity, shaliness and water saturation from pre-stack seismic data. By exploiting the Bayesian inversion formalism, it is possible to propagate uncertainty from seismic to petrophysical properties, including the effect of noise on seismic data and the approximation of physical models. The results of such petrophysical-seismic inversion are spatial probability density distributions of rock and fluid properties that can be effectively integrated in the reservoir modeling workflows. This paper discusses two target-oriented Bayesian petrophysical-AVA inversion techniques: a two-stage approach and a single-stage approach, developed as part of a collaborative research project between Edison and the Earth Sciences Department of the University of Pisa. The two approaches are evaluated on the gas-bearing sands of the Pliocene interval in the Northern area of the offshore Abu Qir field where a 3D seismic survey was acquired using long-offset cables and well-control is available to validate the inversion results. The two-stage approach, is performed over the whole target-interval and is based on two cascade steps: first, seismic angle-gathers are inverted into acoustic and shear impedances using the convolutional model and a narrow-angle, time-continuous approximation of the Zoeppritz equations; then, a rock-physics model is used to transform the elastic parameters into petrophysical properties. Differently, the single-stage approach uses the rock-physics model to re-parameterize the exact Zoeppritz equations in terms of petrophysical variables; the derived equations are used to directly estimate the petrophysical property along the top-horizon of target interval by taking into account wide-angle seismic reflections. Independently from the inversion approach considered, the rock-physics model plays a crucial role in petrophysical-AVA inversion as it provides the link between elastic and petrophysical properties. In the Abu Qir field, borehole data acquired at the target-depths were exploited to derive a single rock-physics model, valid for different lithologies and for the full-ranges of shaliness and water saturation values. Despite the differences in the forward-model parameterization, the results of the two inversions are comparable and consistent with borehole data. In particular, the described inversion approaches were both able to identify the increase of porosity and the decreases of shaliness and water saturation in the target sands. It results that porosity is well resolved by both two-stage (narrow-angle) and single-stage (wide-angle) inversions. The water saturation remains poorly resolvable in both inversions due to its limited influence in determining the AVA response. Finally, wide-angle reflection inversion has demonstrated to be particularly effective in better constrain the shaliness estimations.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.47)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.30)