3D Seismic Interpretation Research Articles

Integrated outcrop, 3D seismic, and geochronologic interpretation of Red Sea dike-related deformation in the Western Desert, Egypt – The role of the 23 Ma Cairo “mini-plume”

Most of the northern Red Sea and Gulf of Suez formed as a non-volcanic rift. This is in stark contrast to the Afar province far to the south where flood basalts several kilometers thick cover an area of >600,000km2. The Afar volcanism erupted coevally with the onset of Gulf of Aden rifting and the two events are generally thought to be genetically linked. The lack of northern Red Sea exposed volcanic rocks suggests that this segment of the rift system initiated through a mechanism very different from Afar-Aden. However, a large late Cenozoic basalt field covering >15,000km2 does exist in northern Egypt centered on the city of Cairo. Large-scale basaltic dikes, monogenetic volcanoes, and coeval extensional faults and grabens are associated with these alkali basalts and physiographically and structurally link this province to the Gulf of Suez. Compositionally the northern Egypt basalts are very similar to the initial 31–30Ma flood basalts of Afar. New 40Ar/39Ar dating indicates that this widespread and voluminous Egyptian volcanism occurred over a short time interval of less than 2Ma at the Oligocene–Miocene boundary (23Ma). In the subsurface west of Cairo, high-quality 3D reflection seismic data indicate that narrow, linear grabens formed above the intruding dikes and show that the structural effects of Red Sea rifting extended far into the Western Desert. Circular depressions within the grabens probably formed first as conduits to overlying cinder cones and then underwent collapse when magma was evacuated from below. Some outliers of basalt flows were erupted at the cores of Late Cretaceous Syrian arc anticlines as at Bahariya oasis.The northern Egypt 40Ar/39Ar ages are indistinguishable from those of early syn-rift Red Sea-parallel dikes in western Arabia, Sinai and the Eastern Desert of Egypt. This suggests that the Red Sea propagated through Arabia/Sudan and into Egypt as a single, very rapid pulse and only stopped at the interface with stronger Neotethyan oceanic crust near the coast of the modern Mediterranean Sea. Extension almost immediately thereafter became focused in the Gulf of Suez where it evolved into well-developed rift basins, and deformation in the Western Desert and vicinity of Cairo ceased. Prior to extrusion of the northern Egypt basalts there was no identifiable surface extension and the lithosphere was not yet thinned. The relatively constant thickness of the basalts suggests that there was little pre-rift topography or uplift in northern Egypt. The volcanism of northern Egypt was volumetrically smaller than that of Afar some 7–8 My earlier, but we suggest that it played a similar role as a trigger for a large-scale rift event. We propose that this volcanic center be referred to as the Cairo mini-plume. Similar modest, focused magmatic events may have played equivalent roles in other older “non-volcanic” rift systems.

4D seismic interpretation in a Nigerian deepwater field

To improve the management of a Nigerian deep water field, two vintages of 4D data have been acquired since field start up in 2005. The first Nigerian 4D seismic (monitor-I) in water depths greater than 1000 m was taken in this field in 2008, and the second monitor (monitor-II) was acquired in 2012. Compared to monitor-I, better geometric repeatability was achieved in monitor-II as the lessons learned from monitor-I were incorporated to achieve better results. The final normalized root mean square of monitor-II fast-track volume was 12% compared to 25% for monitor-I. The improved quality is attributed to improvements in the acquisition methodology and prediction of the effects of currents. Seismic interpretation of the field revealed two distinct turbidite depositional settings: (1) An unconfined amalgamated lobe system with low relief, high net-to-gross reservoir sands that exhibit fairly homogeneous water flooding patterns on 4D and (2) an erosional canyon setting, filled with meander belts having a more complex 3D connectivity within and between the channels resulting in a challenging 4D interpretation. The time lapse data were instrumental for better understanding the reservoir architecture, enabling improved wells and reservoir management practices, the identification of infill opportunities, and more mature subsurface models. We evaluated the seismic acquisition and the 4D interpretation of the deepwater 4D seismic data, highlighting the merits of a multidisciplinary collaborative understanding to time-lapse seismic. At present, the value of information of the 4D monitor-II is conservatively estimated at 101 million United States dollars, equivalent to the cost of a well in this deepwater operating environment.

