A new approach to separate seismic time-lapse time shifts in the reservoir and overburden

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. Q67-Q78 ◽  
Author(s):  
Yi Liu ◽  
Martin Landrø ◽  
Børge Arntsen ◽  
Joost van der Neut ◽  
Kees Wapenaar
Keyword(s):  
Linear Equations ◽  
Time Lapse ◽  
Velocity Model ◽  
Borehole Data ◽  
Lapse Time ◽  
Surface Reflection ◽  
The North ◽  
Reflection Data ◽  
The North Sea ◽  
Velocity Changes

For a robust way of estimating time shifts near horizontal boreholes, we have developed a method for separating the reflection responses above and below a horizontal borehole. Together with the surface reflection data, the method uses the direct arrivals from borehole data in the Marchenko method. The first step is to retrieve the focusing functions and the up-down wavefields at the borehole level using an iterative Marchenko scheme. The second step is to solve two linear equations using a least-squares minimizing method for the two desired reflection responses. Then, the time shifts that are directly linked to the changes on either side of the borehole are calculated using a standard crosscorrelation technique. The method is applied with good results to synthetic 2D pressure data from the North Sea. One example uses purely artificial velocity changes (negative above the borehole and positive below), and the other example uses more realistic changes based on well logs. In the 2D case with an adequate survey coverage at the surface, the method is completely data driven. In the 3D case in which there is a limited number of horizontal wells, a kinematic correct velocity model is needed, but only for the volume between the surface and the borehole. Possible error factors related to the Marchenko scheme, such as an inaccurate source wavelet, imperfect surface multiples removal, and medium with loss are not included in this study.

Long-offset time-lapse seismic: Tested on the Valhall LoFS data

Geophysics ◽  
2011 ◽  
Vol 76 (2) ◽  
pp. O1-O13 ◽  
Author(s):  
Hossein Mehdi Zadeh ◽  
Martin Landrø ◽  
Olav Inge Barkved
Keyword(s):  
Synthetic Data ◽  
Maximum Amplitude ◽  
Time Lapse ◽  
Velocity Change ◽  
Seismic Properties ◽  
The North ◽  
Long Offset ◽  
The North Sea ◽  
Offset Time ◽  
Velocity Changes

Conventional time-lapse seismic has been less successful for stiff-rock reservoir monitoring, such as carbonates. This is mainly because of the negligible time-lapse changes in the seismic properties. Therefore, we propose to use long-offset time-lapse seismic as an alternative method to estimate small velocity changes. More specifically, we monitor the maximum amplitude offset that is beyond critical offset. The properties of the maximum amplitude offset are similar to critical offset, except that they appear for longer offsets and are frequency dependent. Increased frequency reduces the gap between this offset and the critical offset. We find that the maximum amplitude offset is a function of overburden and reservoir velocity and practically independent of density. This method requires a velocity increase across the interface that is to be analyzed. This criterion usually is satisfied for stiff-rock reservoirs. Also, by long-offset acquisition, we mean typically 1 to 2 km beyond the critical offset for typical depths. The method is tested on the Valhall chalk field in the North Sea. The predicted velocity change using this method is in-line with an independent acoustic impedance study. The velocity changes quantitatively match reasonably well with the synthetic data.

Time-lapse seismic surveys in the North Sea and their business impact

2000 ◽  
Vol 19 (3) ◽  
pp. 286-293 ◽  
Author(s):  
Klaas Koster ◽  
Pieter Gabriels ◽  
Matthias Hartung ◽  
John Verbeek ◽  
Geurt Deinum ◽  
...  
Keyword(s):  
North Sea ◽  
Time Lapse ◽  
Seismic Surveys ◽  
Business Impact ◽  
The North ◽  
The North Sea

scholarly journals Hydrogeological characterisation of a glacially affected barrier island – the North Frisian Island of Föhr

2012 ◽  
Vol 9 (4) ◽  
pp. 5085-5119 ◽  
Author(s):  
T. Burschil ◽  
W. Scheer ◽  
R. Kirsch ◽  
H. Wiederhold
Keyword(s):  
North Sea ◽  
Underground Structure ◽  
Empirical Relation ◽  
Geophysical Methods ◽  
Strong Impact ◽  
Hydrogeological Model ◽  
Borehole Data ◽  
The North ◽  
The North Sea ◽  
D Model

