Joanne M. Wolcott

Stereochemistry of reactions in the 1,2-dimethylsilacyclopentane ring system. II. Stereoselective transformation

Abstract Preparations, separations of geometric isomers, and structural assignments based on nmr and on chemical evidence are described for a number of 1-substituted 1,2-dimethylsilacyclopentanes. A number of stereospecific reactions have been observed, and the stereochemistry is in all cases the same as that observed for acyclic silanes. A discussion of the role of ring strain in determining stereochemical outcome and reaction rates is presented.

Solvent-catalyzed cis-trans isomerization of halosilacyclo-butanes and -pentanes. Evidence for cationic intermediates with expanded coordination

Abstract 1-Chloro-l,2,-dimethylsilacyclo-butane (IV)and-pentane (V) undergo cis-trans isomerization catalyzed by a variety of nucleophilic species, including polar aprotic solvents. Kinetics of the process have been investigated for HMPT in CCl4. Rate laws and the observation of HMPT-catalyzed halogen exchange between bromo- and chloro-silanes lead to the conclusion that 5-coordinate siliconium ions are intermediates in this process. Evidence is also presented that pentacoordinate species formed from V (but not from IV) undergo rapid pseudorotations.

Improved Cyclic Stimulation Using Gas Mixtures

Cyclic gas injection processes have been primarily restricted to the use of pure CO{sub 2} or CO{sub 2} that has been slightly contaminated with reservoir gases. However, it is difficult to employ CO{sub 2} in certain circumstances due to transport, economic, or corrosion problems. This paper presents the results of laboratory investigations of the cyclic gas injection process using methane, nitrogen and mixtures of these gases with CO{sub 2}. Cyclic gas injections were performed at immiscible conditions in consolidated sandstone cores that contained waterflood residual oil. Cyclic CO{sub 2} injections were performed under analogous conditions for comparative purposes. Pure methane recovered approximately the same amount of waterflood residual oil as CO{sub 2} whereas pure nitrogen recovered about half that amount. Pure CO{sub 2} was more mobile in porous media than pure CH{sub 4} or N{sub 2}. Certain CO{sub 2}/N{sub 2} and CO{sub 2}/CH{sub 4} mixtures yielded outstanding results, recovering 2-3 times the waterflood residual oil produced by pure CO{sub 2}. Maximum recovery was obtained with mixtures containing 10-25% CO{sub 2}.

Screening Criteria for Application of Carbon Dioxide Miscible Displacement in Waterflooded Reservoirs Containing Light Oil

In conjunction with a joint Texaco/DOE research project, the LSU Department of Petroleum Engineering developed an improved method of screening reservoirs for the application of the carbon dioxide miscible enhanced oil recovery (EOR) process. This method, which can be applied to a large number of reservoirs, considers both the technical and economic feasibility of the EOR process. The technical parameters of each reservoir are first compared to those of an ideal reservoir ; and from that comparison, each reservoir is assigned a technical ranking. The technical ranking is used to estimate expected recovery. Key technical parameters used in the screening process are remaining oil in place, minimum miscibility pressure, reservoir depth, oil API gravity, and formation dip angle. The reservoirs are subsequently screened for economic feasibility based on standardized capital costs and operation expenses that are representative of the reservoirs under consideration. The reservoirs are finally ranked based on the present worth value of revenues to costs ratio. Using this method, we screened a database containing 197 light-oil reservoirs in Louisiana. The database includes three reservoirs where CO 2 miscible floods are ongoing ; these reservoirs ranked first, fifth, and thirtieth. The high ranking of these reservoirs, which were identified based on detailed and comprehensive reservoir studies, validates the screening method. Different application options in a specific reservoir can be screened, if warranted, by using CO 2 -PROPHET, a PC compatible software. CO 2 -PROPHET is a relatively simple numerical model capable of simulating water and gas floods. An example of its application is included.

