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Collaborating Authors
Drillstem/well testing
Summary A great deal of research has been focused on transient two-phase flow in wellbores. However, there is lack of a comprehensive two-fluid model in the literature. In this paper, we present an implementation of a pseudo-compositional, thermal, fully implicit, transient two-fluid model for two-phase flow in wellbores. In this model, we solve gas/liquid mass balance, gas/liquid momentum balance, and two-phase energy balance equations to obtain five primary variables: liquid velocity, gas velocity, pressure, holdup, and temperature. This simulator can be used as a stand-alone code or can be used in conjunction with a reservoir simulator to mimic wellbore/reservoir dynamic interactions. In our model, we consider stratified, bubbly, intermittent, and annular flow regimes using appropriate closure relations for interphase and wall-shear stress terms in the momentum equations. In our simulation, we found that the interphase and wall-shear stress terms for different flow regimes can significantly affect the model's results. In addition, the interphase momentum transfer terms mainly influence the holdup value. The outcome of this research leads to a more accurate simulation of multiphase flow in the wellbore and pipes, which can be applied to the surface facility design, well-performance optimization, and wellbore damage estimation.
Summary Deconvolution is a technique for converting the pressure and rate data obtained from a well operating under variable-rate conditions into a much simpler form of constant-rate drawdown-pressure response function from the same well. However, deconvolution should only be applied to pressure and rate data that result from fluid flow in the reservoir that is governed by a linear set of equations. In gas reservoirs, the fluid-flow problem is nonlinear because the gas properties are strongly dependent on pressure. In some specific situations, this gas-flow problem can be linearized by the use of a pseudopressure transform that allows deconvolution to be successfully applied to tose data. However, there are situations in which a pseudopressure transform alone does not fully linearize the gas-flow problem, and the resulting data will exhibit nonlinear behavior caused by the pressure dependence of the gas compressibility. Direct application of deconvolution to such data will produce erroneous results. This paper presents an enhancement of the deconvolution algorithm that allows it to be used with pressure data affected by a nonlinear pressure-dependent compressibility. We discuss the detailed considerations for this enhancement of the deconvolution algorithm and demonstrate its performance on simulated test data exhibiting this nonlinear behavior. We also demonstrate the application of this enhanced deconvolution algorithm to a set of pressure data from a gas well fitted with a permanent gauge and covering the first 3 years of production from that well.
- Europe (1.00)
- North America > United States > Massachusetts (0.28)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Pressure transient analysis (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
- Reservoir Description and Dynamics > Fluid Characterization > Phase behavior and PVT measurements (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
Gravimetric Monitoring of Water Influx Into a Gas Reservoir: A Numerical Study Based on the Ensemble Kalman Filter
Glegola, M.. (Delft University of Technology) | Ditmar, P.. (Delft University of Technology) | Hanea, R.G.. G. (TNO/Delft University of Technology) | Vossepoel, F.C.. C. (Shell International Exploration and Production) | Arts, R.. (TNO) | Klees, R.. (Delft University of Technology)
Summary Water influx into gas fields can reduce recovery factors by 10โ40%. Therefore, information about the magnitude and spatial distribution of water influx is essential for efficient management of waterdrive gas reservoirs. Modern geophysical techniques such as gravimetry may provide a direct measure of mass redistribution below the surface, yielding additional and valuable information for reservoir monitoring. In this paper, we investigate the added value of gravimetric observations for water-influx monitoring into a gas field. For this purpose, we use data assimilation with the ensemble Kalman filter (EnKF) method. To understand better the limitations of the gravimetric technique, a sensitivity study is performed. For a simplified gas-reservoir model, we assimilate the synthetic gravity measurements and estimate reservoir permeability. The updated reservoir model is used to predict the water-front position. We consider a number of possible scenarios, making various assumptions on the level of gravity measurement noise and on the distance from the gravity observation network to the reservoir formation. The results show that with increasing gravimetric noise and/or distance, the updated model permeability becomes smoother and its variance higher. Finally, we investigate the effect of a combined assimilation of gravity and production data. In the case when only production observations are used, the permeability estimates far from the wells can be erroneous, despite a very accurate history match of the data. In the case when both production and gravity data are combined within a single data assimilation framework, we obtain a considerably improved estimation of the reservoir permeability and an improved understanding of the subsurface mass flow. These results illustrate the complementarity of both types of measurements, and more generally, the experiments show clearly the added value of gravity data for monitoring water influx into a gas field.
- Europe > Netherlands (0.69)
- Europe > Norway > North Sea (0.28)
- North America > United States > Texas (0.28)
- Research Report > New Finding (0.88)
- Research Report > Experimental Study (0.54)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Sognefjord Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Heather Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Fensfjord Formation (0.99)
- (13 more...)
- Reservoir Description and Dynamics > Reservoir Simulation > History matching (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
Summary In this paper, we present a new deconvolution method that removes the dependency of the deconvolved constant-rate drawdown responses on the initial reservoir pressure. It is well known that the late-time periods in particular of the deconvolved responses from the recent pressure-rate deconvolution methods are dependent on the initial reservoir pressure. A small error in the initial reservoir pressure could make a significant difference in the late-time periods of the deconvolved responses that can lead to an incorrect interpretation model, particularly misinterpretation of the boundaries. The new method presented is based on pressure-derivative data rather than pressure data that are used in all published deconvolution algorithms. Using pressure-derivative data in deconvolution leads to a nonlinear least-squares objective function that is different from those used in the earlier deconvolution methods and eliminates the dependency of the deconvolved responses on the initial reservoir pressure. Therefore, the new method minimizes incorrect interpretation because of an error or uncertainty in the initial reservoir pressure. We apply the new method to both simulated and field pressure-transient data sets. The results show that the new method offers a significant advantage over the earlier deconvolution methods for pressure-transient-test interpretation in cases where the initial reservoir pressure is unknown or uncertain.
- North America > United States (1.00)
- Europe (1.00)
- Overview (0.94)
- Research Report > New Finding (0.48)
- Research Report > Experimental Study (0.34)