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The objectives of this study are to develop numerical models to investigate the rutting of asphalt concrete pavements and to find optimal design of asphalt pavement mix for rutting resistance. Previous study’s experimental tests including triaxial repeated compression loading and wheel track testing were used to evaluate the visco-elasto-plastic behavior and rutting resistance of different pavement mixes. Three-dimensional Finite Element models were first developed to simulate both the axial compression and wheel track testing in which a visco-elasto-plastic material model with the material parameters developed from experimental testing was used to predict the rutting (time-dependent characteristics) of the asphalt concrete pavements. The results were validated against the experimental wheel track testing results. Finally, optimization techniques using the Design Of Experiments method were applied to the simulation rutting results of varying material parameters to promote asphalt pavements mixes that had the most effective performance against rutting. The results of this paper clearly demonstrate an efficient and effective experimental-numerical method and tool set towards optimal design for asphalt concrete pavements for rutting resistance.

Oil production has been declined in the fractured basement reservoir from these fields of the Cuu Long Basin as those reservoir pressures were highly decreased. To produce oil, those reservoirs from these fields have been stimulated by using various techniques for enhanced oil production. Water injection at secondary recovery to maintain the reservoir pressure has been flooded because this technique has still brought high efficiently oil production, but the high-water cut has been very challenged while producing oil from the reservoirs. The most efficient way to recover oil in the Cuu Long basin is to stimulate the lower Miocene reservoir by hydraulic fracturing. This study presents the effective multi-stage hydraulic fracturing in the lower Miocene reservoir for single X well of the Cuu Long basin on the continental shelf offshore Viet Nam. The calculated results of multistage fracturing show that the average effective wellbore radius, average pseudo-skin, average productivity ratio, fracture conductivity are higher than those of the blanket and un-stimulated case. The integrated model of multistage fracturing consists of fracture geometry, fracture parameters, conductivity and production model.

Asphalt pavement rutting is a major safety concern because it affects the handling of vehicles. Research into effectively predicting of asphalt pavement rutting is extremely necessary as it can help develop an optimal design of asphalt mixture against rutting. The primary objectives of this study are to develop numerical models to investigate the asphalt pavement rutting. Previous study’s experimental tests including triaxial repeated compression loading and wheel track testing were used to evaluate the visco-elasto-plastic behavior and rutting resistance of different pavement mixes. Based on the test results, sets of visco-elasto-plastic creep parameters for the asphalt pavement mixes were characterized and related to their rutting resistances. Numerical simulations using three-dimensional Finite Element models were developed to simulate both the triaxial compression and wheel track testing. A ‘strain hardening’ creep material model with the material parameters developed from experimental testing was employed in the Finite Element modelling to the time-dependent characteristics of the asphalt concrete pavements. The Finite Element results were validated against the experimental results to demonstrate that the Finite Element simulations can be used to effectively evaluate the rutting behavior of asphalt concrete pavements.

The paper presents an approach for optimizing the design of hydraulic fracture treatment in the low permeability lower Oligocene sandstone reservoir in the Cuu Long Basin, offshore Viet Nam. Several design variables including low behavior index, leak-off coefficient, pumping time, injection rate and proppant, which are generally affecting the fracture mechanics, were considered in the optimization process in order to improve oil production. The influence of those variables and interaction variables on fracture conductivity and net present value (NPV), hence, the production performance was analyzed using Box-Behnken design–based statistical modeling, which are experimental designs for response surface methodology. The results show that the maximum NPV was 50.5 million USD from optimal variables including injection rate of 36bpm, injection time of 78 minutes, slurry concentration end of the job of 9.1ppg and the leak-off coefficient of 0.0034ft/min0.5.

The lower Miocene reservoir are high heterogeneity, complex geology structure, low connectivity among the fractures, low effective well bore radius, high temperature up to 120 °C, the closure pressure up to 6680 psi, reservoir pressure up to 4500 psi, reservoir depth up to 3000 m and the reservoir porosity ranging from 1% to 10% and the average permeability is also lower, ranging from 1 md to 10 md. By considering various oil recovery methods, the integrated hydraulic fracturing stimulation is the best tool to enhance oil successfully for reservoir, which allows increase in oil production rate. In the post fractured well, oil productivity has been shown an increase in over 3 folds with fracture half-length nearly 75 m and fracture conductivity about 5400 md.ft in comparison with the base case. In pumping schedule, the propped mass has been used the total about 133,067 lbs at which the first step is to pump proppant type of 20/40 sinter lite bauxite proppant into the fractures and the next step is to pump up sintered ball bauxite proppant size of 16/30, which is not only prevented proppant flow back but also increase in conductivity. In order to transport proppant, fracturing fluid systems consist of Guar polymer concentration of 11.2 pptg with fluid additives to design total leak-off coefficient at 0.00227 ft/min0.5 have been presented in the study.

Selection of proper failure criterion is one of the most important task in analyzing wellbore stability analysis. While the Mohr-Coulomb criterion is still commonly used, its prediction of the safe mud weight supporting the wellbore wall is usually too high because this zone is predicted to yield without any shear failure around the borehole. The main purpose of the paper is to discuss pros and cons of some existing criteria such as Mohr-Coulomb, Hoek-Brown and modified Lade failure criterion. Then the allowable drilling mud pressures calculated by using these methods are compared with each other and with the field data. Two wellbores in two Bach Ho oilfields are considered as case studies in order to identify the criterion that is able to provide the closest agreement with the field data.

In the recent years, the most severe operational hazards of pipelines related to transportation of multiphase fluids because of the oil in Vietnam with the high concentration of paraffin, for instance the oil of Bach Ho field. The detrimental problems that could occur, for example, wax and asphaltene can deposit on the wall and block the flowline; water and hydrocarbon fluids can form hydrate pipeline systems or scale will form and deposit inside the pipeline due to the pressure and temperature change along the pipeline. As a result, the severe slugging forms inside the pipeline and cause operational problems to downstream processing facilities. In this paper will discuss the proposed operational management system. Some typical situations will be simulated, ranging from steady flow at different flow rates, to start-up and shutdown procedures also for emergency conditions will be affected by differential pressures and the temperatures losses in the pipeline.

This paper presents the reservoir pressure depletion will cause rock stress changes, which results in an increasing likelihood of serious sand production in the unconsolidated sandstone reservoir. This paper aims at offshore unconsolidated sandstone oil reservoir, analyzes rock stresses of the borehole wall with impact of reservoir pressure depletion on in-situ stresses on rock strength. A full review basic theory in geomechanics will be presented, such as: rock failure criterions, sanding critical drawdown pressure calculating model and a numerical calculating method for the model are developed. Furthermore, a case study sanding prediction method for pressure depletion of offshore oil reservoir in Cuulong Basin, Vietnam also is presented. Using the model analysis, on the other hand the chart of sanding onset is relatively large with the high formation pressure depletion. On the other hand, the sand will be appeared no matter how small the drawdown is.