Numerical Techniques Used for Predicting Subsidence Due to Gas Extraction in the North Adriatic Sea

Settari, A.; Walters, D.A.; Stright, D.H.; Aziz, Khalid

doi:10.1080/10916460701833889

Cited by 21 publications

(23 citation statements)

References 10 publications

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“…The process is theoretically described by the 3-D fully coupled poroelasticity model originally developed by Biot [1941]. Gambolati et al [2000] and Settari et al [2005] have shown that in the reservoirs and aquifers of the Po River basin coupling between the flow and the stress fields is weak and uncoupling, as is usually assumed by hydrogeologists and petroleum engineers, is fully warranted on any timescale of practical interest.…”

Section: Methodsmentioning

confidence: 99%

“…Great care has been devoted to the gridding issues as suggested by Settari et al [2005]. The layers where the reservoir and the surrounding aquifers are located have been vertically discretized, consistent with the field production model.…”

Section: Geomechanical Modelmentioning

confidence: 99%

“…[25] An isotropic stress-strain relation is the most common assumption in reservoir geomechanics, also because only the vertical component of the land displacement or in situ deformation is usually available for the model calibration [e.g., Teatini et al, 2000;Settari et al, 2005;Rutqvist et al, 2008]. For an isotropic elastic medium the constitutive matrix D relating the effective stress tensor s to the displacement u via the strain tensor is given by …”

Section: Geomechanical Modelmentioning

confidence: 99%

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Geomechanical response to seasonal gas storage in depleted reservoirs: A case study in the Po River basin, Italy

et al. 2011

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[1] Underground gas storage (UGS) in depleted hydrocarbon reservoirs is a strategic practice to cope with the growing energy demand and occurs in many places in Europe and North America. In response to summer gas injection and winter gas withdrawal the reservoir expands and contracts essentially elastically as a major consequence of the fluid (gas and water) pore pressure fluctuations. Depending on a number of factors, including the reservoir burial depth, the difference between the largest and the smallest gas pore pressure, and the geomechanical properties of the injected formation and the overburden, the porous medium overlying the reservoir is subject to three-dimensional deformation with the related cyclic motion of the land surface being both vertical and horizontal. We present a methodology to evaluate the environmental impact of underground gas storage and sequestration from the geomechanical perspective, particularly in relation to the ground surface displacements. Long-term records of injected and removed gas volume and fluid pore pressure in the "Lombardia" gas field, northern Italy, are available together with multiyear detection of vertical and horizontal west-east displacement of the land surface above the reservoir by an advanced permanent scatterer interferometric synthetic aperture radar (PSInSAR) analysis. These data have been used to calibrate a 3-D fluid-dynamic model and develop a 3-D transversally isotropic geomechanical model. The latter has been successfully implemented and used to reproduce the vertical and horizontal cyclic displacements, on the range of 8-10 mm and 6-8 mm, respectively, measured between 2003 and 2007 above the reservoir where a UGS program has been underway by Stogit-Eni S.p.A. since 1986 following a 5 year field production life. Because of the great economical interest to increase the working gas volume as much as possible, the model addresses two UGS scenarios where the gas pore overpressure is pushed from the current 103%p i , where p i is the gas pore pressure prior to the field development, to 107%p i and 120%p i . Results of both scenarios show that there is a negligible impact on the ground surface, with deformation gradients that remain well below the most restrictive admissible limits for the civil structures and infrastructures. Citation: Teatini, P., et al. (2011), Geomechanical response to seasonal gas storage in depleted reservoirs: A case study in the Po River basin, Italy,

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Section: Methodsmentioning

confidence: 99%

Section: Geomechanical Modelmentioning

confidence: 99%

Section: Geomechanical Modelmentioning

confidence: 99%

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Geomechanical response to seasonal gas storage in depleted reservoirs: A case study in the Po River basin, Italy

et al. 2011

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“…Examples of such layered compacting reservoirs from the North Adriatic are found in Stright et al, 2008 andSettari et al, 2008. However, retaining even relatively large shale layers in the gridding may be prohibitively expensive in modeling and they are often upscaled into NTG for flow models.…”

