Complex Geological Features Research Articles

A Multiple Training Image Approach for Spatial Modeling of Geologic Domains

Characterization of complex geological features and patterns remains one of the most challenging tasks in geostatistics. Multiple point statistics (MPS) simulation offers an alternative to accomplish this aim by going beyond classical two-point statistics. Reproduction of features in the final realizations is achieved by borrowing high-order spatial statistics from a training image. Most MPS algorithms use one training image at a time chosen by the geomodeler. This paper proposes the use of multiple training images simultaneously for spatial modeling through a scheme of data integration for conditional probabilities known as a linear opinion pool. The training images (TIs) are based on the available information and not on conceptual geological models; one image comes from modeling the categories by a deterministic approach and another comes from the application of conventional sequential indicator simulation. The first is too continuous and the second too random. The mixing of TIs requires weights for each of them. A methodology for calibrating the weights based on the available drillholes is proposed. A measure of multipoint entropy along the drillholes is matched by the combination of the two TIs. The proposed methodology reproduces geologic features from both TIs with the correct amount of continuity and variability. There is no need for a conceptual training image from another modeling technique; the data-driven TIs permit a robust inference of spatial structure from reasonably spaced drillhole data.

SEISMIC STRATIGRAPHIC ANALYSIS AND STRUCTURAL DEVELOPMENT OF AN INTERPRETED UPPER CAMBRIAN TO MIDDLE ORDOVICIAN SEQUENCE IN THE NW BLANTYRE SUB‐BASIN, DARLING BASIN (WESTERN NEW SOUTH WALES, AUSTRALIA)

In this paper, a new interpretation is presented of the seismic stratigraphy of units equivalent to the upper Cambrian to middle Ordovician Scropes Range Formation in the NW Blantyre Sub‐basin in the central part of the Palaeozoic Darling Basin, western New South Wales. This succession was previously unrecognised, attributed to the lower part of the overlying Winduck Interval, or regarded as basement. The structural development of the study area is described, and may contribute to a better understanding of the regional stratigraphic evolution of the Lower Palaeozoic section in this part of the Darling BasinThis study presents interpretations of a regional two‐dimensional seismic survey which investigated the upper Cambrian to middle Ordovician Scropes Range Formation in the NW Blantyre Sub‐basin. A shallow marine Cambro‐Ordovician succession is well established in the Bancannia Trough in the western Darling Basin but this interval appears to have been ignored in the central Darling Basin where a deeper‐marine environment and suitable kitchen conditions may have provided greater petroleum potential. Data from two shallow wells in the 831 km2 study area were available to support the seismic investigations. Seismic sequences were defined by a combination of horizon mapping, the configuration of internal reflections, termination patterns and thicknesses. Six seismic reflection horizons were defined and used to identify five seismic sequences named Units A, B, C, D and E. These features were identified in three seismic lines and demonstrate the continuity of the Scropes Range Formation throughout the NW Blantyre Sub‐basin. All seismic sequence boundaries are based on fair to good continuous markers, with strong amplitudes throughout the study area. The acoustic basement beneath the Scropes Range Formation was metamorphosed in the Delamerian Orogeny (around 500 Ma). Acoustic facies recognized in the three seismic lines can be correlated with sedimentary facies observed in outcrops in the Scropes Range, 130 km west of the study area, and are comparable to acoustic facies in modern fluvial sandstones associated with local braided delta deposits. Complex geological features suggest potential structural and stratigraphic hydrocarbon traps.This study emphasizes the reservoir potential of the Scropes Range Formation in the central Darling Basin where extensive exploration efforts are currently occurring. The detailed interpretation of the seismic stratigraphy may lead to the definition of new exploration plays in this under‐explored region.

Diacritical Seismic Signatures for Complex Geological Structures: Case Studies from Shushan Basin (Egypt) and Arkoma Basin (USA)

Seismic reflection techniques show an imperative role in imaging complex geological structures and are becoming more acceptable as data interpreting tools in 2D/3D view. These subsurface geological structures provide complex seismic signature due to their geometrical behavior. Consequently, it is extremely difficult to interpret these seismic sections in terms of subsurface configuration. The main goal of this paper is to introduce seismic attributes as a powerful tool to interpret complex geological structures in different geological settings. In order to image these complex geological features, multiple seismic attributes such as coherence and curvature have been applied to the seismic data generated over the Shushan Basin (Egypt) and Arkoma Basin (USA). Each type of geological structure event usually generates a unique seismic “signature” that we can recognize and identify by using these seismic attributes. In Shushan Basin (Egypt), they provide a framework and constraint during the interpretation and can help prevent mistakes during a 3D structural modeling. In Arkoma Basin (USA), the seismic attributes results provide useful information for broader analyses of the complex structural relations in the region where the Ouachita orogenic belt intersects with the southern Oklahoma aulacogen. Finally, complex geological structures provide dramatically diacritical seismic signatures that can be easily interpreted by collaborating conventional seismic interpretation techniques with multiple seismic attributes.

