Steam-assisted gravity drainage (SAGD) is one of the latest and the most advanced technique in heavy oil recovery processes. The determination of the swept volume in a steam chamber process provides an early means to evaluate the project's progress. The pseudosteady state method has been used to estimate the swept volume, from pressure falloff testing of horizontal wells. This method is easy to use and is identical in form to the well-known productivity equation for a vertical well.
In this paper accuracy and applicability of the pseudosteady state (PSS) method in estimating the swept volume for steam injection through a horizontal well is thoroughly investigated. A commercial thermal numerical simulator (CMG, STARS) is used to generate pressure falloff data. More than 31 simulated pressure falloff tests were analyzed in order to investigate the accuracy of the analytically estimated swept volume with the simulated swept volume in the SAGD model. In addition, several parameters, such as gridblock density, duration of injection time, permeability ratio?v h??k k, steam quality, and the location of the producer, were also studied.
Results of the study show that the pseudosteady state method can be used to estimate the swept volume for steam injection through a horizontal well. Within the norms of the independent parameters, the analytically estimated swept volume is in good agreement with the simulated swept volume. The standard error of estimation swept volume using the analytic technique compared to the simulated swept volume ranges from 0.3 to 30 percent
Unconventional oil reservoirs are becoming more important to the world economy as new conventional sources of hydrocarbons are becoming harder to locate. Historically, oil reserves that are difficult to recover using primary, secondary, and chemically enhanced tertiary methods have been neglected in the search for more favourable hydrocarbon reservoirs. Canada and the province of Saskatchewan in particular, contain vast resources of immobile hydrocarbons. Because of this present market, Canada has proven to be a world innovator with respect to heavy oil recovery technology. Economically feasible technologies, such as steamflooding, (SAGD), and vapour extraction (VAPEX) have been developed in order to meet world market demand.
Thermal methods are the most researched area within heavy oil recovery. The most economically feasible method of transferring heat into a reservoir and the flux thereof is by the use of steam. This medium is fully utilized within the area of SAGD1,2.
Recently, the innovative idea of combining horizontal well technology with heavy oil steam recovery technology has been achieved. This coupling of technology aids in the crucial heat transfer process and subsequent viscosity reduction and gravity drainage. Because SAGD processes involve transferring heat into the reservoir, a qualitative analysis of heat loss must be investigated. ccurately monitoring the swept volume over time is important for the assessment of a thermal project14. Success of a SAGD thermal project depends upon certain operational parameters such as the optimum well spacing and length of injection time. Accurately monitoring the swept volume over time is important for the assessment of a thermal project14.