Application of Stratal Slicing in Sandbody Interpretation of the Channel

Stratal Slicing technology is a common method of 3D seismic data interpretation, studying its physiognomy and lithologic characteristics by acquiring variation characteristics of the seismic attributes on the plane. The purpose stratum in the study area is wedged, it is more proper to use stratal slicing than time slicing and horizontal slice. Based on stratal slicing technology, this paper characterizes the Akshabulak formation sedimentary system in block D of South Turgai Basin, Kazakstan. The results show that, making clear of the seismic attributes on behalf of the depositional facies combine with stratal slicing and regional depositional environment can judge that the block D develops fluvial deposit and delta deposit, Another finding is that by using stratal slicing can characterize channel‘s boundary, plane geometry and discontinuity accurately.

Identification of Gas Sand Horizons of the Rashidpur Structure, Surma Basin, Bangladesh, Using 2D Seismic Interpretation

A total of 13 seismic sections were used for 2D seismic interpretation in order to assess the subsurface geometry of gas sand horizons and hydrocarbon prospect of the Rashidpur structure, Surma Basin, Bangladesh. Out of five reflectors, two selected reflectors were mapped for the study. The top of the Upper Gas Sand (R3) reflector was elongated in N-S with the axis swinging slightly to the east on the northern plunge. North-South trending thrust fault was identified in the eastern part which is parallel to the axial line of the structure. The reflection patterns of the gas sand horizons were parallel to each other and similar in nature. The reflection coefficients were positive at the base and negative at the top of the each gas sand horizons. Velocity dropped from 2562 m/s to 2177 m/s in the Upper Gas Sand (R3) and 4320 m/s to 3413 m/s in the Lower Gas Sand (R5) reflector. Bright spot and amplitude anomalies were identified on the top of the both gas sand horizons. The result depicts that the shape of the gas sand horizons is asymmetric anticline. The structure is compressed and elongated NNW-SSE trending anticline. The study reveals hydrocarbon potentiality of the structure.

小断块油藏低级序断层识别与构造建模研究

本文以贝尔凹陷小断块油藏构造建模实践为例，针对低级序断层存在的断点组合困难、延伸距离短和落差小而难以发现和描述等问题，利用三维地震解释技术、petrel及RMS软件，对小断块油藏低级序断层特征进行深入研究，定量识别和描述了低级序断层，建立了小断块油藏精细构造模型，指导了油田中后期剩余油挖潜，且取得了好效果。 Taking structure modeling practice as an example of Beier depression small fault block reservoirs, we aim at the problems such as the existing difficult breakpoint combination, short extension distance, small falling which are difficult to find and describe and so on in the low-order faults. By using 3D seismic interpretation technology, petrel and RMS software, we further study the characteristics of small fault block reservoirs of low-order faults, then quantitatively identify and describe the low-order faults, establish its fine structure model, guide the dig of remaining oil in the middle-later period of oilfiled development and achieve good results.

Geometry and kinematics of the Arlar strike-slip fault, SW Qaidam basin, China: New insights from 3-D seismic data

The right-stepping en-échelon Kunbei fault system, consisting of the Hongliuquan, Arlar, XIII, and Kunbei faults, features importantly in the tectonic evolution of the southwest Qaidam basin. The 3D seismic cross-section interpretation and key horizon similarity attribute analysis show that the NWW-striking Arlar fault is composed of two steeply dipping faults (F1 and F2) in cross-sectional view, and branches eastward into two west-dipping faults (F5 and F6) in map view. The fact that the strata above T2 (the base of the early Miocene Xiayoushashan Formation) become dramatically thinner toward the high points of the Arlar fault suggests an early Miocene initiation (ca. 22.0Ma) for this fault. As indicated by the windowed amplitude-related attribute maps, the Arlar fault and F5 (one branch of the Arlar fault) have cumulative sinistral offsets of ∼8.6–8.7km and ∼5.2–5.4km, respectively. These considerably greater strike-slip components, in conjunction with the respective maximum true dip-slip displacements of <2.2km and <1.5km, convincingly demonstrate that the Arlar fault and F5 are two predominantly left-lateral strike-slip faults. The other faults in the Kunbei fault system are similarly of strike-slip types. This means that the southern boundary of the Qaidam basin is not governed by south- or north-directed thrusting but rather strike-slip faulting, implying that the Qaidam basin is not a foreland basin of the Eastern Kunlun Range. Taking the Altyn Tagh fault into account, the Qaidam basin is essentially a strike-slip superimposed basin developing between two large left-lateral strike-slip faults.

