Feasibility Study of WAG Injection in Naturally Fractured Reservoirs (2006)

Feasibility Study of WAG Injection in Naturally Fractured Reservoirs Joost Clemens Heeremans; Joost Clemens Heeremans Delft University of Technology Search for other works by this author on: This Site Google Scholar Talal Ebraheem Esmaiel; Talal Ebraheem Esmaiel Delft University of Technology Search for other works by this author on: This Site Google Scholar Cor P.J.W. Van Kruijsdijk Cor P.J.W. Van Kruijsdijk Shell Canada Ltd. Search for other works by this author on: This Site Google Scholar Paper presented at the SPE/DOE Symposium on Improved Oil Recovery, Tulsa, Oklahoma, USA, April 2006. Paper Number: SPE-100034-MS https://doi.org/10.2118/100034-MS Published: April 22 2006 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Heeremans, Joost Clemens, Esmaiel, Talal Ebraheem, and Cor P.J.W. Van Kruijsdijk. "Feasibility Study of WAG Injection in Naturally Fractured Reservoirs." Paper presented at the SPE/DOE Symposium on Improved Oil Recovery, Tulsa, Oklahoma, USA, April 2006. doi: https://doi.org/10.2118/100034-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Improved Oil Recovery Conference Search Advanced Search AbstractThe fundamental aspects of Water Alternating Gas (WAG) injection are still not well understood. There are a few applications in fractured media and these show potential.[1] This study looks at the sensitivity of production to reservoir and fluid properties on a pattern scale using tools derived from experimental design. Also a look has been taken into the drive mechanisms in the fractured media that play an important role during WAG injection.Earlier studies claimed that WAG injection in fractured reservoirs is not the best improved oil recovery (IOR) method.[2] However when the conditions are fully understood and the injection is modeled correctly, it is optimal in some fractured reservoirs. The proper modeling of fractured reservoirs remains difficult. The standard dual porosity formulation in commercial simulators is based on a continuous matrix grid overlaid by a continuous fracture grid. The transfer of fluid from matrix to fracture is described by a transfer function. The heart of this transfer function is the shape factor, sigma. As can be seen in a fine-scale grid, the shape factor is different for different reservoir properties and injection types. The upscaling of this sigma from the fine-scale grid to the pattern scale model is important for correct modeling. This study performs several fine scale single porosity simulations to properly upscale the flow model to a dual system.The process of determining sensitivities in an organized manner on properly upscaled models will be shown here with a limited number of parameters. Fractured reservoirs can be divided into different categories.[3] Based on a fine grid model of one type of fractured media, a dual porosity model with varying parameters is set up. This yields recovery outputs across a range of reservoir properties that are represented by two dimensionless numbers. These numbers represent the capillary over viscous and gravity over viscous forces. By looking into the mechanisms that are behind the recovery in different balances of forces, an insight into when and why WAG is working is given.IntroductionIn the last few years some studies about WAG injection have been performed. These studies concentrate on the application of smart wells during WAG injection[4] or a sensitivity analysis in a conventional reservoir.[5] Little is known about the application of WAG injection in naturally fractured reservoirs. It was believed that it was not possible to use the advantages of water flooding and gas injection together due to the existence of fractures in the reservoir.[2] Fractures cause rapid advancement of the injected fluids that changes a major advantage of WAG injection; namely water cycles that are stabilizing the flooding front. However there are some examples from the field that show that there is potential of WAG injection in naturally fractured reservoirs.[1] This paper concentrates on the feasibility of WAG injection in naturally fractured reservoirs.Experimental Design methods are used to determine the optimal fluid-, reservoir- and injection-parameters for WAG injection. These parameters are scaled in two dimensionless numbers that represent the different physical flow mechanisms inside the reservoir. A detailed sensitivity analysis was performed to determine the sensitivity of production to these dimensionless numbers. Based on that a proxy model that can represent the recovery as function of the main physical forces was built and optimized.Results from this model show significant scope for the application of WAG injection in naturally fractured reservoirs. To get more insight in what is actually happening when the WAG injection is working well or not two typical runs are chosen to look into more detail.To make a valid proxy model a simulation model is needed that is fast enough for multiple runs and accurate enough to produce valid results. This was achieved by performing the study with a commercial simulator on a pattern scale dual porosity model with one injector and one producer. Note that upscaling of the shape factor from the fine-scale grid to the pattern scale model is important for correct modeling.[6]Naturally fractured reservoirs Naturally fractured reservoirs exist throughout the world and represent a large portion of the world's oil reserves. A reservoir can be classified as fractured if there exist a continuous path of intersecting fractures across the reservoir.[6] Keywords: enhanced recovery, breakthrough, sensitivity, matrix, machine learning, porosity model, Efficiency, gas injection, Upstream Oil & Gas, Simulation Subjects: Improved and Enhanced Recovery This content is only available via PDF. 2006. Society of Petroleum Engineers You can access this article if you purchase or spend a download.