T. Q. C. Dang

Investigation of Isotherm Polymer Adsorption in Porous Media

The injection of chemical solutions plays an important role in increasing the recovery factor of mature fields. Chemical flooding is considered as an attractive alternative to conventional waterflooding; it can improve the area sweep efficiency not only at the macroscale but also in the microscale by control mobility of displaced fluid. Adsorption of polymer in reservoir rock is an extremely important parameter for chemical flooding. Adsorption represents a loss of chemical agent from solution and, consequently, a net reduction in the surfactant–polymer slug. Therefore, the efficiency of polymer flooding is significantly diminished both technically and economically. However, numerical simulation of multicomponent adsorption is still limited and adsorption processes in a polymer–rock system have not yet been well developed, especially for highly heterogeneous reservoirs. In this article, adsorption was modeled by the Langmuir isotherm theory. The simulation results indicated that polymer adsorption strongly depends on polymer concentration, shear rate, pH, salt concentration, and reservoir heterogeneity. Effective control of such parameters can reduce the effect of polymer adsorption to minimize chemical loss and improve the economic efficiency of chemical flooding processes.

Numerical Simulation of SAGD Recovery Process in Presence of Shale Barriers, Thief Zones, and Fracture System

This study presents a numerical investigation for evaluating the potential applicability of the steam-assisted gravity drainage (SAGD) recovery process under complex reservoir conditions such as shale barriers, thief zones with bottom and/or top water layers, overlying gas cap, and fracture systems in the McMurray and Clearwater formation. The simulation results indicated that the near-well regions were very sensitive to shale layers, and only long, continuous shale barriers (larger than 50 m or 25%) affect the SAGD performance in these well regions. In addition, the thief zones had a strongly detrimental effect on SAGD. The results also showed that the SAGD recovery process was enhanced in the presence of vertical fractures but horizontal fractures were harmful to recovery. Fracture spacing is not an important parameter in the performance of a steam process in fractured reservoirs and extending horizontal fractures will reduce ultimate oil recovery in the SAGD process. This article provides a guideline for SAGD operations in complex geological reservoirs.

Rheological Modeling and Numerical Simulation of HPAM Polymer Viscosity in Porous Media

Polymer flooding is a commercially proven approach for enhanced oil recovery from mature oil fields. The fundamental mechanism of polymer flooding for improving oil recovery is to increase the viscosity of displacing fluid, thereby creating a favorable mobility ratio for improved volumetric sweep efficiency. Therefore, development of an adequate model for prediction of polymer viscosity is the successful key of this process. This article presents a comprehensive investigation of hydrolyzed polyacrylamide viscosity for a wider and better understanding of the polymer flooding process. A fundamental mathematic model of polymer viscosity in porous media is described and a series of numerical simulations have been done to determine the dependence of polymer viscosity on polymer solution properties and reservoir conditions. The simulation results indicate that pH, salinity, polymer concentration, molecular weight, and alkaline are the main parameters that strongly influence the viscosity of hydrolyzed polyacrylamide. With an appropriate control of these factors, the efficiency of chemical flooding will be significantly improved in both economic and technical aspects.

Improvements of Mixed-surfactants in Alkaline/Surfactant/Polymer Solutions

The authors present a comprehensive evaluation of phase behaviors of alkaline/surfactant/polymer (ASP) systems. The experimental results proved that the phase behavior of mixed-surfactant solutions (single- and double-tail anionic surfactants) would be better than the one of single surfactant. These mixtures were also more compatible with polymer, and adjusted optimum salinity to the reservoir brine. They next examined the role of alkalis in ASP process. Three types of alkalis were tested to select the optimum one for high-temperature reservoir. This study showed that sodium metaborate is the best choice.