Abstract. We present the application of geophysical investigations to characterise and improve the geological/hydrogeological model through the estimation of petrophysical parameters for groundwater modelling. Seismic reflection and airborne electromagnetic surveys in combination with borehole information enhance the 3-D geological model and allow a petrophysical interpretation of the subsurface. The North Sea Island of Föhr has a very complex underground structure what was already known from boreholes. The local waterworks use a freshwater body embedded in saline groundwater. Several glaciations disordered the Youngest Tertiary and Quaternary sediments by glaciotectonic thrust-faulting as well as incision and refill of glacial valleys. Both underground structures have a strong impact on the distribution of freshwater bearing aquifers. An initial hydrogeological model of Föhr was built from borehole data alone and was restricted to the southern part of the island where in the sandy areas of the Geest a large freshwater body was formed. We improved the geological/hydrogeological model by adding data from different geophysical methods, e.g. airborne electromagnetics (EM) for mapping the resistivity of the entire island, seismic reflections for detailed cross sections in the groundwater catchment area, and geophysical borehole logging for calibration of these measurements. An integrated evaluation of the results from the different geophysical methods yields reliable data. To determinate petrophysical parameter about 18 borehole logs, more than 75 m deep, and nearby airborne EM inversion models were analyzed concerning resistivity. We establish an empirical relation between measured resistivity and hydraulic conductivity for the specific area – the North Sea island of Föhr. Five boreholes concerning seismic interval velocities discriminate sand and till. The interpretation of these data was the basis for building the geological/hydrogeological 3-D model. We fitted the relevant model layers to all geophysical and geological data and created a consistent 3-D model. This model is the fundament for groundwater simulations considering forecasted changes in precipitation and sea level rise due to climate change.

scholarly journals 4D Travel-Time Tomography as a Tool for Tracking Fluid-Driven Medium Changes in Offshore Oil–Gas Exploitation Areas

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5878
Author(s):  
Grazia De Landro ◽  
Ortensia Amoroso ◽  
Guido Russo ◽  
Aldo Zollo
Keyword(s):  
Seismic Velocity ◽  
Fluid Pressure ◽  
Time Lapse ◽  
Velocity Model ◽  
Target Volume ◽  
Fluid Injection ◽  
Pressure Perturbation ◽  
Operational Conditions ◽  
Starting Point ◽  
Velocity Changes

The monitoring of rock volume where offshore exploitation activities take place is crucial to assess the corresponding seismic hazard. Fluid injection/extraction operations generate a pore fluid pressure perturbation into the volume hosting the reservoir which, in turn, may trigger new failures and induce changes in the elastic properties of rocks. Our purpose is to evaluate the feasibility of reconstructing pore pressure perturbation diffusion in the host medium by imaging the 4D velocity changes using active seismic. We simulated repeated active offshore surveys and imaged the target volume. We constructed the velocity model perturbed by the fluid injection using physical modeling and evaluated under which conditions the repeated surveys could image the velocity changes. We found that the induced pressure perturbation causes seismic velocity variations ranging between 2–5% and 15–20%, depending on the different injection conditions and medium properties. So, in most cases, time-lapse tomography is very efficient in tracking the perturbation. The noise level characterizing the recording station sites is a crucial parameter. Since we evaluated the feasibility of the proposed 4D imaging strategy under different realistic environmental and operational conditions, our results can be directly applied to set up and configure the acquisition layout of surveys aimed at retrieving fluid-induced medium changes in the hosting medium. Moreover, our results can be considered as a useful starting point to design the guidelines to monitor exploitation areas.

scholarly journals Reconstructing the primary reflections in seismic data by Marchenko redatuming and convolutional interferometry

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. Q15-Q26 ◽  
Author(s):  
Giovanni Angelo Meles ◽  
Kees Wapenaar ◽  
Andrew Curtis
Keyword(s):  
Velocity Model ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Surface Reflection ◽  
Reflection Data ◽  
Reference Velocity ◽  
Time Migration ◽  
Recorded Data

