Executive Summary

Serving as Executive Editor of SPE Journal continues being a great experience and I am delighted to see that the journal is now ranked by Scopus as #4 out of 189 journals in Geotechnical Engineering and Engineering Geology (98th percentile). The journal’s impact factor has improved to 3.372 (9% increase compared to last year), and the time to first decision has been reduced to 29 days. I anticipate that with the excellent research being conducted by our authors, and the hard work of all editors, reviewers and SPE staff, SPE Journal will continue improving in the coming years.

There is excellent research going on in the areas of drilling and completions. As a result, I want to place the spotlight on the first 14 papers of this issue that deal with this topic.

A total of 40 peer-reviewed papers are organized in seven categories, although obviously there is overlapping among some of the categories. For example, we do not have a geomechanics category, but there are many geomechanical papers in the various categories discussed below. The seven categories include drilling and completions, geologic aspects, production and facilities, unconventionals, reservoir engineering, naturally fractured reservoirs, and machine learning and data analytics. A brief description of the papers in each category is presented next.

Spotlight on Drilling and Completions. There are 14 research papers in this category, discussing several topics of practical interest including mud losses, cleaning of horizontal wells, looking ahead of the bit while drilling, deepwater drilling, rheological properties, perforating, hydraulic fracturing, wellbore cement, acid diversion, matrix acidizing and fracturing, wellbore stability, rheological properties, slotted liners, and wormhole propagation in carbonates.

  • Jinasena and Sharma develop a model for estimation of mud losses during the removal of drill cuttings in oil drilling. Their real-time estimation of the amount of fluid losses with the cuttings removal could significantly help for kick detection and automation.
  • Hirpa and Kuru perform an experimental study of drilling-fluid properties on the bed-erosion dynamics in a horizontal pipe.  The authors quantify the individual effect of the fluid elasticity (independent from shear viscosity) on the critical flow rate for bed erosion.
  • Nejadi et al. discuss potential impacts and challenges of acoustic seismic while drilling in the McMurray Formation by looking ahead of the bit while drilling. The imaging workflow provides sufficient time to precisely control the borehole trajectory and stay within the desired reservoir zone.
  • Kan et al. present an experimental study on critical displacement for drill-conductor injection during deepwater drilling. It is anticipated that this research will provide the basis for predicting conductor stability and wellhead-bearing settlement.
  • Huang et al. discuss how to regulate rheological properties of water-based drilling fluid by high-frequency and high-voltage alternating current electric field. For two typical drilling fluids, their plastic viscosity and consistency coefficient both started to increase when voltage reached 4 kV.
  • Araki and Morita investigate the effect of perforation interaction on perforation stability using the finite element method. Their quantitative analysis provides the optimal perforation design that yields the highest productivity while maintaining mechanical stability.
  • Liu et al. discuss rock deformation and strain-rate characterization during hydraulic-fracturing treatments. They demonstrate that low-frequency distributed acoustic-sensing (LF-DAS) data are promising attributes for detecting fracture hits and fracture characterization.
  • Yang et al. quantify the impact of 2D and 3D fractures on permeability in wellbore cement after uniaxial compressive loading. They conclude that the fractures in cement matrix created by the monotonic compressive stress (up to the limit of uniaxial compressive strength) are not likely to form continuous leakage pathways.
  • Sarmah et al. present a new cationic polymer system that improves acid diversion in heterogeneous carbonate reservoirs. The strong elastic nature of the gel formed by the partially neutralized acid system proves its suitability as a candidate for use as a diverting agent.
  • Palharini Schwalbert et al. ask the question: matrix acidizing or acid fracturing? To provide an answer, they develop a single dimensionless number that incorporates all pertinent reservoir properties and determines which stimulation method yields the most productive well, without needing any simulations.
  • Gao et al. demonstrate a semianalytical poroelastic solution for evaluating wellbore stability in a porous medium saturated with two immiscible fluids. The paper considers an inclined borehole subjected to nonhydrostatic stresses
  • Fu et al. evaluate the effect of xanthan gum (XG) on rheological properties of a methane hydrate slurry. This is an important problem for drilling in a deepwater environment. In the proposed equations, the non-Newtonian factor and the consistency factor are expressed as functions of XG concentration empirically.
  • Liu and Morita use laboratory tests and the 3D finite element method for analyzing bending and collapse of slotted liners. They recommend re-evaluating the use of a lower-grade base pipe before using a thinner high-grade base pipe for some applications.
  • Aldhayee et al. discuss wormhole propagation during fracture-acidizing stimulation in tight-carbonate formations. Their study optimizes the acid volumes and injection rates that can be used in conducting close-fracture acidizing (CFA).

Geologic Aspects. The four papers in this category discuss sequential exploration, evaluation of mineralogy, turbidite channels, and geological uncertainty.

  • Jafarizadeh and Bratvold discuss how to improve sequential exploration depending on geological dependencies and uncertain oil prices. This is important because the outcome of drilling a well can change the chance of success in nearby prospects, affecting their economics and drilling decisions.
  • Bruned et al. discuss how to evaluate mineralogy with the use of an approximate Bayesian computation. the approach is to explore all possible mineralogy hypotheses that match the wellbore data.
  • Vargas Grajales et al. use an object-based algorithm for simulating properties of a turbidite channel. A commercial finite difference simulator is used to compare the reference data to the simulated data. The comparison is good.
  • Zhao et al. discuss a multiobjective evolutionary algorithm (MOEA) for optimizing production under geological uncertainty. The method is more efficient when compared with traditional MOEAs and surrogate-assisted optimization methods.

Production and Facilities. The four papers in this category discuss sucker-rod pumping, removal of residual oil, leakage prevention in pipelines, and experimental work in horizontal pipes.

