The vertical image projection method for migration stretch compensation

True amplitude inversion is often carried out without taking into account migration distortions to the wavelet. Seismic migration leaves a dip-dependent effect on the wavelet that can cause significant inaccuracies in the inverted impedances obtained from conventional inversion approaches based on 1D vertical convolutional modelling. Neglecting this effect causes misleading inversion results and leakage of dipping noise and migration artifacts from higher frequency bands to the lower frequencies. I have observed that despite dip-dependency of this effect, low-dip and flat events may also suffer if they are contaminated with cross-cutting noise, steep migration artifacts, and smiles. In this paper I propose an efficient, effective and reversible data pre-conditioning approach that accounts for dip-dependency of the wavelet and is applied to migrated images prior to inversion. My proposed method consists of integrating data with respect to the total wavenumber followed by the differentiation with respect to the vertical wavenumber. This process is equivalent to applying a deterministic dip-consistent pre-conditioning that projects the data from the total wavenumber to the vertical wavenumber axis. This preconditioning can be applied to both pre- and post-stack data as well as to amplitude variation with offset (AVO) attributes such as intercept and gradient before inversion. The vertical image projection methodology that I propose here reduces the impact of migration artifacts such as cross-cutting noise and migration smiles and improves inverted impedances in both synthetic and real data examples. In particular I show that neglecting the proposed pre-conditioning leads to anomalously higher impedance values along the steeply dipping structures.

Reliability tests of moment tensor inversion of anthropogenic seismicity

<p>Seismic moment tensor becomes part of basic seismic data processing. For anthropogenic events mostly common and available method to determine mechanism is amplitude inversion. However essential for correct amplitude inversion are good quality data. Factors commonly occurring in anthropogenic seismicity like high noise to signal ratio, low magnitude and shortage of seismic stations with unfavorable focal coverage can introduce undetected errors to inversion solution. In this work, synthetic tests for two seismic networks are presented to examine the reliability of P-wave first peak amplitude inversion for these areas. The synthetic tests of the noise influence on the results of full MT solutions were carried out for two surface networks monitoring anthropogenic seismicity: VERIS network in Vietnam and LUMINEOS network in Poland. Various mechanisms with double couple component variability from 10% to 100% were considered to take into account mechanisms caused by different types of human activity. High variability of solutions in tests shows that some spurious components cannot be avoided in full moment tensor solutions obtained for presented networks in certain cases.</p><p>This work was partially supported by research project no. 2017/27/B/ST10/01267, funded by the National Science Centre, Poland, under agreement no. UMO-2017/27/B/ST10/01267.</p>

A Novel Approach for a better exploitation of a 3D seismic on a development field

<p>The main hydrocarbon-bearing reservoirover the study area is the lower Triassic Argilo-Gréseux reservoir. The Triassic sand is deposited as fluvial channels and overbank sands with a thickness ranging from 10 to 20 m, lying unconformably on the Paleozoic formations. Lateral and vertical distribution of the sand bodies is challenging which makes their mapping very difficult andnearly impossible with conventional seismic analysis. </p><p>In order to better define the optimum drilling targets, the seismic attribute analysis and reservoir characterization process were performed targeting suchthin reservoir level, analysis of available two seismic vintages of PSTM cubes as well as post and pre stack inversion results were carried out.The combination of various attributes analysis (RMS amplitude, Spectral decomposition, variance, etc.) along with seismic inversion results has helped to clearly identify the channelized feature and its delineation on various horizon slices and geobodies, the results were reviewed and calibrated with reservoir properties at well location and showed remarkable correlation.</p><p>Ten development wells have been successfully drilledbased on the seismic analysis study, confirming the efficiency of seismic attribute analysis to predicted channel body geometry.</p><p>Keywords: Channel, Attributes, Amplitude, Inversion, Fluvial reservoir.</p>

Magnetic amplitude inversion for depth-to-basement and apparent magnetization-intensity estimates

We have developed an inversion method to recover the depth and the total magnetization intensity of the basement under a sedimentary basin using the amplitude of the magnetic anomaly vector (amplitude data). Because the amplitude data are weakly dependent on the magnetization direction, our method is suitable for interpreting areas with remanent magnetization. Our method assumes constant magnetized basement rocks overlain by nonmagnetic sediments. To overcome the inherent ambiguity of potential field data, we assume knowledge of the average depth of the basement and use it as a constraint to regularize the inversion. A sensitivity analysis with synthetic data shows the weak dependency of the magnetic amplitude inversion on the magnetization direction. Different combinations of magnetization directions recover the interface separating sediments from basement rocks. Test on field data over the Foz do Amazonas Basin, Brazil, recovers the shape of the basement relief without any knowledge about the magnetization intensity and direction. The estimated basement relief reveals a smooth basement framework with basement highs in the central part of the area. In a regional-scale perspective, the deeper and constant estimated basement relief at the northernmost limit of the area may suggest changing in crustal domains from a hyperextended continental crust to homogeneous oceanic crust.