State-of-the-art methods to image the earth’s subsurface using active-source seismic reflection data involve reverse time migration. This and other standard seismic processing methods such as velocity analysis provide best results only when all waves in the data set are primaries (waves reflected only once). A variety of methods are therefore deployed as processing to predict and remove multiples (waves reflected several times); however, accurate removal of those predicted multiples from the recorded data using adaptive subtraction techniques proves challenging, even in cases in which they can be predicted with reasonable accuracy. We present a new, alternative strategy to construct a parallel data set consisting only of primaries, which is calculated directly from recorded data. This obviates the need for multiple prediction and removal methods. Primaries are constructed by using convolutional interferometry to combine the first-arriving events of upgoing and direct-wave downgoing Green’s functions to virtual receivers in the subsurface. The required upgoing wavefields to virtual receivers are constructed by Marchenko redatuming. Crucially, this is possible without detailed models of the earth’s subsurface reflectivity structure: Similar to the most migration techniques, the method only requires surface reflection data and estimates of direct (nonreflected) arrivals between the virtual subsurface sources and the acquisition surface. We evaluate the method on a stratified synclinal model. It is shown to be particularly robust against errors in the reference velocity model used and to improve the migrated images substantially.

Processing and quality-control strategies for consistent time-lapse seismic attributes: A case history on an internal blowout using vintage data

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. B135-B146 ◽  
Author(s):  
Hung Nho Dinh ◽  
Mirko van der Baan ◽  
Martin Landrø
Keyword(s):  
Quality Control ◽  
Control Strategies ◽  
Time Lapse ◽  
Reflection Seismic ◽  
The North ◽  
Processing Strategies ◽  
3D Data ◽  
Site Survey ◽  
The North Sea ◽  
Legacy Data

Many vintage reflection seismic surveys exist that have nonrepeated acquisition geometries or final-stacked/migrated sections are obtained using different or nonconsistent processing flows. This may lead to derived time-lapse attributes that are not internally consistent or even conflicting. For instance, we have focused on a subsurface gas blowout that occurred in 1989 in the Norwegian sector of the North Sea. The 2D site survey data were acquired in 1988 and 1990, and the 3D data were acquired in 1991 and 2005. The various sets of legacy data are plagued by poor repeatability among data acquisitions, application of different processing strategies, missing prestack data, and the presence of multiples. All of these factors severely complicate even qualitative interpretation of the gas migration associated with the underground blowout. Careful time-lapse processing may provide useful information even from such challenging legacy data by first computing numerous attributes including instantaneous amplitude differences, time shifts, time-lapse attenuation, and impedance inversions. Then, judicious quality control, invoked by comparing the various attributes, was used to check for internally consistent results.

Improved seismic interpretation of a salt diapir by utilization of diffractions, exemplified by 2D reflection seismics, Danish sector of the North Sea

2020 ◽  
Vol 8 (1) ◽  
pp. T77-T88 ◽  
Author(s):  
Mahboubeh Montazeri ◽  
Lars Ole Boldreel ◽  
Anette Uldall ◽  
Lars Nielsen
Keyword(s):  
North Sea ◽  
Seismic Imaging ◽  
Seismic Velocity ◽  
Velocity Model ◽  
Salt Diapir ◽  
The North ◽  
Reflection Seismics ◽  
The North Sea ◽  
Sediment Layers

Development of salt diapirs affects the hydrocarbon trapping systems in the Danish sector of the North Sea, where the reservoirs mainly consist of chalk. Seismic imaging and interpretation of the salt structures are challenging, primarily due to the complex geometry of the salt bodies and typically strong velocity contrast with the neighboring sediment layers. The quality of seismic imaging in the North Sea is highly dependent on the quality of the estimated velocity model. We have studied diffracted arrivals originating from the salt flanks and adjacent sedimentary structures using a diffraction imaging technique. The diffracted waves carry valuable information regarding seismic velocity and the location of geologic discontinuities, such as faults, fractures, and salt delimitations. We apply a plane-wave destruction method to separate diffractions from our stacked data. We optimize imaging based on diffraction analysis by using a velocity continuation migration technique, which leads to an estimation of the optimum focusing velocity model. We determine that the diffraction-based approach significantly improves the seismic imaging adjacent to the salt diapirs and the neighboring layers when compared with a standard approach in which we mostly ignore the diffractions. The new poststack time-migrated results provide detailed information that optimizes our interpretation of the salt diapir itself (e.g., the width of the salt neck) as well as the sediment layers related to the rim synclines. Processing schemes such as prestack depth migration and full-waveform inversion may potentially provide high-resolution images of the salt structures. We only account for diffractions in nonmigrated stacked data to better constrain seismic velocity and improve imaging around the salt diapir. The obtained results are critical for reservoir characterization.

