Inverse methods and kinetic models of hydrocarbon generation: I. Theoretical considerations     

I. Lerche 《Mathematical Geology》1991,23(1):137-155

Several different proposed models of thermocatalytic cracking of kerogen to hydrocarbons are exhibited. The specific models are then combined into a single generic, encompassing framework. For laboratory pyrolysis measurements of kerogen degradation and of thermal generation of hydrocarbons, inverse methods are used to show how to determine the relevant distributions of kinetic parameters consistent with the measured data.  相似文献   

Representation of normal slant faults in a 2D burial history model     

I. Lerche  Z. Yu  J. Liu 《地学学报》1995,7(4):459-466

A discussion is given of the impact of normal slant faults on basinal structure, compaction, fluid overpressure development, and thermal effects in sedimentary basins. Faults which are hydraulically closed or open to fluid flow are examined in a dynamical two-dimensional fluid/ flow compaction model.
From this numerical investigation three dominant factors characterize the effects of single and multiple faults with open or closed hydraulic behaviours: (i) there is a difference in excess pressure for fault planes with open or shut hydraulic conditions, but the neighbourhood where the effect of the fault is dominant is fairly localized (to within about half a kilometre or so laterally from the fault plane); (ii) the lateral and vertical motion of sediments between faulted blocks induces a thermal difference prior to, during, and post-faulting, which can play a role in influencing hydrocarbon generation, migration, and accumulation; (iii) porosity retention and permeability modification by fault development could influence hydrocarbon exploration decisions regarding sealing, migration pathways, and fluid retention.
The general patterns of slant fault effects described here should prevail in most geological situations, because the numerical experiments are designed to illuminate sharply the dominant response characteristics within the framework of simplified situations.  相似文献   

A variational approach to the question of temporal stability of equilibrium models of solar prominences     

I. Lerche  B. C. Low 《Solar physics》1981,69(2):327-342

Using a Lagrangian approach to the equations describing small amplitude departures from equilibrium of solar prominences, we derive seven quantities which, by analogy to the concepts of energy, momentum and angular momentum, are conserved under circumstances corresponding to ignorable coordinates of classical mechanics. In a pragmatic sense it is expected that these conservation laws will be useful as criteria of accuracy in obtaining eigen-frequencies for the perturbation equations when numerical techniques are employed.We also demonstrate that: (i) the perturbation equations (which are not self-adjoint) follow from an external variation of a Lagrangian; (ii) the equations adjoint to the perturbation equations also follow from an extremal variation of the same Lagrangian; (iii) the Lagrangian approach automatically gives the conserved quantities, together with a variational principle for computing the eigen-frequencies of the perturbation equations.In view of the paucity of analytic solutions (and their eigen-frequencies) to the perturbation equations (due essentially to the complicated spatial dependence of thermodynamic quantities describing the equilibria) we believe that the technique developed here - which is capable of handling complicated spatial dependences and which has internal criteria for assessing accuracy of any given numerical convergence scheme - is a valuable addition to the arsenal of methods used for discussing the equilibria, and their stability, of models thought to represent the basic physical processes underlying the quiescent solar prominence phenomenon.  相似文献   

Pulsed and continuous radiation from white dwarfs     

I. Lerche 《Astrophysics and Space Science》1972,17(1):117-125

We demonstrate that the detection of steady kV X-ray emission from the vicinity of a white dwarf star possessing a magnetic field of the order of 10⁷ G will provide strong evidence that the white dwarf is rotating with a period of about one minute. We also show that detection of pulsed radiation at about 1 mm wavelength would confirm this. Also some of the interesting dynamical consequences for the interstellar medium due to such white dwarfs are outlined.  相似文献   

