Nuclear structure studies in the Te isotopes: The Te(d, p)Te reaction

The reaction ¹²⁵Te(d, p)¹²⁶Te has been studied at a bombarding energy of 7.5 MeV in order to get information about the ¹²⁶Te nuclear level scheme. Forty-two levels were observed below an excitation energy of 5.1 MeV. The angular distributions of 25 of the emitted proton groups were compared with DWBA calculations to determine the angular momentum of the captured neutrons. Contributions from more than one l_n value were observed for two of the transitions. Transition strengths were extracted and compared to pairing-theory calculations.     

Capillary Pressures by Fluid Saturation Profile Measurements During Centrifuge Rotation

A novel centrifuge technique to obtain the capillary pressure curve by measuring the local fluid distribution in a spinning core is presented. The Nuclear Tracer Imaging Centrifuge (NTIC) method measures the fluid saturation profile along the length of the core to directly obtain the capillary pressure curve. The proposed method is superior to conventional centrifuge techniques because (1) the capillary pressure curve is obtained at one rotational speed, (2) core plugs are not removed from the spinning centrifuge for imaging, and (3) no mathematical solution is needed to calculate the capillary pressure curve. The literature states that the various mathematical solutions used in conventional centrifuge tests are the greatest source of error, not the uncertainty in the experimental data. By eliminating the dependence of such solutions, the NTIC represents an alternative to conventional centrifuge tests, and may be used to validate the various mathematical procedures applied in conventional centrifuge capillary pressure tests. NTIC may also confirm the applicability of other imaging techniques that rely on core plug removal for saturation imaging, by verifying if there is no fluid re-distribution at static conditions.     

Ekatantal

Ohne Zusammenfassung     

A study of the S levels and the analogue levels of P by the P(He, d)S reaction

The ³¹P(³He, d)³²S reaction has been studied with high resolution at 12 MeV bombarding energy. A detailed level scheme for ³²S has been determined up to an excitation energy of 9.5 MeV revealing several previously unobserved states. The l_p values and absolute spectroscopic factors extracted from a DWBA analysis of the experimental deuteron angular distributions have provided information on the wave functions for the T = 0 states as well as for the T = 1 isobaric analogue states of ³²P. A comparison between the present data and those of previous experiments is made, and the results are discussed in terms of existing theoretical work in this mass region. Information on Coulomb displacement and symmetry energies is also extracted.     

Wetting Phase Bridges Establish Capillary Continuity Across Open Fractures and Increase Oil Recovery in Mixed-Wet Fractured Chalk

The effect of fractures on oil recovery and in situ saturation development in fractured chalk has been determined at near neutral wettability conditions. Fluid saturation development was monitored both in the matrix and in the fractures and the mechanisms of fracture crossing were determined using high spatial resolution MRI. Capillary continuity across open oil-filled fractures was verified by imaging the water bridges established within the fracture. Despite an alternate escape fracture for the water, separate water bridges were shown to be stable for the entire duration of the experiments. The established capillary contact resulted in oil recovery exceeding the spontaneous imbibition potential in the outlet-isolated cores by ca. 10% PV. This is explained by viscous recovery provided by water bridges across open fractures. The size of the bridges seemed to be controlled by the wettability of the rock and not by the differential pressure applied across the open fracture.     

Die spektrometrische Schlackenanalyse von Roheisen und Stahlschmelzen

Zusammenfassung Die metallurgische Entwicklung erfordert neben der Analyse der Metallschmelzen auch schnelle und rationelle Verfahren zur Schlackenanalyse. Da der Zeit- und Personalbedarf naßchemisch zu hoch ist, wurden die Voraussetzungen und Ergebnisse eines spektrometrischen Verfahrens überprüft. Als wichtig erwies sich die richtige Qualität der Graphit-Radelektroden, die nach Aufschluß und Lösung der Schlacke die Probe in die Anregungszone bringen. Die sonstigen Anregungsbedingungen wurden geklärt, wobei sich besondere Schwierigkeiten beim Silicium zeigten, die aber keine entscheidende Rolle spielen, wenn die Konstanz der Anregungsbedingungen weitgehend gewährleistet ist. Unter dieser Voraussetzung entspricht die Genauigkeit des spektrometrischen der des naßchemischen Verfahrens, doch ist der Zeit- und Personalbedarf der Spektrometrie wesentlich geringer.

