Light Hydrocarbon Components Research Articles

Application of multivariate modelling to detect hydrocarbon components for optimal discrimination between two source rock types

The present study presents a multivariate procedure to reveal light hydrocarbon components which significantly distinguish between source rock thermal extracts. The two source rocks included in this study are the marine shales of the Late Jurassic Spekk Formation and the coals and paralic shales of the Early Jurassic Åre Formation offshore Mid-Norway. Because of the large number of components in the C 4–C 13 hydrocarbon fraction of source rock extracts a multivariate approach was required. The procedure consists of three distinct steps: (1) Principal component analysis of the whole data set for detection of non-significant individual components. This reduced the number of individual components from 46 to 22. (2) Separate principal component analysis of the two source rocks (Åre and Spekk) to detect outliers. (3) Principal component modelling of each of the two source rocks after deletion of outliers and non-discriminating variables to detect those hydrocarbon components which are most significant and robust for the separation of the two source rocks. The resulting model shows that there is a definitive compositional difference between the source rocks investigated.

Acetylene eliminated in ethylene processes

A research group at the French Petroleum Institute (IFP) has modified the conventional approach for eliminating acetylene in ethylene processes to good effect. By applying some technology from catalytic olefin production, the researchers have increased ethylene yields, simplified equipment, and lowered the necessary investment. Some acetylene is produced during manufacture of ethylene by steam cracking of hydrocarbons. For high-purity ethylene streams (greater than 99%), the acetylene must be removed. Conventionally, this is done by catalytic hydrogenation of the ethylene, but in a few cases the acetylene is removed by the more expensive method of solvent extraction. For catalytic hydrogenation, placement of the hydrogenation reactor can be critical, according to the IFP group, which includes J. Cosyns, L. Quicke, and P. Sarrazin. If the hydrogenation reactor is placed upstream from the demethanizer, the feed to the reactor will contain light hydrocarbon components and carbon monoxide from the cracking fu...

A Numerical Simulation Model for Thermal Recovery Processes

Abstract This paper describes a model for numerically simulating thermal recovery processes. The primary locus is on the simulation of in-situ combustion, but the formulation also represents fire-and-water flooding, steamflooding, hot water flooding, steam stimulation, and spontaneous ignition as well. The simulator describes the flow of water, oil, and gas, and includes gravity and capillary effects. Heat transfer by conduction, convection, and vaporization-condensation of both water and hydrocarbons are included. The rigorous but general nature of the simulator is obtained by employing conservation balance equations for oxygen, inert gases, a light hydrocarbon pseudocomponent, a heavy hydrocarbon pseudocomponent, water, coke, and energy. pseudocomponent, water, coke, and energy. Vaporization-condensation is governed by vaporliquid equilibrium using temperature and pressure-dependent equilibrium coefficients. Four pressure-dependent equilibrium coefficients. Four chemical reactions are accounted for: formation of coke from the heavy hydrocarbon component and the oxidation of coke and both heavy and light hydrocarbon components. Formulation details, numerical solution procedures, and computational results are presented. procedures, and computational results are presented. The computational results include both one- and two-dimensional cross-sectional studies. The simulator represents a major improvement in the ability to simulate thermal recovery processes under complex conditions. Introduction Considerable progress has been made in numerically simulating thermally enhanced oil-recovery processes during the last few years. This is particularly true for-processes involving steam, where we have seen a continual improvement of our ability to treat the problem. The most recent contributions provide an analysis capability for steam displacement and steam stimulation recovery methods, accounting for all the important physical mechanisms of these processes. Progress in simulating the performance of in-situ combustion processes is not so advanced. Initial simulation attempts were concerned primarily with the heat-transfer aspects of combustion. The most sophisticated heat-transfer model was developed by Chu. His numerical model considers the energy effects of vaporization and condensation on the temperature distribution, but neglects the accompanying phase changes by assuming constant fluid saturations. More recent heat transfer or heat-wave models for the in-situ combustion process were proposed by Kuo in 1969 and by Smith and Farouq-Ali in 1971. Kuo's model allows two temperature fronts-one at the combustion zone and one at a heat front. The heat-front position is predicted by gas flow that is allowed to have a velocity different from the velocity of the combustion front. The simulator proposed by Smith and Farouq-Ali is designed for proposed by Smith and Farouq-Ali is designed for predicting sweep efficiencies in confined well predicting sweep efficiencies in confined well patterns. Their numerical model accounts for heat patterns. Their numerical model accounts for heat generation by a combustion zone (assuming fixed fuel content all through the reservoir), heat transfer by conduction and convection (single-phase gas flow) in the reservoir, heat losses by conduction to adjacent formations, and different permeability-to-gas (air) flow on either side of the combustion zone. Special cases of the in-situ combustion process were studied by Gottfried and Khelil. These authors examine the heat transfer and oxygen use in reservoirs composed of an oil-bearing layer and an overlying "clean" porous zone containing only gas. These models were designed primarily to investigate the various transport mechanisms present when combustion is initiated in a reservoir present when combustion is initiated in a reservoir containing a gas cap. Because of the many assumptions invoked and the specialized geometry to which they apply, they do not satisfy the need for a general purpose simulator. SPEJ P. 37

