Abstract: In this paper we will first review the industry-standard simultaneous inversion method (which derives continuous impedances) and subsequently identify some pitfalls. We will then introduce our new Joint Impedance and Facies Inversion technology (which we call Ji-Fi for short in this paper), which overcomes these pitfalls by recasting the seismic inverse problem as mixed discrete/continuous. Having so captured the correct physics, we apply this first on a wedge model, followed by a case study, before drawing some conclusions. Note that in this paper, it is assumed that the seismic to be inverted is an ensemble of true amplitude partial angle stacks with corresponding wavelets derived from well ties.

Abstract: P.-F. Roux, J. Kostadinovic, T. Bardainne, E. Rebel, M. Chmiel, M. Van Parys, R. Macault and L. Pignot present an acquisition and processing technique to further decrease the noise recorded at the surface of the Earth when monitoring hydraulic stimulation. It is well known that fluid injection into reservoirs, be it in the context of enhanced geothermal systems or for the stimulation of hydrocarbon reservoirs, generates so-called ‘induced’ seismic activity (Evans, 1966). Early on, the link between the stimulation and this activity has been established, and it has become increasingly obvious that measuring the microseismicity generated by the injection would provide a wealth of information on the mechanical processes at work during the stimulation. Historically, downhole geophone tools have been used to monitor microseismic activity during stimulation programmes. Such tools usually offer a very high sensitivity to the microseismic sources, provided that the observation well is close enough to the treated well (Rutledge and Phillips, 2003). However, this becomes limited when more information on the source mechanism (usually termed focal mechanism and represented by the infamous moment tensor) is required. This is because of the three-dimensional nature of the focal mechanism, which means it cannot be retrieved properly using a single observation point. In addition, a poorly situated observation well may indeed lead to a reduced detection capability.

Abstract: Migration of seismic data is the process that attempts to build an image of the Earth’s interior from recorded field data, by repositioning these data into their ‘true’ geological position in the subsurface, using various numerical approximations of either a wave-theoretical or ray-theoretical description of the propagation of sound waves in the subsurface. This migration can be described as being performed in a number of stages, both for ray and wave-extrapolation based methods. The final stage of the migration process is that which forms the image, via what is known as an imaging condition. In this tutorial, I will outline the various methods involved in forming imaging conditions, primarily for the case of wave-extrapolation methods, and describe some of the techniques used to build gathers of pre-stack-migrated data for use in post-migration velocity analysis.

Abstract: Fusen Xiao, Jinli Yang, Bo Liang, Meng Zhang, Rong Li, Fang Li, Hongping Xiao, Xue Lei, Qinglin Liu and Thomas Heesom present the planning, acquisition, processing and results from a full-azimuth high-density point-source, point-receiver broadband seismic survey over part of the Gongshanmiao structure in the Sichuan Basin, southwest China.

Abstract: M.R. Alvers, H.J. Gotze, L. Barrio-Alvers, C. Plonka, S. Schmidt and B. Lahmeyer present a technique whereby triangulated facets and voxel-cubes are treated in parallel, allowing integrated models for seismic, magnetic and EM data. It is a commonly accepted truth in the oil industry that ‘the easy oil has been found’. Finding the remaining hydrocarbons requires better technologies. Examples are exploration projects below salt and basalt, which are difficult to image with seismic. The main exploration method is still seismic but it has become more important to integrate seismic with other methods in order to improve imaging. In areas of strong lateral velocity and density changes, gravity modelling can help to improve velocity models used for seismic imaging. Efforts of joint interpretation of e.g., seismic, gravity and EM methods lead to more and more realistic and therefore more complex models.

