Rocks under strain: Strain-induced time-lapse time shifts are observed for depleting reservoirs

Hatchell, Paul; Bourne, Stephen

doi:10.1190/1.2149624

Cited by 195 publications

(166 citation statements)

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“…For instance, [11] present a 1D empirical formulation to describe vertical travel time perturbation due to changes in vertical strain and vertical velocity from 4D seismic data. Authors [12][13][14] use third-order elasticity theory to characterize 3D stress dependence elasticity and anisotropy.…”

Section: Rock Physics Modelmentioning

confidence: 99%

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

Angus

Fisher²,

Verdon³

2012

IJG

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Stress dependent rock physics models are being used more routinely to link mechanical deformation and stress perturbations to changes in seismic velocities and seismic anisotropy. In this paper, we invert for the effective non-linear microstructural parameters of 69 dry and saturated sandstone core samples. We evaluate the results in terms of the model input parameters of two non-linear rock physics models: A discrete and an analytic microstructural stress-dependent formulation. The results for the analytic model suggest that the global trend of the initial crack density is lower and initial aspect ratio is larger for the saturated samples compared to the corresponding dry samples. The initial aspect ratios for both the dry and saturated samples are tightly clustered between 0.0002 and 0.001, whereas the initial crack densities show more scatter. The results for the discrete model show higher crack densities for the saturated samples when compared to the corresponding dry samples. With increasing confining stress the crack densities decreases to almost identical values for both the dry and saturated samples. A key result of this paper is that there appears to be a stress dependence of the compliance ratio N T B B within many of the samples, possibly related to changing microcrack geometry with increasing confining stress. Furthermore, although the compliance ratio N T B B for dry samples shows a diffuse distribution between 0.4 and 2.0, for saturated samples the distribution is very tightly clustered around 0.5. As confining stresses increase the compliance ratio distributions for the dry and saturated samples become more diffuse but still noticeably different. This result is significant because it reaffirms previous observations that the compliance ratio can be used as an indicator of fluid content within cracks and fractures. From a practical perspective, an overarching purpose of this paper is to investigate the range of input parameters of the microstructural models under both dry and saturated conditions to improve prediction of stress dependent seismic velocity and anisotropy observed in time-lapse seismic data due to hydro-mechanical effects related to fluid production and injection.

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Section: Rock Physics Modelmentioning

confidence: 99%

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

Angus

Fisher²,

Verdon³

2012

IJG

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“…At present there is a push towards developing methods to image-induced geomechanical deformation (e.g., Verdon et al 2011;He et al 2016a;Angus et al 2015). Normal incidence travel-time shifts characterized by ''R-factors'' (e.g., Hatchell and Bourne 2005;He et al 2016b) have been the most common observation used to do so. However, R-factors do not provide a full characterization of the changes in triaxial state, nor do all modes of geomechanical deformation lead to normal incidence travel-time shifts (for example changes in horizontal stresses).…”

Section: Discussionmentioning

confidence: 99%

“…Rock physics models should incorporate phenomena observed in both laboratory core experiments and in the field, such as the nonlinear stress-velocity response (e.g., Nur and Simmons 1969;Sayers 2007;Hatchell and Bourne 2005) and the development of stress-induced anisotropy in initially isotropic rocks (e.g., Dewhurst and Siggins 2006;Olofsson et al 2003).…”

Section: Micro-structural Nonlinear Rock Physics Modelmentioning

confidence: 99%

“…Rocks also display stress hysteresis (e.g., Helbig and Rasolofosaon 2000), and this hysteresis has been observed to occur not only at large strains but also small strains (e.g., Johnson and Rasolofosaon 1996). This observation represents a potentially important rock characteristic in explaining the asymmetric behaviour of 4D seismic observations of producing reservoirs (e.g., Hatchell and Bourne 2005). Thus, it is important to incorporate such nonlinear and hysteretic properties within a constitutive model for coupled flow-geomechanical simulation.…”

