Selected Topics on Improved Oil Recovery

Determination of water saturation, S_w in clean sand is more or less straightforward using the Archie equation. In shaly formation where the resistivity data is affected by clay conductivity, the Archie equation is no longer valid and S_w has to be modelled using other equations. The Waxman-Smits was one of the equations that has been developed to account for the clay effect in shaly sand. Nevertheless parameters used in the Waxman-Smits equation (i.e. formation resistivity factor, \({\text{F}}^{ *}\) and cementation factor, \({\text{m}}^{ *}\)) rely upon the expensive core analysis data, which is not necessarily available for the particular reservoir of interest. The current method in core analysis could also contribute to inaccurate value of the determined parameters; the issues on averaging and representation of the selected core plugs to the whole reservoir and the effect of core treatment to the rock properties. In this paper, we reviewed some previous works to understand mechanism of clay surface conductivity and induced polarization (IP) concept and proposed a potential method for determination of more accurate \({\text{m}}^{ *}\) using this concept.

This paper provides the experimental studies on parameters affecting the performance of epoxy based polymer used to be injected to unproductive layers in a water shut-off application. In this paper, we observe a parameter that can affect the performance of epoxy-based polymer which is ionic strength. By focusing the research on epoxy-based polymer, this study tackles the environmental problem and operation cost in water shut-off operation by proposing more environmental friendly and much cheaper polymer. The epoxy-based polymer can replace the use of the conventional Cr(III)-Carboxylate/Acrylamide-Polymer (CC/AP) which is more expensive and creates environmental problems. The epoxy-based polymer is tested at various ionic strength to determine the effect of ionic strength on density, rheological properties, gelation time and hard gel compressive strength after the polymer has gelled and hardened. The density of the polymer is determined analytically. The mass of the polymer is determined by weighing the gel, and the volume of the polymer was measured using the Archimedes method that measures the volume of irregularly shaped object to measure the gel volume. The density of the polymer is then calculated as the mass of the gel divided by the volume of the gel. To determine the rheological properties, the epoxy based polymer tested on a rotational viscometer at various time. Then, we observe the gelation time of epoxy-based polymers with semi-quantitative method by comparing the gel strength development with gel strength code US Patent No. 4688639. After it has gelled and hardened, the polymer is tested on hydraulic press equipment to determine the compressive strength of the polymer.

The Enhanced Oil Recovery (EOR) method is a widely used for increasing oil recovery, one of which is by injecting ionic surfactants in sandstone reservoirs. The Sandstone Reservoir in Benakat Air Formation is composed of grains with dominant quartz, and cement with dominant calcite and silica. Brown clay (montmorillonite) fill in the rock matrix. The mineral montmorillonite is highly reactive to water, so that the sodium in montmorillonite will be hydrated with surfactant solution and result in swelling which can result in shrinking of the pore size of the rock and decrease the permeability so that the surfactant injection results are not optimum. Clay minerals and calcite have a positive surface charge at the fluid pH conditions in the reservoir so that it will affect the degree of adsorption and or precipitation of the anionic surfactant. Such adsorption and precipitation may affect the incremental oil recovery by injection of surfactant solution in the Sandstone reservoir, Air Benakat formation, either positively or negatively. Reservoir characterization has been done by examining the mineral content of sandstones reservoir on thin section. Two types of outcrops were analyzed in this study which consist of two thin section (L1 and L2). The mineral content of L1 outcrop consists of quartz, Potassium feldspar, plagioclase, gluconite and fossils, where matrix is composed of quartz, potassium feldspar and clay with dominant calcite cement. The L2 outcrop consists of grains filled with quartz, glauconite, plagioclase, biotite and fossil, where matrix is dominated by quartz and then clay, with calcite cement. The objectives of this study are to characterize the minerals contents in the sandstone core of Lahat outcrop for consideration of surfactant injection in Air Benakat Sandstone reservoir.