Abstract: Diffraction imaging is a novel technology that uses diffractions to image very small subsurface elements. Diffraction imaging may: (1) improve prospect characterization and pre-drill assessment of the local geology; (2) improve production and recovery efficiency; (3) reduce field development cost; and (4) decrease environmental impact. Field development may be accomplished with fewer wells to optimally produce the reservoir using high-resolution images of small-scale fractures in shale or carbonate intervals. Standard approaches to obtain high-resolution information, such as coherency analysis and structure-oriented filters, derive attributes from stacked, migrated images. Diffraction imaging, in comparison, acts on the pre-stack data, and has the potential to focus super-resolution structural information. Diffraction images can be used as a complement to the structural images produced by conventional reflection imaging techniques, by emphasizing small-scale structural elements that are difficult to interpret on a conventional depth image. An efficient way to obtain diffraction images is to first separate the migration events according to the value of the specularity angle, in a similar way to offset gathers, and subsequent post-stack processing. The high-resolution potential is demonstrated by the diffraction images from the Kenedy 3D survey over the Eagle Ford shale, which show much more detail than conventional depth migration or coherence.

Abstract: Shaoping Lu, Dan Whitmore, Alejandro Valenciano and Nizar Chemingui present applications of separated wavefield imaging to a deepwater wide-azimuth survey in the Gulf of Mexico and to a narrow azimuth data set from offshore Malaysia.

Abstract: The exploration and development of shale plays in Europe show that the ‘statistical drilling’ approach used in some basins in recent years cannot be extend­ed to areas where local stress in rocks or fracture distribution varies both laterally and in depth. Moreover, drilling and fracturing practices confirm the presence of local geobodies resistant to hydraulic fracturing. This paper discusses the application of a new seismic data imaging method full-azimuth angle domain depth imaging, which is particularly useful when working with rich-azimuth seismic data. This innovative technology was applied to meet the challenges of imaging in a complex geological environ­ment, and is a pioneering solution in Polish shale gas geology. Results obtained in the study from the analysis of seismic data were in line with results of the geologic and geophysical analysis of the borehole data, as well as with information from microseismic monitoring of fracturing treatment. The technology delivered high-quality images of the reservoir and geomechanical characterization of rocks with the precision needed to steer horizontal drilling, detect sweet spots, and locate geobodies resistant to fracturing. The seismic imaging workflow is based on software spe­cifically developed to meet the challenges of shale gas seismic (Koren and Ravve, 2011, Koren et al., 2013, Canning and Malkin, 2013). One of the main advantages of this approach is that it works directly in the local angle domain (LAD) instead of the surface offset/azimuth domain. The use of in situ azimuth in LAD, visualized together with dedicated seis­mic attributes, provides information about the intensity and orientation of geological stress/fracture systems. Geothermal prospecting and seismic imaging of conventional hydrocar­bon plays can also profit from this method. This technique is particularly suitable for Poland, where conventional seismic migration of reflections from geology covered by a complex overburden has frequently resulted in improper imaging.

Abstract: The gravitational effect of the topography and near-building structures and their contribution on the vertical gradient of gravity (VGG) was studied. The strong impact of near topography on the VGG values was found in the case of the mountainous areas – deviations of up to 88% of normal value were obtained by means of relative gravity measurements in selected parts of Slovakia. Newly developed software and a high-quality detailed digital terrain model of Slovakia was used for the evaluation of the topographical effect. The gravitational effect of near-building structures was estimated by means of simple 3D bodies approximation, i.e., rectangular or polygonal prisms. A very specific non-linear behaviour of VGG is demonstrated on model examples. A relatively good agreement between the measured and calculated (predicted) VGG values was achieved for a set of selected 32 real measurement points. The application of estimated (predicted) values of the VGG instead of the normal ones can lead to a quality improvement of global and local gravimetric reference networks, as well as prospecting VGG measurements.

Abstract: This paper focuses on the attenuation of Water-Layer-Related Multiples (WLRMs or peg-leg multiples) which reflect at least once between the water bottom and the water surface. WLRMs are often the most dominant multiples in shallow-water seismic data. We propose a Model-based Water-layer Demultiple (MWD) algorithm to calculate the Green's functions of the Water-Layer Primary Reflections (WLPRs: Green's functions convolved with source signature) based on the known seabed and water-layer velocity model and then convolve them with the recorded data to predict the WLRMs. Combined with adaptive subtraction, MWD can effectively attenuate WLRMs. We apply MWD to field data from the Hibernia oilfield area which has a water depth of 70-90 m. The results show that while Surface-Related Multiple Elimination (SRME) by itself has limited success, MWD is effective in attacking WLRMs. Once the WLRMs have been removed by MWD, successive SRME can then be applied to predict and eliminate other types of surface-related multiples (SRMs).�The combination of MWD and SRME is demonstrated as an effective multiple attenuation package for shallow-water data and results in fewer residual multiples and better preserved pri- maries over tau-p gapped deconvolution. This, in turn, contributes to a more realistic velocity model and higher-quality images. from the auto-correlation, to predict WLRMs. DWD pre- dicts WLRMs with correct amplitudes. However, when the water-bottom is complex (and thus multi-arrivals of WLPRs present) the water-layer model derived from the time-domain