Multiple-Point Simulation with an Existing Reservoir Model as Training Image

The multiple-point simulation (MPS) method has been increasingly used to describe the complex geologic features of petroleum reservoirs. The MPS method is based on multiple-point statistics from training images that represent geologic patterns of the reservoir heterogeneity. The traditional MPS algorithm, however, requires the training images to be stationary in space, although the spatial distribution of geologic patterns/features is usually nonstationary. Building geologically realistic but statistically stationary training images is somehow contradictory for reservoir modelers. In recent research on MPS, the concept of a training image has been widely extended. The MPS approach is no longer restricted by the size or the stationarity of training images; a training image can be a small geometrical element or a full-field reservoir model. In this paper, the different types of training images and their corresponding MPS algorithms are first reviewed. Then focus is placed on a case where a reservoir model exists, but needs to be conditioned to well data. The existing model can be built by process-based, object-based, or any other type of reservoir modeling approach. In general, the geologic patterns in a reservoir model are constrained by depositional environment, seismic data, or other trend maps. Thus, they are nonstationary, in the sense that they are location dependent. A new MPS algorithm is proposed that can use any existing model as training image and condition it to well data. In particular, this algorithm is a practical solution for conditioning geologic-process-based reservoir models to well data.

Improved geostatistical models of inclined heterolithic strata for McMurray Formation, Alberta, Canada

The McMurray Formation of northern Alberta in Canada contains multiscale complex geologic features that were partially formed in a fluvial-estuarine depositional environment. The inclined heterolithic strata deposited as part of fluvial point bars contain continuous centimeter-scale features that are important for flow characterization of steam-assisted gravity drainage processes. These channels are common, extensive, and imbricated over many square kilometers. Modeling the detailed facies in such depositional systems requires a methodology that reflects heterogeneity over many scales. This article presents an object-based facies modeling technique that (1) reproduces the geometry of multiscale geologic architectural elements seen in the McMurray Formation outcrops and (2) provides a grid-free framework that models these geologic objects without relating them to a grid system. The grid-free object-based modeling can be applied to any depositional environment and allows for the complete preservation of architectural information for consistent application to any gridding scheme, local grid refinements, downscaling, upscaling, drape surface, locally variable azimuths, property trend modeling, and flexible model interaction and manipulation. Features millimeters thick or kilometers in extent are represented very efficiently in the same model.

Hydrogeomorphological mapping as a tool in groundwater exploration

Hydrogeomorphological maps have a useful importance in exploration hydrogeology, engineering geosciences, geotechnical engineering and planning. The role of geomorphology is decisive to correctly evaluate groundwater resources. Hard-rock hydrogeological systems commonly exhibit complex geological and morphological features. This study highlights methodological guidelines for the preparation of hydrogeomorphological maps to support groundwater conceptual modelling, as well as for hydrogeological surveys and environmental sustainability issues. Cartographic techniques can provide an accurate way of improving the knowledge on groundwater and surface water circulation and the overall functioning of aquifer systems. A comprehensive evaluation of these subjects has been completed during the preparation of hydrogeomorphological maps for the Alardo groundwater system and Touca hydromineral system, both located on Gardunha mountain in Central Portugal. Thematic maps were prepared mainly from satellite imagery analysis, topographic, geological, geomorphological and hydrogeological field surveys. This information was presented to outline the recharge potential areas and infiltration rates. The paper also contributes to hydrogeomorphological mapping design and the conceptual model of groundwater in fractured hard-rock aquifer systems.

