Pore-size distribution of natural sandstones was analyzed by mercury poro-simetry. Cumulative pore-size distribution curves drawn on the log-probability diagram can be regarded as consisting of two to five linear segments which reflect the porosity and petrographic types of Sandstones. Effects of grain size, sorting, roundness, matrix and porous mudrock fragments on the cumulative curves were experimentally elucidated by UCHIDA and TADA (1991) with investigating five series of artificially packed sands as follows: (1) ES series composed of equigranular glass beads, (2) VS series composed of variably sorted glass beads, (3) BS series bimodally composed of two mixtures of sand-size glass beads and either 4-phi glass beads or normally distributed matrix-size glass beads, (4) VR series composed of mixtures of equigranular sphere glass beads and angular quartz grains, and (5) PRF series composed of equigranular glass beads and porous mudrock fragments. Natures of pores in various petrographic types of natural sandstones, such as Mississippian and Tertiary quartz arenites, Miocene lithic arenites and Miocene lithic wacke, were estimated from the cumulative pore-size distribution curves based on the experimental results of UCHIDA and TADA (1991). As a matter of fact, cumulative distribution curves of these sandstones are regarded as consisting of two to five linear segments, which designate the framework distribution and the toroidal void distribution of intergranular porosities, the framework distribution and the toroidal void distribution of matrix and the intragrain distribution of lithic fragments of mudrocks including in sandstones, respectively. The gradient and position of the segments are influenced by grain size, sorting and porous mudrock fragments as well as by porosity types. Consequently, shapes of the cumulative curves should correspond to rock types of sandstones. Thus, porosity properties, such as the intergranular porosities, matrix porosities and intragrain porosities of mudrock fragments can be quantitatively estimated from the pore-size distribution analyses.
A study has been performed to delineate the spatial distribution of the reservoirs and to infer reservoir rock properties in the Amarume oil field. Reservoir rocks consist of lenticular sandstones which are considered to be sediment gravity flow deposits of Neogene. Productive sandstone reservoirs lie approximately 900m below the surface and vary from 5m to 20m in thickness. 3-D seismic data was processed carefully and the filter operator which matches the seismic data to VSP data was applied to time migrated 3-D data volume to compensate for the phase shift. The reliable information of acoustic impedance was extracted from 3-D seismic data by lithologic inversion. It provided us the spatial distribution of thin sandstone reservoirs. The lateral variation of acoustic impedance observed in each sand reservoir suggests that the reservoir rock properties such as porosity change laterally. P-wave and S-wave velocity tomograms between two wells were derived from cross-well seismic data by traveltime inversion and Vp/Vs ratio profile was estimated. The resultant P-wave velocity tomogram was generally consistent with the well log data. Its resolution was less than that of the velocity profile derived from 3-D seismic data. However, cross-well seismic data provided both P-wave and S-wave velocity information which can be powerful tools to infer the reservoir rock properties.
An optimization program for single point mooring floating production systems, which are currently employed for marginal offshore oil field, was developed. This program is applicable for typical six kinds of single point mooring systems, i.e., CALM-Yoke type, Turret Mooring type, SALM hawser type, Articulated Column-Yoke type, SALS type, and Tower Soft Yoke type. Type program contains detail analysis programs and simplified optimization program. The detail analysis programs are developed based on the up-to-data theory and are capable of performing dynamic and static analysis of mooring system and flexible riser, vibration and fatigue analysis of mooring chain, downtime analysis of floating production system and other analysis. These functions were verified by using model test results and full-scale test results. Some results are presented. The simplified optimization program was developed for preliminary evaluation of mooring system for a specific oil field. Using the detail analysis programs, a series of calculation was carried out and the results were compiled as built-in database, which contributes to shor-ter calculation time. By using this program, the optimized dimensions of mooring system will be derived from the input of water depth, environmental data, and storage capacity.
Biomarker compositions were examined for bitumen extracts of two borehole sequences from the Niigata sedimentary basin by GC/MS. Maturity parameters based on sterane and triterpane isomeric compositions revealed that the Teradomari Formation of both sequences has not reached the primary zone of oil formation, yet. The maturity parameters reversely correlate with depth in the upper part of immature zones. Highly matured isomeric compositions in shallower samples might result from addition of reworked biomarkers or production of thermodynamically stable isomers, such as 20S, α β β and α β configurations, by double bond isomerizations of sterenes and triterpenes, and subsequent reduction. The reversal maturation trend is explained by the supply of more matured biomarkers reworked from Neogene sediments, successively uplifted and eroded at the margin of the basin. Alternative explanation is dilution of the matured biomarkers with products from free, or kerogen- and/or asphaltene-bound precursors with biological configurations, such as ααα 20R-steroids and ββ 22R-triterpenoids, through early diagenesis.
