Analyzing Production Data From Tight Oil Wells

Abstract

Summary Performance prediction of wells producing from tight (microdarcy) formations is a daunting task. Complexities of geology (the presence/absence of naturally occurring fractures and contribution from different lithological layers), completion and fracture geometry complexities (multiple transverse or longitudinal fractures in long horizontal boreholes), and two-phase flow are impediments to simple performance forecasting. We demonstrate the use of various analytical and numerical tools to learn about both short- and long-term reservoir behaviours. These tools include (a) traditional decline-curve analysis (Arps 1945), (b) Valko's stretched-exponential (SE) method (Valko 2009), (c) the Ilk et al. (2008, 2010) power-law exponential (PLE) method, (d) rate-transient-analysis (RTA) and transient-PI analyses to ascertain the stimulated-reservoir volume (SRV), and (e) numerical-simulation studies to gain insights into observed flow regimes. The benefits of collective use of analytical modelling tools in history matching and forecasting both short- and long-term production performance of tight oil reservoirs are demonstrated with the use of real and simulated data. Diagnosing natural fractures, quantifying stimulated-reservoir volume, and assessing reliability of future performance predictions all became feasible by using an ensemble of analytical tools.

The Critical Role of Rock and Fluid in Unconventional Shale Reservoir Performance

“…The results demonstrate significant depletion in the fracture system with limited pressure drop in the matrix away from the fractures after 30 years of production. Similar performance is reported by other investigators (Kabir at al., 2011).…”

Waterflood performance evaluation in a chalk reservoir with an ensemble of tools

“…The duration of linear flow is governed by the fracture spacing, whereas the unit-slope response signifies the stimulated-reservoir volume (SRV). Interestingly enough the overall response is akin to those observed in unconventional wells, as shown by Kabir et al (2011b) and Note that the SRV does not imply reservoir boundary; rather, the imaginary ellipsoidal flow geometry, which is a manifestation of fracture stimulation. This volumetric-SRV response appears to suggest that the water production occurs over limited well length, thereby raising questions about the volumetric sweep efficiency.…”

Statistical Detection of Flow Regime Changes in Horizontal Hydraulically Fractured Bakken Oil Wells

“…The graphical characterization of the problem is shown in Figure 1, which provides a framework for the analysis. Embedded in that framework is the assumption (previously noted) that in log space the inverse of daily production versus the number of days during the transient period follows the linear path with a slope of 1/2 and that immediately following the change to boundary-dominated flow the inverse of production follows a linear path (in log space) with a slope of 1.0 (Kabir et al 2011).…”

“…For the current illustration the original values of a and b are taken to be 100 and 1000 days in real space, respectively. In theory, if one has the point estimates of the reservoir parameters plus information about well spacing, then one can estimate parameters for a prior distribution for t* (Kabir et al 2011;Ran 2016). The implementation of the Bacon-Watts approach presented here, along with the associated computations, follows the approach of the SAS Institute (2016).…”

“…For horizontal hydraulically fractured Bakken wells, production commonly follows two general flow regimes (Kabir et al 2011). Early in the life of the well, production is dominated by linear flow as the reservoir fluids flow through the induced fractures.…”