  • Yin et al. present a method for diagnosing sucker-rod pumping systems based on the polished-rod load vibration in vertical wells. The study develops a new analytic solution of the 1D wave equation of the sucker-rod string.
  • Theurer et al. use magnetic nanoparticles for removing residual oil from produced water. The residual oil removal uses uncoated, recyclable, and less expensive maghemite (𝛾-Fe2O3) nanoparticles.
  • Cintra et al. develop an approach for real-time leakage detection in pipelines using a built-in wireless information and communication network. The internal leak is detected by an external central unit connected to the linear wireless network.
  • Mohammadikharkeshi et al. conducted experiments and modeling studies of slug dissipation in a horizontal enlarged impacting tee-junction (EIT). The paper considers both flowing-slug injection and stationary-slug injection into the EIT.

Unconventionals. The five papers in this category discuss shales, including molecular dynamics, stress variations, use of nuclear magnetic resonance (NMR), data-driven analysis, and geomechanics in a coal reservoir.

  • Perez and Devegowda investigate primary production from shale organic pores through a molecular dynamics study. A sensitivity analysis shows that the produced fluid composition strongly depends on the initial composition of the fluids in organic pores.
  • Ma and Zoback present an interesting study for predicting lithology-controlled stress variations in the Woodford Shale with the use of well log data by considering viscoplastic relaxation.
  • Tandon and Heidari use experimental data of the hydrocarbon/kerogen intermolecular-interfacial-relaxation mechanism for improving analysis of NMR measurements in organic-rich mudrocks.
  • Klie and Florez predict dynamics of shale reservoirs using data-driven analytics. The paper introduces extended dynamic mode decomposition (EDMD) for learning the reservoir dynamics entailed by flow/fracture interactions in shales.
  • Raza et al. estimate the anisotropic stress-dependency of coal permeability by pore-volume distribution and stress-strain measurements using a stochastic method. The method is described as simple, economical, and time-effective.

Reservoir Engineering. The five papers in this category discuss countercurrent imbibition, scale inhibitors, polymer flooding, viscosity of bitumen/solvent mixtures, and heavy-oil reservoirs.

  • Liu and Sheng use NMR technology to investigate countercurrent spontaneous imbibition in oil-wet tight cores. This is important because this imbibition is one of the most significant mechanisms for the mass transfer between fractures and matrixes in tight reservoirs.
  • Mohammadi and Riahi discuss experiments conducted to investigate water incompatibility and rock/fluid and fluid/fluid interactions with and without scale inhibitors (SI). In addition, phase-behavior study and interfacial tension (IFT) measurement illustrate a salinity-dependence effect of SIs on the interfacial behavior of the oil/water system.
  • Husveg et al. present the development of a low-shear valve suitable for polymer flooding. The paper demonstrates that polymer degradation with the new valve at very-shear-sensitive test conditions is less than 10% at 40- to 45-bar pressure drop, compared with 60 to 80% for a standard valve.
  • Nourozieh et al. apply a nonlinear double-log mixing rule for viscosity calculation of bitumen/solvent mixtures applicable for reservoir simulation of solvent-based recovery processes.
  • Abdelfatah et al. use microemulsion formulations with tunable displacement mechanisms for the case of heavy-oil reservoirs. The authors propose a platform for designing ultralow IFT solutions for reducing the capillary pressure and mobilizing the heavy oil.

Naturally Fractured Reservoirs. The four papers in this category discuss a quadruple porosity model for petrophysical evaluation, water imbibition in a carbonate reservoir, strain evaluation in chalk cores, and a data-driven evolutionary-optimization method.

  • Issoufou Aboubacar and Cai develop a quadruple-porosity model for petrophysical evaluation of naturally fractured vuggy reservoirs. The approach is based on the volume-model method and rules of electric-resistance networks in porous media.
  • Wang et al. discuss an aqueous solution of ketone solvent for enhanced water imbibition in fractured carbonate reservoirs. The analysis provides a quantitative evaluation of the imbibed fraction of the injected components and the relative contribution of these components to the oil displacement in the matrix.
  • Kallesten et al. discuss modeling of permeability and strain evolution in chemical creep compaction experiments conducted at reservoir conditions with fractured and unfractured chalk cores. Results indicate that recovery can be maximized for a small amount of chemical injection.
  • Ma et al. present a multiscale-network structure inversion of fractured media based on a hierarchical-parameterization and data-driven evolutionary-optimization method. Empirical studies on hypothetical and outcrop-based cases demonstrate that the method can model and estimate the complex multiscale-fracture network on a limited computational budget.

Machine Learning and Data Analytics. The four papers in this category discuss the use of machine learning for prediction of relative permeabilities, incorporation of dynamic production and logging data, classification of lithology, and optimization of well placement. Machine learning is also discussed in some of the papers mentioned in previous categories.

  • Zhao et al. discuss a hybrid approach for the prediction of relative permeability using machine learning of experimental and numerical proxy SCAL data. The study presents a reliable correlation to determine the relative permeability based on Euler number and saturation.
  • Guimarães et al. use machine learning for incorporating dynamic production and logging data to their permeability-estimation workflow. The proposed procedure provides more accurate permeability curves than the ones obtained from conventional methods.
  • Singh et al. discuss the use of unsupervised and supervised machine-learning algorithms for automatic well-log processing and lithology classification. The workflow is demonstrated using two wells from two different reservoirs on the Alaska North Slope to distinguish four different rock types along the well.
  • Alrashdi and Stephen apply reservoir-engineering methods to well-placement optimization algorithms for estimating improved performance. The results show that considerable computation time can be saved by applying the engineering aspects considered in the paper.

Roberto Aguilera, SPE J. Executive Editor,
University of Calgary