In this paper, vibration theory of elastic body is applied as an analogy to the quantitative analysis of resistance factor of polymer solution measured when it flows through porous media. Resistance against flow of polymer solution through porous media is not caused only by viscosity of polymer solution, but also affected by the energy dissipation by experiencing rarefaction and compression of polymer solution while flowing alternately in the throat connecting pores and in the open pore spaces. Euler Equation is modified to express such elastic resistance of polymer solution caused by the oscillation of normal stress in the fluid. Flow equation comprised of both Euler Equation and Darcy Equation is introduced to calculate both elastic and viscous resistances against flow through porous media. New equation is applied successfully to demonstrate the dilatant flow behavior of polymer solution in the flooding experiences through a capillary tube packed by glass beads and through Berea sand cores. Diffusion equation modified to express the vibration effect of viscoelastic fluid is applied to solve the pressure loss of polymer solution flowing through porous media. Quantitative analysis of the resistance factor of flow of polymer solution through porous media is presented by the use of analytical solution of diffusion equation.
The Arabian-Zagros sedimentary basin, renowned as a huge oil pool-bearing field, is composed of a large quantity of carbonate strata associated with a considerably limited argillaceous strata. During the past quarter century, various studies on the mechanisms of hydrocarbon generation and accumulation in the Persian Gulf area have been carried out. As the result, the following two different opinions concerning the oil generation and migration have been raised: A) catagenetic origin and long distance migration, and B) diagenetic origin and short distance migration. However, at present, the opinions and points of these two groups are independent each other and there are no sufficient discussions between them. The basic conception of the opinion (A) is that a possible source sediment should be placed to a deep burial depth through a sufficient geological time to generate petroleum via so-called “Kerogen”. This is a conception derived mostly from the studies on the argillaceous rocks. On the other hand, if we pay special attention to the organic and inorganic characteristics of carbonate rocks, particularly its efficient capability of hydrocarbon generation and the very likely possibility of generating hydrocarbons which directly generated from the organic matter of carbonate's own without via “Kerogen stage” as pointed out by TAGUCHI (1989), it is possible to accept the conception of (B) rather than (A). Based on the such previous studies and the geological evidences obtained from the actual exploration and exploitation in the studied area, conceivable characteristics for the oil production in this area should be summarized as follows. Namely, (1)extremely high volume of carbonate sediments in comparison with argillaceous sediments, (2)a difficulty of large scale vertical migration due to extensive distribution of dense evaporite (anhydrite, in particular) and (3)the existence of many depletion type oil fields which may have been formed by deterioration of reservoir in the down flank area during the course of the structural growth by high saturation of formation water, etc. Consequently, it is inferred that most of oil in the southern part of the Persian Gulf area might have originated from organic matter of carbonate rocks and accumulated in the favorable structures at the relatively early diagenetic stage through short primary migration pass. In future, more detailed geochemical studies on the carbonate rocks (especially pure carbonates) will be required to solve the diversities among those opinions mentioned above. (This abstract covers the contents of this Part 1 and Part 2 which is to follow. The subtitle of Part 2 is-“Noticeable points on the carbonate source rocks and the specific characters of the accumulation mechanism”-).
The present author has reported that non-clastic siliceous and carbonate rocks have a tendency to generate “immature oils” at shallow depth, while clay-rich rocks generate oils at relatively deeper burial depth, and with this results as background, has proposed a petroleum generation model (e.g. TAGUCHI, 1986, 1989, 1990, 1991) revised conventional “kerogen origin theory of petroleum”, which is based on the concept that kerogen is a random condensation product of various biomonomers which were formed during diagenesis by hydrolysis of biopolymers and only fossil kerogen can form economic oil pools under thermal stress at the catagenetic stage. In the meantime, recently, a new alternative mechanism for formation of kerogen based on the concept of selected preservation of resistant biopolymers has been proposed by several researchers (e.g. TEGELAAR et al., 1989 and others). In this paper, the relationships between the new concept of kerogen formation and the modified model of conventional petroleum generation theory proposed by the present author are examined from a standpoint of oil formation.