In order to get the information on the dynamic strength of a vertical pipe for transporting mineral resources under the sea floor to a platform on the sea surface, the lateral vibration of the pipe due to external forces, such as waves, currents, impacts of icebergs, etc., must be analysed. As the first step for this purpose, the natural frequency of lateral vibration of the pipe has been analysed theoretically and experimentally, especially taking the effect of the flowing fluid in the pipe into consideration. The results obtained are summarized as follows: (1) The natural frequency of lateral vibration of the pipe decreases gradually as the velocity of inner fluid increases. There is the critical fluid velocity at which the natural frequency of the pipe becomes zero and its lateral vibration corresponding to the frequency vanishes. The value of the critical fluid velocity is smaller in cases of larger length and own weight of the pipe, larger compressive load applied axially at the top of the pipe, larger specific gravity of the inner fluid and smaller dimension of the cross-section of the pipe. (2) The natural frequency of the pipe also decreases as the length and own weight of the pipe increase, and as the above-mentioned compressive load increases. Furthermore, the frequency becomes zero when the own weight and compressive load reach the buckling load of the pipe. (3) In the practical range, the natural frequency of the pipe is little affected by the damping force due to the surrounding water. (4) As the ratio of the mass of the surrounding water to that of the pipe with inner fluid increases, the natural frequency of the pipe decreases, but the ratio does not affect the critical fluid velocity. (5) The same relationship between the natural frequency and the other quantities as mentioned above can be seen in cases of pipes with various kinds of supports. However, the frequency itself depends upon the condition for supporting the pipe at its ends. The frequency pertaining to the fixed-fixed supports of the pipe is almost twice as large as that pertaining to the pinned-pinned supports of the pipe. Besides, the frequency pertaining to the pipe which is fixed at the sea floor and pinned at the sea surface is about one and half times greater than that pertaining to the pinned-pinned supports of the pipe.
Dump water flooding is a method utilizing a cross flow within a wellbore. The dumping water is established by the difference of flow potentials between a natural aquifer as a water source and an oil reservoir. Therefore, once the perforation is made into the both of aquifer and oil reservoir and the potential of aquifer is kept higher than that of the oil reservoir, water is continuously injected without any artificial drive. Obviously, the simple nature of the method indicates extreme dominance in economy. However, the injection performance is very sensitive with the conditions of aquifer and oil reservoir. Accordingly, the applicability of the method is highly limited. In the first part, the basic mechanism of dump water flooding is presented and the advantage and disadvantage of the method are briefly discussed. In the latter part, the examples of three projects in Khafji and Hout fields, Saudi Arabia are presented and the keys to the successful operation are briefly discussed.
This report describes the results of simulation study performed on a single five spot pattern of water injection. The study is intended to analyse the reservoir performance under various injection pattern alternatives that can be considered by infill drilling, i.e. five spot, nine spot (normal and inverted) and line drive pattern, and also to investigate the effect on the areal sweep efficiency when the timing of infill drilling is delayed. The main results are: -Under the five spot pattern case, both production capacity and recovery efficiency at water breakthrough are the highest. The delay of the infill drilling distorts the areal symmetry of the initial flood pattern and thus, cause less recovery efficiency at water breakthrough. Although the above results are to some extent, inferable by an analytical method, reservoir performance under each case have been more quantitatively analysed by a simulation approach in this study, and also a three dimensional description has been utilized to aid in the quick understanding of the behaviour of water front advance under the different injection patterns.
Dynamic adsorption tests of petroleum sulfonates were conducted using Berea core to study the effects of average EW of micellar slugs, cosurfactants, oil volume contained in micellar slugs and salinity as main factors which affect adsorption of sulfonates on rocks. The influence of divalent cations removed from the rock surface by ion exchange on sulfonates or micellar slugs were examined, and the correlation between phase behavior investigating fluid-fluid interaction and that of effluent samples including rock-fluid interaction in cores was studied. The effect of preflush of sodium orthosilicate solution was also investigated. 1) More hydrophilic slugs with lower EW showed less adsorption of sulfonates than higher EW slugs. Cosurfactants had the effect to reduce adsorption of sulfonates. More hydrophilic cosurfactants with larger HLB value are more effective to decrease adsorption. Increase of oil volume contained in slugs led to reduction of sulfonate adsorption. 2) Salinity had a great influence on sulfonate adsorption. Especially, salinity of a slug itself and salinity of a polymer solution which interacts with a slug seriously affected adsorption of sulfonates. 3) Microemulsion phase in cores shifted from lower phase to middle or upper phase. These transitions of microemulsion phase are attributed to formation of bonds between divalent cations removed from cores by ion exchange and sulfonates or micelles. 4) Adsorption of sulfonates was reduced considerably by the preflush of sodium orthosilicate solution. The preflush of sodium orthosilicate solution is considered to have the effect to restrain the formation of bonds between divalent cations and sulfonates.
This paper presents a steamflood project at Ishinazaka oil field in Yamagata Prefecture, Japan. The purpose of this project is to improve oil recovery by viscosity reduction, thermal expansion, steam distillation and so on. This project consists of the next three phases. Phase 1: Data Gathering Phase 2: Reservoir Study Phase 3: Pilot Test Plan We have already finished Phase 1 and Phase 2, and some of their results are shown in this paper.