Applications of oil-in-water emulsion (O/W) emulsification technology in enhanced recovery and pipeline transportation of heavy oil can be limited by several factors including salinity of the reservoir or process water, process temperature, and water cut. In this investigation, laminar flow of O/W was simulated in a pipeline to investigate the effect of salinity of aqueous phase (NaCl) and water cut on flow characteristics of the fluid. The case was simplified by considering the O/W as a stable, pseudo-homogeneous, single-phase fluid within the conditions operated. Pertinent to the objective of the study, at flow reference temperature, Tref 30oC, the pressure drop at 30% water cut was 931Pa compared to 84.6 Pa at water cut of 50% (reference working fluid without NaCl). In contrast, the pressure drop was 239Pa, 142Pa, 124Pa, and 82.9Pa at 70000ppm, 40000ppm, 20000ppm, and 10000ppm salinity in the aqueous phase, respectively. In addition, the maximum dynamic viscosity imposed by the fluid, was 81000cP at 30% water cut compared to 14000cP from the reference fluid. The dynamic viscosity obtained from 70000ppm salinity content was 34000cP. Moreover, the results confirm facile application of emulsification technology for pipeline transportation of bitumen from large reduction in pressure drop (99%) regardless of the water cut and salinity.
Surfactin is an anionic surfactant generated by bacteria. Although it has high ability to decrease interfacial tension (IFT) between oil and water, it binds with bivalent cations and forms precipitation. Because the precipitation causes the significant reduction of reservoir permeability, surfactin cannot be applied to EOR in oil reservoir whose bivalent cations concentration is more than 100 ppm. This study investigated methods for applying surfactin to reservoir containing bivalent cations with high concentration.
Screening of an effective binding inhibitor was carried out by measuring turbidity of the solution containing 0.3 wt% of surfactin, 900 ppm of calcium ion, and inhibitor candidates such as alcohols, chelating agents, cationic surfactants, and ion capturing substances. Influence of the inhibitors on surfactin capacity for decreasing IFT was also evaluated by measuring IFT between the solution and oil. The best inhibitor was finally selected through the injectivity tests using Berea sandstone core which was saturated with calcium solution. EOR potential of the solution containing the inhibitor was evaluated by the core flooding experiments.
Citric acid and trisodium citrate inhibited binding of surfactin with calcium ion with lower concentration such as 0.6 wt%, they were selected as potential inhibitors and subjected to the IFT measurements. Both of them had strong potential as co-surfactants of the surfactin because IFT was greatly decreased to less than 0.1 mN/m which was less than a tenth as compared with IFT between the pure surfactin solution and oil. Trisodium citrate however caused significant permeability reduction on the injectivity tests whereas citric acid could be injected into the core without permeability reduction. The high pH value of trisodium citrate solution might cause the dissolution of ferrum and aluminum in the core and the colloids of ferrous hydroxide and aluminum hydroxide were formed in the core, which brought the significant permeability reduction. Citric acid was selected as the best inhibitor and subjected to the core flooding experiments. 25 % of oil remaining after primary recovery was recovered by injecting the solution containing 0.3 wt% of surfactin, 0.6 wt% of citric acid and 900 ppm of calcium ion. Rise in the differential pressure was not found during the injection of the solution, which suggested that citric acid was effective for inhibiting the precipitation in oil reservoir. Moreover, 25 % of recovery factor was 5 % higher than the recovery factor obtained by injecting pure surfactin solution. Citric acid is also effective for enhancing the surfactin capacity for increasing the recovery factor.
Citric acid has dual role as the binding inhibitor and co-surfactant. Because citric acid is environmentally friendly and cheap chemical, it can be promising additive which increase the applicable reservoir and potential of surfactant EOR.
