Executive Summary


In this issue of SPE Reservoir Evaluation & Engineering, I would like to welcome new Associate Editor Aysegul Dastan. Sometimes the number of manuscripts we receive can be overwhelming, and having an extra set of expert eyes will help ease the burden on the editorial board. I would also like to welcome our new Editor-in-Chief Russell T. Johns, who came aboard early this year. Moreover, I want to wish all the best to our outgoing EIC Dean Oliver, and thank him for his outstanding tenure.

This second issue of 2018 brings a special section with six papers on unconventional reservoirs in the spotlight. These papers will set the table for our November special issue on unconventional reservoirs, with special guest editor Gary Teletzke. Additionally, we have included fourteen regular papers covering various topics, such as enhanced oil recovery, formation evaluation, geomechanics, heavy oil, reservoir characterization, reservoir simulation, and well testing. Finally, we also present an erratum to amend Eq. 14 in paper SPE-183640-PA (Potsch and Toplack 2017).

Spotlight on Unconventional Reservoirs

As a preamble to our special issue on unconventional reservoirs, we introduce six spotlight papers on the topic. Zhu et al. describe an experimental study performed on calcite-filled fractures from outcrops of Wufeng-Longmaxi shale in China. They argue that their results may be helpful for understanding fracture-propagation mechanisms and the evolution of permeability under in-situ loading processes. Tian et al. use spatial statistics to quantify key geological properties that control production in the Eagle Ford Shale. Yassin et al. evaluate the wettability of shale plugs from the Duvernay Formation in Canada. Their results demonstrate that the shale samples have stronger wetting affinity toward oil compared with brine, among other conclusions that may help to better understand these complicated rocks. Liu et al. offer a quantitative analysis of the geometry of a partially propped fracture and highlight its effects on water flowback and gas production. Gherabati et al. present a multidisciplinary study to generate hydrocarbon-in-place and recovery factor distribution maps that help improve the estimation of the amount of recoverable hydrocarbon in the Eagle Ford Shale. In the final spotlight paper, Ojha et al. demonstrate a method to estimate relative permeability and production performance in four North America formations. The estimated relative permeability curves in this study allow the authors to predict the expected production performance using a numerical simulator. Relative permeability curves remain a big unknown in unconventional reservoirs, and this paper brings some light at the end of the tunnel.

Enhanced Oil Recovery (EOR)

The EOR section presents two papers covering laboratory and modeling work flows. Liang et al. present a decision-making work flow that helps geoscientists understand the most important factors in an EOR project to select the optimal alternative. Then, Abbaszadeh et al. propose a methodology for the development of a laboratory-based foam model to be used in the numerical simulation of EOR.

Formation Evaluation (Petrophysics)

This section brings you two papers—one dealing with borehole measurements and the other dealing with laboratory experiments on rock samples. Tietze et al. investigate whether electrical resistivity changes can be used for reservoir monitoring by applying borehole controlled-source electromagnetics to monitor hydrocarbon saturation in a field located onshore Germany. Their preliminary results have shown that their results agree with seismic surveys and resistivity logs from calibration wells.

Ojha et al. propose a joint laboratory and theoretical work flow to estimate pore-network characteristics and irreducible saturations in shales using low-pressure-nitrogen-adsorption/desorption measurements and effective-medium and percolation theory, among other techniques.

Geomechanics

This section features two papers characterizing elastic properties in unconventional reservoirs. Hamza et al. use core-measured static and dynamic geomechanical properties to assess elastic anisotropy and stress. Their study showed horizontal Young’s moduli higher than the vertical one, which suggested a horizontally layered structure.

Yang et al. conduct nanoindentation testing to characterize changes in mechanical properties of shale samples after different surface treatments. Measured properties include hardness, Young’s modulus, and fracture toughness to examine the alteration of such properties caused by fluid/rock interaction.

Heavy Oil

The two papers presented in this section have a link with the previous section on geomechanics, but are focused on heavy oil. Asl and Chalaturnyk study the effect of in-situ dilation on solvent-assisted steam-assisted-gravity-drainage (SA-SAGD) well systems in an oil-sand reservoir in Canada. Their numerical study reveals that geomechanics considerations directly affect the optimal solvent-type selection and injection strategy during the SA-SAGD process.

Wang et al. performed an experimental study on geomechanical dilation of oil sands. They show promising results to potentially enhance effective permeability to water in the dilated zone using cold-water injection at low-stress anisotropy. Results also provide support for the development of numerical models used in predicting SAGD performance.

Reservoir Characterization

This section features three papers using different reservoir-modeling techniques. Shahamat and Clarkson discuss the application of flowing material balance (FMB) to the analysis of single-phase and multiphase flow in different scenarios. The work flow presented in their paper maintains the simplicity of FMB, yet accounts for multiphase flow and multiwell complications.

Liang et al. present an integrated modeling work flow that includes hydraulic fracturing, reservoir simulation, and uncertainty analysis for the development of a conventional field in the US Permian Basin. They show the importance of considering complex interactions among multiple clusters, stages, and wells to evaluate the impacts on well spacing, completions, and development sequence.

Chen et al. estimate the carbon-sequestration capacity under different engineering parameters, which allows them to provide guidelines to selecting wells and monitoring facilities for CO 2 storage in residual-depleted shale reservoirs.

Reservoir Simulation

This section features one paper in unconventional and one in conventional reservoir simulation. Yu et al. use public data to perform a numerical model for simulating the pressure response of well interference and performance in the Eagle Ford Shale in the US. The model incorporates complex-fracture geometries using the fast embedded-discrete-fracture-model method, which helps them formulate practical conclusions for improved production performance.

Correia and Schiozer present an upscaling work flow to integrate highly laminated or interbedded reservoirs with thin, highly permeable layers in reservoir simulation through a combination of an explicit modeling using the Parsons formula and dual-medium flow models, and compare the method with two conventional upscaling approaches from commercial software packages.  

Well Testing

The sole paper on this section by Raghavan and Chen describes a new source function to predict well responses to evaluate long-term injectivity and late-time responses of fractured wells after the injection of a non-Newtonian fluid. Predictions stemming from the proposed method are compared with numerical solutions available in the pressure-transient-analysis literature and incorporate appropriate corrections that adjust for linearization.

The editorial board has made every effort to bring you a robust issue by selecting innovative and useful manuscripts from industry and academia. All papers were carefully reviewed by at least two technical reviewers under the coordination of an associate editor. However, conclusions and interpretations stemming from these papers are opinions and observation of the authors. I would like to express my appreciation to the technical reviewers who selflessly dedicate their time to perform outstanding reviews to keep the quality of our journal.

Because knowledge sharing and open discussions are important, SPE welcomes further discussion from our readers. I look forward to receiving discussion letters.

Happy reading!

Jesús M. Salazar, Executive Editor of  SPE Res Eval & Eng,
ConocoPhillips, Houston