Carbon dioxide flooding is known for increasing the production of oil as enhanced oil recovery (EOR). Conventional carbon dioxide flooding aims to reach minimum miscibility pressure (MMP) before altering oil properties in the reservoir. However, current conditions are that most fields have reached the mature state, so the reservoir pressure is depleted, thus it is hard to reach MMP. Carbonated water is water into which carbon dioxide has been dissolved, under certain conditions. The carbonated water injection (CWI) technique might be a solution for injecting carbon dioxide bellow MMP. The performance of this technique is examined using a physical model designed to show the wettability alteration mechanism of carbonated water. The physical model was made from a glass chamber filled with unaltered water. A saturated core was then placed inside the chamber below a funnel shaped narrow tube that read the oil recovery for each milliliter scale. The chamber was sealed and carbon dioxide injected into the water body. The water inside the chamber was therefore altered to become carbonated water after a period of soaking time. The oil expelled from the core was spontaneously measured by reading the scale on the top of the graduation tube, which showed how the milliliters oil was gathered, a process that known as imbibition. The process repeated for several concentrations of carbon dioxide in water. The change of injection pressure, power of hydrogen (pH), and oil recovery were measured respected to soaking time. The value of every case, including the unaltered-water-saturation case, were compared. This injection technique could result in 0–37% oil recovery.

Natural gas has one of the main energy sources in the world. In the cryogenic processes of natural gas, the present of carbon dioxide remains a concern because it can cause the blockage of equipment. Membrane technologies are widely used in natural gas separation processes because of their compact size, simple operating conditions, no chemical additive. The type of membrane that used in this research is hollow fiber membrane type. The membrane optimization is aimed to obtain the best performance of membrane in term of technical and economical point of view by determine optimum membrane length that provide adequate residence time. Optimization of design hollow fiber membrane requires three components i.e. problem formulation, model and optimization techniques. The problem formulation of this research is to obtain the efficient designed hollow fiber membrane that provide maximum revenue, minimum cost and fouling, smaller size, and minimum cleaning. Modeling of dissolution and diffusion were built by utilizing Fick’s law method, meanwhile pressure drop of hollow fiber membrane was modeled by Darcy equation. Optimization techniques were used in this research is Killer Whale Algorithm. Optimization results using Killer Whale Algorithm with parameters 20 matrilines, 5 leaders and 20 iterations were obtained the length of membrane 4 m, cleaning time interval 664 min, price of membrane 25,533,000 IDR/m² and the optimum revenue 1,162,000,000 IDR. Based on this research, the proposed techno economy optimization method can be applied in other the applications to solve energy problem.

In achieving the program goals of CO₂ injection, as one of enhanced oil recovery method, some parameters are needed to be highly considered. Sensitivity study is usually aim to evaluate the effect of varying parameters on the reservoir performance. In this work, CO₂ injection simulation was conducted using simulator named COZView. The main objective of this paper is to analyze sensitivity of parameters that affect CO₂ injection performance to oil rate. Those parameters are temperature, API gravity and injection rate. The results have showed that, after two years of production, the model is found to be most sensitive to temperature and API gravity. The higher API gravity, the greater oil rate. This relation have similar to temperature and injection rate. But, for the injection rate case, there is critical condition as depending of reservoir itself conditions. Thus, it is recommended that these data must be properly selected and analyze to optimization of CO₂ injection performance for the good results in the oil field.

In this paper, a new quick look method has been generated for faster placement of oil and/or gas wells from reservoir static data only. A new customized method has been developed to easily analyze intersections of qualities that form proper characteristics of good oil and gas wells, ranging from reservoir fluid and rock properties to predictions of liquid flowrate from log data. This method is then analyzed using Lagrangian multiplier to find optimum location of production wells. The resulting model has been tested against a set of field data and has provided a better production profile from the aspects of quantity and longevity.