Section: Introductionmentioning

confidence: 99%

Upscaling of Geomechanics in Heterogeneous Compacting Reservoirs

Settari

Alruwaili

Sen

2013

SPE Reservoir Simulation Symposium

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Upscaling of properties for reservoir simulation has reached a stage of maturity and uses sophisticated techniques. In contrast, little work has been done on upscaling of mechanical properties for coupled modeling, and the geomechanical model is usually assumed to be representative (upscaled) without actually being subjected to the same rigor of process or scrutiny. Compacting reservoirs often contain fine sand-shale sequences on sub-grid scale (compared to flow modeling grid) and are typically represented in simulators by the net-to-gross (NTG) concept, while being ignored in geomechanical modeling.In this work, we present a method to upscale shales in the geomechanical component of a coupled simulation by computing dynamically changing equivalent moduli. The method is based on estimating the depletion of interbedded shales, coupled with analytical solutions for equivalent moduli under the assumption of uniaxial deformation. The technique has been verified by sub-grid scale simulations and requires geometric characterization of the shales but is relatively simple and can be easily implemented in coupled simulators. The analysis shows that the inclusion of the shales generally reduces computed compaction, with the controlling variables being NTG, dimensionless pressure depletion of the shales (which in turn depends on their flow properties) and mechanical properties of the shales.The approach developed was incorporated in the subsidence and compaction analysis over a complex offshore oil reservoir. The reservoir zone consisted of a number of intervals that included relatively undeformed as well as highly deformed layers, and on reservoir model scale had significant NTG ratios. A comprehensive study (based on coupled flow and geomechanics simulation) was conducted to evaluate well integrity, fault slip (reactivation) and compaction drive. A large full field model was built using data from a multitude of sources and production data was modeled and history matched, allowing us to estimate the magnitude of reservoir subsidence and the contribution of the NTG effect on predictions. The study presented here showed that in the absence of any consideration of the NTG effect, predictions (for compaction and subsidence) could be significantly overestimated. In addition, the method can be used to study the phenomena of "time-lag" of subsidence which has been observed in some reservoirs.

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“…Therefore, uncoupled or loosely coupled models are used by many researchers/practitioners by which a reservoir model is coupled to a geomechanics model by staggering in‐time flow and deformation via a sophisticated interface that repeatedly calls first flow and then mechanics (see e.g. Settari et al 1, 7 and Minkoff et al 6). Although not able to account for fully coupled effects, the procedure has its advantages such as computational savings, by allowing for the reservoir and geomechanical grids to not to coincide, etc.…”

Section: Introductionmentioning

confidence: 99%

Cell to node projections: An assessment of error

Goumiri

Prévost

2011

Num Anal Meth Geomechanics

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SUMMARYReservoir simulators typically use cell-centered finite volume schemes and do not model directly the coupling of the flow processes with the geomechanics. Coupling of geomechanics with fluid flow can be important in many cases, but introducing fully coupled geomechanical effects in those simulators is not a trivial issue, because the geomechanics is better done by using the Galerkin vertex-centered finite element methods by which the solid displacements are computed at the vertices of the cells. This creates difficulties in interfacing cell variables with nodal variables. Uncoupled or loosely coupled models are used by many researchers/practitioners by which a reservoir model is coupled to a geomechanical model by staggering in-time flow and deformation via a sophisticated interface that repeatedly calls first flow and then mechanics. The method therefore requires projection of the reservoir cell variables onto the nodes of the geomechanics Galerkin finite element mesh.In this note, we attempt to quantify the errors associated with cell to node projection operations. For that purpose, we use a simple model of the pressure equation for a heterogeneous medium in one dimension. We are able to derive the exact analytical solution for this problem for both nodal and cell pressures. This allows us to compute the errors due to projection analytically, function of meshing refinement and permeability field variations. We compute upper and lower bounds for the errors, and analyze their magnitude for a variety of cases. We conclude that, in general, cell to node projection operations lead to substantial errors.

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Numerical Techniques Used for Predicting Subsidence Due to Gas Extraction in the North Adriatic Sea

Cited by 21 publications

References 10 publications

Geomechanical response to seasonal gas storage in depleted reservoirs: A case study in the Po River basin, Italy

Geomechanical response to seasonal gas storage in depleted reservoirs: A case study in the Po River basin, Italy

Upscaling of Geomechanics in Heterogeneous Compacting Reservoirs

Cell to node projections: An assessment of error

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