Abstract: P. Tsourlos, G.N. Vargemezis, I. Fikos1 and G.N. Tsokas present four case studies of geoelectrical methods to investigate different types of landfills in Greece. There is a growing demand for monitoring both operating and rehabilitated municipal solid waste (MSW) landfills. In this framework, geophysical investigation and particularly geoelectrical techniques are considered as a valuable tool in environmental management. The DC geoelectrical methods are probably the most popular geophysical techniques applied to landfill investigations (Meju, 2000). The conductive signature of the leachate renders geoelectrical methods ideal for the investigation of active or decommissioned landfills with respect to mapping their structure (i.e., shape, size) as well as for locating potential leakage and migration of leachate into the deeper geological layers. A large number of relevant studies can be found in literature, among others: Cartwright and McComas, 1968; Klefstad et al., 1995; Barker, 1990; Carpenter et al., 1991; Binley et al., 1997; Stanton and Schrader 2001; Karlik and Kaya, 2001; Porsani et al., 2004.

Abstract: Accurate sub-surface image reconstruction from prestack depth migration of surface seismic wavefields requires precise knowledge of the local propagation velocities between the recording location and the image location at depth. Such velocity information has traditionally been derived by tomographically inverting residual moveout information of common image gathers, which have been computed using an initial velocity field. This methodology proves to be challenging in shallow water environments, particularly when strong and rapid velocity variations in the very shallow overburden need to be recovered, while moveout information from reflected arrivals is very sparse or not available.

Abstract: Folke Engelmark, Johan Mattsson, Allan McKay and Zhijun Du reflect on ten years of the first commercial towed EM system.

Abstract: Reservoir characterization is often used to guide field developments and therefore requires the ‘best’ seismic data possible. Furthermore, at the end of the data processing, one should make sure that the propagating wavelet has constant properties: its amplitude, phase and bandwidth should remain as stable as possible across the area and target depth interval. There is therefore a trade-off between the wavelet’s ‘best’ characteristics required and its stability. These conditions also apply to the incidence and azimuthal angle dimensions of the dataset for dedicated reservoir characterization workflows. To insure that a processing sequence will lead to a dataset that meets the above-stated requirements, adequate quality control should be performed at numerous key processing stages. First, desired directions for improvement should be defined with the interpreter and translated into the relevant seismic attributes. Attributes which can be mapped are privileged, so that the lateral variations of the wavelet characteristics can be visualized, confronted with other interpretative information and, hopefully, its stationary behavior quantified. Then, milestones should be set at relevant steps of the processing sequence to quantify the selected attributes with intermediate migrated 3D seismic volumes. Finally, relative scores can be established to monitor the ongoing processing quality improvement and to eventually compare it with a vintage dataset if available.

Abstract: Farrukh Qayyum and David Smith explore an analytical method that combines the relative lateral continuity of seismic imaging with the greater vertical resolution of well log data to optimize both types of data.

Abstract: Caroline Milliotte and Stephan K. Matthai show how a former structurally complex oil reservoir that is evaluated as a geological CO2 storage complex, can be modelled at a very high level of geological detail using a new workflow involving unstructured finite element meshes. The resulting simulation model includes discrete representations of complex intersecting faults.

Abstract: Gabino Castillo, Simon Voisey, Kevin Chesser, Norbert van de Coevering, Antoine Bouziat, Guy Oliver, Chi Vinh Ly and Lih Kuo illustrate a workflow integrating reservoir and geomechanical properties obtained from pre-stack seismic inversion and incorporating stress and fracture information extracted from azimuthal analysis of the seismic data.