A parametric investigation of the cyclic CO2 injection process

Abstract The influences of important process and reservoir parameters on the cyclic CO 2 injection process were investigated. The parameters examined included gravity segregation, remaining oil saturation, reservoir dip, the presence of a gas cap, and the use of a drive gas. Experiments were performed in Berea Sandstone cores using a light crude oil from the Timbalier Bay field. Gravity segregation, the presence of a gas cap, and a higher remaining oil saturation improved process performance. Oil recovery efficiencies and gas utilization factors were affected by the inclination of the core and the site of injection. Process performance was benefitted when CO 2 was injected into the lower end of a core tilted at an angle of 45 ° or more. A poorer response was obtained when the core was horizontal or when CO 2 was injected into the top of a tilted core. The use of a nitrogen drive (or chase) gas dramatically boosted oil recovery as compared to injection of the same mass of CO 2 alone. Over twice as much oil was recovered by the first cycle injection of CO 2 followed by nitrogen as compared to first cycle injection of that mass of CO 2 alone. The second injection cycle of the drive gas experiment recovered over three times as much oil as recovered by a second cycle injection of that mass of CO 2 alone.

AN INVESTIGATION OF THE FACTORS INFLUENCING TRANS [ENT INTERFACIAL TENSION BEHAVIOR IN CRUDE OIL/ALKALINE WATER SYSTEMS

Abstract The interfacial tension (IFT) dynamics of crude oil/alkaline water systems have been examined using the spinning drop interfacial tensiometer. Both synthetic and natural crudes were employed in the study; however, it was found that synthetic crudes frequently exhibited behavior quite different from that observed with natural crudes. Two crude oils were fractionated and the interfacial tension behavior of the fractions against alkaline water was investigated. Interfacial tension reduction was related to the presence of carboxylic acid components. The stabilities of the interfacial tension minima with time were related to the water solubility of the surface active species, and the ease of formation of their surface inactive, undissociated acid salts, as well as, the temperature and oil viscosities. The use of the spinning drop interfacial tensiometer in evaluating the IFT behavior of crude oil/alkaline systems was assessed.

Alcohol-assisted alkaline flooding for enhanced oil recovery

Abstract Alcohol additives were found to improve alkaline flood performance under certain conditions. Only crude oils that emulsified during alkaline flooding were more efficiently recovered with alcohol. Improved recovery with alcohol was attributed to modification of emulsion characteristics. Alcohol additives reduced emulsion viscosities and accelerated emulsion coalescence rates, which improved oil bank stability and promoted oil recovery. Oil recovery efficiency was affected by the chemical structure of the alcohol. Oil recovery generally improved with increasing molecular weight from methanol to butanol and then decreased for the less water soluble pentanol isomers. Alcohol additives were found to affect the interfacial shear viscosities (IFSV) and interfacial tensions (IFT) of crude oil/alkaline water systems. Improvements in recovery efficiency was found to correspond directly to reduced IFSV. Poor recovery was also related to elevated interfacial tensions.

An improved model for the interfacial behavior of caustic/crude oil systems

The effects of crude oil acid number and brine concentration on the interfacial behavior of caustic/crude oil systems were investigated. The effect of increased brine concentration was generally to increase the minimum interfacial tension (IFT) while low IFT values were retained for longer periods of time. Varying the crude oil acid number caused the shape of the IFT versus time curve to change, while the minimum IFT remained constant. These combined results imply that Lagmuir and not Henry soption (adsorption/desorption) kinetics were operative A phenomenological surface phase model for the IFT behavior of caustic/crude oil systems is proposed which incorporates Langmuir kinetics. The model takes into account interfacial activities of the acidic components in the crude and the detailed chemistry of the oil phase, the water phase, and the interface. To allow for realistic comparison of model results with interfacial tensiometer data, drastic interfacial volume changes which accompany the transient interfa...

Lithium aluminum hydride reduction of 1,2-dimethyl-1-fluorosilacylopentane; The role of extra-coordinate intermediates

Abstract Isomerization occurs in the course of LiAlH 4 reduction of the geometric isomers of 1,2-dimethyl-1-fluorosilacyclobutane (I). Neither I nor the hydr

Effect of pressure on solid-liquid equilibrium for the system carbon dioxide/n-decane/n-octacosane

Abstract Solid-liquid saturation lines (pressure vs temperature for a saturated solution of given composition) were determined for n-octacosane in mixtures of n-decane and carbon dioxide. The carbon dioxide content of the solutions ranged from 0 to 90 mol %, at pressures up to 25 MPa. The data were correlated by means of the perturbed hard sphere chain equation of state. The equation of state requires three pure component constants for each component plus three binary interaction parameters. Two of the interaction parameters were obtained from binary data. The third was adjusted to fit the ternary data. The correlation was satisfactory for carbon dioxide contents up to 80 mol %. For higher carbon dioxide levels the octacosane solubility predicted by the correlation was consistently low.