Calcium or paraffin deposition causes the decrease of tubig diameter. It is one of the problems in many oil fields that the increase of pressure drop is resulted from the decrease of tubing diameter. The effects of presence of smaller diameter section in a tubing string in two phase vertical flow were studied. The measurements were carried out at atmospheric pressure using air as gas and water as liquid. The vertical flow strings used in the experimental works were consisted of the about 5-m-long and 2.5-cm in diameter main section and the smaller dia meter section placed in the middle part of main section (shown in Fig. 1). The smaller size pipes were long between 2-cm and 50-cm and 0.52cm in diameter. From the results of the tests, the correlation was developed. The pressure drop in smaller size section is able to be calculated by using Eq. (5) and Eq. (6) with Fig. 7. The pressure drop is expressed in terms of the pipe length, liquid flow rate and gas liquid ratio.

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Carbonate concretions and lensy and banded carbonate rocks are distributed in the Cretaceous, Paleogene and Neogene strata of the Joban area. These carbonate rocks were studied from the stratigraphic, chemical and mineralogical points of view to clear their origin. The results are summarized as follows:
1. These carbonate rocks are composed of detrital materials and carbonate minerals, the latter minerals are filled in the pore spaces of the former particles.
2. Only calcite and dolomite are found in these rocks.
3. The carbonate content of these rocks ranges from 25 to 85 per cent in weight. The variation originates from their stratigraphic position and their host rocks. In a single carbonate rock body, however, the content shows only a little difference between the inner and outer parts.
It is considered that calcium and magnecium in these rocks have been supplied from porewater and sedimentary materials. CO₂ must be derived from organic materials, because these carbonate rocks have high content of P₂O₅ compared with low content of their host rocks and contain rich molluscan fossils.
These carbonate rocks have low ratio of SiO₂/Al₂O₃ as compared with high ratio of their host rocks. This may indicate that the concentration of carbonate minerals and the release of SiO₂ in these rocks have been occured at the same time. The action separating SiO₂ and carbonate in sediments might promote the concentration of carbonate minerals.
These transformations must be occured during early diagenesis when the pore-water in sediments have been rich considerably and the flexibility of sediments have been still good.

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Most of the present Japanese micropaleontologists consider that the Orbulina surface of Japan lies within the Lower Miocene Saigo Formation of the Kakegawa region. However, it is reascertained by the writer that Orbulina appears first in the unconformably overlying Upper Miocene Sagara Group. The Orbulina surface of this region should be placed in the stratigraphic break between the Saigo and Sagara. In the Takasaki region, the writer finds that Orbulina first occurs in the uppermost part of the Fukushima Formation (Globigerinatella insueta Zone).
Based on the revision of the previous planktonic foraminiferal zones of the Takasaki region, the writer gives some remarks on the zonation of the Lower-Middle Miocene of Japan as follows: (1) the main part of the type section of SAITO's Globorotalia fohsi barisanensis Zone is included in the Globigerinatella insueta Zone and its uppermost part in the Globorotalia fohsi peripheroronda Zone, (2) SAITO's Globorotalia fohsi fohsi (sensu BOLLI) Zone is correlated with the interval from the Globorotalia fohsi fohsi Zone to Globorotalia fohsi robusta Zone of the tropical region (Zones N.10 to N.12), (3) the writer here proposes the Globorotalia mayeri Zone above this zone.

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Owing to the recent advancements in technology of geophysical exploration and drilling, many geological data concerning to the deep seated formations have been accumulated. Recent studies about surface and subsurface geology and about planktonic foraminiferal fossils have made clear the lower and middle Miocene stratigraphy. The writer proposes, in this paper, to divide the Miocene to lower Pleistocene formations into 7 stages in this district.
Stage I-Mikawa stage (lower to middle Miocene)
Formations included in this stage are the Aikawa group (Sado Island), Matsukawa group (Kita-Uonuma County) and Jonai group (Minami-Uonuma County). The formations consist mainly of pyroclastic rocks (lower part of the "green tuff") including propyrite and contain Aniai-type flora in the intercalating non-marine-shallow marine sediments.
Stage II-Nanatani stage (middle Miocene)
Lithology of the formations of this stage is composed of various kinds of pyroclastic rocks (upper part of the "green tuff"), coarse elastic sediments which may have been deposited in the shallow marine and fine clastic sediments of rather deep marine origin.
This stage belongs to Globorotalia fohsi zone and Hopkinsina morimachiensis - Gyroidina orbicularis zone. Fossils such as Daijima-type flora, Miogypsina - Operculina fauna, Acid - Potamid fauna and Pectinid fauna characterize this stage.
According to planktonic foraminiferal zonation newly established by Japex's paleontologists, the Iwafune group, the Tsugawa formation and the Nanatani formation, which had been considered to be deposited in this order and to be unrelated stages, have been concluded to constitute only one stage. However, in Akita region, two stages are recognized in the age corresponding to the
stage II of this province. To solve this discrepancy, more detailed studies should be carried out.
Stage III-Teradomari stage (lower part of the upper Miocene)
Main lithology is black mudstone being deposited under stagnant water. Benthonic foraminiferal fauna is mostly composed of arenaceous forms belonging to Spirosigmoilinella compressa-Martinottiella communis zone.
In the area west of the Nagaoka plain, alternations of sandstone and mudstone are predominant and some planktonic foraminifers with calcareous Benthonic forms are found.
Volcanic rocks mainly of andesite and dacite are found in places. Submarine eruption and
intrusion of basalt are highly characteristic in this stage.
Stage IV-Shiiya stage (upper Miocene)
Lithology is alternation of sandstone/mudstone and mudstone. The former is called Shiiya alternation and the latter, being grey mudstone, called Araya mudstone.
Benthonic foraminifers are characterized by coexistence of arenaceous and calcareous forms of Miliammina echigoensis zone. Planktonic foraminiferal zone is "Orbulinna" universa - Globigerina woodi zone which contains Globigerina pachyderma (dextral) and Globorotalia inflata.
It is noted that the volcanic activity subsided during this stage as compared with the previous stages. Andesitic and dacitic pyroclastic rocks are found in some places.
Stage V-Nishiyama stage (lower Pliocene)
Characteristic lithology is greenish grey mudstone named the Nishiyama mudstone. Frequently, especsally in the lower part of this stage, alternation of sandstone and mudstone, so called the Hamatsuda alternation, is found.
The middle and the lower parts of this stage are distinguished by Globigerina pachyderma (dextral)-Globorotalia in flata (s.l.) zone, in which Globorotalia in flata group appears in two zones. Coiling direction of fossil Globigerina pachyderma changes from dextral to sinistral at the middle of this stage. The upper part of this stage belongs to Globigerina pachyderma (sinistral) - Globigerina gninqueloba zone.

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