Analysis of production data for tight gas reservoirs is based on pressure transient (PT) analysis, which is now a conventional procedure for fractured tight gas reservoirs. Key parameters can be estimated during the analysis: fracture conductivity, fracture half-length and reservoir properties. Most PT analysis methods deal with bilinear, formation linear, and pseudo-radial flow regimes. It is well known that an elliptical flow regime can appear between formation linear and pseudo-linear flow regimes. Sometimes the period is very short and cannot be identified. But there are many cases when only formation linear and elliptical flow regimes are present in production data records and the time needed to reach the pseudo-radial period is more than decades. Most PT analysis methods substitute elliptical flow regime for pseudo-radial, which may lead to the incorrect calculation of key parameters of reservoirs and fractured wells. In this study, we present the development of an approach for elliptical regime analysis in the production data record for calculation of key parameters of finite-conductivity fractured wells and reservoirs: fracture conductivity, fracture half-length, reservoir permeability, and effective drainage area. This method uses an analytical equation for elliptical flow period and estimation of parameters from the equation. The development is based on more stable deconvolution analysis of production data with variable rate/pressure and more reliable analysis of response function after deconvolution. We present here some synthetic and field cases to demonstrate the results of calculations. Introduction Classic well testing approaches for fractured wells involving pseudo-radial flow models cannot be applied since the pseudo-radial regime is reached in decades or years of production in tight gas reservoirs. In many cases, we cannot observe pseudo-radial flow. Really, we deal with elliptical flow after the formation linear period. To receive more realistic results of production data analysis, the best solution is to use elliptical flow model for early- and mid-time production periods (which could actually last for years). Under this assumption we are able to extract approximate permeability and fracture half-length and conductivity values. At the moment, there is literature (Cheng et al. 2007; Hale and Evers 1981; Amini et al. 2007) that presents methods of work with elliptical data. It is reasonable for commercial tools to have robust algorithms for work with production data where elliptical flow regime is exhibited. Integration of the algorithms in production modeling workflow will allow more reliable results of production data analysis. Reservoir characterization and well completion efficiency evaluation involve a multilayer commingled reservoir using commingled system well production performance data. Commingled well production data from a system with a number of different layers with varying reservoir and well completion properties generally should not be evaluated using an equivalent single layer reservoir analog. The results of the analysis for determining estimates of the reservoir properties and completion efficiencies of each of the individual reservoir layers will be very inaccurate in this case. Splitting production data for each layer is an important step for correct analysis. Helpful information on splitting can be found in (Poe et al. 2006).

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A method of nonintrusive hydraulic fracturing monitoring based on high frequency pressure measurements has been known since 1985. Since that time, multiple attempts of its implementation into a commercial product have been tried. A new method using a wellhead pressure sensor during well stimulation was developed in 2017. The method discussed here is a continuation and improvement of this method. It is based on an advanced signal processing algorithm used for detection and analysis of tube waves in a wellbore and on the data science approaches for further processing of tube wave parameters and providing the answers of fluid entry point depth, plug failure probability, and casing leak detection. Use of the wellhead pressure sensor with a data acquisition box eliminates the need for sophisticated hardware. This enables cost-effective and timely decisions at the wellsite. The technique was validated in the field in several fracturing and refracturing jobs.

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