Harmonic-Pulse Testing for Non-Darcy-Effects Identification

Abstract

Summary Gas reservoirs are generally subject to non-Darcy effects, especially in the near-wellbore zone. In fact, the assumption of Darcy-flow regime is no longer valid because of inertial phenomena and/or turbulence. These could significantly reduce the peak performance of a gas well. Therefore, characterization and monitoring of the non-Darcy effects is key for defining an optimal reservoir-exploitation strategy. This is particularly true in the case of storage fields, where withdrawal- and injection-gas rates are typically very high (hundreds of thousands of m3/d) and determining and monitoring well performance is key to ensuring that deliverability meets demand and/or contract obligations. Pulse testing, which is dependent on a periodic variation of produced/injected rate, is an effective methodology to test a well during ongoing field operations without stopping production. Although pulse testing is very promising for monitoring well performance, it has never been exploited for this purpose. In this paper, the development of a method for pulse testing high-performing gas wells is presented and discussed. The pressure response to the imposed rates is analyzed in the frequency domain to evaluate reservoir and well properties. An analytical solution in the frequency domain taking into account wellbore-storage effects was derived. The method was applied to test a real gas well of a storage reservoir under two different pressure conditions to assess the effect of turbulence on deliverability. Although the pulse-testing technique might not replace traditional well testing for determining reservoir properties, it can be successfully applied to monitor well performance as a function of reservoir pressure.

Harmonic pulse testing for well performance monitoring

“…The dimensionless solution of the diffusivity equation for an infiniteacting homogeneous and isotropic gas reservoir drained by a fully penetrating vertical well, under radial symmetry, was already published by the authors (Salina Borello et al, 2017) in terms of Hankel functions. In the present paper the dimensionless solution is given in terms of modified Bessel functions K 0 and K 1 in a form analogous to Kazi-Aoual et al, 1991:…”

“…The concept of harmonic testing was first proposed by Kuo (1972) and later developed by other authors (Black and Kipp, 1981;Kazi-Aoual et al, 1991;Rosa and Horne, 1997;Hollaender et al, 2002b;Copty and Findikakis, 2004;Despax et al, 2004;Renner and Messar, 2006;Rochon et al, 2008;Ahn and Horne, 2010;Fokker and Verga, 2011;Fokker et al, 2012Fokker et al, , 2013Morozov, 2013;Vinci et al, 2015;Sun et al, 2015;Salina Borello et al, 2017). The main advantage of this testing approach is it does not require the interruption of production nor the knowledge of previous rate history (Hollaender et al, 2002b).…”

What’s Conventional and What’s Special in a Reservoir Study for Underground Gas Storage

“…The need to acquire this information, which would call for expensive traditional testing campaigns, can be better satisfied by alternative well testing procedures, such as harmonic pulse testing [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] and injection testing [41,42]. A harmonic test is characterized by a periodic sequence of alternating production or injection rates that can be imposed after a long shut-in of the tested well, similar to conventional well testing, or can be superposed to ongoing production, minimizing or avoiding economic losses.…”

What’s Conventional and what’s Special in a Reservoir Study for Underground Gas Storage

“…The need to acquire this information, which would call for expensive traditional testing campaigns, can be better satisfied by alternative well testing procedures, such as harmonic pulse testing [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and injection testing [39,40]. A harmonic test is characterized by a periodic sequence of alternating production or injection rates that can be imposed after a long shut in of the tested well, similar to conventional well testing, or can be superposed to ongoing production, minimizing or avoiding economic losses.…”