Combining reflection and transmission information in time-lapse velocity inversion: A new hybrid approach

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. R601-R611 ◽  
Author(s):  
Maria Kotsi ◽  
Jonathan Edgar ◽  
Alison Malcolm ◽  
Sjoerd de Ridder
Keyword(s):  
Waveform Inversion ◽  
Hybrid Approach ◽  
Time Lapse ◽  
Velocity Model ◽  
Nonlinear Inversion ◽  
Image Domain ◽  
Velocity Inversion ◽  
Reflected Waves ◽  
Deep Diving ◽  
Velocity Changes

Full-waveform inversion (FWI) uses the information of the full wavefield to deliver high-resolution images of the subsurface. Conventional time-lapse FWI primarily uses the transmitted component (diving waves) of the wavefield to reconstruct the low-wavenumber component of the velocity model. This requires large-offset surveys and low-frequency data. When the target of interest is deep, diving waves cannot reach the target and FWI will be dominated by the reflected component of the wavefield. Consequently, the retrieved model resembles a least-squares migration instead of a velocity model. Image-domain methods, especially image-domain wavefield tomography (IDWT), have been developed to obtain a model of time-lapse velocity changes in deeper targets using reflected waves. The method is able to recover models of deep targets. However, it also tends to obtain smeared time-lapse velocity changes. We have developed a form of time-lapse waveform inversion that we call dual-domain time-lapse waveform inversion (DDWI), whose objective function joins FWI and IDWT, combining information from the diving waves in the data-domain FWI term with information from the reflected waves in the image-domain IDWT term. During the nonlinear inversion, the velocity model is updated using constraints from both terms simultaneously. Similar to sequential time-lapse waveform inversion, we start the time-lapse inversion from a baseline model recovered with FWI. We test DDWI on a variety of synthetic models of increasing complexity and find that it can recover time-lapse velocity changes more accurately than when both methods are used independently or sequentially.

Iterative asymptotic inversion in the acoustic approximation

Geophysics ◽  
1992 ◽  
Vol 57 (9) ◽  
pp. 1138-1154 ◽  
Author(s):  
Gilles Lambaré ◽  
Jean Virieux ◽  
Raul Madariaga ◽  
Side Jin
Keyword(s):  
Short Wavelength ◽  
Inverse Operator ◽  
Velocity Model ◽  
Oil Field ◽  
Perfect Reconstruction ◽  
Inversion Method ◽  
Seismic Profiles ◽  
Seismic Section ◽  
The North ◽  
The North Sea

We propose an iterative method for the linearized prestack inversion of seismic profiles based on the asymptotic theory of wave propagation. For this purpose, we designed a very efficient technique for the downward continuation of an acoustic wavefield by ray methods. The different ray quantities required for the computation of the asymptotic inverse operator are estimated at each diffracting point where we want to recover the earth image. In the linearized inversion, we use the background velocity model obtained by velocity analysis. We determine the short wavelength components of the impedance distribution by linearized inversion of the seismograms observed at the surface of the model. Because the inverse operator is not exact, and because the source and station distribution is limited, the first iteration of our asymptotic inversion technique is not exact. We improve the images by an iterative procedure. Since the background velocity does not change between iterations. There is no need to retrace rays, and the same ray quantities are used in the iterations. For this reason our method is very fast and efficient. The results of the inversion demonstrate that iterations improve the spatial resolution of the model images since they mainly contribute to the increase in the short wavelength contents of the final image. A synthetic example with one‐dimensional (1-D) velocity background illustrates the main features of the inversion method. An example with two‐dimensional (2-D) heterogeneous background demonstrates our ability to handle multiple arrivals and a nearly perfect reconstruction of a flat horizon once the perturbations above it are known. Finally, we consider a seismic section taken from the Oseberg oil field in the North Sea off Norway. We show that the iterative asymptotic inversion is a reasonable and accurate alternative to methods based on finite differences. We also demonstrate that we are able to handle an important amount of data with presently available computers.

Time-Lapse Seismic Analysis of the North Sea Fulmar Field

1998 ◽  
Author(s):  
D.H. Johnston ◽  
R.S. McKenny ◽  
T.D. Burkhart
Keyword(s):  
North Sea ◽  
Seismic Analysis ◽  
Time Lapse ◽  
The North ◽  
The North Sea
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