Pore structure is represented by using a three-dimensional network model. In the model, a porous material is assumed to be a three-dimensional network which is composed of a large number of pore segments of a constant length. The pore diameter distribution is assumed to be the normal, the Rosin-Rammler, and the beta distribution function. Permeability is evaluated on the basis of Poisuiell's equation and Kirchhoff's and Darcy's law. There is little difference among the calculated values of the dimensionless permeability K calculated from the model in which the pore diameter distribution is assumed to be the normal, the Rosin-Rammler or the beta distribution. The calculated values of K from the three-dimensional network model also agree well with that from the two-dimensional network model reported previously. The estimated values of K from the model by using experimental pore size distributions agree approximately with the Purcell's factor.
The rheological behavior of polyacrylamide solution is measured with cone-and-plate viscometer and damped oscillation torsion pendulum equipment. The relationship between viscosity, relaxation time and shear rate is analyzed by a three-element fluid model. The pressure drop of the flow of viscoelastic fluid through porous media consists of two parts, that is a viscous part and an elastic part. The modified Blake-Kozeny model represents the flow of a power-law fluid through the porous media. A dimensionless number, which is equivalent to the Deborah number, is formulated to represent the elastic effect. An equation is proposed to calculate the elastic pressure drop, which contains the dimensionless number, velocity, core properties (permeability and porosity), fluid properties (flow behavior index and consistency index) and coefficients which are determined experimentally. A modified bed factor is defined to expand the modified Blake-Kozeny model into the proposed model for the viscoelastic fluid. Equations of pressure drop, Reynolds number, apparent viscosity and resistance factor for the flow of viscoelastic fluid through porous media are formulated with the modified bed factor. The model is compared with the experimental data of the flow of polyacrylamide solutions through Berea sandstone. The relationship of fRe=1 exists in the experimental ranges. The calculated values of the apparent viscosity approximately agree with the experimental data.
In this paper, we studied the effects of the chemical structure and compositions of polymer and brine on the flow properties with the aim of mobility control. Five kinds of partially hydrolyzed polyacrylamides were used as polymer samples. We used brine which contained mono-valent (Na+, K+) or divalent (Mg2+, Ca2+) ions. We measured the flow properties of polymer solutions as apparent viscosity, screen factor, resistance factor and residual resistance factor and discussed the relation between each other. The results were as follows: (1) The resistance factor, residual resistance factor and screen factor, respectively, increased with a polymer molecular weight increase. From these results, it was confirmed that the resistance factors had a positive correlation with the screen factors. (2) The resistance factor and apparent viscosity decreased with a brine concentration increase. These behaviors become extremely remarkable in divalent ion solutions. However, the screen factors decreased relatively little and the residual resistance factors were almost constant in these brines. (3) The resistance factor increased at a frontal velocity of over 5ft/day, but there was a reverse tendency at a rate less than 5ft/day.
A mathematical model is developed for predicting reservoir behavior in the Mobara type water-dissolved natural gas field. The model consists of the mathematical description of the flow of water and gas in the reservoir which is composed of the alternation of sandstone and mudstone. This description considers gas exudation at the face of the mudstone and horizontal radial flow in the sandstone. An application of the model to the practical reservoir problem (in the Sencho district) has revealed that the calculated values of gas water ratio and bottom hole pressure are in general agreement with the measured ones and that gas exudation at the face of the mudstone is a principal cause of the peculiar performance such that the gas water ratio rapidly increases with production in the field.
Remarkable fossil plants and marine animals were found from the Oarasawa Formation distributing along the upstream of the Isawa River, southwestern part of Iwate Prefecture, near Akita-Iwate border. The Oarasawa Formation, the lowest Neogene sequence in the Ou Backbone Mountain range area, has been correlated to the Nishioga Group or the Monzen Group of Oga Peninsula on the basis of characteristic lithofacies called “Oarasawa-Semi facies” without enough fossil evidence. The Oarasawa Formation outcropping along the Isawa River is composed mainly of subaqueous basaltic to andestic volcanic rocks and intercalates conglomerate, sandstone and siltstone layers, in which the fossil were newly found. The plant fossils include some characteristic species of the Daijima-type fossil flora such as Cyclobalanopsis nathorstii, Quercus miovariabilis, Liquiclamber miosinica and Smilax trinervis being determined by Professor emeritus K. Huzioka. The fossil marine animals are not abundant and poorly preserved, but the fossils contain a few common species of the Kadonosawa fauna that is nearly equivalent of the fauna in the Nishikurosawa stage. The fossil evidences show that the Oarasawa Formation is now placed in the Daijima-Nishikurosawa age. Therefore, by biostratigraphical and lithological facts, the Oarasawa Formation can be correlated consistently with the formations which were established or redefined recently, such as the Okachigawa Formation of Dewa mountoins, southern Akita Prefecture and the Sunakobuchi Formation distributting along the eastern margin of the Akita Oil Field. The litho- and biostratigraphical informations obtained recently from the lower Green Tuff, indicate that the Green Tuff volcanism took place in the Daijima-Nishikurosawa age in many places of the inland region of the northeast Japan.