Abstract: The quick turnaround of seismic processing of a 4D time lapse survey over the Halfdan oil field allowed for interpretation and integration of the new 4D results seven weeks after completion of the seismic acquisition. Analysis of the first fast track 4D dataset led to improved processing parameters and an additional demultiple application which yielded a significantly improved fast track dataset 11 weeks after the seismic acquisition was completed. The repeat 4D seismic survey was acquired in the summer of 2012 in order to provide a better understanding of the sweep efficiency from the line drive water flood, guide future well interventions and improve the reservoir model. The baseline 3D seismic data was acquired in 1992/1993, prior to field development, and the first monitor 3D seismic was acquired in 2005. The rock physics model shows that increased water saturation due to the water flooding along the injectors in the Tor oil-bearing reservoir dominates the 4D change in acoustic impedance yielding a hardening response. The rock physics model was used to convert the reservoir model pressure and saturation changes from the three time-steps to modelled acoustic impedance changes. Examples will be shown from the 4D time lapse and the reservoir model acoustic impedance changes.

Abstract: Marianne Rauch-Davies, Kostya Deev, Danil Pelman and Maria Kachkachev-Shuifer demonstrate how naturally occurring fractures in tight rocks can be detected using conventionally acquired seismic data.

Abstract: Geomechanical models have many purposes in reservoir management Applications include the prediction of reservoir compaction, subsidence and long-term well-bore integrity, optimization of drilling trajectories and mudweights, and the design of hydraulic stimulation and perforation campaigns The basis for all geomechanical applications is an accurate knowledge of the subsurface stress state, pore pressure and the mechanical properties, which in combination form a geomechanical (or mechanical earth) model To increase trust in their predictions, these models need to match data observations that are linked to the subsurface stress-state In the initial phases of reservoir production, such observations typically include observations during drilling (eg, loss of drilling mud allows estimation of an upper bound for pore pressure, and inflow events give a lower bound for pore pressure), observations of drilling-induced fractures and wellbore breakouts, as well as leak-off and formation integrity tests During reservoir production wellbore failure in shear and compaction gives indications of production-induced localized strain On a field-wide scale, time-lapse seismic time shifts in the overburden are now commonly ascribed to reservoir compaction and serve as a field-wide calibration method for geomechanical models Reservoir compaction causes overburden elongation and an associated velocity slow-down (Hatchell and Bourne, 2005), and this causes an increase in two-way traveltime between base- and monitor survey, termed time-lapse time shift This close link between observed time-lapse time shifts and the modelled reservoir compaction and overburden elongation is now being used as a field-wide calibration tool for geomechanical models (eg, Staples et al, 2007; Herwanger and Koutsabeloulis, 2011)

Abstract: Clark Chahine, Leigh Truelove and Mauricio Herrera Volcan propose a new approach to preconditioning steps designed to avoid degradation of data.

Abstract: Richard Wrigley, Anna Marszalek, Karyna Rodriguez and Neil Hodgson present an exciting hydrocarbon province in the Adriatic which will soon be opening up for exploration.

Abstract: Nicholas Cooke, Peter Szafian, Robert Gruenwald and Lothar Schuler present a modelling technique to understand the colour response from an HDFD blend above and below a known gas water contact of a proven gas accumulation in the Sofala Concession.

Abstract: Interesting points can be made about hydrocarbon volumes discovered in the past decade: - 350 bboe of 2P (Proved and Probable) discovered volumes were found, and 91 of the fields have 2P volumes in excess of 500 million boe (‘elephant’) totalling approximately 200 billion boe, based on publicly available information. - This compares with 120 bboe in the period 1991-2001, and 140 bboe in the period 1981-1991 (From AAPG Memoir data) - six petroleum plays can be defined and ranked against the corresponding volumes: - Carbonates below salt and Large Delta Systems account for more than 85% of the discovered volumes; - A new play concept: Abrupt Margins has been proven, with the Jubilee Field in Ghana (disc 2007). Foinaven Field (West of Shetlands, disc. 1991) also goes into this category; - New Exploration Techniques will be needed in mature plays such as Foreland fold and Thrust belts. These discovered volumes are far from negligible in sustaining current worldwide production (2013) of almost 90 mmboe/d and 400 bcf/d, rates that will increase to 100 mboe a day by 2020 for oil and to 500 bcf/d by 2030 for gas, depending on demand and investment rates.