Origin, characteristics and significance of collapsed-paleocave systems in Sinian to Permian carbonate strata in Central Sichuan Basin, SW China

Abstract The origin, characteristics and geological significance of the collapsed-paleocave systems in the Sinian to Permian carbonate strata in Central Sichuan Basin are studied based on 3D seismic interpretation and attributes analysis, as well as imaging logging and cores. Collapsed-paleocave systems are distributed in the Sinian to Permian carbonate strata vertically and along the ends, releasing offsets and intersections of faults horizontally. On profile, they occur as seismic events push-down. The collapsed-paleocave systems mainly originated from fault movements at three main structural phases, the first stage of Tongwan, the second and third stages of Tongwan and the Early Caledonian, and eventually got into shape at the end of the Permian. The collapsed-paleocave systems are featured by multi-layers, wide distribution and good reservoir quality, in which reservoir space is made up of pre-existing pores, structure genetic fractures and collapsed genetic fractures. According to seismic response characteristics, three types of collapsed-paleocave systems are identified in this area, including multi-layer cave system collapsed complex, multi-layer cave passage collapsed system and intra-bed cave collapsed system. The multi-layer cave system collapsed complex and multi-layer cave passage collapsed system in the overlying deformed layers where fractures are widely distributed may be the favorable targets for future exploration.

Study on 3D Fine Structural Modeling of Typical Block in Sanan Oilfield, Daqing

Sanan oilfield has entered late stage of high water cut development. It urgently needs accurate prediction of remaining oil distribution. But previous studies on 3D structure were far could not meet the requirements of fine reservoir description. This paper applied RMS, a piece of excellent geological modeling software establishing the 3D fine structural model of typical block in Sanan oilfield on the bases of 3D fine seismic structural interpretation data. It included the 28 faults’ model, 11 horizons’ model and the structural model. And then measured and analyzed the faults elements data. Based on abundant geologic data, well data and seismic data of the block, this structural model reproduced the fine seismic interpretation results accurately. It was really fine enough to meet the requirements of the fine reservoir description. This research solved the problem that traditional modeling techniques could not handle complex cutting relationship of faults’ model. It laid a solid foundation for reservoir numerical simulation and remaining oil distribution prediction.

Seismic interpretation of the Aptian Alamein Dolomite in the Razzak oil field, Western Desert, Egypt

The Razzak oil field lies in the northern part of Abu Gharadig Basin (northern part of the Western Desert). Aptian Alamein Dolomite is a reservoir rock, in which the oil is trapped in the fractures of the dolomite, depending on structural framework affecting it. The Razzak field structure is one of the most complex structures in the Western Desert of Egypt. The integration of borehole data and 3D seismic interpretation shows that the Jurassic forms a horst block separating the Razzak field into north and south Razzak fields. This horst block is bounded on the southeast by NE-SW trending normal faults (sigma fault) and on the north by several normal faults which step down into the Alamein Basin to the north. The behavior of the sigma fault gives a new concept that the migration of hydrocarbons from the south to the north direction could not be sealed by the NE-SW horst block. Time- and depth-structure maps of Alamein Dolomite illustrate different structure features that play an important role in the hydrocarbon potentialities and prospect identification in the area. One primary component of exploration and development success is to identify the faults that provide structural closure and traps. Two main faults run in the NE-SW direction and form a pattern of horst and graben blocks. In addition, NW-SW trending faults cut these blocks and form a right-lateral strike-slip component of displacement. Four- and three-way dip structural closures represent the fruitful locations for high production and new prospect wells in the Razzak oil field and other similar setting elsewhere.

Seismic correlated Mallik 3D gas hydrate distribution: Effect of geomechanics in non-homogeneous hydrate dissociation by depressurization