Drilling fluid or commonly called mud, is used to lift drilling cutting to the surface, cool and lubricate the bit and drill string, as supporting walls in the borehole using mud cake, and control the formation pressure. The injection pressure is very important because if the injection pressure of the mud is not right, it is going to cause various effects, such as causing fracture in the wellbore, causing heat in the bit and drill string, weak wall since weak mud cake formed in the well, and being able to cause kick or stuckpipe. Because of the impact of the mud injection pressure is significant to drilling performance, the pressure of mud injection in the oil drilling needs to be optimized using Duelist Algorithms to minimize the amount of pressure drop at each hole diameter, i.e. at 17 in. hole diameter in 1269.68 ft depth and at 12.25 in. hole diameter in 2132.55 ft depth. Before being optimized, the pressure of mud injection was modeled first using bingham-plastic method for calculating pressure drop in six different sections of the wellbore, i.e. surface equipment, drill pipe, drill collar, bit, annulus around drill collar, and annulus around drill pipe. Afterwards, it was summed to calculate the total pressure drop in each hole diameter. The total initial pressure drop for 17 in. hole diameter was 978 psi and for 12.25 in. hole diameter was 1875 psi. In order to minimize the pressure drop, it was necessary to do optimization using Duelist Algorithm. The optimized variables were mud density and flow rate. Sensitivity analysis was utilized to obtain behaviour of the system. Duelist Algorithm optimization was performed using 200 iterations, 200 duelists, 80% learning probability, 10% innovate probability, 95% luck coefficient, and 10% board of champion. After being optimized using Duelist Algorithm method, for 17 in. hole diameter, mud density became 9 ppg and flow rate became 505 gpm. Therefore, the pressure drop became 695 psi. Meanwhile, for 12.25 in. hole diameter, mud density became 9.18 ppg and flow rate became 603 gpm. Therefore the pressure drop became 1145 psi. The results show that the optimization of mud injection operating condition in drilling process provide reduction of pressure drop in mud injection that would be give good impacts in the drilling efficiency and safety. This result will be useful for drilling engineer to set up the drilling equipment and mud properties.

Oil production have several stage i.e. primary, secondary and tertiary. In tertiary stage, the effort to increase oil production is called as enhanced oil recovery (EOR). EOR is performed by injecting material or energy from outside reservoir. There are several EOR methods that have been developed and implemented in the oil field, including thermal recovery, chemical flooding, and solvent flooding. One of solvent flooding is CO₂ EOR by injecting CO₂ to reservoir. CO₂ EOR method has capability to increase 5–15% oil recovery. In addition, injecting CO₂ to reservoir have good impact to reduce global warming effect. However, to obtain the optimum result of CO₂ EOR needs several parameter to be optimized, such as mass flow rate, pressure and temperature injection. There are several equation that have been used to build a model of CO₂ EOR pressure drop. There are Fanning equation for injection well, Darcy equation for reservoir formation and Beggs-Brill equation for production well. The model has been validated using PIPESIM software for injection well model and have mean error 2.204%. Meanwhile reservoir formation model has been validated using COMSOL Multiphysics software and have mean error 3.863%. The optimization of CO₂ EOR using Duelist Algorithm provide increasing the net profit 42.47% from 26,548.62 USD/day to 37,826.39 USD/day.

Enhanced Oil Recovery is a method to increase oil recovery from 30% till 60% depend on primary and secondary recovery. One of the proven EOR method to increase oil recovery is CO₂ injection. This injection has 2 conditions: miscible and immiscible. In this research, the purpose of MMP determination is to know the effect of temperature, pure and impurities CO₂ (methane, ethane, propane and H₂S). Simulator is used to determine of MMP. The result is the increase in temperature will increase the MMP. The influence of pure and impure from CO₂ with 80% CO₂ + 20% non CO₂ (C₁, C₂, C₃) components. With CO₂ 100% as reference, the additions of 20% methane will increase 86% MMP, 20% ethane will decrease 13% MMP and for 20% propane will decrease 33% MMP.