Calculating Stimulated Reservoir Volume (SRV) with Consideration of Uncertainties in Microseismic-Event Locations

Abstract

Stimulated reservoir volumes (SRV) calculated from microseismic-event distributions have been successfully used to establish correlations with the production for tight-oil and -gas reservoirs. Although only applicable in reservoirs where complex fracture networks are created, the calculation of SRV numbers has proven to be a valuable measure of the stimulation effectiveness and, in some circumstances, prediction of the well's production. It is important to note that, while SRV is an important baseline measurement of the total rock volume affected by the stimulation, other factors, such as the density and conductivity of fractures within the SRV, are just as important for well performance. Calculating SRV from microseismic-event distributions often involves "shrink-wrapping" the event locations without any consideration of the location uncertainty of the individual event. Not just the amount of location uncertainty, but the directionality of the nonuniform uncertainty space as well as its definition impact the calculated SRV number. Other impacts are the radiation pattern, viewing distance, and accuracy of the underlying velocity model. In this paper, the quantitative impact of these factors on the SRV number is discussed and the developed methodology is applied to several datasets, resulting in the calculation of uncertainty bars for the SRV number. These SRV uncertainty ranges help explain some of the anomalous deviations of the SRV number in individual projects from the general trend in a certain area, which is demonstrated using an example from the Barnett shale.

Understanding the True Stimulated Reservoir Volume in Shale Reservoirs

“…The concept of SRV was initially introduced by Fisher et al (2004) and presented as a means to correlate microseismic images to well performance in the Barnett shale (Cipolla and Wallace, 2014). Several works present the volume affected by hydraulic fracturing stimulation slightly differently in terms of definition, names and detailed calculations, although the overall concept is very similar (Zimmer et al 2011). For example, Mayerhofer et al (2010) uses SRV or stimulated reservoir area (SRA) and Cipolla et al (2011) refers to effective stimulated volume (ESV).…”

“…For example, Mayerhofer et al (2010) uses SRV or stimulated reservoir area (SRA) and Cipolla et al (2011) refers to effective stimulated volume (ESV). Microseismic-event (MS) clouds, which were generated due to hydraulic fracturing activities, have been commonly used as a proxy to map out and estimate SRV (Mayerhofer et al 2010, Zimmer 2011, Gajraj et al 2013. Mayerhofer et al (2010) presents how the SRV can be estimated from MS clouds and is then related to total injected-fluid volume and well performance.…”

“…Mayerhofer et al (2010) also describes the importance of fracture conductivity and spacing within a given SRV and both can affect the production and ultimate recovery. Zimmer (2011) discusses the SRV calculation from MS-event distributions to establish correlations with the production for tight-oil and-gas reservoirs. In Zimmer (2011), the quantitative impacts of few factors such as radiation patter, viewing distance, and accuracy of the underlying velocity model were discussed.…”

“…Zimmer (2011) discusses the SRV calculation from MS-event distributions to establish correlations with the production for tight-oil and-gas reservoirs. In Zimmer (2011), the quantitative impacts of few factors such as radiation patter, viewing distance, and accuracy of the underlying velocity model were discussed. The methodology was developed and applied to several datasets, yielding the range of uncertainty for the SRV numbers.…”

A Simplified Engineering Model Integrated Stimulated Reservoir Volume (SRV) and Tight Formation Characterization With Multistage Fractured Horizontal Wells

“…3 They have applied streamline simulation method. Zimmer et al (2011) presented the uncertainties in calculating SRV from Microseismic events. They also summarized that bining and shrink-wrapping are two conventional methods to calculate SRV through microseismic-event locations, and quantifying SRV uncertainties helps prevent erroneous interpretations.…”