Simulation of sulfate-dependent sulfate reduction using Monod kinetics     

Leonard Robert Gardner  Ian Lerche 《Mathematical Geology》1987,19(3):219-239

A simple computer code is presented for simulating the dependence of sulfate reduction on sulfate concentration using Monod kinetics. Unlike previous models, the code provides a numerical initial value problem solution, rather than a two-point boundary value solution, for the Monod model using a search procedure to find the correct starting value for the derivative of sulfate concentration with respect to depth. Accordingly the code is not restricted to cases where sulfate vanishes at finite depth but also can be used to model situations where organic matter is exhausted before total depletion of sulfate can occur. In such situations, the code demonstrates that profiles generated using Monod kinetics differ significantly from those generated using the simple sulfate-independent model proposed by Berner (1964), even when the asymptotic concentration of sulfate at depth remains well above the Monod saturation constant.  相似文献   

Faraday rotation and signal dispersion: The geometrical optics approximation,an exact solution,and first order smoothing theory     

I. Lerche 《Astrophysics and Space Science》1971,13(1):48-52

We critically discuss the three approximations which have been employed to estimate the influence of interstellar fluctuations in both electron density and magnetic field on Faraday rotation measure and signal dispersion measure in the radio band. We demonstrate that: (i) the geometrical optics approximation employed by Ginzburg and Eruhimov (1971) relies on the unproven assertion thatall ray paths are essentially the same as the geometrical distance between source and observer; (ii) the exact solution is physically meaningless; (iii) the purported proof of Ginzburg and Eruhimov that earlier work by Lerche is in error, is itself in error and also self-contradictory; (iv) the first order smoothing theory employed earlier by Lerche gives the exact correction to the phase of the ordered field provided only that theirreducible part of a three-point correlation function is negligible.Receipt delayed by postal strike in Great Britain.  相似文献   

Radiative modes of a weakly ionized,collision-dominated,turbulent plasma     

I. Lerche 《Astrophysics and Space Science》1972,18(1):94-103

We obtain, and discuss, the roots of the dispersion relation describing normal mode propagation in a weakly ionized, collision dominated turbulent plasma with an isotropically distributed turbulent magnetic field. We demonstrate that, depending on the level of the turbulent field relative to the collision frequency, there may, or may not, be propagating, but decaying, modes present in the system. The structure and properties of the modes depend on both the precise level of the turbulent magnetic field and its spatial and temporal correlation.For simple correlation functions we estimate the decay rate of the radiative modes. Using galactic parameters as an illustration we show that only the long-wavelength (low-frequency) modes last for a significant length of time ( a collision time).We have done this calculation to demonstrate that the response of turbulent plasma systems is more complicated than simple order of magnitude calculations indicate; and to illustrate a method which may, perhaps, be gainfully employed in more complex turbulent astrophysical plasma situations than considered here.  相似文献   

An inversion method for separating apparent and intrinsic attenuation in layered media   总被引：1，自引：0，他引：1  

I. Lerche  William Menke 《Geophysical Journal International》1986,87(2):333-347

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Reply to foregoing comments     

I. Lerche 《Astrophysics and Space Science》1973,22(1):197-197

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Numerical basin modelling of the Sleipner field, North Sea     

Z.P. Wei  C. Hermanrud  I. Lerche 《地学学报》1990,2(1):31-42

Both one-dimensional (1-D) and two-dimensional (2-D) basin modelling has been carried out in the Sleipner area in the North Sea. Thermal refraction by salt and more minor convection by fluid transport combine to provide a temperature regime which is hotter at the Sleipner East field relative to the Sleipner West field by approximately 5°C at the same sub-surface depth. These results are obtained only with 2-D modelling, and show that such simulations are necessary to explain the spatial variations of temperature distribution at the least. Modelling of hydrocarbon generation in the Sleipner kitchen shows that the source rocks are presently in a late gas generation state, and that a gas-condensate is to be expected in fields draining this kitchen. Such hydrocarbon phases are encountered in the Sleipner field, confirming that the model can simulate satisfactorily hydrocarbon generation in the Sleipner area.  相似文献