Effects of Reservoir Heterogeneities, Thief Zone, and Fracture Systems on the Fast-SAGD Process

This study presented a numerical investigation for evaluating the potential applicability of Fast-steam-assisted gravity drainage recovery process under complex reservoir conditions, such as shale barriers, thief zones with bottom and/or top water layers, and fracture systems in Clearwater formation. The simulation results indicated that the near well regions are very sensitive with shale layers and only long, continuous shale barriers (larger than 50 m or 25%), which can effect Fast-steam-assisted gravity drainage performance at the above well regions. Besides that, the thief zones have a strongly detrimental effect on Fast-steam-assisted gravity drainage. The results also proved that Fast-steam-assisted gravity drainage recovery process enhanced in the presence of vertical fractures, but horizontal fractures were harmful on the recovery. This article is a worthy guideline for Fast-steam-assisted gravity drainage operations in complex geological reservoirs.

The Development and Optimization of a Polymer Conformance Control Technology in Mature Reservoirs: Laboratory Experiments vs. Field Scale Simulation

This article presents a successful investigation of polymer gel behavior from laboratory experiments to full field scale simulation. First, a series of laboratory experiments are conducted to achieve a deep understanding of polymer gel behavior. The results show that the polymer viscosity, gelation time, and gel strength strongly depend on the reservoir temperature, polymer type, polymer concentration, cross-linker concentration, pH, and salt concentration, which are the keys of a polymer conformance control process. According to the laboratory experiments, polymer gel flooding is applied for the White Tiger field, which is the biggest oil field in Viet Nam. The polymer gel treatment is simulated in the full field scale and the results indicate that it is an excellent candidate for conformance control. Water production decreases from 4,800 m3/d to slightly less than 2,000 m3/d, while a significant increase in oil production has been achieved from unswept zones, which is a really successful evidence of the polymer conformance control technology in heterogeneous reservoirs.

The Potential of Enhanced Oil Recovery by Micellar/Polymer Flooding in Heterogeneous Reservoirs

The performance prediction of a micellar polymer flood in a complex reservoir requires an accurate model that represents the reservoir features, chemical properties, and displacement mechanisms that affect the flood performance. First, this article provides a comprehensive comparison of micellar polymer flood with other recovery techniques, such as waterflooding, polymer flooding, and surfactant flooding. Then, the article states the successful evidences of micellar polymer flooding in a highly heterogeneous oil field in Vietnam. The results indicate that waterflooding is only efficient for homogeneous reservoirs and it is necessary to apply chemical flooding for highly heterogeneous reservoirs in tertiary hydrocarbon recovery processing. A significant value of increasing oil recovery is a reliable evidence for the worth of micellar polymer flooding.

A Review of Geological Characteristics and Improved Oil Recovery for a High Temperature Fractured Basement Reservoir, Vietnam

The White Tiger field is currently the biggest fractured basement reservoir on the continental shelf of Vietnam. This reservoir has a complicated geological structure with high temperature and closure stress. Thus, experiences that have been learned from this field operation are good lessons. This article reviews significant events in geological development, achievements in the early development, and late stage to improve oil recovery by special methods for fractured granite basement reservoirs, such as hydraulic fracturing, water flooding, water shut-off, surfactant flooding, and changing pressure regime. It is a worthy case study for both current and future development planning of basement reservoirs in the world.

An Approach for the Prediction of Optimum Conditions for the Steam Assisted Gravity Drainage Process by Response Surface Methodology

In this study, the application of response surface methodology and central composite design for modeling the influence of some operating variables on the performance of steam-assisted gravity drainage process for oil recovery was discussed. The maximized net present value of 105.16

Numerical Simulation of Surfactant Adsorption in Micellar Polymer Flooding

mm was obtained when the optimum conditions of steam-assisted gravity drainage operation process was designed following as injector/producer spacing of 5 m, injection pressure of 5,440 kPa, maximum steam injection rate of 725 m3/d, and spacing between two well pairs of 40 m. The predicted values match the experimental values reasonably well, with R2 of 0.967 and Q2 of 0.82 for net present value response.