Naka, Ryosuke (Hokkaido University) | Tatekawa, Takuto (Hokkaido University) | Kodama, Jun-ichi (Hokkaido University) | Sugawara, Takayuki (Hokkaido University) | Itakura, Ken-ichi (Muroran Institute of Technology) | Hamanaka, Akihiro (Kyushu University) | Deguchi, Gota (NPO Underground Resources Innovation Network)
Underground Coal Gasification is expected to be efficient technique for coal energy recovery from deep or complex coal seam since directional drilling technique is advancing in these days. Authors have been performing small-scale UCG model tests to clear gasification and combustion process in UCG. Then, we found that radial cracks were initiated from the cavity formed in the artificial coal seam. Understanding mechanism of the crack initiation is important for clarification of the detail process of combustion and gasification and assessment for environmental risks. In this study, thermal stress analysis was performed on the small-scale UCG model tests to consider the initiation mechanism of the cracks by assuming that combustion and gasification of coal were progressing through the following three processes which are often observed in coal carbonization: (A) thermal expansion, (B) softening and melting and (C) thermal contraction. It was found that tensile stress was induced in the vicinity of the cavity in the tangential direction in process C. Direction of principal stress in the coal was almost parallel to tangential or radial direction of the cavity and the magnitude of it exceeded coal tensile strength. It was also found that tensile stress zone was extended into deeper coal seam with increase in temperature and time and compressive stress zone was formed outside of the tensile stress zone. It can be considered that the radial cracks initiated at the surface of the cavity since tangential tensile stress exceeded tensile strength of coal. Then, radial cracks were arrested at the boundary of tensile stress zone and compressive stress zone after they were propagating in coal seam.
Underground Coal Gasification (UCG) is a technique to use coal energy more efficiently and cheaply. In UCG, oxidant is injected into underground through an injection well to gasify coal seam, and syngas is recovered from a production well (Fig. 1). It is expected that UCG increases available amount of coal energy because even low-grade, complex and deep coal can be used by UCG.
It is pointed out that UCG has risks of surface subsidence and groundwater pollution because cracks are likely to initiate in coal seam by combustion and gasification. Therefore, clarification of initiation and growth mechanisms of the cracks is significant for stability assessment of ground as well as assessing environmental risks.
We performed small-scale UCG model tests on massive coal and crushed coal samples to clear gasification and combustion process in UCG. It was found that radical cracks were initiated in an artificial coal seam made by massive coal as well as crushed coal (Fig. 2 (Kodama et al., 2016)). Similar radial cracks were also observed in large-scale UCG model test (NPO Underground Resources Innovation Network, 2016).
Pipe-roofing technology has been widely used to develop larger or more complicated underground spaces in urban cities in Japan. Rapid installation of roof pipes plays an important role in reducing underground construction cost and improving construction safety. Pipe-roofing has been attracting more attention to engineers and is one of the auxiliary construction and temporally support methods with less disturbing surrounding ground. However, ground conditions are very complicated and unknown and also a lot of underground utilities and facilities on the surface have been already constructed in the project sites. Cutting tool wear or failure due to hard rock layer or hard stones such as cobbles and boulders leads to tunneling work stoppage and in some cases, unforeseen obstacles make tunneling stop.
This paper describes the recent pipe-roofing technology and the development of a micro-tunnel boring machine (MTBM), considering ground conditions. A newly developed MTBM shows many outstanding features in pipe-roofing under difficult ground conditions.
Our society depends very much on infrastructures such as roads, railroads, gas, electric power, water, sewer system, communication line, and so on. Sewage coverage has already reached 78% in Japan, and the market for constructing the sewage system is saturated especially in urban areas (Matsui et al., 2015). A new trend in this field is urban renewal, utilizing more underground spaces. Required underground spaces are becoming much larger or much more complicated shape. However, underground in urban areas is already congested with many utilities as well as many buildings on the surface. In order to keep ground stability during construction of underground spaces, pipe-roofing technology has been used at the project sites these days. Ground conditions and used construction system play an important role in reducing the construction cost and improving safety.
Unfortunately fully understanding the ground conditions is very difficult or impossible in spite of pre-geological survey. Difficult ground conditions, machine troubles, or unexpected obstructions in the ground sometimes stop the tunneling operation.
This paper describes the recent pipe-roofing technology and the development of a micro-tunnel boring machine (MTBM) used in pipe-roofing considering ground conditions.
