Abstract: A compositional reservoir simulation model (CMG-GEM) was used for cyclic CO2 injection process in unconventional tight reservoir. Cyclic CO2 injection is an enhanced oil recovery process consisting of injection, shut-in, and production. The study of cyclic CO2 injection and hydrocarbon recovery in ultra-low permeability reservoirs is mainly a function of rock, fluid, and operational parameters. CMG-GEM was used to study several design parameters of cyclic CO2 injection process to distinguish the parameters with maximum effect on the oil recovery and to comprehend the behavior of cyclic CO2 injection in tight reservoir. On the other hand, permeability reduction induced by asphaltene precipitation is one of the major issues in the oil industry due to its plugging onto the porous media which reduces the oil productivity. In addition to asphaltene deposition, solubility of CO2 in the aquifer is one of the safest and permanent trapping techniques when considering CO2 storage mechanisms in geological formations. However, the effects of the above uncertain parameters on the process of CO2 enhanced oil recovery have not been understood systematically. Hence, it is absolutely necessary to study the most significant parameters which dominate the process. The main objective of this study is to improve techniques for designing cyclic CO2 injection process while considering the effects of asphaltene deposition and solubility of CO2 in the brine in order to prevent asphaltene precipitation, minimize CO2 emission, optimize cyclic CO2 injection, and maximize oil production.
Abstract: South Africa is in its post-industrial era moving from
the primary and secondary sector to the tertiary sector. The study
investigated the impact of the disaggregated energy consumption
(coal, oil, and electricity) on the primary, secondary and tertiary
sectors of the economy between 1980 and 2012 in South Africa.
Using vector error correction model, it was established that South
Africa is an energy dependent economy, and that energy (especially
electricity and oil) is a limiting factor of growth. This implies that
implementation of energy conservation policies may hamper
economic growth. Output growth is significantly outpacing energy
supply, which has necessitated load shedding. To meet up the excess
energy demand, there is a need to increase the generating capacity
which will necessitate increased investment in the electricity sector as
well as strategic steps to increase oil production. There is also need to
explore more renewable energy sources, in order to meet the growing
energy demand without compromising growth and environmental
sustainability. Policy makers should also pursue energy efficiency
policies especially at sectoral level of the economy.
Abstract: The sand production problem has led researchers into making various attempts to understand the phenomenon. The generally accepted concept is that the occurrence of sanding is due to the in-situ stress conditions and the induced changes in stress that results in the failure of the reservoir sandstone during hydrocarbon production from wellbores. By using a hypothetical cased (perforated) well, an approach to the problem is presented here by using Finite Element numerical modelling techniques. In addition to the examination of the erosion problem, the influence of certain key parameters is studied in order to ascertain their effect on the failure and subsequent erosion process. The major variables investigated include: drawdown, perforation depth, and the erosion criterion. Also included is the determination of the optimal mud pressure for given operational and reservoir conditions. The improved understanding between parameters enables the choice of optimal values to minimize sanding during oil production.
Abstract: Monoculture and mixed cultures of microalgae and
the oleaginous yeast for microbial oil productions were investigated
using sugarcane juice as carbon substrate. The monoculture of yeast
Torulaspora maleeae Y30, Torulaspora globosa YU5/2 grew faster
than that of microalgae Chlorella sp. KKU-S2. In monoculture of T.
maleeae Y30, a biomass of 8.267g/L with lipid yield of 0.920g/L
were obtained, while 8.333g/L of biomass with lipid yield of
1.141g/L were obtained for monoculture of T. globosa YU5/2. A
biomass of 1.933g/L with lipid yield of 0.052g/L was found for
monoculture of Chlorella sp. KKU-S2. The biomass concentration in
the mixed culture of the oleaginous yeast with microalgae increased
faster and was higher compared with that in the monocultures. A
biomass of 8.733g/L with lipid yield of 1.564g/L was obtained for a
mixed culture of T. maleeae Y30 with Chlorella sp. KKU-S2, while
8.010g/L of biomass with lipid yield of 2.424g/L was found for
mixed culture of T. globosa YU5/2 with Chlorella sp. KKU-S2.
Maximum cell yield coefficient (YX/S, g/L) was found of 0.323 in
monoculture of Chlorella sp. KKU-S2 but low level of both specific
yield of lipid (YP/X, g lipid/g cells) of 0.027 and volumetric lipid
production rate (QP, g/L/d) of 0.003 were observed. While, maximum
YP/X (0.303), QP (0.105) and maximum process product yield (YP/S,
0.061) were obtained in mixed culture of T. globosa YU5/2 with
Chlorella sp. KKU-S2. The results obtained from the study shows
that mixed culture of yeast with microalgae is a desirable cultivation
process for microbial oil production.
Abstract: In the last decades, the problem of perforation
damage has been considered as the major factor for the
reduction of oil productivity. Underbalance perforation is
considered as one of the best means to minimize or overcome
this problem. By maintaining wellbore pressure lower than
formation pressure, perforation damage could be minimize or
eliminated. This can be achieved by the use of nontraditional
lightweight completion fluid. This paper presents the effect of
natural clay in formulating nontraditional completion fluid to
ensure successful perforation job and increase of production
rate. Natural clay is used as homogenizing agent to create a
stable and non-damaging low-density completion fluid.
Results indicate that the addition of natural clay dramatically
increase the stability of the final fluids. In addition, field test
has shown that the application of nontraditional completion
fluid increases oil production by three folds.
Abstract: In this work, the precipitation of asphaltene from a Malaysian light oil reservoir was studies. A series of experiments were designed and carried out to examine the effect of CO2 injection on asphaltene precipitation. Different pressures of injections were used in Dynamic flooding experiment in order to investigate the effect of pressure versus injection pore volume of CO2. These dynamic displacement tests simulate reservoir condition. Results show that by increasing the pore volume of injected gas asphaltene precipitation will increases, also rise in injection pressure causes less precipitation. Sandstone core plug was used to represent reservoir formation during displacement test; therefore it made it possible to study the effect of present of asphaltene on formation. It is found out that the precipitated asphaltene can reduce permeability and porosity which is not favorable during oil production.
Abstract: In gas lifted oil fields, the lift gas should be distributed optimally among the wells which share gas from a common source to maximize total oil production. One of the objectives of the paper is to show that a linear MPC consisting of a control objective and an economic objective can be used both as an optimizer and a controller for gas lifted systems. The MPC is based on linearized model of the oil field developed from first principles modeling. Simulation results show that the total oil production is increased by 3.4%. Difficulties in accurately measuring the bottom hole pressure using sensors in harsh operating conditions can be resolved by using an Unscented Kalman Filter (UKF) for estimation. In oil fields where input disturbance (total supply of gas) is not measured, UKF can also be used for disturbance estimation. Increased total oil production due to optimization leads to increased profit.