Geoheritage values of one of the largest maar craters in the Arabian Peninsula: the Al Wahbah Crater and other volcanoes (Harrat Kishb, Saudi Arabia)

AbstractAl Wahbah Crater is one of the largest and deepest Quaternary maar craters in the Arabian Peninsula. It is NW-SE-elongated, ∼2.3 km wide, ∼250 m deep and surrounded by an irregular near-perpendicular crater wall cut deeply into the Proterozoic diorite basement. Very few scientific studies have been conducted on this unique site, especially in respect to understanding the associated volcanic eruption processes. Al Wahbah and adjacent large explosion craters are currently a research subject in an international project, Volcanic Risk in Saudi Arabia (VORiSA). The focus of VORiSA is to characterise the volcanic hazards and eruption mechanisms of the vast volcanic fields in Western Saudi Arabia, while also defining the unique volcanic features of this region for use in future geoconservation, geoeducation and geotourism projects. Al Wahbah is inferred to be a maar crater that formed due to an explosive interaction of magma and water. The crater is surrounded by a tephra ring that consists predominantly of base surge deposits accumulated over a pre-maar scoria cone and underlying multiple lava flow units. The tephra ring acted as an obstacle against younger lava flows that were diverted along the margin of the tephra ring creating unique lava flow surface textures that recorded inflation and deflation processes along the margin of the post-maar lava flow. Al Wahbah is a unique geological feature that is not only a dramatic landform but also a site that can promote our understanding of complex phreatomagmatic monogenetic volcanism. The complex geological features perfectly preserved at Al Wahbah makes this site as an excellent geotope and a potential centre of geoeducation programs that could lead to the establishment of a geopark in the broader area at the Kishb Volcanic Field.

Estimating Moho basement and faults using gravity inversion in Yushu-earthquake area, China

A gravity survey was conducted one month after the 2010 Yushu earthquake in the epicenter area. The cross-fault survey line was 500 km long, from Langqian county to Qingshuihe county, in a transition zone between Bayan Har block and Qiangtang block, in an area of high elevation, large undulating terrain, and complex geological features. An interpretation of the data was carried out together with other kinds of data, such as seismic exploration and magnetic exploration. The result shows that gravity is sensitive to fault boundary; the geologic structure of the region is complex at middle and upper depths, and the density profile reveals an eastward-pushing fault movement.

Reproduction of microseism H/V spectral features using a three-dimensional complex topographical model of the sediment-bedrock interface in the Osaka sedimentary basin

SUMMARY Estimating the velocity structure of microseisms based on the horizontal-to-vertical spectral ratio (HVSR) is an extremely practical means of modelling the subsurface structure necessary for strong ground motion predictions. Thus, beyond the traditional framework of the 1-D velocity structure, the HVSR, derived from observation records of microseisms (microtremors with a frequency of about 1 Hz or lower originating from ocean waves) in areas where the sediment-bedrock interface has irregular topographies, was reproduced by finite differential method (FDM)-based simulation. This study was conducted for the Osaka sedimentary basin, the sediment-bedrock interface of which is three-dimensionally complicated and contains grabens, steps and ramps, because high-precision models for this basin have been constructed based on a wide range of existing exploration information. The HVSRs of two components (the east–west direction and the north–south direction to the vertical direction) derived from the FDM simulations were both well reproduced in terms of not only the peak frequency (HVfp) but also the spectral curves for a number of observation sites above the sediment-bedrock interface with complex geological features. These results suggest that with a sufficient number of observation sites for microtremors and highly accurate a priori information on geophysical constants in the sedimentary layer that spatially serves as the reference, the irregular-shaped sediment-bedrock interface may be estimated based on how well the HVSR curves and the HVfp agree between the observations and simulations. Furthermore, the FDM simulations confirmed observed phenomena such as the polarization of the amplitude of horizontal motions and broad or ‘plateau-like’ HVSR peaks of microseisms in grabens and step structures. It was determined that the HVfps in areas with these strong irregularities are higher than the peak frequency of Rayleigh wave ellipticity for the fundamental mode (RHVfp) based on the 1-D velocity structure. In addition, there was a difference of about 20 per cent at most between the HVfp derived from FDM simulations and the RHVfp in areas where the depth of the sediment-bedrock interface varies only slightly.

