Capillary Pressure

http://store.elsevier.com/Core-Analysis-A-Best-Practice-Guide/Colin-McPhee/isbn-9780444635334/ In the evaluation of oil and gas reservoirs, core analysis provides the only direct and quantitative measurement of the reservoir properties and should provide the foundation or ground truth upon which formation evaluation rests. Geologists, reservoir engineers, and petrophysicists rely on accurate and representative core analysis data to provide key data input for building static and dynamic reservoir models. However, variable laboratory test and data reporting standards have resulted in variable data quality. Coupled with an inconsistent and inexperienced approach to the design and management of the laboratory test programmes, this has led to a situation where, in the authors’ extensive global experience, around 70% of legacy special core analysis (SCAL) data are not fit for purpose. There are few books on core analysis and its applications, and only one industry-recognised recommended practice, which although largely still relevant and appropriate, does not fully cover SCAL and has not been updated for almost over 25 years. The objective of this book is to provide the end users of core analysis data with the essential information that they need to enable a more pro-active, more coherent, and more consistent approach to programme design, data acquisition, and quality control of core analysis data. The authors are actively engaged in the design and management of laboratory core analysis programmes and in interpreting and using the data. Frustrated by the lack of standards and the often inadequate utility of core analysis data, we have written practical and pragmatic guidelines for core analysis best practice that should maximise data quality, encourage more effective engagement between the end users and the data acquisition laboratories, and thereby add value to core analysis investments. Obtaining high-quality, undamaged core is the essential prerequisite for representative and reliable core analysis data. We therefore start by describing the principal coring systems and fluids, and how to identify and minimise damage to the core on its journey from the reservoir to the test laboratory. Analysis is usually performed on plug samples cut from core, so we discuss the methods and equipment used to cut plugs and prepare them for analysis and their impact on the measured properties. Specialist preparation methods for wettability conditioning and preservation of delicate mineralogies are described. Routine core analysis typically involves “as received” fluid saturation measurements, and porosity and permeability measurements on dry plugs, which are used to characterise the reservoir properties and for log-core integration. As the test equipment and methods vary between laboratories, we list the advantages and drawbacks/issues associated with each test and summarise quality control checks and diagnostics. SCAL measures fundamental static and dynamic reservoir rock properties, often at reservoir-appropriate fluid, stress, and temperature conditions. Correct planning for SCAL tests is fundamental to the acquisition of high-quality, formation-representative data, so we focus on: the preparation and characterisation of test fluids; how to select and screen representative test plugs; and how to determine the equivalent reservoir effective stress. Formation wettability is a fundamental rock property. We describe laboratory wettability tests but, more importantly, the controls on native wettability and how wettability can be altered during coring, core recovery, and core handling, and the methods used to try and restore native wettability conditions. We then focus on the principal SCAL tests: porosity and permeability at overburden stress; electrical properties for clean formations and shaly sands; capillary pressure; nuclear magnetic resonance (NMR); and relative permeability. We explain the various core test conditions, test methods, equipment, and procedures, and data reporting requirements. The advantages and drawbacks/issues of each suite of tests are described, and the quality control checks and diagnostics are summarised. We clarify the corrections and refinement protocols used to process laboratory data for static and dynamic model input. As core also supplies a source for geomechanical measurements for faster and safer drilling and better completions, we include a chapter on rock mechanics tests and particle size analysis tests. Finally, we provide generic examples of core analysis test programmes that the reader can use as guide or template to design and specify the workflow for core test programmes on oil and gas reservoirs. Following the best practice guidelines in this book will benefit petrophysicists, geoscientists, reservoir engineers, and production engineers who use the data but are often unaware of the uncertainty range. These are merely guidelines, gained from years of experience, and are necessarily…

Production decline in several fields in Concordia Parish, Louisiana, has sparked interest in the economic feasibility of producing the remaining bypassed oil in the lower Wilcox. One of these fields, the Bee Brake field, located in townships 4N, 6E and 4N, 7E, has been one of the more prolific oil-producing areas in east central Louisiana. The producing interval in the

