Experimental Study of Polymer-Free and Polymer-Added Foams for Underbalanced Drilling: Are Two Foam-Flow Regimes Still There?

SPE Journal ◽  
2013 ◽  
Vol 19 (01) ◽  
pp. 55-68 ◽  
Author(s):  
A.R.. R. Edrisi ◽  
R.N.. N. Gajbhiye ◽  
S.I.. I. Kam
Keyword(s):  
Steady State ◽  
Flow Pattern ◽  
Plug Flow ◽  
Flow Regimes ◽  
High Quality ◽  
Pressure Drops ◽  
Foam Flow ◽  
Underbalanced Drilling ◽  
Segregated Flow ◽  
State Pressure

Summary The foam-assisted underbalanced-drilling technique is more advantageous than the traditional overbalanced drilling near the productive water-sensitive formations because of its reduced formation damage, improved rate of penetration, higher cuttings-transport capacity, and lower circulation losses. However, the complicated nature of foam rheology has been a major impediment to the optimal design of field applications. Earlier studies with surfactant foams without oils and polymers show that foam flow in pipe can be represented by two different flow regimes: the low-quality regime showing either plug-flow or segregated-flow pattern, and the high-quality regime showing slug-flow pattern. The objective of this study is to investigate foam-flow characteristics in horizontal pipes at different injection conditions, with or without oils, by using polymer-free and polymer-added surfactant foams. The results of this study were presented in two different ways—by steady-state pressure drops (or, apparent foam viscosity, equivalently) measured by multiple pressure taps and by the visualization of bubble size, size distribution, and flow patterns in transparent pipes. The results with surfactant foams and oil showed that first, oil reduced the stability of foams in pipes, thus decreasing the steady-state pressure drops and foam viscosities, and second, the presence of oil tended to lower the transition between the high-quality and the low-quality regimes (i.e., lower foam quality at the boundary, or lower f*g equivalently). In addition, the results with surfactant foams with polymer showed that first, polymer thickened the liquid phase and, if enough agitation was supplied, could make foams long-lived and increase foam viscosities, and second, the system sometimes did not reach the steady state readily, showing systematic oscillations. In both cases, though, the experiments carried out in this study showed the presence of two distinct high-quality and low-quality flow regimes.

scholarly journals Quantitative Modeling of the Effect of Oil on Foam for Enhanced Oil Recovery

SPE Journal ◽  
2019 ◽  
Vol 24 (03) ◽  
pp. 1057-1075 ◽  
Author(s):  
Jinyu Tang ◽  
Mohammed N. Ansari ◽  
William R. Rossen
Keyword(s):  
Steady State ◽  
Pressure Gradient ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Flow Regimes ◽  
Multiple Steady States ◽  
High Quality ◽  
Foam Model ◽  
Model Oil ◽  
Dry Out

Summary The effectiveness of foam for mobility control in the presence of oil is key to foam enhanced oil recovery (EOR). A fundamental property of foam EOR is the existence of two steady-state flow regimes: the high-quality regime and the low-quality regime. Experimental studies have sought to understand the effect of oil on foam through its effect on these two regimes. Here, we explore the effect of oil on the two flow regimes for one widely used foam model. The STARS (CMG 2015) foam model includes two algorithms for the effect of oil on foam: In the “wet-foam” model, oil changes the mobility of full-strength foam in the low-quality regime, and in the “dry-out” model, oil alters the limiting water saturation around which foam collapses. We examine their effects as represented in each model on the two flow regimes using a Corey relative permeability function for oil. Specifically, we plot the pressure-gradient contours that define the two flow regimes as a function of superficial velocities of water, gas, and oil, and show how oil shifts behavior in the regimes. The wet-foam model shifts behavior in the low-quality regime with no direct effect on the high-quality regime. The dry-out model shifts behavior in the high-quality regime but not the low-quality regime. At fixed superficial velocities, both models predict multiple steady states at some injection conditions. We perform a stability analysis of these states using a simple 1D simulator with and without incorporating capillary diffusion. The steady state attained after injection depends on the initial state. In some cases, it appears that the steady state at the intermediate pressure gradient is inherently unstable, as represented in the model. In some cases, the introduction of capillary diffusion is required to attain a uniform steady state in the medium. The existence of multiple steady states, with the intermediate one being unstable, is reminiscent of catastrophe theory and of studies of foam generation without oil.

scholarly journals Experimental Investigation of the Effect of Oil on Steady-State Foam Flow in Porous Media

SPE Journal ◽  
2018 ◽  
Vol 24 (01) ◽  
pp. 140-157 ◽  
Author(s):  
Jinyu Tang ◽  
Sebastien Vincent-Bonnieu ◽  
William R. Rossen
Keyword(s):  
Porous Media ◽  
Steady State ◽  
Fixed Ratio ◽  
Shear Thinning ◽  
Flow In Porous Media ◽  
Oil Composition ◽  
Fractional Flow ◽  
High Quality ◽  
Oil Saturation ◽  
Foam Flow