A Highly Implicit Steamflood Model

Abstract This paper describes a three-dimensional, highly implicit numerical model for simulating steamflooding with distillation or solution gas. The model uses direct solution to solve simultaneously three and four equations for the dead oil and two-component oil cases, respectively. The model is compared in stability and computing time with a model reported earlier. The paper includes comparative discussion of alternate steamflood model formulations, one of which we have adopted as a highly stable, isothermal, black-oil model formulation. Introduction A brief review of published descriptions of steamflood models is given in an earlier paper. That paper described a partially compositional, three-dimensional model that solves first a single-variable pressure equation, then two simultaneous saturation equations. In our experience with dead-oil steamflood problems, that model exhibits adequate stability in most cases and marginal stability in some cases. In some compositional problems, the formulation of that model leads to problems, the formulation of that model leads to deteriorating material balances for light hydrocarbon components. The model described here was developed to gain improved stability for all types of steamflood problems and to eliminate the material balance problems and to eliminate the material balance shortcoming of the earlier model formulation in compositional problems. This highly implicit, three-dimensional model treats oil as a two-component mixture to accommodate problems involving solution or inert gas or distillation. The model simultaneously solves three equations for the dead-oil case and four equations for the compositional case. Transmissibilities, capillary pressures, and production terms are treated pressures, and production terms are treated implicitly in saturations and composition; they also are treated implicitly in temperature in grid blocks where no free gas is present. The term "implicit" refers to evaluation of interblock flow terms and production rates at the new time level, n + 1. We have found insensitivity to explicit or implicit dating of molar densities and viscosities in these terms and therefore simply evaluate them explicitly. We evaluate relative permeabilities at time level n + 1 by the first-order permeabilities at time level n + 1 by the first-order approximation, which ignores second- and higher-order Taylor series terms . Temperature dependence of relative permeability, if present, is treated explicitly. We present the model equations, and describe the highly implicit formulation and method for solution. This model is compared with the earlier steamflood model in stability and efficiency through discussion and example field problems. MODEL DESCRIPTION BASIC EQUATIONS The model consists of five equations expressing conservation of energy, conservation of mass, and phase equilibrium. The mass conservation equations phase equilibrium. The mass conservation equations apply to water and to two hydrocarbon components. In finite-difference form, these equations are Energy Balance (1) Mass Balance on H2O (2) SPEJ P. 369

Geochemical Characterization of Oils in Yabase Oil Field and its Geological Significance

The purpose of this study is to acertain the origin of crude oils accumulated in the Katsurane Formation in the Yabase oil field by geochemical characterization.The characterization of crude oil types is carried out on light hydrocarbon components in the range C4 through C8 and heavy normal alkanes in the range C14 through C34. For the light hydrocarbon components a four-parameter procedure is used. It includes (1) determination of the straight chain, branchedchain and cyclic constituent in C7-compounds; (2) the order of relative concentration in C7-compounds; (3) the change of n-heptane/1 trans 3-dimethylcyclopentane ratio with depth; and (4) the correlation between dimethylpentanes and dimethylcyclopentanes. It has been revealed by this procedure that crude oils in the shallow zone are obviously different from those in the deep zone in the Yabase oil field. The boundary between the shallow and deep zone is located in the middle of the Funakawa Formation, and it coincides with an abnormal pressure zone.In contrast with light hydrocarbons, the distribution of heavy normal alkanes show no difference between the shallow and deep zone, and also fairly maturation.From these results the origin of oils in the shallow zone is concluded to be different from those in the deep zone, and therefore the shallow oils seem to have migrated from the adjacent down-dip area where burial depth is deep enough to originate oil.

