Secondary Imbibition Research Articles

Effect of Capillary Heterogeneity on Buckley-Leverett Displacement

Summary The Buckley-Leverett (BL) equation has been routinely used for the description of immiscible displacement in laboratory Dperations and for parameter estimation and prediction. Recent advances, however, have led to a serious challenge of the validity of many of the traditional theories. For the case of BL displacement, most studies have examined heterogeneity effets as they relate to. viscous fingering. In this paper, we investigate the effects of capillary heterogeneity induced by variations in permeability in the direction of displacement. We study a variety of heterogeneity profiles, both uncorrelated and correlated spatially. We find that capillary heterogeneity significantly affects the saturation distributions, which closely follow the heterogeneity variation. The saturation response is stronger at lower rates, at more unfavorable mobility, under drainage conditions, and for smaller spatial correlations. The results are in agreement with available experimental data for primary drainage and secondary imbibition. They may be useful in the interpretation of saturation profiles and the identification of heterogeneity.

Low-contrast secondary imbibition in long rock cores

The chemical-shift-resolved N.M.R. imaging method developed by Horsfield et al. 10, 11 for quantification of two-phase saturations in permeable rock samples exhibiting broad spectral lines is applied to the observation of secondary imbibition processes in long rock cores. Time-lapsed, semi-quantitative water saturation profiles are obtained during a secondary imbibition in a moderate permeability (< 0.028 μm 2) limestone exhibiting imperfectly resolved aqueous and hydrocarbon proton resonances. Imaging of a core 30 cm long, in a magnet with a nominal 5 cm diameter spherical volume usable for chemical shift imaging, is accomplished by multiple image acquisition and overlapping segmentation of the desired field of view. Local B 0 field correction is achieved by analysis of a Dixon opposed-phase image 5 by the phase-slope method. 2 Although vulnerable to failure where the aqueous and hydrocarbon saturations are nearly balanced, successful observations are made of secondary imbibition fronts of low water-oil contrast where the water saturation may cross 0.5.

Saturation Distributions During Displacements Generated by the Simultaneous Injection of Oil and Water

Summary Linear oil/water displacement behavior in a water-wet Berea sandstone is examined experimentally with a scanning microwave absorption system. It is observed that simultaneous injection of oil and water into a core initially at residual oil saturation (ROS) produces a region of anomalously high oil saturation and fractional flow, or an oil hump, at the leading edge of the displacement. This region grows in both saturation and breadth as the flood progresses. Studies at different injection rates and WOR’s indicate that the saturation, fractional flow, and propagation behavior of the oil hump are strongly influenced by rate and ratio. The displacements from ROS confirm the secondary imbibition and drainage results for fractional flow obtained by a sequence of small displacements. A strong hysteresis effect is indicated by these results. The displacements from ROS also reveal the existence of a complex network of inner scanning loops in the steady-state fractional flow behavior. These studies indicate that for sufficiently high injection rate, all displacements above a minimum injected WOR will eventually produce a displacement front approaching that of an oilflood. The frontal saturation and fractional flow for the oilflood case are found to be significantly greater than that predicted by the graphic tangent-point construction of Buckley-Leverett (B-L) theory. This result, along with the observed rate dependence of the hump, suggests that traditional B-L theory, even with fractional flow hysteresis included, might not adequately describe oil/water displacement. It is suggested that transient flow response near a wave front is responsible for the observed displacement behavior.

Simulation of capillary pressure curves using bond correlated site percolation on a simple cubic network

A stochastic approach to network modelling has been used to simulate quasi-static immiscible displacement in porous media. Both number-based and volume-based network saturation results were obtained. Number-based results include: number-based saturation curves for primary drainage, secondary imbibition and secondary drainage, fluid distribution data, and cluster trapping history. Using pore structure data of porous media, it is possible to convert the number-based curves to capillary pressure — saturation relationships. Pore size distribution functions and pore shapes which are thought to closely represent Berea sandstone samples were used to predict the capillary curves. The physical basis of these calculations is a one-to-one correspondence between the cumulative node and bond index fractions in the network analysis, and the cumulative number-based distributions of pore body and pore throat diameters, respectively. The oil-water capillary pressure curve simulated for primary drainage closely resembles those measured experimentally. The agreement between the simulated and the measured secondary imbition and secondary drainage curves is less satisfactory.

Lupus erythematosus with fatal hemorrhage into the liver and lesions resembling those of periarteritis nodosa and malignant hypertension: Immunocytochemical observations

Immunocytochemical studies were made in a patient with lupus erythematosus also exhibiting lesions resembling those seen in periarteritis nodosa and malignant nephrosclerosis, including healed and healing vascular lesions in medium-sized arteries in various abdominal organs, rupture of an aneurysm of a branch of the hepatic artery, and necrotizing lesions in the renal arterioles. Gamma globulin, complement, albumin and fibrinogen were found in the vascular lesions; in the renal glomeruli, gamma globulin was associated only with complement. It is suggested that these lesions have a common pathogenesis: harmful antigenantibody complexes and complement are localized in glomeruli and vessels, the latter injured by hypertension, producing increased permeability and secondary imbibition with plasma proteins.