Abstract: A s exploration evaluations for the 28th UK Licensing round draw to a close, the industry can reflect on the fierce competition for acreage in the Dinantian (Early Carboniferous) play at the northern margin of the Southern Gas Basin. First gas production from the Breagh Field in October 2013, confirming the commerciality of the play, prompted a regional play-fairway study which was quickly followed by the acquisition of a dense 2D seismic programme (Figure 1) in 2013. Intended to define the prospectivity of the Base Permian, this survey has imaged the intra-Carboniferous remarkably well allowing, for the first time, the potential of this sequence to be mapped and evaluated with confidence. Furthermore, post-salt charge modelling and seismic AVO-modelling reveal prospects at higher stratigraphic levels, indicating multi-level exploration potential in an exciting new play-fairway.

Abstract: Kelsey Schiltz, Loren Zeigler and David Gray demonstrate how the integration of timelapse compressional and multi-component seismic data has resulted in a geologic model of low permeability shales and enhanced the understanding of the steam chamber through imaging of the heat and pressure fronts in the Long Lake bitumen field in Alberta, Canada. Long Lake is a bitumen field covering 63,000 acres within the Athabasca oil sands in Alberta, Canada. Bitumen is a special type of heavy oil that is less than 10 API and is immobile at in situ conditions. Long Lake bitumen (~8 API) is produced from the Lower Cretaceous McMurray Formation using an in situ thermal recovery method called steam-assisted gravity drainage (SAGD).

Abstract: Several different methods have been evaluated for calculating tract participation in diverse reservoir situations where a unitized field straddles a domestic or international licence boundary. There are three key elements. The first concerns the choice of a static or dynamic basis for tract participation or a hybrid method that falls somewhere between the two. The second involves the introduction of any conversion or weighting factors that are designed to take account of systematic differences in hydrocarbon type or reservoir quality across the field. The third relates to adopted practices for the volumetric calculations, specifically the equity-sensitive areas of scale considerations, fluid levels, net-to-gross ratio, and reservoir mapping. These key elements are analysed from the standpoint of securing a fair and equitable (re)determination of tract participation. Recommendations for a more technically substantive approach reinforce the pareto-efficiency of unitization, so that the cost of the exercise to each partner is a good deal smaller than the greater revenue that can be secured by that partner through the integrated development of a straddling field. However, every unitization and redetermination situation is different, and each case should be considered on its merits if maximum benefits are to be attained.

Abstract: The Ordos Basin, located in the central part of China, contains abundant oil and gas shale resources. This study took place in an area southwest of Yan’an City, Shaanxi province, and its main exploration targets were the Mesozoic Yanchang Formation, with a maximum depth of around 1500 m, and the Upper Paleozoic Benxi Formation, with a maximum depth of around 3550 m. The tectonic structure at the target levels is almost flat, with dips of only around one degree. The objective of the survey was to identify ‘sweet spots’ in a heterogeneous gas shale reservoir beneath thick deposits of loess, which is sediment formed by the accumulation of wind-blown silt. Variations in the topography, thickness, and seismic velocity of the loess were identified as key factors that had led to inadequate imaging results from previous 2D exploration surveys in the area (Yao and Li, 2004). The new 3D survey, acquired by CNPC Sichuan Geophysical Company (SCGC) during 2013 using the WesternGeco UniQ integrated point-receiver land seismic system, delivered imaging results that improved the characterization of the gas shale. Several features of the project area presented challenges for seismic exploration, many of which are typical of a loess plateau. The area is covered by unconsolidated loess with severe variations in thickness and velocity that can result in serious statics problems. The loess also causes dramatic signal absorption, leading to poor signal-to-noise ratio and potentially contributing to low resolution in the seismic data. As shown in Figure 1, surface conditions include rapid variations in topography that further complicate near-surface statics correction and can be the cause of various types of interference and noise. Survey logistics needed to account for heavily forested areas, hills and gulches. Also, more than 500 oil wells were pumping and some rigs were drilling during survey acquisition, representing additional sources of noise (Figure 2).