In this paper, firstly, the establishment of quantitative evaluation techniques of capabilities of anaerobes in improving oil recovery is discussed, and then results of flooding experiments based on the techniques are presented. Strain 9A, which was recognized as one of useful anaerobes through the studies reported in previous papers, was incubated in porous media to investigate effects of kerosine on its growth. As a result, the cultivation showed that kerosine itself had no influence upon the microbial multiplication and metabolism. The flooding apparatus includes the sandpack which was comprised of an acrylic pipe packed with silica sands, injection pump and pressure measurement tools. The evaluation method was specified in this paper as follows; (1) making a sandpack, (2) measurement of water permeability, (3) saturating oil into the sandpack, (4) water flooding, (5) injecting microbes into the sandpack, (6) cultivation, and (7) recovering additional oil by injecting water. Regarding the microbial injection specified above at 5th clause, the minimum amount of liquid medium with microbes for uniform injection was decided through the investigation. Filteration of microbes did not occur. Then flooding experiments based on the above method were carried out using 9 kinds of anaerobes. Consequently, the oil recovery was improved at all cases. Especially, the maximum oil recovery obtained with strain 9A amounted to 30% of residual oil.
Vibration analysis on downhole forces and motions of roller bits could be a new realtime diagnosis method of bit state and lithology to be drilled. Drilling experiment and data acquisition were performed using atmospheric full-scale bit test machine. Data include weight on bit, bit torque and acceleration of axial bit motion at the bit sub for a couple of new and worn 8-1/2″ roller bits drilling samples of granite and andesite. Measured data were analyzed through power spectral densities and cross correlations. The power spectral densities of measured data presented characteristic peaks in frequency domain due to successive impacts of bit teeth on the rock surface. Bit tooth wear causes shifts of locations of these spectral peaks to higher frequencies. Variations of rock type and penetration rate have effect on vibration amplitude of axial bit motion rather than on the power spectral peak frequencies within the limits of the experiments. Dominant frequencies are quite sensitive to cone rotary speeds. Considerable correlation between weight on bit and bit torque vibrations was observed, and cross-correlation function showed that weight on bit is delayed in time from bit torque.
Diatom biostratigraphy is established for the Middle Miocene Kinone and lower Amatsu Formations in Boso Peninsula, central Japan. Diatom zones of Denticulopsis lauta Zone through D. praedimorpha Zone are recognized in 15 calcareous nodules out of 79 collected samples in the study area. The middle and upper part of the Kinone Formation is assigned to Denticulopsislauta and Denticulopsis hyalina Zones. The Crucidenticula nicobarica Zone is recognized at around the boundary between Kinone and Amatsu Formations. The lower Amatsu Formation is assigned to Denticulopsis praedimorpha Zone. The diatom biostratigraphy established in this study can be correlated directly with the calcareous microfossil biostratigraphy previously reported. Based on the integrated biostratigraphy of the study area it is revealed that the sedimentation rate decreased abruptly around the boundary between the Kinone and Amatsu Formations.
The radiolarian biostratigraphy on the Middle Miocene marine sequence in the Boso Peninsula was firstly established through this work, which enables us to discuss the direct stratigraphic relations between siliceous and calcareous microfossil biostratigraphy. Calcareous nodules in hemipelagic mudstones of the Kinone and Amatsu Formations contain Middle Miocene radiolarian species characterizing the low- and high-latitude North Pacific regions. The low-latitude species, including Dorcadospyris alata, D. dentata, Didymocyrtis tubaria, D. mammifera, D. laticonus, Calocycletta costata and Lithopera thornburgi indicate presence of two tropical radiolarian zones, C. costata and D. alata Zones; however, the boundary between these zones is not well determined due to the very rare occurrence of D. alata and D. dentata. The high-latitude species elements include common Eucyrtidium asanoi and E. inflatum, and rare Lychnocanoma magnacornuta. These species indicate four high-latitude zones, C. costata, E. asanoi, E. inflatum and L. magnacornuta Zones. There are also common occurrences of Cyrtocapsella tetrapera, C. cornuta, C. japonica, Stichocorys delmontensis and S. wolffii. A synthesis of the biostratigraphic studies on the Kinone and Amatsu Formations presents correlation of radiolarian, diatom, calcareous nannofossil and planktonic foraminiferal zones, providing a local biochronologic framework for Middle Miocene sediments of Japan.
Optimum design analysis in engineering is generally formulated as a problem of nonlinear programming. For casing design problem, there are combinatorial variables, integer variables, which select a casing to be used among alternatives. In spite of including integer variables, nonlinear programming may be able to optimize the casing design problem, since it has an enough optimization potential for continuous variable problem. In this paper, an application study is presented to verify the usefulness of nonlinear programming termed SUMT for casing design problem.
Oil production potential could be predicted by an Oil Field Depletion Model. Production calculated by the existing model declines earlier than field cases. Therefore we propose the following new model which is based on reserves and production data of 225 Large Giant Oil Fields (LGO) in the world (1) LGO can be classified by Production Ratio (PR): Cumulative production/Recoverable reserves, that is, PR>50%: Declining fields, PR=50%-10%: Plateau fields, PR<10%: New fields. (2) Production Profile ‘Stacking Theory’ can be recognized. A group of LGO sustain production until 60% of reserves have been produced, though single field declines production at 50% of the reserves produced. Plateau rate of the group is 60% of the sum of the peak rates of each oil field. Reserves vs. Production ratio (R/P) of the group is nearly doubled. (3) Decline curve defined by exponential decline of which rate is reciprocal of R/P at decline started, can be applied. (4) Build-up production may be assumed 10% of reserves. The model interprets each LGO groups: (1) 97 Declining group had declined since 1988 at the decline rate 6.25% per annum and will continue to decline exponentially. (2) 71 Plateau group will sustain its maximum production potential until the year 2014. Relatively smaller production rate results in slower decline of 3.6% per annum. (3) 57 New group would start production to fill up reduction of declining group. Ceiling of production rate will be calculated by R/P=16. A future production profile curve of the world LGO is illustrated by assuming 1.5% per year ascent of world oil demand. The curve may represent the production from the world proved oil reserves because remaining reserves and production rates of LGO are dominant, accounting for 66% and 58% of the world total, respectively.