Executive Summary

In this issue, we have 15 new papers in four categories.

Chemical Enhanced Oil Recovery. Koh et al. experimentally investigate the effect of polymers on residual oil saturation. Using low flow rates and capillary numbers during HPAM injection to displace 166 to 1,590-cp oils, they find that oil recovery is explainable by sweep-improvement arguments, rather than by true reduction of trapped residual oil.

Jouenne et al. characterize HPAM polymer stability after successive mechanical-degradation events, such as flow through pipe constrictions, followed by injection into porous media. The level of mechanical degradation of HPAM polymers is predicted to stabilize within 6 mm of an injection sand face.

Panthi and Mohanty experimentally examine pH-insensitive polymeric particles for reducing the flow capacity of fractures. The particles swell by a factor of 35 in deionized water versus by a factor of 3 at high salinity. 

Dalsania et al. introduce asymmetrical-flow field-flow fractionation coupled with multiangle light scattering as a means to resolve molecular-weight distributions for polyacrylamides in solution. Although the method is purported to separate polymers as large as 1012 g/mol, this application appears limited to 1.5×107 g/mol or less.

Tagavifar et al. study the rheological behavior of microemulsions and identify a number of experimental artifacts that can influence measurements. A model is developed to account for the effects of cosolvent, shear rate, and presence of polymer. Polymers apparently do not partition into the oil phase associated with microemulsions.

Yutkin et al. examine bulk and surface aqueous speciation of calcite and its implications for low-salinity waterflooding of carbonate reservoirs. The authors argue against several oil-recovery mechanisms in carbonates, including mineral dissolution for releasing adhered oil, release of fines and clays, and low-interfacial-tension alkaline flooding.

Heavy Oil and Unconventional Recovery. Okamoto et al. study slip velocity and permeability for methane flow in nanopores using molecular-dynamics simulations. Relationships between slip velocity and Knudsen number and between permeability-correction factors and Knudsen number agree well with the Beskok-Karniadakis analytical solution for large nanopores (12–34 nm) in both quartz and kerogen.

Zargar and Farouq Ali develop an analytical model of steam-assisted gravity drainage incorporating two stages: steam-chamber rise (or unsteady stage) and sideways expansion (or steady stage). The sideways-expansion phase is modeled by two different approaches—constant volume displacement and constant heat injection.

Gao et al. present experimental data for phase equilibrium, viscosity, density, and asphaltene precipitation for 11 mixtures of Athabasca bitumen with n-hexane and 10 mixtures with n-octane. Phase-boundary measurements are conducted up to 160°C and 10 MPa.

Yi et al. investigate use of nickel nanoparticles for promoting aquathermolysis reactions during cyclic steam stimulation. More effective utilization of nickel nanoparticles might be realized if they could propagate deep into a reservoir.

Fracture Characterization. Mahadevan develops a wave model to understand tracer transport in a fracture with differential-diffusion properties. The model predicts that diffusion and adsorption of tracer can retard tracer propagation through a fracture. This retardation can be used to calculate the length of a fracture.

Pandurangan et al. present a new method to map asymmetric hydraulic-fracture propagation using tiltmeters. The technique uses the extended Kalman filter to assimilate tilt data into a hydraulic-fracture model to track the geometry of the fracture front. The implicit level-set algorithm is used as the dynamic model to locate the boundary of the fracture by solving the coupled fluid-flow/fracture-propagation equations, and the Okada half-space solution relates fracture geometry to measured tilts.

Drilling and Completion. Demirci and Wojtanowicz provide a pilot-scale experimental study and mathematical modeling of buoyant settling of immiscible heavy fluid in mud to stop annular gas migration above leaking cement.

Feng and Gray develop a model of lost circulation through drilling-induced fractures. The model estimates time-dependent wellbore pressure, fluid-loss rate, and fracture profile during drilling. In contrast, previous models could not capture fluid loss in a growing, induced fracture that was driven by dynamic circulation pressure during drilling.

Chen and Gao investigate the maximum allowable well depth for ultra-extended-reach (e.g., 20,000–30,000 ft) drilling from shallow water to a deepwater target. The work provides a tool for enhancing the design of ultra-extended-reach wells to develop satellite oil and gas reservoirs in deep water.

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