2. Pipe-roofing using a micro-tunnel boring machine (MTBM)
Fig. 1 shows an example of pipe-roofing works that before constructing an underpass beneath the existing freeway, a lot of pipes are installed to control surface settlement or ground failure during the underpass construction afterward. After pipe installation, the installed pipes are filled with concrete in order to reinforce the strength of the pipe roof structure. Now, it is recognized that pipe-roofing is one of auxiliary construction and temporally support methods without severe ground settlement or collapsing surrounding ground. Currently, underground spaces such as tunnels, subway stations, pedestrian underpasses etc., in urban areas are larger and more complicated shape and constructed near existing facilities and structures both in the underground and on the ground surface. Therefore, pipe-roofing has been attracting close attention of engineers as a supplementary construction method.
Sasaoka, T. (Kyushu University) | Urata, K. (Kyushu University) | Shimada, H. (Kyushu University) | Hamanaka, A. (Obayashi Corporation) | Hoshino, T. (Obayashi Corporation) | Hattori, T. (Obayashi Corporation) | Hatori, T. (Obayashi Corporation)
It is unavoidable to have cutter bit wear during shield tunnel excavation. In recent years, because of excavation in a variety of ground conditions, problems caused by excessive cutter bit wear sometimes occur during projects. Many studies on cutter bit wear have been done in past but a quantitative evaluation method for cutter bit wear has not been established. In particular, there is little research on the characteristics of bit wear in gravel ground. This paper discusses the effects of characteristics of gravel, gravel contents and binding material on bit wear based on the results of a series of laboratory tests in order to understand the mechanism of bit wear in gravel ground and develop a prediction method of bit wear under those conditions.
The shield method is now widely applied to the construction of tunnels for infrastructure. Because this method can be applied in various geological conditions and has small impacts on road traffic and the surrounding environment. This method is that the shield is pushed into the ground with cutting and maintaining the stability of the cutting face (Clark, 1987). The shield machine has a cutter head with bits and the ground is drivaged by rotating the cutter head and pushing it by thrust. Bit wear during cutting operation is inevitable, as shown in Fig. 1.
Nowadays, as a closed type shield machine has mainly been adopted and the conditions of tunnel construction have become various, the operating issues due to the bit wear often occurs and becomes serious. As the bit wear has an obvious impact on the construction cost and constraints, such as lowering of drivage efficiency, increasing the frequency of bit replacement, etc. (Shimada et al, 1989). Therefore, the prediction of cutter bit wear is very important in order to make adequate construction plans and calculate estimated cost. However, there is little research on the characteristics of bit wear in gravel ground and the prediction method of the bit wear both theoretically and quantitatively. The mechanism of bit wear in gravel ground seems to be very complicated compared with rock mass ground, as shown in Fig. 2.
From the results of previous research (Yamamoto et al, 2016), the bit wear when a gravel ground is excavated can be evaluated and predicted based on the abrasiveness of gravel itself. So, it can be expected that the characteristics of gravel itself and the gravel contents have an obvious impact on the characteristics of bit wear when the gravel ground is excavated by shield machine.
Shimada, Hideki (Kyushu University) | Wahyudi, Sugeng (Kyushu University) | Asano, Satoru (Kyushu University) | Maehara, Kazuki (Kyushu University) | Sasaoka, Takashi (Kyushu University) | Hamanaka, Akihiro (Kyushu University)
In recent years, demand for infrastructure development is increasing due to satisfy the high rates of economic growth in Indonesia. Therefore, it is desired to introduce the chemical grouting which is widely used in Japan as ground improvement in underground construction. The chemical grouting constructions have been prohibited since the accidents, because of polymeric chemicals pollution. Considering it, in order to reduce environmental issues, sodium silicate chemicals as lowest toxicity material is considered in the chemical grouting. Furthermore, there is no study about sodium silicate chemicals in Indonesia. Hence, in this paper, applicability of the chemical grouting of sodium silicate chemicals in Indonesia is discussed from the aspects of its functions. In this study, the chemical grouts were injected into the samples of Indonesian sands. After solidification of the chemical grouts, permeability and strength of the samples have been measured by falling the head hydraulic conductivity test and UCS test. As the conclusion, the study shows that chemical grouting is applicable to improve Indonesian sand.
