Executive Summary

Anil Ambastha, Chevron

Papers in this issue of SPE Res Eval & Eng  focus primarily on various issues around secondary-recovery techniques. A few papers on CO2 storage, gas storage operation, gas hydrates, a coalbed methane pilot, streamline simulation, and gravitational compositional grading provide wide-ranging coverage of research areas of current interest. The following is a brief outline of the papers in this issue:

"Geo-Engineering and Economic Assessment of a Potential Carbon Capture and Storage Site in Southeast Queensland, Australia" uses a numerical reservoir simulator to examine injection rates ranging from 0.5 to 1.5 million tonnes of CO2/year for 25 years of injection. Primary factors affecting the ability to inject CO2 include permeability, formation fracture gradient, aquifer strength, and multiphase flow functions. The economics are assessed using an internally developed technoeconomic model. "Optimizing Recovery for Waterflooding Under Dynamic Induced Fracturing Conditions" presents a new modeling strategy that combines fluid-flow and fracture-growth (fully coupled) within the framework of an existing "standard" reservoir simulator. This coupled simulator is applied for repeated, inverted five-spot patterns to address various aspects of waterflood such as the short circuiting of injector and producer, fracture containment to the reservoir layer, and areal and vertical reservoir sweep. "A New Method for Vertical Leak Detection in Low-to-Moderate Permeability Flooded Reservoirs" discusses the use of existing surface tiltmeter technologies and a new surface deformation calculation regime to zero in on volumetric changes that occur above or below the limits of the given reservoir for water injection situations under fracturing conditions. This method uses measured surface deformation from observed tilt to extrapolate the volumetric change at different specified depths. When volumetric change best fits the measured deformation data (or tilt) at the surface, the depth and areal location are then correlated to the area near a specific well or wells. "Waterflooding Viscous Oil Reservoirs" presents some waterflood results from viscous oilfields around the world, benchmarks the expected performance of the newly-discovered Rajasthan fields to this database, and discusses a few issues associated with waterflooding viscous oils. "Line Tension-Based Modification of Young's Equation for Rock/Oil/Brine Systems"presents an experimental study indicating that the extent of deviation from Young's equation exhibited by rock/oil/brine systems may be directly related to the rock/oil-adhesion interaction. This study reinforces the need to include the rock/oil-adhesion force in our consideration of rock/fluid interactions, wettability, and their impact on enhanced/improved oil recovery processes. "A Systematic Laboratory Approach to Low-Cost, High-Performance Chemical Flooding" describes microemulsion phase behavior testing using various combinations of surfactants, cosolvents and alkalis with a particular crude oil and reservoir conditions of interest. The best chemical formulations were validated in coreflood experiments, and compared in terms of both oil recovery and surfactant retention in cores. "Using Experimental Designs, Assisted History Matching Tools, and Bayesian Framework To Get Probabilistic Gas Storage Pressure Forecast" describes two different uncertainty quantification workflows that integrate dynamic data to forecast a probabilistic operational pressure profile for a given period for a gas storage situation."Development of a New Model for Saturation Calculation in Streamline Simulation" presents a new method to move the saturation forward based on irregular time-of-flight space and compares the results with the common methods. The result of saturation with this method is more accurate, and the averaging of saturations and numerical diffusion are decreased. "Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluation of Technology and Potential" discusses the distribution of natural gas hydrate accumulations, the status of the primary international research and development programs, and the remaining scientific and technological challenges facing commercialization of production. This paper also analyzes the role of numerical simulation in the assessment of the hydrate production potential, identifies the data needs for reliable predictions, evaluates the status of knowledge with regard to these needs, discusses knowledge gaps and their impact, and reaches the conclusion that the numerical simulation capabilities are quite advanced and that the related gaps are either not significant or are being addressed. "Coalbed Methane Pilots: Timing, Design, and Analysis" contains roughly 30 specific recommendations and the fundamental rationale behind each recommendation to help ensure that a coalbed methane pilot will fulfill its primary objectives of demonstrating whether the subject coal reservoir will desorb and produce consequential gas, and gathering the data critical to evaluate and risk the prospect at the next decision point. "Injectivity Characteristics of EOR Polymers" describes an improved test to measure the tendency of enhanced-oil-recovery (EOR) polymers to plug porous media. The new test demonstrated that plugging tendencies varied considerably among both partially hydrolyzed polyacrylamide (HPAM) and xanthan polymers. Rheology and mechanical degradation in porous media were also quantified for a xanthan and an HPAM polymer. For applications in which EOR polymer solutions are injected, this study estimates injectivity losses (relative to water injectivity) if fractures are not open and the degree of fracture extension that may occur if fractures are open. "Numerical Investigation of Gravitational Compositional Grading in Hydrocarbon Reservoirs Using Centrifuge Data" studies the effects of gravitational fluid segregation using experimental data available for five live-oil and condensate systems (at pressures between 6,000 and 9,000 psi and temperatures from 68 to 200°F) by considering the impact of fluid composition and phase behavior. Numerical studies were performed using a calibrated equation of state (EOS) description based on fluid samples taken at selected points from each reservoir. Comparisons of measured data and calibrated model show that the EOS model qualitatively and, in many cases, quantitatively describes the observed equilibrium fluid grading behavior of the fluids tested.

As you study your favorite paper(s) to enhance your own knowledge and/or apply in your work activities, please recognize that SPE welcomes further "discussion" of any of the papers published in any SPE journal, including this one. Therefore, please feel free to submit discussion of a paper either online or by mail to SPE.


Anil Ambastha, Chevron