We have developed a user friendly computational tool, Homogenizer++, for the computation of effective parameters. The platform Homogenizer++ is based on Object Oriented Programming approach. It currently includes modules to compute effective permeability, effective capillary pressures and relative permeabilities, macrodiffusion in solute transport and simples code for computing solutions for flow in porous media

Water management in polymer electrolyte membrane (PEM) fuel cells is of importance due to its impact on the performance, durability and ultimately the cost of the cell. In the gas diffusion layer (GDL), liquid water has a direct effect on species and heat transport. The amount of liquid water in the GDL affects the relative permeability and capillary pressure, which govern the convective and diffusive transport of liquid water. Liquid water acts as a barrier to the diffusion of gases through the void region and facilitates in heat transfer. In this study, the full morphology model was used in order to investigate the effects of liquid water presence on the transport properties of the carbon paper GDL and examine the applicability of using various laws to estimate the transport properties in the presence of liquid water. The numerical results were compared against published experimental data. Further, the method of standard porosimetry was used to experimentally measure the effect of...

Improved oil recovery from fractured oil-wet carbonate reservoirs is a great challenge. The water-flooding efficiency will be low because of higher permeability in fractures than in matrix, and negative capillary pressure retains oil inside the matrix blocks. Studies of oil-wet chalk have shown that sulphate ions in the seawater may alter the wettability towards increased water-wetness. One-dimensional spontaneous imbibition tests of seawater into preferentially oil-wet chalk cores are performed. To get a better understanding, a numerical model has been developed which includes effects of wettability alteration. The experiments are carried out on cylindrical, sealed core plugs with only top open or with both ends open. Only countercurrent imbibition takes place for cores with top end open. For cores with both ends open, both countercurrent and cocurrent imbibition take place, and oil recovery rate is obviously accelerated. Taking formation water as the base case, higher oil recovery...

The study of multiphase flow and heat flow in partially saturated porous media is important in environmental geomechanics engineering because of its relevance to consolidation of porous media in unsaturated zone. A numerical model which describes the thermo–hydro–mechanical (THM) coupled problems in deformable porous material with two–phase flow has been developed. The relationships between capillary pressure, saturation of water and relative permeabilities of water and gas, proposed by Brooks and Corey was used. An extended study of the numerical model, based on the COMES–GEO code was conducted recently to solve unsaturated problems in local condition of Kg. Puteh wellfield, Kota Bahru. This site is a potential shallow aquifer which contribute to the largest groundwater supply in Kota Bahru, Kelantan. Some numerical investigation on the proposed formulation is discussed with illustrative example problems to demonstrate solution procedures and validating of the model.

The purpose of this study is to investigate factors that affect the formation of fluid banks during gravity-driven counter-current flow in porous media. To our knowledge, development of a fluid bank has been observed in only one previous counter-current flow experiment, although there are some hints of fluid banks in other experiments. To confirm or deny the existence of such

A semianalytic method for calculation of relative permeabilities from unsteady-state displacement data is developed. The method is based on the simultaneous solution of the fractional-flow equation and an integro-differential equation, derived from the material-balance and Darcy equations for immiscible displacement of two incompressible phases, including the capillary pressure by use of various volumetric relationships. This method for calculating two-phase relative permeabilities from unsteady-state displacement data is not restricted to the high-flow-rate experimental conditions used to overcome capillary and effects. Removal of this restriction allows the analysis of low-permeability cores with water and oil where the flow rates are low and capillary end effects are important. Our method allows direct calculation from the experimental data without intermediate interpretations of graphs.

Vadose zone description of multi-fluid flow requires measurement techniques capable of determining the capillary pressure and permeability functions of multi-fluid soil systems. Multi-step outflow experiments are presented that use a modified Tempe cell for air–water, oil (Soltrol)–water, and air–oil fluid pairs in Columbia fine sandy loam and a Lincoln sandy loam. In addition to measurements of cumulative outflow and wetting fluid pressure in outflow experiments of air displacing water or oil, pressure changes of the oil (non-wetting fluid) were measured in oil–water experiments. Results from the multi-step measurements were successfully used to directly estimate capillary pressure–saturation and wetting fluid permeability functions. The capillary pressure saturation data for each fluid pair were scaled using their interfacial tension values relative to that of air–water, thereby yielding a combined capillary pressure–saturation curve for the three measured fluid pairs. The combined relative permeability data for both soils nearly coalesce to a single curve, indicating that the relative permeability is solely a function of the porous medium properties. Furthermore, the directly estimated permeability data agreed well with permeability functions obtained using a parameter estimation approach, by which parameters were optimized from comparison of observed and numerically-simulated values of capillary pressure and cumulative outflow.