Section: Introductionmentioning

confidence: 99%

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Reservoir stress path and induced seismic anisotropy: results from linking coupled fluid-flow/geomechanical simulation with seismic modelling

et al. 2016

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We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by non-hydrostatic stress changes. We generate seismic models from coupled simulations to examine the relationship between reservoir geometry, stress path and seismic anisotropy. The results indicate that geometry influences the evolution of stress, which leads to stress-induced seismic anisotropy. Although stress anisotropy is high for the small reservoir, the effect of stress arching and the ability of the side-burden to support the excess load limit the overall change in effective stress and hence seismic anisotropy. For the extensive reservoir, stress anisotropy and induced seismic anisotropy are high. The extensive and elongate reservoirs experience significant compaction, where the inefficiency of the developed stress arching in the side-burden cannot support the excess load. The elongate reservoir displays significant stress asymmetry, with seismic anisotropy developing predominantly along the long-edge of the reservoir. We show that the link between stress path parameters and seismic anisotropy is complex, where the anisotropic symmetry is controlled not only by model geometry but also the nonlinear rock physics model used. Nevertheless, a workflow has been developed to model seismic anisotropy induced by non-hydrostatic stress changes, allowing field observations of anisotropy to be linked with geomechanical models.

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“…The methodology provided an indirect estimate of the c M in loading/reloading conditions. Moreover, 4D seismic data, that is, time-lapse 3D seismic surveys, can be used as indirect information for the prediction of reservoir petrophysical properties (Mezghani et al 2004;Hatchell & Bourne 2005;Herwanger & Horne 2009). …”

Section: Introductionmentioning

confidence: 99%

On the importance of the heterogeneity assumption in the characterization of reservoir geomechanical properties

et al. 2016

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SUMMARYThe geomechanical analysis of a highly compartmentalized reservoir is performed to simulate the seafloor subsidence due to gas production. The available observations over the hydrocarbon reservoir consist of bathymetric surveys carried out before and at the end of a ten-year production life. The main goal is the calibration of the reservoir compressibility c M , i.e., the main geomechanical parameter controlling the surface response. Two conceptual models are considered: in one (a) c M varies only with the depth and the vertical effective stress (heterogeneity due to lithostratigrafic variability); in another (b) c M varies also in the horizontal plane, that is, it is spatially distributed within the reservoir stratigraphic units. The latter hypothesis accounts for a possible partitioning of the reservoir due to the presence of sealing faults and thrusts that suggests the idea of a block heterogeneous system with the number of reservoir blocks equal to the number of uncertain parameters. The method applied here relies on an ensemble-based data assimilation (DA) algorithm (i.e., the Ensemble Smoother, ES), which incorporates the information from the bathymetric measurements into the geomechanical model response to infer and reduce the 2 C. Zoccarato, D. Baù, F. Bottazzi, M. Ferronato, G. Gambolati, S. Mantica, & P. Teatini uncertainty of the parameter c M . The outcome from conceptual model (a) indicates that DA is effective in reducing the c M uncertainty. However, the maximum settlement still remains underestimated, while the areal extent of the subsidence bowl is overestimated.We demonstrate that the selection of the heterogeneous conceptual model (b) allows to reproduce much better the observations thus removing a clear bias of the model structure.DA allows significantly reducing the c M uncertainty in the five blocks (out of the seven) characterized by large volume and large pressure decline. Conversely, land subsidence can constrain only partially the partitions that marginally contributes to the cumulative displacements of the seafloor.

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Rocks under strain: Strain-induced time-lapse time shifts are observed for depleting reservoirs

Cited by 195 publications

References 0 publications

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

Exploring Trends in Microcrack Properties of Sedimentary Rocks: An Audit of Dry and Water Saturated Sandstone Core Velocity–Stress Measurements

Reservoir stress path and induced seismic anisotropy: results from linking coupled fluid-flow/geomechanical simulation with seismic modelling

On the importance of the heterogeneity assumption in the characterization of reservoir geomechanical properties

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