Crustal structure of the southeastern margin of the Ordos Block

We use a profile made up of teleseismic receiver functions to study the crustal thickness and structure of the southeastern margin of the Ordos Block. The Mohorovičić discontinuity(Moho) has been identified beneath all stations. Its depth gradually decreases towards the southeast, from about 43 km in the Ordos Block to ∼30 km near the northern margin of the Qinling Orogen. Our results show clear lateral variations in the structure of the crust and the features of the Moho. Accordingly, the study region can be divided into four parts: (1) Beneath the Ordos Block, the Moho is visible and flat at a depth of ∼40 km. The crustal structure is best characterized by stable cratonic crust. (2) In the Weihe-Shanxi Graben, the Moho is uplifted by about 3 km, which may be the result of upwelling of upper mantle materials. (3) Under the Xionger-Funiu Mountains, the Moho is flat at a depth between 36 and 33 km, but becomes shallower towards the southeast. (4) In the Hehuai Basin, adjacent to the northern margin of the Qinling Orogen, the Moho shows strong lateral variations with a mean depth of ∼31 km. The crustal structure here is complex, which may indicate a complicated tectonic environment. Additionally, the Moho is clearly interrupted at two locations (beneath stations st11 and st18) near major tectonic boundaries. These results suggest that the structure of the deep crust along the southeastern margin of the Ordos Block has great lateral variability, which strongly affects the complex geological features on the surface. Furthermore, these results can help us understand the interrelationships of different parts of the southeastern margin of the Ordos Block.

Numerical Simulation of Mechanical Behavior on Landslides Triggered by Heavy Rainfall

Deformation instability of slope due to rain was one of the most common geological disasters. Speaking from the mechanism, the destructive action and triggering action of rainfall affected the stability of slope itself, which made the slope deform and even lead to instability. June 28, 2010, Guanling in Guizhou province a large landslide occurred which triggered by continuous heavy rainfall, it caused that in two village-groups 107 villagers were buried, all the tragedy of houses were completely destroyed. Using finite element software ANSYS to simulate the mechanical behavior of the landslide, to analyze the deformation mechanism, we got that the large landslide deformation mechanism was a complex mechanical geological process. From the analysis of interaction between soil and rock, the landslide showed complex mechanical geological features. As rainfall increased the strength of unsaturated soil and weak intercalation reduced, this strengthened the role of the slope deformation and failure. The lock-fixed section first appeared brittle fracture, then that brought shear failure to the creeping section. The interaction between lock-fixed section and creeping section was the key of slope failure.

Seismic data interpretation using the Hough transform and principal component analysis

In this work two novel image processing techniques are applied to detect and delineate complex salt bodies from seismic exploration profiles: Hough transform and principal component analysis (PCA). It is well recognized by the geophysical community that the lack of resolution and poor structural identification in seismic data recorded at sub-salt plays represent severe technical and economical problems. Under such circumstances, seismic interpretation based only on the human-eye is inaccurate. Additionally, petroleum field development decisions and production planning depend on good-quality seismic images that generally are not feasible in salt tectonics areas. In spite of this, morphological erosion, region growing and, especially, a generalization of the Hough transform (closely related to the Radon transform) are applied to build parabolic shapes that are useful in the idealization and recognition of salt domes from 2D seismic profiles. In a similar way, PCA is also used to identify shapes associated with complex salt bodies in seismic profiles extracted from 3D seismic data. To show the validity of the new set of seismic results, comparisons between both image processing techniques are exhibited. It is remarkable that the main contribution of this work is oriented in providing the seismic interpreters with new semi-automatic computational tools. The novel image processing approaches presented here may be helpful in the identification of diapirs and other complex geological features from seismic images. Conceivably, in the near future, a new branch of seismic attributes could be recognized by geoscientists and engineers based on the encouraging results reported here.

Seismic sequence stratigraphy and facies architecture of the Scropes Range Formation in the Blantyre Sub-basin, Darling Basin, NSW

In this paper, we propose and present a seismic stratigraphic interpretation, based on two-dimensional seismic data, of units attributed to the Upper Cambrian to Middle Ordovician Scropes Range Formation within the northwestern portion of the Blantyre Sub-basin in the central part of the Palaeozoic Darling Basin, western New South Wales. Data from only two shallow wells of the 831 km² study area dealt with in this paper were available to support the seismic investigations. Six seismic reflection horizons are defined and used to separate five seismic sequences named Units A, B, C, D and E. These features are identified in three seismic lines and demonstrate the continuity of the Scropes Range Formation throughout the northwestern part of Blantyre Sub-basin. All seismic sequence boundaries are based on good continuous markers, with strong amplitudes throughout the study area. The acoustic basement beneath the Scropes Range Formation, was almost certainly metamorphosed in the Delamerian Orogeny (around 500 Ma) within the study area. In addition, acoustic facies recognized in the three seismic lines can be correlated with sedimentary facies observed in outcrop in the Scropes Range, 130 km west of the study area, and are compared with acoustic facies in modern non-marine (fluvial) sandstone units associated with local braided delta depositional systems. The seismic facies identified from the seismic data show features such as low-angle and high-angle clinoforms, parallel and sub-parallel reflections and a few hummocky/wavy reflections indicating shallow channel-fills and small-scale fluvial channels. A combination of horizon mapping, seismic facies analysis and seismic attribute mapping defines the sequences. Complex geological features suggest many potential structural and stratigraphic hydrocarbon traps. A high-resolution seismic survey could lead to the definition of new exploration plays in this underexplored region.