The effects of shape and contact angle on the behaviour of orthorhombic particles at an interface and in thin films were investigated using Surface Evolver[1]. It is shown that the energetically stable orientations of the particle change with its aspect ratio. Long, wide, flat particles with low contact angles are more stable in flat orientations, i.e. with two faces parallel to the flat film surface. More cubic particles with higher contact angles are more stable in twisted orientations, where the opposite sides of the film can be drawn together at the sharp edges of the particle.The combination of contact angle and orientation has been found to have a large effect on the capillary pressure required to rupture the film. A film containing a particle in a flat orientation will rupture at a capillary pressure up to three times greater than one containing an identical particle in a twisted orientation. Wider, flatter particles with low contact angles stabilise thin liquid films to a greater extent than cubic particles with high contact angles.Simulations of orthorhombic particles of different aspect ratio attached to a thin film are used to identify their energetically stable orientations, which affect the film stability.► Shape and contact angle affect a particle’s stable orientations. ► Orientation affects film stability. ►Four types of orientation: horizontal, vertical, rotated and diagonal. ► Wider, flatter particles require higher failure pressures.

Capillary pressure is considered in packed-beds of spherical particles. In the case of gas–liquid flows in packed-bed reactors, capillary pressure gradients can have a significant influence on liquid distribution and, consequently, on the overall reactor performance. In particular, capillary pressure is important for non-uniform liquid distribution, causing liquid spreading as it flows down the packing. An analytical model for capillary pressure–saturation relation is developed for the pendular and funicular regions and the factors affecting capillary pressure in the capillary region are discussed. The present model is compared to the capillary pressure models of Grosser et al. (AIChE J., 34:1850–1860, 1988) and Attou and Ferschneider (Chem. Eng. Sci., 55:491–511, 2000) and to the experiments of Dodds and Srivastava (Part Part Syst. Charact., 23:29–39, 2006) and Dullien et al. (J. Colloid Interface Sci., 127:362–372, 1989). The non-homogeneity of real packings is considered through particle size and porosity distributions. The model is based on the assumption that the particles are covered with a liquid film, which provides hydrodynamic continuity. This makes the model more suitable for porous or rough particles than for non-porous smooth particles. The main improvements of the present model are found in the pendular region, where the liquid dispersion due to capillary pressure gradients is most significant. The model can be used to improve the hydrodynamic models (e.g., CFD and cellular automata models) for packed-bed reactors, such as trickle-bed reactors, where gas, liquid, and solid phases are present. Models for such reactors have become quite common lately (Sáez and Carbonell, AIChE J., 31:52–62, 1985; Holub et al., Chem. Eng. Sci, 47, 2343–2348, 1992; Attou et al., Chem. Eng. Sci., 54:785–802, 1999; Iliuta and Larachi, Chem. Eng. Sci., 54:5039–5045, 1999, IJCRE 3:R4, 2005; Narasimhan et al., AIChE J., 48:2459–2474, 2002), but they still lack proper terms causing liquid dispersion.

We consider the two-phase flow through a dual-porosity medium, characterized by a period of heterogeneity ω, a ratio of global permeabilities ∈K, and a ratio of the order of capillary forces ∈c. The limit when ω tends to zero at different values of ∈K and ∈c gives four classes of global behavior, differing by the type of elementary flows at the one-cell level. We propose a diagram of their predominance. A macro-scale model is constructed by formal homogenization techniques for one of these classes; it shows a nonlinear kinetic relationship for the averaged capillary pressure functions, and leads to a decomposition for the effective phase permeability tensors. A capillary relaxation time is explicitly determined.