The Groningen Gas Field in Northern Netherlands is the largest gas field in Europe with production starting in 1963. Seismic events were first observed in 1986, but these were generally small with minimal damage. A government study concluded in early 1990’s that tremors were linked to gas production. The objective of the work described here is to utilize advanced geomechanical modeling to (i) characterize subsurface behavior related to production-induced fault reactivation, and (ii) evaluate alternate production strategies to help manage subsurface stresses to reduce fault slippage which can lead to seismicity. Multi-scale 3D geomechanical models were developed using a non-linear quasi-static finite element method. This modeling framework includes a global model to capture full-field phenomena and two sub-models for regions with observed seismic activity which honor conditions of the global model, but also include explicit modeling of multiple faults. This approach considers the following features: i) Irregular stratigraphy and fault surfaces, ii) Variable reservoir rock properties according to porosity changes, iii) Non-uniform pressure depletion derived from field data and reservoir simulations, iv) Relaxed deviatoric salt stresses at start of production, v) Salt creep effects during production, vi) Biot coefficient effects for reservoir rocks, and vii) Coulomb friction behavior to capture slippage along faults. Models are verified by comparing predictions for the production history period (1964 – 2012) with corresponding field data. The model predictions for production forecast period (2012 onwards) are used for relative comparison of various production scenarios. Subsidence and reservoir strains calculated from the full-field global model during production history match well with corresponding field data without the need for calibration of material properties. Model results show that the fault frictional dissipated energy correlates well with the radiated energy from observed seismic events, and that the energy scaling factor associated with this correlation is constant and the same for both sub-model 1 and 2. The dissipated energy during frictional sliding is a scalar quantity that provides a representative measure of fault activity for a given area of interest. Furthermore, because the dissipated energy correlates well with observed radiated energy, the models can be used for relative comparison of production scenarios to identify strategies that reduce fault loading. Several production forecast scenarios are analyzed and evaluated based on predicted frictional dissipated energy to assess fault slippage. These results indicate that curtailment of production alone is not an effective alternative for mitigation of energy dissipation and related seismic activity. This study shows that advanced geomechanical models are a powerful tool that can provide valuable insight into the overall trend of cumulative radiated energy, are useful in understanding seismic activity, and can be used to identify production scenarios that mitigate seismic activity.

The ability to understand and optimize the exact circumstances by which fluids enter the wellbore is increasingly crucial to achieving effective and economic production. The well completion, the connection to the reservoir, must be designed and operated in accordance with the true physics of the near well flow environment. The ability to visualize such flows, then parameterize and extrapolate the results with realistic simulation models, affords a powerful advantage in creating well completions that are simple to install, reliable to operate, and, of course, deliver all the flow the reservoir is capable of yielding. This paper illustrates the use of advanced visualization in this process. Two examples are presented, featuring detailed images of flow through complex sand control completions hardware (gravel pack) and of flow through wormholes in acid-stimulated carbonate rock.

Fiberglass Reinforced Plastic (FRP) bars for concrete reinforcement have been commercially available for several years. The main advantage of such bar relative to the conventional steel reinforcing bars is their resistance to corrosion. The reinforced plastic bars are slightly different from the conventional steel bars both geometrically and mechanically. Thus, research is needed to understand their behavior and to be able to use them in concrete reinforcement with adequate reliability. Bond strength of reinforced plastic bars in concrete is one of the mechanical and behavioral differences with the steel bars. This paper presents the results of pullout and beam tests conducted to determine the bond stress-slip behavior of FRP bars in concrete.

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Cased-hole fracpacks (CHFP) can deliver high-rate, low-skin completions by creating a highly conductive fracture that extends beyond the perforation tunnels, bypassing near wellbore damage and preventing formation sand production. While the industry has a long history of successful CHFP applications, well performance prediction for this type of completions has remained challenged by complex geometrical (fracture geometry and orientation with respect to arbitrarily deviated wellbores) and multi-physics factors (multiphase flow, turbulence). Most fracpack modeling tools are limited to analytical and simplified reservoir simulation models, which can lead to poor accuracy in quantifying near-wellbore effects, such as non-Darcy pressure drop, particularly important for high-rate gas wells. In this paper, we propose a new mechanistic approach to incorporate the cased-hole fracpack completion with non-Darcy flow through explicitly meshed perforation tunnels, fractures and rock formation in real dimensions. The fracture is modeled by Enriched Finite Element Method (EFEM), which flexibly accounts for arbitrary fracture geometry and orientation while enabling multi-physics effects, impact of perforation/gravel packing damage and perforation-fracture communication uncertainty on deviated well productivities. The proposed approach is validated using (1) analytical and numerical models, and (2) two Gulf of Mexico (GOM) CHFP wells, one vertical and one deviated; where skins measured from step-rate tests were history-matched to longitudinal and transverse fracture models. We also introduce the concept of fracture neighborhood width to account for perforation performance relative to its alignment with fracture opening and orientation. Finally, the new approach is used to predict the deliverability of a high-rate, high-pressure gas condensate well. Non-Darcy effects, condensate banking effects, perforation gravel packing, and geological model uncertainties are included in predicting the well production.