Executive Summary


Announcements

Sun-setting of SPE Economics & Management will be complete in October. In the future, readers will see some papers on this topic published in SPE Journal. Christopher Jablonowski (Shell) and Mohammad Mian (Saudi Aramco), former Associate Editors for SPE E&M, have moved to the editorial board of SPEJ. We welcome them and appreciate their service.

An addendum to SPE-178426-PA by Mazda Irani and Sahar Ghannadi is included with this issue. Please refer to the Addendum Notice on the issue page in OnePetro.

SPE switched to a single-column layout for papers to better support the digital format of our journals. This is a rolling change implemented earlier in the year, so readers will see a mix of two-column and single-column papers in OnePetro, with a full change to single column over the next 6 months, depending on the publication schedule.


New Papers

This month, SPEJ publishes 30 new papers, organized in five categories.

Wettability and Pore-Scale Phenomena. Andersen et al. present a method to derive capillary pressure data point by point from measured imbibition data. The method is advocated to provide reliable data between the equilibrium points and demonstrates consistent variations in flow resistance during imbibition tests. 

Zhou et al. provide experimental support for a pore-scale-derived dimensionless capillary pressure function for water imbibition under mixed wet conditions.

Li et al. develop an analytical model to predict surfactant imbibition and oil recovery as a function of vertical and horizontal fracture spacing and rock and fluid properties. The scaling implied by the model is somewhat different from traditional scaling groups in the literature.

Bartels et al. use micromodels with active clays to study low-salinity waterflooding on a pore scale. A change in contact angle during low-salinity exposure is found necessary to mobilize oil.

Schmatz et al. use broad-ion-beam slope cutting and scanning electron microscopy under cryogenic conditions to provide a pore-scale comparison of a fine-grained limestone with a coarse-grained limestone. The technique can test predictions on the morphology and dynamics of contact lines in relation to mineral properties.

Afrough et al. use magnetic-resonance imaging to study fines migration in Berea sandstone. They find that the average pore size increases at the inlet of a core and reduces at the core outlet.

Longoria et al. measure water flowback and effective permeability in 5 to 10-md limestone cores to show that water is effectively held at a fracture face because of the capillary discontinuity. They argue that this effect can be a significant source of permeability reduction by fracturing-fluid invasion in tight reservoirs.


Chemicals for Improving Hydrocarbon Recovery. Al Ayesh et al. use fractional-flow modeling to compare two methods of foam injection (surfactant-alternating-gas versus co-injection of gas and surfactant solution) in their abilities to improve injection profiles. For surfactant-alternating-gas processes, diversion depends critically on how and whether foam collapses at low water saturation.

San et al. examine the effects of different ions and temperatures on nanoparticle-stabilized CO 2 foams. In Berea sandstone cores, foam mobility decreases by a factor of five as NaCl content increases from 1 to 10%. It also decreases by a factor of four as CaCl 2 concentration increases from 0.1 to 1%. Foam mobility increases modestly between 25 and 65°C.

Jin et al. introduce a microemulsion phase-behavior equation of state that depends on the hydrophilic/lipophilic-difference equation and the net-average-curvature model. Their study predicts that an increase in solution gas and pressure enlarges a microemulsion bank and narrows an oil bank.

Using tubes to mimic void-space-conduits (e.g., fractures), Imqam et al. investigate the transport of preformed particle gels through various combinations of flow paths in parallel and series. Gel particles accumulate at choke points. For parallel flow paths, the distance of gel propagation depends strongly on the ratio of conduit diameters and gel strength.

Guo et al. investigate the flow behavior of hydrophobically modified partially hydrolyzed polyacrylamides in micromodels. They find that high resistance factors and residual resistance factors for these polymers are more a result of polymer aggregation than of adsorption.

Salasi et al. examine oxygen scavenging by bisulfite ions in monoethylene glycol (MEG)/water mixtures at concentrations commonly found in gas pipelines. MEG inhibits oxygen removal by bisulfite. pH plays an important role in oxygen removal, as does the presence of transition-metal ions.

To reduce organic components in produced water, Zha et al. fabricate a series of polyethersulfone/cellulose acetate butyrate hybrid hollow-fiber membranes. The membranes are characterized using scanning electron and atomic force microscopes. Membrane performance is evaluated for permeate water flux, organic-matter removal efficiency, flux-decline ratio, and flux-recovery ratio.