The delineation of the Mallik gas hydrate field has utilized extensive well logging and substantial 3D seismic testing and interpretation. This study explores the use of seismic data to quantify the areally heterogeneous gas hydrate distribution. The available Mallik 3D seismic data was compiled and compared/contrasted with available well log data from two adjacent wells. Based on the seismic information, two areally variable (i.e. non-homogeneous) scenarios for gas hydrate distributions are considered: Scenario I having the same initial total hydrate amount as our earlier model areally uniform (homogeneous) distribution, and Scenario II with significantly less overall total hydrate, but honouring the same relative distribution. The scenarios of variable gas hydrate distributions are used in dynamic simulations of the lower Mallik zone. Simulations of each were conducted with and without the role of geomechanics.In Scenario I, we observed multiple gas production peaks (which quite similar to 6 days production behaviour) with higher localized pressure pulses occurred due to strong gas hydrate heterogeneity. In Scenario II, this drastic change in gas production rate was not observed (due to faster pressure evolution in the reservoir). In both Scenarios, the overall reservoir gas production peak is delayed compared to the homogeneous case. This is further delayed by the role of geomechanics. More interestingly, all simulation cases show a very similar overall production trend. This is probably a unique for the Mallik gas hydrate production using single vertical well, including a gas production peak but terminating in a stabilized period of lower but significant gas production.With geomechanics, gas production in general and the gas production peak is shifted and delayed. The geomechanics effect is not purely compaction drive (as in conventional reservoirs, gas production increases with geomechanics). The simulations utilized two set of geomechanical parameters obtained from logs (dynamic parameters) and rocks testing (static parameters). Geomechanical responses based on dynamic parameters were essentially equivalent to simulations ignoring geomechanical effects. The geomechanics simulations indicate an essentially elastic reservoir response (i.e. no plastic failure) assuming a cased vertical well. The Mallik upper zone A and middle zone B are closer to the permafrost and nearer to plasticity limits should be explored.

3D seismic processing and interpretation from 2D seismic data: Application in environmentally sensitive areas of the Neuquén Basin, Argentina

The increasing environmental and regulatory restrictions for recording 3D seismic, along with urban constraints, are limiting the acquisition of new 3D seismic information in some areas. A low-cost methodology can provide a pseudo-3D seismic data set. Geologic complexity is the most important condition to understand to assess the quality of the pseudo-3D volume created. These data can help to reduce many structural uncertainties that can be solved geometrically or at least outlined, giving real improvement in evaluation of prospective areas or in delineation of fields and generating new drilling strategies. In addition, the generated 3D data can be used as input for seismic-attribute calculation that otherwise would not have been possible because of discrete 2D information. The technique basically consists of conducting prestack migration using 24 offset planes, limiting with a structure control, and using the spatial propagation of the migration operator. The results of this data treatment show a homogeneous and consistent distribution of each processing attribute.

A new algorithm for evaluating 3D curvature and curvature gradient for improved fracture detection

In 3D seismic interpretation, both curvature and curvature gradient are useful seismic attributes for structure characterization and fault detection in the subsurface. However, the existing algorithms are computationally intensive and limited by the lateral resolution for steeply-dipping formations. This study presents new and robust volume-based algorithms that evaluate both curvature and curvature gradient attributes more accurately and effectively. The algorithms first instantaneously fit a local surface to seismic data and then compute attributes using the spatial derivatives of the built surface. Specifically, the curvature algorithm constructs a quadratic surface by using a rectangle 9-node grid cell, whereas the curvature gradient algorithm builds a cubic surface by using a diamond 13-node grid cell. A dip-steering approach based on 3D complex seismic trace analysis is implemented to enhance the accuracy of surface construction and to reduce computational time. Applications to two 3D seismic surveys demonstrate the accuracy and efficiency of the new curvature and curvature gradient algorithms for characterizing faults and fractures in fractured reservoirs.

Standards in 4D feasibility and interpretation

Standards for 4D seismic feasibility estimation and interpretation aim to simplify the 4D seismic interpretation process, facilitate understanding of results, and accelerate learning between projects and between disciplines. Standards encode those best practices that have proved to have a more or less universal relevance in the subject area and provide a convenient starting point for individuals and teams new to 4D interpretation. Standards are about casting a result into a familiar format. The main result is a quality improvement of the integration process between different disciplines; a side effect is the efficiency improvement and time saving from increased skill levels within each discipline. There are currently accepted 4D standards in the fields of F = 4D feasibility (fluid effects) P = poststack processing I = seismic inversion and 4D A = 4D interpretation and attributes S = simulator-to-seismic The primary user group is subsurface professionals in asset teams, in particular reservoir engineers, geologists, and geophysicists. Although 4D seismic is seen as a tool originating in the geophysical domain, the fact that it is about observing reservoir dynamics makes it of primary interest to reservoir engineers and geologists alike.