Mapping complex fracture systems as termite mounds—a fast-marching approach

Mapping complex fracture systems can be as difficult as mapping termite mounds. An entomologist casts a real 3D model of a termite mound by pumping 600°C aluminum melt into the tunnel system. We use a fast-marching algorithm to simulate the casting process to help the interpretation of the complex geologic features such as fractures and collapse features. In our example, we find that the algorithm is fast, amenable to user interaction, can handle complex geometry, and can implicitly handle bad picks. Our current research suggests good potential to build an interactive tool to map complex 3D surfaces by utilizing volumetric seismic attributes and adapting traditional algorithms of traveltime modeling using the fast-marching method.

Developing a Managed Pressure Drilling Strategy for Casing Drilling Operations

Casing drilling can be an effective method of reducing drilling costs and minimising drilling problems but its uptake around the world has been slow with only a few wells drilled so far with casing. Complex geological features like the high overburden on top of shallow unconsolidated reservoirs characteristic of offshore West Africa can benefit from casing drilling when effectively combined with Managed Pressure Drilling technique. For the industry to develop a managed pressure drilling capability that will allow today’s generation of complex wells to be drilled safely with casing, it is necessary to develop models that include the effect of eccentricity , rotation and fluid rheology at bottom hole conditions on flow and pressure regimes, and to embed these models within an easy to use, intuitive well design package for pre planning and as a real time tool to monitor and provide forward simulations based on real time rig and downhole data. The paper presents new results of the theoretical predictions of the wellbore pressure regimes incurred when different types of drilling fluid flows in concentric and eccentric horizontal annuli. The concentric and eccentric casing drilling results are compared with parallel predictions from conventional drillstring results from developed analytical solutions integrated into the VisWELL(DeskTop Simulator) , which is used in simulating well operations.

A grand tour of multispectral components: A tutorial

The human interpreter is perhaps the best pattern-recognition engine currently available. Often, interpreting seismic data involves inspection and analysis of multiple seismic attributes. While interpreters are skilled at visualizing complex geologic features in 3D, they are less adept at visualizing a great many attributes at once. Recent software development provides interpreters with the means of corendering three attributes (using a red-green-blue color model) or four attributes (using a hue-lightness-saturation-opacity color model). While analysis of four or more attributes is simple from a mathematical point of view, it is overly taxing on the normal human interpreter who needs to relate these images to the underlying geologic processes.

A Characteristic Analysis of Aeromagnetic Anomalies and Curie Point Isotherms in Northeast China

The Northeast China block lies among the Siberia, North China block and the west Pacific plate, along with complex geological features derived from episodic tectonics. In this paper, we analyzed aeromagnetic anomalies of Northeast China to recognize its characteristics related to the tectonics, and then used magnetic anomaly data to calculate the Curie point depth with the method of power-density spectrum analysis. Characteristics of both aeromagnetic anomalies and Curie point isotherm distribution indicate the inheritance in tectonic evolution. Compared with the heat flow distribution and Man-Sui Global Geoscience Transect (GGT), Curie point isotherms are used to discuss the thermal state of crust in study region, the result shows the close relationship between fluctuation of the Curie point isotherm and that of the asthenosphere. Based on earthquake activities feature and seismic tomography results, here we infer that the uplift of the Curie point isotherm of the study region was due to the stagnancy of the subducting Pacific plate beneath northeast Asia, which also accounts for the magmatism and volcanism there.