Oil Viscosity, Miscible Flooding, CO2 Sequestration. Ramos-Pallares et al. use the generalized Walther correlation to develop a predictive, tunable model of crude-oil viscosity. The model predicts viscosities from a wide range of reservoirs from throughout the world with an overall average deviation of 57%. With a single tuning parameter using a single viscosity data point, the overall average deviation is reduced to 8%.

Mahzari and Sohrabi introduce a method to simulate water-alternating-gas (WAG) experiments for different scenarios. The methodology focuses on automatically history-matching the entire WAG experiment.

Venkatraman et al. use the Gibbs-free-energy function to integrate phase-behavior computations and geochemical reactions to find equilibrium compositions. The method was used to predict saturation pressures of CO 2/oil mixtures in the presence of dissolved CaCl 2 and CaCO 3 solid.

Ibrahim and Nasr-El-Din perform corefloods to study how sodium chloride concentration, injection rate, injected gas composition, and CO 2 pressure affect CO 2 sequestration in coal. The paper suggests that CO 2 sequestration in coal seams should be more efficient as salinity increases, especially at high injection pressures.


Flow Prediction. Sheth and Younis develop an algorithmic theory to enable the localized solution of linear systems that arise during the nonlinear-solution process for a sequential implicit timestep. Using this localized solver, simulations can be many times faster, depending on the underlying heterogeneity and complexity.

Spesivtsev et al. apply the drift-flux model to simulate highly transient gas/liquid slug flows in complex configurations in pipelines and wellbores. Criteria used for evaluation include first slug arrival, average slug amplitude, average period between slugs, average cumulative liquid production per slug, and total produced mass over the observation period.

Hanssen et al. optimize control policies (rather than a sequence of control inputs) to obtain closed-loop predictions. Their method is compared with the more traditional open-loop approach in a case study. The comparison indicates a significant potential for reservoir optimization using closed-loop predictions.

Wang et al. present a waterflooding model that is based on linear dynamical systems to characterize injection/production relations in an oil reservoir during both stationary and nonstationary production phases. The method is suggested to outperform capacitance models in predicting waterflood performance in low-permeability reservoirs and certain dynamic scenarios.

Bao et al. provide an analytical solution to the diffusivity equation for modeling fluid flow into a 3D, arbitrarily oriented plane sink within a box-shaped anisotropic medium with Neumann boundary conditions. The model is demonstrated with two applications: (1) pressure-transient analysis with identified flow regimes and (2) pseudosteady-state pressure mapping, simulating inflow from multiple fractures along a single horizontal well.

Dohmen et al. compare depletion-related microseismic events in the Bakken formation to those that accompanied new offset completions. The slope of the seismic frequency-magnitude distribution (b-value) was found to provide a qualitative assessment of the relative contribution of oil from completions along a wellbore.


Drilling, Completions, Fracking. Strecker et al. propose a model to predict and analyze pressure oscillations when drilling offshore from floating rigs. They find that muds with a yield point can increase pressure amplitudes significantly, and severe downhole pressure oscillations may not be detectable from topside measurements.

Xu et al. present a mathematical model to characterize the performance of fluid loss during drilling in fractured tight reservoirs when lost-circulation material is incorporated. The model is validated using a field test and laboratory tests with different combinations of acid-soluble rigid particles, fibers, and elastic particles.

Lumsden et al. provide a rheological characterization of suspensions of hollow glass beads in cement slurries. The Herschel-Bulkley model best describes suspension rheology. Surface area of the beads correlated linearly to the yield stress for a given bead concentration.

Jafariesfad et al. investigate the use of heat-treated nanosized magnesium oxide as an expansive agent in oilwell cement. Addition of 2% nanoparticles (by weight of cement) with the appropriate reactivity maintained expansion of the cement (i.e., mitigated shrinkage) and improved mechanical flexibility.

Pang et al. use X-ray computed microtomography to examine foamed cement. When generated by field equipment, gas bubbles in foamed cement approximately follow a log-normal distribution with a wide size distribution (20–1000 µm)—with little dependence on foam quality. In contrast, when generated by the API method, the bubble size distribution is completely different (approximately Gaussian) and varies significantly with foam quality.

Yuan et al. develop new models for predicting fracture toughness of gas shale. Their new fracability model considers brittleness, fracture toughness, and minimum horizontal in-situ stress of a gas-shale reservoir.

Randy Seright,  SPE J. Executive Editor;
New Mexico Institute of Mining and Technology