Introduction to special section: Seismic attributes

Seismic attributes are an integral part of modern 3D seismic interpretation workflows. Used in conjunction with seismic amplitude and 3D visualization, attributes accelerate conventional analysis and highlight subtle features that may otherwise be overlooked. Because attributes quantify frequency,

Using palaeogeographic reconstructions to understand lithological variability within the Early Cretaceous Gage Sandstone and South Perth Shale in the Vlaming Sub-Basin, offshore southern Perth Basin

The Early Cretaceous Gage Sandstone and South Perth Shale formations are a prospective reservoir-seal pair in the Vlaming Sub-basin. Plays include post-breakup pinch-outs in the Gage Sandstone with the South Perth Shale forming top seal. The Gage reservoir has porosities of 23–30% and permeabilities of 200–1,800 mD. It was deposited in palaeotopographic lows of the Valanginian breakup unconformity and is the lowstand component of the thick deltaic South Perth (SP) Supersequence. To characterise the reservoir-seal pair, a detailed sequence stratigraphic analysis was conducted by integrating 2D seismic interpretation, well log analysis and new biostratigraphic data. Palaeogeographic reconstructions for the SP Supersequence were derived from mapping higher-order prograding packages and establishing changes in sea level and sediment supply. Higher resolution Gage reservoir reconstructions were based on seismic facies mapping. The Gage reservoir forms part of a sand-rich submarine fan system and ranges from canyon confined inner fan deposits to middle fan deposits on a basin plain. Directions of sediment supply are complex, with major sediment contributions from a northern and southern canyon adjacent to the Badaminna Fault Zone. The characteristics of the SP Supersequence differ markedly between the northern and southern parts of the sub-basin due to variations in palaeotopography and sediment supply. Palaeogeographic reconstructions reveal a series of regressions and transgressions leading to infilling of the palaeo-depression. Palaeogeographic reconstructions for the SP Supersequence portray a complex early post-rift depositional history in the central Vlaming Sub-basin. The developed approach is applicable for detailed studies of other sedimentary basins.

Application of 3D fine seismic interpretation technique in Dawangzhuang Area, Bohai Bay Basin, Northeast China

One of the major problems in subsurface seismic acquisition, procession, and exploration we are facing today is the uncertainty in geologic interpretation because of the complexity of subsurface geology and the limited dimension of the subsurface data available (including drilling data, well logging, and core samples). Case studies from worldwide exploration projects indicate that an integrated, three-dimensional seismic volume visualization and interpretation workflow contributes greatly to resolving the problems we mentioned by extracting critical geologic information from within 3D seismic datasets. Over the last decade, with the increasing employment and improvement of geophysical technology and following 3D seismic data acquisition and processing, the subsurface seismic interpretation workflow is composed of four integrated stages from data selection and pre-procession, to structures, stratum, and facies characterization; to prospect prediction and evaluation; and to well-bore planning. In the data selection and pre-procession phase, the most favorable and frequently used datum is the full and limited angle and limited azimuth post-stack amplitude with significant structures, stratum, and facies enhancements. Signal-to-noise ratio, color scheme, dynamic range, bit resolution, and visual contrast all affect the visibility of features of interest. During the structures, stratum, and facies characterization phase, vertical slicing along arbitrary traverses demonstrates structure styles, stratigraphic architecture, and reservoir geometry in the cross-sectional view. Time/depth slicing defines lateral and vertical variability in the structural trend and areal extent in the map view. Stratal slicing and fault slicing suggest chronostratigraphic seismic facies, associated depositional information, and cross-stratal, along fault seismic signature. Volume flattening and structure restoration aid in unraveling paleo-structural framework, stratigraphic architecture, evolution, and filling histories. In the prospect prediction and evaluation phase, a combination of volume trimming, co-rendering, transparency, attribute analysis, and attribute body detection is instrumental in delineating volumetric extent and evaluating spatial connectivity of critical seismic features. Finally, in the well-bore planning phase, decision making relies on the integration of all the information and knowledge extracted from 3D seismic datasets. Most importantly, interpreters' geologic insights and employments of geophysical technology are crucial to optimal well-bore planning with high geologic potential and low economic risk. The structure of the study area, which is poorly understood to be primarily due to the complexity of subsurface geology and the limited dimension of the subsurface data available, and therefore, we design the integrated workflows and use some of the methods mentioned above to carry out fine seismic interpretation in an analysis of high-resolution 3D seismic data and other geological data in the study area. Finally, we finished the fine interpretation of 3D seismic data and achieved a series of success and good application results. The evolution of tectonics resulted in sub-tectonic units containing the sequences of Ek, Es, Ed, Ng, and Nm. Interpretation reveals that tectonic transition zone which controlled the evolution of the sequences because of its strength, and also, the structural pattern resulted in types of fault (such as “Y” type). The seismic interpretations provide new information on subsurface geology, including the recognition of complex structural patterns in rift lacustrine basin and the presence of a tectonic transition zone at the structural center. The interpretation of these seismic reflection profiles provides new insights into the structure, geological evolution, and petroleum potential of the study area.