Summary Foam flow in porous media without oil shows two regimes depending on foam quality (gas fractional flow). Complexity and limited data on foam/oil interactions in porous media greatly restrict understanding of foam in contact with oil. Distinguishing which regimes are affected by oil is key to modeling the effect of oil on foam. We report steady-state corefloods to investigate the effect of oil on foam through its effect on the two flow regimes. We fit the parameters of a widely used local-equilibrium (LE) foam model to data for concurrent foam/oil flow. This research provides a practical approach and initial data for simulating foam enhanced oil recovery (EOR) in the presence of oil. To ensure steady state, oil is coinjected with foam at a fixed ratio of oil (Uo) to water (Uw) superficial velocities in a Bentheimer Sandstone core. Model oils used here consist of a composition of hexadecane, which is benign to foam stability, and oleic acid (OA), which can destroy foam. Varying the concentration of OA in the model oil allows one to examine the effect of oil composition on steady-state foam flow. Experimental results show that oil affects both high- and low-quality regimes, with the high-quality regime being more sensitive to oil. In particular, oil increases the limiting water saturation (Sw*) in the high-quality regime and also reduces gas-mobility reduction in the low-quality regime. Unevenly spaced ▿p contours in the high-quality regime suggest either strongly shear-thinning behavior or an increasingly destabilizing effect of oil. In some cases, the pressure gradient (▿p) in the low-quality regime decreases with increasing Uw at fixed gas superficial velocity (Ug), either with or without oil. This might reflect either an effect of oil, if oil is present, or easier flow of bubbles under wetter conditions. Increasing the OA concentration extends the high-quality regime to lower foam qualities, indicating more difficulty in stabilizing foam. Thus, oil composition plays as significant a role as oil saturation (So). A model fit assuming a fixed Sw* and including shear thinning in the low-quality regime does not represent the two regimes when the oil effect is strong enough. In such cases, fitting Sw* to each ▿p contour and excluding shear thinning in the low-quality regime yield a better match to these data. The dependency of Sw* on So is not yet clear because of the absence of oil-saturation data in this study. Furthermore, none of the current foam-simulation models captures the upward-tilting ▿p contours in the low-quality regime.

A New Foam Model in Pipes for Drilling and Fracturing Applications

SPE Journal ◽  
2013 ◽  
Vol 19 (04) ◽  
pp. 576-585 ◽  
Author(s):  
A.R.. R. Edrisi ◽  
S.I.. I. Kam
Keyword(s):  
Flow Pattern ◽  
Power Law ◽  
Relative Size ◽  
Experimental Studies ◽  
Unstable Flow ◽  
High Quality ◽  
Foam Flow ◽  
Foam Model ◽  
Power Law Fluids ◽  
Foam Rheology

Summary A series of recent experimental studies revealed that foam flow can be represented by two distinct flow regimes in general—low-quality regime, showing stable plug-flow pattern, and high-quality regime, showing unstable slug-flow pattern. This study, for the first time, presents how to develop a comprehensive foam model that can handle a variety of bubble-size distributions and both stable and unstable flow patterns with a two-flow-regime concept. Building an improved foam model on the basis of such a new concept can potentially help to better design and optimize many foam-associated processes including tight-gas and shale-gas foam fracturing, foam underbalanced drilling, foam liquid unloading, and cuttings transport. Analyzing the experimental data of surfactant foams and polymer-added foams shows that (i) in the low-quality regime, foam rheology is governed by bubble slippage at the wall with no significant change in its fine foam texture and (ii) in the high-quality regime, foam rheology is governed by the relative size of free-gas segment to fine-textured foam-slug segment. With these governing mechanisms, this improved foam model successfully reproduces foam-flow characteristics as observed in the experiments, including almost-horizontal pressure contours in the low-quality regime and inclined pressure contours in the high-quality regime. Although the model is built with a power-law fluid model, the same procedure can be applied for Bingham-plastic or yield-power-law fluids.

Steady State Measurement of Oxygenation Capacity

1985 ◽  
Vol 17 (2-3) ◽  
pp. 303-311
Author(s):  
Kees de Korte ◽  
Peter Smits
Keyword(s):  
Steady State ◽  
Activated Sludge ◽  
Plug Flow ◽  
Usual Method ◽  
Steady State Method ◽  
State Measurement ◽  
Flow Systems ◽  
Air System ◽  
State Method ◽  
Steady State Measurement

The usual method for OC measurement is the non-steady state method (reaeration) in tapwater or, sometimes, in activated sludge. Both methods are more or less difficult and expensive. The steady state method with activated sludge is presented. Fundamentals are discussed. For complete mixed aeration tanks, plug flow systems with diffused air aeration and carousels the method is described more in detail and the results of measurements are presented. The results of the steady state measurements of the diffused air system are compared with those of the reaeration method in tapwater. The accuracy of the measurements in the 3 systems is discussed. Measurements in other aeration systems are described briefly. It is concluded that the steady state OC measurement offers advantages in comparison with the non-steady state method and is useful for most purposes.

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