Methanol as a Gasoline Extender: A Critique

The tests conducted with the three vehicles at different emission control levels suggest that, in the area of fuel economy and emissions, potential benefits with methanol blends are related to carburetion and are only significant in the case of the rich-operating cars built before emission control standards were imposed. Theoretical considerations related to methanol's leaning effect on carburetion support this conclusion. Potential advantages for methanol in these areas are therefore continuously diminishing as the older cars leave the roads. At present, these older cars use only about one-fourth of the totalc motor gasoline consumed and, before methanol could be used on a large scale, this fraction would be much smaller. The use of methanol in gasoline would almost certainly create severe product quality problems. Water contamination could lead to phase separation in the distribution system and possibly in the car tank as well, and this would require additional investment in fuel handling and blending equipment. Excess fuel volatility in hot weather may also have adverse effects on car performance if the methanol blends include typical concentrations of butanes and pentanes. Removal of these light hydrocarbon components would detract from methanol's role as a gasoline extender and if current fuel volatility specifications were maintained, its use could lead to a net loss in the total available energy for use in motor fuels. Car performance problems associated with excessively lean operation would also be expected in the case of a significant proportion of late-model cars which are adjusted to operate on lean fuel-air mixtures. If methanol does become available in large quantities, these factors suggest that it would be more practical to use it for purposes other than those related to the extending of motor gasoline, such as for gas turbines used for electric power generation. In this case, the "pure" methanol would act as a cleanburning fuel, having none of the potentially severe product quality problems associated with its use in motor gasoline, while the fuel oil or natural gas cLirrently burned in these tuLrbines CotLild be diverted to other ulses.

Effects of Depositional Environment and Postdepositional History on Chemical Composition of Lower Tuscaloosa Oils

The crude oils in lower Tuscaloosa Cretaceous reservoirs in the central Gulf Coast fall into two groups on the basis of their chemical compositions. One of these groups appears indigenous to the lower Tuscaloosa interval. The oils in this group, all in unfaulted structural and stratigraphic traps, are in south-central and southwestern Mississippi, where the lower Tuscaloosa has been subjected to the deepest burial and greatest diagenetic influence. The second group of oils commonly is in lower Tuscaloosa reservoirs on faulted structures. The oils of this group are trapped where secondary migration routes across formational boundaries may have been created, or where younger and/or older source rocks have been brought into contact with the reservoir sandstones. The chemical compositions of the crude oils were determined primarily by chromatographic and mass-spectrometric methods. Most useful were the analyses of the individual light-hydrocarbon components, the sterane naphthenes, the saturate and aromatic hydrocarbon compound types, and the stable carbon-isotope ratios.

Effects of Depositional Environment and Postdepositional History on Chemical Composition of Lower Tuscaloosa Oils: ABSTRACT

The crude oils in lower Tuscaloosa Cretaceous reservoirs in the central Gulf Coast fall into two groups on the basis of their chemical compositions. One of these groups appears indigenous to the lower Tuscaloosa interval. The oils in this group, all in unfaulted structural and stratigraphic traps, are in south-central and southwestern Mississippi, where the lower Tuscaloosa has been subjected to the deepest burial and greatest diagenetic influence. The second group of oils commonly is in lower Tuscaloosa reservoirs on faulted structures. The oils of this group are trapped where secondary migration routes across formational boundaries may have been created, or where younger and/or older source rocks have been brought into contact with the reservoir sandstones. The chemical compositions of the crude oils were determined primarily by chromatographic and mass-spectrometric methods. Most useful were the analyses of the individual light-hydrocarbon components, the sterane naphthenes, the saturate and aromatic hydrocarbon compound types, and the stable carbon-isotope ratios.