Phenomenology of Baneberry Nuclear Event Revisited with 3-D Finite Element Transient Simulation

This paper highlights a three-dimensional (3-D) transient numerical simulation of the Baneberry event of December 18, 1970, with a 10-kT yield and a 278-m source depth, conducted at the Nevada Test Site. This site has complex geological features with preexisting faults and layered geological strata characterized by a hard Paleozoic layer below the source, and saturated tuff on the west side of the source and clay-rich tuff toward the east side, both overlaid by top alluvial layers. In addition, a layer of 50% montmorillonite is sandwiched between two layers of 20% montmorillonite on the east end. This event is reported to have vented because of fault rupture and shock-wave reflections from a closer hard Paleozoic layer near the source. Here, the shock-induced slip along the preexisting fault plane has an important bearing on the containment efficiency of this event. None of the earlier reported simulation studies address the above slip phenomenon and the influence of variation in geological strata in the presence of the preexisting fault in a 3-D framework for underground nuclear events. The paper describes the capabilities of the SHOCK-3D finite element code for simulating short-time shock-wave propagation, fault rupture leading to sliding along the fault plane, and subsequent crater formation at ground zero with a long-duration transient computation to study the quasi-static behavior of the Baneberry event. Precise modeling schemes of the composite geological strata and fault system demonstrate that a dip-slip mechanism had developed for this event, leading to final venting. The present numerical computation results with SHOCK-3D are in excellent agreement with site observations. In addition, the limitations of earlier reported simulation results from the TENSOR two-dimensional axisymmetric code presented by Terhune et al. have also been overcome.

An unstructured edge-based finite volume formulation for solving immiscible two-phase flows in porous media

Unstructured mesh based discretization techniques can offer certain advantages relative to standard finite difference approaches which are commonly used in reservoir simulation, due to their flexibility to model complex geological features and to their ability to easily incorporate mesh adaptation. Within such class of methods the most frequently used are the finite element method (FEM) and the finite volume method (FVM). The latter is particularly attractive in reservoir problems due to its local and global conservation properties. The main goal of the present paper is to describe an unstructured edge-based FVM formulation which is used to solve the partial differential equations resulting from the modelling of two-phase fluid flow of oil and water in homogeneous porous media, when an IMPES (IMplicit Pressure Explicit Saturation) approach is used. This finite volume formulation is similar to the edge-based FEM formulation when linear triangular or tetrahedral elements are employed. Some model examples are presented in order to validate the presented formulation. Copyright © 2005 John Wiley & Sons, Ltd.

Effect of Scaleup and Aggregation on the Use of Well Tests To Identify Geological Properties

Summary This paper discusses specific issues encountered when pressure tests are analyzed in reservoirs with complex geological properties. These issues relate to questions concerning the methodology of scaleup, the degree of aggregation, and the reliability of conventional methods of analysis. The paper shows that if we desire to use pressure-transient analysis to determine more complex geological features such as connectivity and widths of channels, we need a model that incorporates reservoir heterogeneity. This complexity can lead to significantly more computational effort in the analysis of the pressure transient. The paper demonstrates that scaleup criteria, based on steady-state procedures, are inadequate to capture transient pressure responses. Furthermore, the number of layers needed to match the transient response may be significantly greater than the number of layers needed for a reservoir-simulation study. The use of models without a sufficient number of layers may lead to interpretations that are in significant error. The paper compares various vertical aggregation methods to coarsen the fine-grid model. The pressure-derivative curve is used as a measure of evaluating the adequacy of the scaleup procedure. Neither the use of permeability at a wellbore nor the average layer permeability as criteria for the aggregation was adequate to reduce the number of layers significantly. Introduction The objectives of this paper are to demonstrate the impact of the detailed and small-scale heterogeneities of a formation on the flow characteristics that are obtained from a pressure test and how those heterogeneities affect the analysis of the pressure test. The literature recognizes that special scaleup procedures are required in the vicinity of wells located in heterogeneous fields. Our work demonstrates that these procedures apply only to rather small changes in pressure over time and are usually inadequate to meet objectives for history-matching well tests. Using a fine-scale geological model derived by geological and geophysical techniques, this work systematically examines the interpretations obtained by various aggregation and scaleup techniques. We will demonstrate that unless care is taken, the consequences of too much aggregation may lead to significant errors on decisions concerning the value of a reservoir. Current scaleup techniques presume that spatial (location of boundaries, location of faults, etc.) variables are maintained. In analyzing a well test, however, one of our principal objectives is to determine the relationship between the well response and geometrical variables. We show that a limited amount of aggregation will preserve the spatial and petrophysical relationships we wish to determine. At this time, there appears to be no method available to determine the degree of scaleup a priori. Because the objective of well testing is to estimate reservoir properties, the scaleup process needs to be made a part of the history-matching procedure. By assuming a truth case, we show that too much vertical aggregation may lead to significant errors. Comparisons with traditional analyses based on analytical techniques are made. Whenever an analytical model is used in the analysis, unless otherwise stated, we use a single-layer-reservoir solution.