Mallik 2002 cross-well seismic experiment: project design, data acquisition, and modelling studies

Abstract

Crosshole seismic experiments were carried out using two, 1160 m observation wells (JAPEX/JNOC/GSC et al. Mallik 3L-38 and 4L-38), each located 42.5 mfrom the central, 1188 mproduction research well (JAPEX/JNOC/GSC et al. Mallik 5L-38). These provide images of a gas-hydrate-bearing interval between 900 m and 1100 m depth, and portions of the surrounding sedimentary sequences. Following a baseline survey, three time-lapse monitor surveys were carried out during a production experiment to evaluate the seismic detection of gas hydrate dissociation. Initial, 1-D and 2-D studies of the P-wave arrivals indicate that the highly saturated gas-hydrate-bearing sediments are associated with high velocities, strong attenuation, and some seismic anisotropy. Modelling studies indicate that the dissociation caused by the production test will introduce only very weak changes in the seismic data. Advanced processing will be required to detect these effects.

Time‐lapse changes in tube and guided waves in cross‐well Mallik experiment

“…The tube-wave monitoring method (Korneev et al, 2005 has claimed that such converted tube waves can be used for sensitive cross-well reservoir monitoring. In this study we analyze time-lapse changes in tube and guided waves in the cross-well Mallik experiment (Bauer et al, 2005, Watanabe et al, 2004. We demonstrate traveltime shifts and amplitude changes that are substantially larger than similar time-lapse signatures of direct P-wave arrivals reported in previous studies (Bauer et al, 2005, Watanabe et al, 2004.…”

Tube‐wave monitoring at Mallik field: comparing modeled and experimental time‐lapse responses

“…Time-lapse cross-well acquisition was acquired at the Mallik field, Canada as a part of the 2002 Mallik Gas Hydrate Production Research Well Program (Bauer et al, 2005 and references therein). Three repeated surveys were acquired from 6 to 8 of March 2002 shortly after thermal stimulation and during methane production from gashydrate-bearing layers.…”

“…Two cased boreholes were used for observations, both located 42.5 m away from production well . Detailed description of the experiment is given by Bauer et al (2005). Multiple shots and receivers covered depth from 800 to 1050 m with a very dense spacing of 0.76 m. Fluid-coupled piezoelectric Figure 1: Computed models: a) baseline model; b) monitor model with time-lapse change in elastic properties.…”

“…We start with a simple layered model for the produced interval of 870-960 m. Velocity and densities are taken from acoustic well logs (Bauer et al, 2005) and blocked as shown on Figure 1a. Aiming to reproduce tube-wave arrivals we utilize 2D radially symmetric code developed by Keldysh Institute of Applied Mathematics and Shell International E & P. This code allows to reproduce tube waves in the source well and model their conversion into various other waves propagating towards the receivers.…”

Neural network analysis of crosshole tomographic images: The seismic signature of gas hydrate bearing sediments in the Mackenzie Delta (NW Canada)

“…The crosshole tomography conducted in Mallik was the first experiment of this kind to study the in‐situ seismic properties of GHBS. A 2‐D cross section of 90 m width was covered between 800 m and 1150 m depth [ Bauer et al , 2005b]. The processing included ray‐based [ Bauer et al , 2005a] and waveform inversion [ Pratt et al , 2005] to determine the seismic properties of the GHBS, and time lapse analysis to detect production test effects [ Watanabe et al , 2005].…”