Executive Summary

Mustafa Onur, Universiti Teknologi PETRONAS

This issue brings you 15 outstanding papers, covering a wide spectrum ofsubjects that reflect areas of current activity and interest in the industryand academia. There are five papers providing new insights, materials, andapproaches on various topics of enhanced oil recovery (EOR), such as gas,chemical, and steam flooding. I have chosen four papers providing improvedunderstanding of production and its mechanisms from unconventional reservoirs,including shale and coalbed methane, and four papers that cover advanced fluidscharacterization for phase equilibrium, flash computations for compositionalmodels, and determination of Joule-Thomson coefficient for gas reservoirs. Thelast two papers provide new pressure-transient-analysis models for vertical andhorizontal wells producing in naturally fractured conventional and/orunconventional reservoir systems. The following is a brief overview of eachpaper.

The issue begins with five papers addressing important topics on EOR. Thefirst paper introduces a new dynamic wettability-alteration model for oil-wetcores during surfactant-solution imbibition. The second paper introduces a newfamily of anionic surfactants for EOR applications. The third paper presents animproved three-phase relative permeability and hysteresis model for awater-alternating-gas (WAG) injection. The fourth paper in this categorypresents a low-tension-gas (LTG) flooding method, extending surfactant floodingfor improved oil recovery in tight sandstone and carbonate formations wherepolymer flooding is impractical. The last paper on EOR provides new insightsinto steam/solvent-coinjection-process mechanism by use of numerical model withhomogeneous properties and various solvents.

The next four papers address unconventional reservoirs hydrocarbon recovery.The first paper in this category proposes an efficient methodology on the basisof a multivariate statistics approach by use of theprincipal-component-analysis (PCA) and principal-component-regression (PCR) toanalyze historical production data from unconventional reservoirs for thepurpose of mitigating the risks for developing such reservoirs. The secondpaper investigates the effect of water-induced stress to enhance hydrocarbonrecovery in shale reservoirs. The third paper in this category extends ourunderstanding of the impact of various parameters, such as gas desorption timeconstant, initial fracture permeability, fracture spacing, and swellingcapacity, on the production of coalbed methane from complex fractured coalseams. Last but not least, the fourth paper in this category proposes a newinterpretation method for gas-storage measurements, combining porosity andsorption measurements.

The issue continues with four papers on fluids characterization. The firstpaper presents a detailed comparative study on the tie-line-table-look-up-basedmethods that can improve the efficiency of flash calculations in compositionalsimulations. The second paper proposes a four-phase flash calculation algorithmon the basis of a reduced method for carbon dioxide/hydrocarbon/water systems.The third paper in this category also presents a comparative study ofreduced-variables-based flash and conventional flash methods for the efficiencyof flash calculations in compositional transient simulations. The last paperdescribes a simple and reliable approach for estimating the Joule-Thomsoncoefficient of gas mixtures, including reservoir gas at bottomholeconditions.

The last two papers in this issue address pressure transient test analysis.The first paper presents a new mathematical formulation for dual-porosityfractured reservoirs to more accurately capture the flow contributions frommatrix blocks of various size, permeability and porosity--especially inunconventional reservoirs. The second in this category presents analyticexpressions for the pressure distribution in a three-region composite reservoirof finite thickness produced by a finite-length horizontal well orientedperpendicular to interfaces (represented by a fracture having a finite width,but infinite extent).

In closing, I hope that you enjoy the October issue and its 15 manuscripts.See you in the New Year (February 2014 issue). Cheerio and thank you!