Decline curve analyses revisited

Empiricaldecline curve forecasts of future production rates and cumulative production to be expected from certain classes of petroleum reservoirs has been a methodology practiced and relied on by petroleum geologists for many years. New ways to consider the subject are described in this paper. Thereby it is seen that these forecasts sometimes can be made even when some of the record of the past performance history is sparse (say, because it has been lost, or never recorded).SI Units D, D _i initial reference production rate,s ^–1 - n dimensionless constant [cf. Eq. (1)] - N cumulative production, m³ - Q, Q _i production rate att and initially, m³/s - R dimensionless time variable [cf. Eq. (9)] - t time, s     

Geochemical evidence for Se mobilization by the weathering of pyritic shale, San Joaquin Valley, California, U.S.A.

Acidic (pH 4) seeps issue from the weathered Upper Cretaceous-Paleocene marine sedimentary shales of the Moreno Formation in the semi-arid Coast Ranges of California. The chemistry of the acidic solutions is believed to be evidence of current reactions ultimately yielding hydrous sodium and magnesium sulfate salts, e.g. mirabilite and bloedite, from the oxidation of primary pyrite. The selenate form of Se is concentrated in these soluble salts, which act as temporary geological sinks. Theoretically, the open lattice structures of these hydrous minerals could incorporate the selenate (SeO₄⁻²) anion in the sulfate (SO₄⁻²) space. When coupled with a semi-arid to arid climate, fractional crystallization and evaporative concentration can occur creating a sodium-sulfate fluid that exceeds the U.S. Environmental Protection Agency limit of 1000 μg l⁻¹ for a toxic Se waste. The oxidative alkaline conditions necessary to ensure the concentration of soluble selenate are provided in the accompanying marine sandstones of the Panoche and Lodo Formations and the eugeosynclinal Franciscan assemblage. Runoff and extensive mass wasting in the area reflect these processes and provide the mechanisms which transport Se to the farmlands of the west-central San Joaquin Valley. Subsurface drainage from these soils consequently transports Se to refuge areas in amounts elevated to cause a threat to wildlife.     

On the bulk parameterization of snow and its application to the quantitative studies of precipitation growth

Appropriate formulation of bulk parameterization of snow growth and evaporation based on observational characteristics of snow particles is presented. The parameterization is compared to that of S. A. Rutledge and P. V. Hobbs and to detailed treatment in which snow particles are assumed to grow or evaporate in each size bin separately. On the contrary to bulk parameterization of rain, snow diffusional growth or evaporation is accurately represented in the suggested bulk formulation, but growth by riming is overpredicted. Integrations of water budget equations in a one-dimensional updraft have shown that quantitative results, e.g., precipitation intensity, cloudwater content, supersaturation with respect to ice, depend on the parameterization scheme employed, which suggests that comparisons of field measurements with parameterized model outputs is usually not straightforward.     

Criticism of reconnection models of the magnetosphere

Reconnection involves singular lines called X-lines on the day and night sides of the magnetosphere, and the reconnection rate is proportional to the component of the electric field along the X-line. Although there is some indirect support for this model, nevertheless direct support is totally lacking. However, there are two distinct pieces of clearly contradictory observational evidence on the dayside. First is the failure to account for the implied energy dissipation by the magnetopause current, over 10¹¹ W, which should be easily observable as heating or enhanced flow of the plasma near the magnetopause. In marked contrast to this prediction, HEOS-2 satellite data reveal a plasma with decreased energy density and reduced flow. Second, the boundary of closed magnetic field lines is in the wrong location. In the reconnection process the plasma outflow would cut across open field lines toward higher latitudes; there should be a band of open field lines equatorward of the cleft. Observations of trapped energetic particles indicate closed field lines within the entry layer and cleft. Either one of these pieces of evidence is sufficient by itself to require drastic revision, even rejection, of the reconnection model. There is also contradictory evidence on the night side. The last closed field line capable of trapping energetic particles is poleward of auroral arcs. The implication is that the X-line is at the distant magnetopause, and not in the plasma sheet. Consequently, even if the reconnection process were operative at the nightside X-line, it would be isolated from steady state plasma sheet and auroral processes. On the other hand, substorm phenomena, in which stored magnetic energy is converted into particle kinetic energy, necessarily involve an induced electric field; that is excluded in theories of the reconnection process in which it is assumed that curl E = 0. Nevertheless, the observed easy access of energetic solar flare particles to the polar caps, and especially the preservation of interplanetary anisotropies as differences between the two polar caps, argues strongly for an open magnetosphere, with interconnection between geomagnetic and inter-planetary magnetic field lines. It is suggested that the resolution of this apparent paradox involves electric fields parallel to the magnetic field lines somewhere on the dawn and dusk sides of the magnetosphere, with an equipotential dayside magnetopause.     

Physical properties of solar chromospheric plages

We compute a new grid of plage models to determine the difference in temperature versus mass column density structure T(m) between plage regions and the quiet solar chromosphere, and to test whether the solar chromosphere is geometrically thinner in plages. We compare partial redistribution calculations of Mg ii h and k and Ca ii K to NRL Skylab observations of Mg ii h and k in six active regions and Ca ii K intensities obtained from spectroheliograms taken at approximately the same time as the Mg ii observations. We find that the plage observations are better matched by models with linear (in log m) temperature distributions and larger values of m ₀ (the mass column density at the 8000 K layer in the chromosphere), than by models with larger low chromosphere temperature gradients but values of m ₀ similar to the quiet Sun. Our derived temperature structures are in agreement with the grid originally proposed by Shine and Linsky, but our analysis is in contrast to the study by Kelch which implies that stellar chromospheric geometrical thickness is not affected by chromospheric activity. We conclude that either the stellar Mg ii observations upon which the Kelch study was based are of poorer quality than had been assumed, or that the spatial averaging of inhomogeneous structures, which is inherent in the stellar data, does not lead to a best fit one-component model similar in detail to that of a stellar or a solar plage.Visiting Astronomer at Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Staff member, Quantum Physics Division, National Bureau of Standards.     

On high-latitude convection field inhomogeneities,parallel electric fields and inverted-V precipitation events

Assuming a certain horizontal distribution of the convection field at a certain altitude above the ionosphere, the associated electric field and current distributions in a vertical plane are calculated using a model with finite current-dependent conductivity along the magnetic field lines. It is seen that given the kind of horizontal distribution of E₆ commonly observed by polar-orbiting satellites at inverted-V electron precipitation events, the calculated distribution of E_∥ is able to reproduce the basic spatial structure of the precipitation. It is also seen that the combined effect of a locally increased ionization within auroral forms and a large potential difference (ΔV)_∥ along the magnetic field lines at higher altitudes is a strong reduction of E₆ within the auroral forms. From the basic features of the electric field, it is concluded that an interpretation of auroral precipitation in terms of a static E_∥ may require a mechanism that can support a large (ΔV)_∥ even at relatively weak current densities and at the same time allow local enhancements of the parallel conductivity within the region of non-zero E_∥. It is suggested that the magnetic mirroring combined with gyro-resonant wave-particle interactions may be a suitable mechanism.