Buried pockmarks on the Top Chalk surface of the Danish North Sea and their potential significance for interpreting palaeocirculation patterns

Three-dimensional (3D) seismic data from the southern Danish North Sea were used to analyse the morphology and spatial distribution of depressions in the Danian Chalk deposit. Previously, these depressions were either interpreted as karst structures or pockmarks. The observed depressions occur in an interval from 25 ms below to 12 ms above the Top Chalk surface. Three types of depressions were differentiated based on their plan-view geometry and their degree of symmetry: Type 1, comprising sub-circular and symmetrical depressions, is the dominant group (ca. 70 %). Type 2, elongated and symmetrical depressions, represents only a small fraction (ca. 5 %). The elongated and asymmetrical depressions of Type 3 compose ca. 25 %. In cross section, each depression type can be either characterised by a V- or a U-shape. The maximum size of the depressions ranges from 50 to 580 m, with an average internal depth of 10 m. We interpret the depressions as pockmarks formed by the expulsion of biogenic or thermogenic fluids at the Danian seafloor. Likely, the initial form of the pockmarks has been circular (Type 1) and was subsequently modified for Types 2 and 3 to an elongated form by currents. The long axis of the pockmarks is interpreted to represent the effective current direction. The inferred direction is sub-parallel to the palaeobathymetric contours. The 3D seismic interpretation of pockmarks presented in this paper contributes to the understanding of fluid migration and palaeocirculation patterns during the sedimentation of the terminal Chalk Group in the southern Danish North Sea.

Multi-Attributes and Neural Network-Based Fault Detection in 3D Seismic Interpretation

Seismic attributes have been widely used in seismic object detection. While no unique attribute is expected to perfectly identify the targeted object, various attributes contributing to the same purpose should be utilized simultaneously when performing detection. Artificial neural network has been successfully applied in seismic object detection by combining multiple attributes into a single object-sensitive attribute. An optimized neural network fault detection approach was introduced by a case study from Stratton field, south Texas, United States. Results indicate that the new produced fault probability attribute could suppress the surrounding noises and highlight the faults. Application of ant-tracking to the fault-cube shows more convincible results than to individual attributes. In addition, several potential cross-strike fractures increase the structural complexity. The neural network-based fault detection contributes to better structural interpretation and is of great significance to hydrocarbon exploration, especially in area with complex fault system.

Integrated application of 3D seismic and microseismic data in the development of tight gas reservoirs

The development of unconventional resources, such as shale gas and tight sand gas, requires the integration of multi-disciplinary knowledge to resolve many engineering problems in order to achieve economic production levels. The reservoir heterogeneity revealed by different data sets, such as 3D seismic and microseismic data, can more fully reflect the reservoir properties and is helpful to optimize the drilling and completion programs. First, we predict the local stress direction and open or close status of the natural fractures in tight sand reservoirs based on seismic curvature, an attribute that reveals reservoir heterogeneity and geomechanical properties. Meanwhile, the reservoir fracture network is predicted using an ant-tracking cube and the potential fracture barriers which can affect hydraulic fracture propagation are predicted by integrating the seismic curvature attribute and ant-tracking cube. Second, we use this information, derived from 3D seismic data, to assist in designing the fracture program and adjusting stimulation parameters. Finally, we interpret the reason why sand plugs will occur during the stimulation process by the integration of 3D seismic interpretation and microseismic imaging results, which further explain the hydraulic fracture propagation controlling factors and open or closed state of natural fractures in tight sand reservoirs.

Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome formed by tectonic folding and faulting, curvature helps define the crestal portion of reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In fractured reservoirs at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to evaluate fracture volume and connectivity, and to model fracture networks.