Infrastructure development in Indonesia has been evolving to an advanced level by solving complex problems. In the infrastructure development area, construction work is increasing along with government expenditure budget. Infrastructure projects such as train railways, highways, ports and tunnels are required to strengthen effective support for countermeasures for construction of the project in Indonesia.
Since 1950, the demand of chemical grouting material, such as acrylamide chemical grouting, were increased for soil stabilization in all around the World, including Japan and Indonesia, owing to the ability to increase load-bearing capacity, arrest settlement and lateral movement of foundations, and control the flow of water in earthwork engineering projects (Fig. 1). However, a series of environmental issues have arisen in the use of this type of chemical grouting. In 1974, it has been reported that acrylamide chemical grouting contaminated citizen’s water source, which cause several people suffered from drink the water. One year later, in 1975, a same case was happened in Indonesia. These cases urged the government of Indonesia to issue a policy of banning the use of chemical grouting material for any construction and/or engineering works in Indonesia.
A vertical cut off wall for water barrier was constructed at the final landfill disposal site in Oita prefecture of Japan to prevent the inflow of groundwater from the surroundings of the landfill site and leakage of leachate (sewage) to the outside. Due to existence of hard rock formations existed in the target ground to construct the cut off wall for water barrier, a Trench cutting Re-mixing Deep wall (TRD) construction method using a pre-drilling by a double rock auger in combination was planned for excavation of cut off wall for water barrier, initially. However, if this plan was adopted, there should be tight schedule for the construction due to pre-drilling. The alternative with CSM (Cutter Soil Mixing) construction method which does not require pre-drilling even in hard rock formation was proposed and the excavation was carried out with CSM method against relatively less hard rock formations. Also, a new machine imported from overseas was used for CSM construction method. Since, in Japan, there is no previous experience for drilling of hard formation layer with the new CSM machine, a pre-test was carried out. In the pre-test, the quality of the soil mixing wall and its drilling capacity against the hard rock formation were checked. The pre-test result was included in the construction cycle for CSM method with the new machine.
From this point of view, case study of construction with CSM method which was applied to vertical cut off wall for water barrier of waste landfill waste disposal site in Japan is described and the pre-test performance of rock drilling is summarized in this paper.
The final landfill disposal site of waste in Oita prefecture of Japan was developed for final landfill site of general disposals such as burning residual, non-inflammables and bulky garbage choice residual. Its landfill area and volume are 14,200 m2 and 71,000 m3 respectively, and its landfill has been completed already. However, this disposal site was designated as an inappropriate disposal site, and required to take a countermeasure in order to satisfy the national landfill closing criteria with the state aid business. Measures were mainly planned to construct a vertical water barrier for preventing the inflow of groundwater from the surroundings to the landfill site and the outflow of leached water (wastewater) to the downstream groundwater, and to perform final earth capping for controlling the penetration of rainwater into the landfill site. Initially, the cut off wall for water barrier was planned with a Trench cutting Re-mixing Deep wall (TRD) method using a pre-drilling by a double rock auger in combination due to existence of hard rock formations in the target ground. However, in the actual construction, both the TRD method which is the in-situ stirring and mixing method, and the CSM (Cutter Soil Mixing) method which does not use the supplementary method, were used in combination to shorten the construction schedule. This change of the construction method was attributed to the corroboration of the pre-test results of the CSM machine for the applicability to hard rock carried out when it was introduced from overseas, and the results of the pre-test at the actual construction site. In this report, based on these construction progress, we report a track record in which the CSM method was used for of the vertical cut off wall for water barrier of the final landfill disposal site of waste firstly in Japan, and a pre-test results of rock drilling performance, approximately 10 years ago.