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Summary The metallurgical development of the iron and steel industry demands, besides the analysis of metal-melts, quicker and more rational methods for the analyses of slags. As the amount of time and personnel required for wetchemical procedures is too high, conditions and results of a spectroscopic method have been examined. It was found that the appropriate quality of the graphite-wheelelectrodes is most important; these exert, after dissolution of the slag, the sample to the exitation-zone. Further excitation conditions have been examined. Silicon showed some difficulties, but they were not so important, when the exitation conditions were kept as constant as possible. Under these circumstances the accuracy of the spectroscopic method ist equal to that of the wet-chemical method however, the demand of time and personnel, is considerably smaller in spectrometry.

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Vorgetragen auf dem XI. Colloquium Spectroscopicum Internationale, Beograd 31. 10. 1963.     

The 207Pb(d,p)208Pb reaction with high resolution

The reaction ²⁰⁷Pb(d, p)²⁰⁸Pb has been studied at E_d = 18.0 MeV using the MPI Heidelberg Emperor tandem accelerator and multiple-gap spectrograph. The average resolution of 18 keV was better than previous measurements, and this, combined with the long beam exposure, allowed many finer details of the neutron particle-hole structure of ²⁰⁸Pb to be examined. In all, 45 levels were seen up to E_x = 6.3 MeV, many of which had never been seen before. A DWBA analysis of the stripping transitions angular distributions is made, and values of (2J + 1)S_ij, energy centroids, and summed strengths are given. An interesting cluster of 1i_{$\text{11}\text{2}$} and 2g_{$\text{9}\text{2}$} levels at E_x ≈ 4.2 MeV are resolved and are compared to recent isobaric analog state data. A search for weak stripping strength to known pairing vibrations in ²⁰⁸Pb gave essentially negative results and points to the need for improved ultra-resolution measurements.     

Miscible and Immiscible Foam Injection for Mobility Control and EOR in Fractured Oil-Wet Carbonate Rocks

Foam injection is a proven enhanced oil recovery (EOR) technique for heterogeneous reservoirs, but is less studied for EOR in fractured systems. We experimentally investigated tertiary \(\text {CO}_{2}\) injections, and \(\text {N}_{2}\) - and \(\text {CO}_{2}\) -foam injections for enhanced oil recovery in fractured, oil-wet limestone core plugs. Miscible \(\text {CO}_{2}\) and \(\text {CO}_{2}\) -foam was compared with immiscible \(\text {CO}_{2}\) - and \(\text {N}_{2}\) -foam as tertiary recovery techniques, subsequent to waterfloods, in fractured rocks with different wettability preferences. At water-wet conditions waterfloods produced approximately 40 % OOIP, by spontaneous imbibition. Waterflood oil recovery at oil-wet conditions was below 20 % OOIP, due to suppressed imbibition where water predominantly flowed through the fractures, unable to mobilize the oil trapped in the matrix. Tertiary, supercritical \(\text {CO}_{2}\) -mobilized oil trapped in the matrix, particularly at weakly oil-wet conditions, by diffusion. Recovery by diffusion was high due to small core samples, high initial oil saturation and a continuous oil phase at oil-wet conditions. Both immiscible \(\text {CO}_{2}\) - and \(\text {N}_{2}\) -foams and miscible, supercritical \(\text {CO}_{2}\) -foam demonstrated high ultimate oil recoveries, but immiscible foam was less efficient (30 pore volumes injected) compared to miscible foam (2 pore volumes injected) to reach ultimate recovery. This is explained by the capillary threshold pressure preventing the injected \(\text {N}_{2}\) gas from entering the matrix, verified by computed X-ray tomography, and the mobilized oil was displaced by the aqueous surfactant in the foam. At miscible conditions, there exists no capillary entry pressure between the oil-saturated matrix and the injected \(\text {CO}_{2}\) , allowing foam to invade the matrix for efficient oil recovery.     

Using magnetic resonance imaging to monitor CH4 hydrate formation and spontaneous conversion of CH4 hydrate to CO2 hydrate in porous media

Magnetic resonance imaging was used to monitor and quantify methane hydrate formation and exchange in porous media. Conversion of methane hydrate to carbon dioxide hydrate, when exposed to liquid carbon dioxide at 8.27 MPa and ∼4°C, was experimentally demonstrated with MRI data and verified by mass balance calculations of consumed volumes of gases and liquids. No detectable dissociation of the hydrate was measured during the exchange process.