Radial Numerical Model Research Articles

Outcomes for geothermal conceptual models from numerical pressure transient analysis

The outcome of geothermal numerical pressure transient analysis of greatest practical use is an indication of the overall shape of the network of flow pathways in the reservoir surrounding the well. The shape of this network will be controlled by reservoir-scale structural features, of clear significance to the conceptual model. The basic two-dimensional radial numerical model grid can be altered to any dimension in the range 1.0–3.0 (a continuum including linear and spherical flow), using a non-integer fractional dimension parameter. This concept reveals upflow along a basement fault at Ohaaki, New Zealand, and explains reservoir compartmentalisation at Theistareykir, Iceland.

Numerical investigation of the mechanisms in co-injection of steam and enriched air process using combustion tube tests

Co-injection of steam and enriched air process has great potential to recover oil sands especially when the oil sands are sufficiently preheated by SAGD. Before applying such a process in the field, it is important to understand the involved reaction kinetics and displacement mechanisms. In this work, numerical modelling has been performed to investigate the performance of co-injection processes, in which enriched air (95% oxygen) was introduced after a period of hot water and steam flooding. A group of combustion tube tests were conducted to measure combustion front velocity, temperature profiles along the tube, oil production, and produced gas compositions. A three-dimensional radial numerical model was developed using CMG STARS to reproduce the combustion tube test results. A reaction kinetic model derived from Ramped Temperature Oxidation (RTO) tests was incorporated and further tuned to match dynamic experimental measurements. The close agreement between the measured and simulated combustion characteristics, including combustion front velocity, temperature profiles, and gas production, confirms that the key chemical reactions have been captured. Also, there is a great match between the measured and simulated liquid production, indicating that the drive mechanisms have been adequately understood. It is found co-injection of steam and enriched air has the potential to improve oil recovery because ISC is able to recover a portion of the residual oil left behind by the steam flooding. Steam still plays a dominant role in displacement of bitumen. The ultimate recovery factor was about 90% of OOIP for the aforementioned combustion tube tests. Using enriched air concentration of 12 to 35 vol.%, the steam front propagated faster than the combustion front, the velocity of which is controlled by the fuel consumption rate and oxygen injection rate. Even at low oxygen injection rates, high temperature oxidation (HTO) was observed. It is suggested that high initial temperature for co-injection of steam and enriched air helps reduce the amount of low temperature oxidation (LTO) and therefore decreased coke deposition, leading to higher combustion front velocity and stable high temperature combustion. The reaction model is able to reproduce all measured results and represent all of the aforementioned phenomena.

Experiments on gas supply capability of commingled production in a fracture-cavity carbonate gas reservoir

Abstract The CT scan, mercury intrusion test and commingled production physical simulation experiment of pore-, cavity-, and fracture–cavity-type cores were conducted to study the effects of interlayer heterogeneity, drawdown pressure, water saturation and water invasion on gas supply capacity. The experimental results were verified by the radial numerical model of multilayer commingled production based on the Eclipse software. The experimental results show that: the fracture–cavity-type reservoir with strong seepage capability makes great contribution to gas production in the early stage, while the pore- and cavity-type reservoirs with weak seepage capability make more contribution to gas production in the middle and late stages; the absolute permeability of reservoir affects its contribution to productivity, while the relative permeability of reservoir affects the total recovery; the “dynamic supply balance” state among various reservoirs can be achieved under a reasonable drawdown pressure; although the gas production capacity of the fracture–cavity-type reservoir is less affected by edge and bottom water, water breakthrough will first occur in this type reservoir and block other reservoirs, significantly reducing the commingled gas supply capacity and recovery.

Estimating Hydraulic Properties Using a Moving‐Model Approach and Multiple Aquifer Tests

A new method was developed for characterizing geohydrologic columns that extended >600 m deep at sites with as many as six discrete aquifers. This method was applied at 12 sites within the Southwest Florida Water Management District. Sites typically were equipped with multiple production wells, one for each aquifer and one or more observation wells per aquifer. The average hydraulic properties of the aquifers and confining units within radii of 30 to >300 m were characterized at each site. Aquifers were pumped individually and water levels were monitored in stressed and adjacent aquifers during each pumping event. Drawdowns at a site were interpreted using a radial numerical model that extended from land surface to the base of the geohydrologic column and simulated all pumping events. Conceptually, the radial model moves between stress periods and recenters on the production well during each test. Hydraulic conductivity was assumed homogeneous and isotropic within each aquifer and confining unit. Hydraulic property estimates for all of the aquifers and confining units were consistent and reasonable because results from multiple aquifers and pumping events were analyzed simultaneously.

Hydrodynamic Response of Plasma Channels to Propagating Ion Beams

Hydrodynamic response of plasma channels induced by intense propagating ion beams is examined with use of both analytical estimates and a one-dimensional radial numerical model. It is found that mega-ampere, 3--5-MeV proton beams can be propagated in deuterium background over several meters.