Hamanaka, Akihiro (Kyushu University) | Itakura, Ken-ichi (Muroran Institute of Technology) | Su, Fa-qiang (Henan Polytechnic University) | Deguchi, Gota (Underground Resources Innovation Network) | Kodama, Jun-ichi (Hokkaido University)
Underground coal gasification (UCG) is a process of producing combustible gases by the in-situ conversion of coal into gaseous products. Coal resources abandoned under the ground for either technical or economic reasons can be recovered with economically and less environmental impacts by UCG; therefore, this technology is regarded as a clean coal technology. UCG has several advantages of low investments, high efficiency, and high benefits compared to conventional coal gasification. However, some environmental risks such as gas leakage, surface subsidence, and underground water pollution are difficult to control because the process is invisible. The reactor in UCG is unstable and expands continuously due to fracturing activity caused by coal combustion. It is, therefore, considered that acoustic emission (AE) is an effective tool to monitor the fracturing activities and visualize the inner part of coal. For this study, UCG model experiments were conducted using coal blocks of 0.55 × 0.60 × 2.74 m to discuss the applicability of AE monitoring for the estimation of the crack generations during UCG process and the extent of the gasification area. Temperatures were also monitored because the crack generations were strongly related to thermal stress occurred by coal combustion and heat transfer. The monitoring results of AE agreed with the measured data of temperatures and the gasification area; the source location of AE was detected around the region temperature increased and the gasification area. Additionally, the gasified coal amount can be predicted by using the data of product gas. Therefore, AE monitoring combined with the prediction of reacted coal amount are expected to be a useful tool as monitoring system of the gasifier in the underground.
Underground coal gasification (UCG) is a technique to extract energy from coal in the form of heat energy and combustible gases through the chemical reactions in the underground gasifier. This technique enables to utilize coal resources that remain unrecoverable in underground due to either technological or economic reasons. Most coal mining in Japan was closed by 2001 because of complicated geological conditions for mining development and high prices of domestic coal. However, abundant unused coal resources remain underground, but they are not recoverable because of technical and economic reasons. Such coal resources are estimated to be 30 billion tons. For that reason, UCG has a great potential to recover vast amounts of energy from these coal resources.
In Japan, work observation in industrial engineering (IE) has been applied in various ways at shipyards to increase productivity. While maintaining a certain quality level, work observation in IE serves as a route for reducing both production costs and the wastage of resources. However, the disadvantage of work observation in IE is that it requires considerable time and effort to identify the work status of current productivity. On the other hand, recently, pattern recognition, which focuses on the recognition of patterns and regularities in image data, has made progress through the use of deep neural networks (DNN). DNN is an artificial neural network method with multiple hidden layers between the input and output data. DNN can be expected to analyze human image recognition using a useful model to represent complex nonlinear relationships. This research aims to develop a methodology of using DNN in work observation that can substitute the current work observation methods in IE. We have attempted to employ DNN for analyzing work observation image data that is recorded as movie data by attaching a small head-mounted camera to a worker. The challenge is to reduce some problems in work recognition accuracy that are associated with the application of DNN for extracting the work status.
In recent years, Carbon capture and storage technology (CCS) has been recognized as one of the potential methods to reduce greenhouse gas emission and for mitigating global climate change. This practice can be done in the depleted reservoir as well as saline aquifer reservoir. Geological modeling is an important process to prove the suitable geologic formation in CCS project. The CO2 plume behavior depends on geology structure of storage formation. This study focuses on geological modeling and the simulation of CO2 plume behavior in saline sandstone of fluvial deposit, Nam Vang field, Cuu Long Basin, Vietnam. Channel sand and floodplain are defined based on well-logging data. Fluvial facies are distributed in the three-dimensional grid by using the object-based method with consideration of lateral continuity, vertical range and orientation in each facies. The porosity and permeability are modeled stochastically to conditioning to facies. The advantage of object-based modeling constrained the petrophysical model to facies model to assign the high porosities and permeability distributed within channel sand-dominated facies. The low porosities and permeability populated within floodplain-dominated facies. CO2injections were simulated using ECLIPSE300-CO2STORE. Sensitivity analysis has been conducted to investigate the behavior of CO2 plume for reservoir saline sandstone. Simulation results indicate the extent of CO2 plume dynamic is sensitivity to the geometry and sinuosity of the fluvial channel. The object-based modeling can construct the geological model to relate with fluvial channel facies correctly. This method is used to support for geological CO2 storage modeling in the fluvial deposit. As a general evaluation, this study can contribute to CO2 storage in an offshore area in Vietnam.