Issue with Stone-II Three Phase Permeability Model, and A Novel Robust Fundamentals-Based Alternative to It

The objective of this paper is to present a fundamentals-based, consistent with observation, three-phase flow model that avoids the pitfalls of conventional models such as Stone-II or Baker's three-phase permeability models. While investigating the myth of residual oil saturation in SAGD with comparing model generated results against field data, Gupta et al. (2020) highlighted the difficulty in matching observed residual oil saturation in steamed reservoir with Stone-II and Baker's linear models. Though the use of Stone-II model is very popular for three-phase flow across the industry, one issue in the context of gravity drainage is how it appears to counter-intuitively limit the flow of oil when water is present near its irreducible saturation. The current work begins with describing the problem with existing combinatorial methods such as Stone-II, which in turn combine the water-oil, and gas-oil relative permeability curves to yield the oil relative permeability curve in presence of water and gas. Then starting with the fundamentals of laminar flow in capillaries and with successive analogical formulations, it develops expressions that directly yield the relative permeabilities for all three phases. In this it assumes a pore size distribution approximated by functions used earlier in the literature for deriving two-phase relative permeability curves. The outlined approach by-passes the need for having combinatorial functions such as prescribed by Stone or Baker. The model so developed is simple to use, and it avoids the unnatural phenomenon or discrepancy due to a mathematical artefact described in the context of Stone-II above. The model also explains why in the past some researchers have found relative permeability to be a function of temperature. The new model is also amenable to be determined experimentally, instead of being based on an assumed pore-size distribution. In that context it serves as a set of skeletal functions of known dependencies on various saturations, leaving constants to be determined experimentally. The novelty of the work is in development of a three-phase relative permeability model that is based on fundamentals of flow in fine channels and which explains the observed results in the context of flow in porous media better. The significance of the work includes, aside from predicting results more in line with expectations and an explanation of temperature dependent relative permeabilities of oil, a more reliable time dependent residual oleic-phase saturation in the context of gravity-based oil recovery methods.

Modeling of oil phase displacement processes in heterogeneous anisotropic reservoirs

Methods of computer modeling of slightly permeable anisotropic oil-bearing layers are needed nowadays because they give us a possibility to obtain a concept on filtration processes near producing and forcing wells in different practical situations and in this way to raise the level of exploitation of such layers significantly. On the other hand, they allow evaluation and taking into account some uncertainties which appear as a result of inefficient information on the structure and properties of the layer outside the wells. In order to investigate the practical aspects of supporting efficiency of oil production in anisotropic heterogeneous low permeable reservoirs on the base of combined finite-element-difference method for solving the non-stationary anisotropic piezoconductivity problem, modeling of distribution of layer pressure was carried out in the vicinity of the production and forcing wells taking into account the anisotropy of the permeability and conditions of the oil phase infiltration on the margins of the examined layer. It has been found that the intensity of filtration process between producing and forcing wells depends essentially on their spacing in both shear-isotropic and anisotropic oil-bearing layers. In addition the effect of oil phase permeability in shear direction dominates over the effect of permeability in axes directions. Starting from the obtained information for the effective exploitation of anisotropic slightly permeable layers we need to locate producing and forcing wells in the areas with relatively low permeability of the layer and especially to avoid the places with presence of shear permeability. It is important to locate the wells in such a way that blocking the oil in the direction of reduced permeability and fast depletion of the layer in the direction of increased permeability would not happen as well as mutual exchange between producing and forcing wells would not stop. While locating the system of specified wells within anisotropic layers of oil deposit it is necessary to conduct a systemic analysis of environmental anisotropy of layers aimed at such a location of these wells which would guarantee the effective dynamics of filtration processes around them. Application of quadratic isoparametric approximation of finite-elemental net of examined area of oil-bearing layer and implicit differential time approximation brings to increase of precision and stability of numerical solution of the problem.

Experimental studies of the capillary desaturation curve in polymer-surfactant flooding

The paper presents the results of laboratory studies of polymer-surfactant flooding on core samples of different permeability. The obtained data are used in hydrodynamic modeling. Experimental studies included: • study of the dynamics of oil displacement, plotting the dependence of the residual oil saturation on the surfactant concentration – interfacial tension at the interface of the surfactant-oil solution; • comparative experimental studies of residual oil saturation when oil is displaced by surfactant compositions of various manufacturers; • comparative studies of phase permeability in flood experiments for the filtration of oil and water, oil and polymer-surfactant solution at different ratios in the flow.

Performance evaluation and application of a new phase permeability improver system

A novel hydrophobically associating polymer (HHA-RPM) was synthesized by a solution polymerization method with a modified acrylamide (AM) as the main component and implanting an anionic group. The static adsorptivity of the polymer was measured by an ultraviolet visible light photometer with an adsorption amount of about 11.0 mg/g. The influence of concentration, temperature and salinity on the apparent viscosity of the polymer solution system was investigated indoorally, and the HHA-RPM system was prepared. In view of the on-site requirements for the timeliness of the phase permeability improver, an antioxidant was added to the system to evaluate the durability of the HHA-RPM system.

TOWARDS THE PRESENCE OF REGULARITIES BETWEEN THE FUNCTION OF INTERFACIAL INTERACTION AND THE FILTRATION CAPACITY PROPERTIES

This paper discusses the results of identifying possible regularities between the parameters describing the function of interfacial interaction and filtration capacity properties of rocks. The studies have employed real laboratory data, forming four clusters. The capillary pressure curve data and relative phase permeability data were obtained on the same core samples. The authors describe the factors determining the interphase interaction during multiphase fluid flow in a porous medium. On this basis, a method for calculating discrete values of the interfacial interaction function based on the results of laboratory studies of relative phase permeability is proposed. For the approximation of the interfacial interaction function, the four-parametric formula following from derivative of Buckley — Leverett function at assignment of relative phase permeability functions by means of Corey functions is substantiated. The authors suggest two variants of interphase interaction function formulation. They prove that for the first variant, there is a stable dependence only for one parameter, and for the second variant — with three parameters. Thus, one of the parameters in all cases has appeared close to one. The results show that the error of the detected dependencies on the deviation of the parameters has a linear dependence, and for both variants of the interfacial interaction function, the ranking of the parameters is different according to their influence on the error. Using a test sample, the authors show that the dependencies obtained allow determining the parameters of the interphase interaction function with an acceptable error.

A WAY TO INCREASE THE EFFICIENCY OF WATER ISOLATING WORKS USING WATER REPELLENT

A method for isolating water inflow in gas wells is proposed, which consists in pumping a water-insulating composition into the water saturated interval using gas as a blowing fluid. The results of studies on physical models of the reservoir are presented, which prove an increase in the penetrating ability of the water repellent, blockage density of water-permeable channels and a decrease in phase permeability of water. These results were obtained in both water and gas saturated porous mediums. It is observed also that the gas blowing of a water isolating composition contributes in reduction of the reverse removal of the composition from theporous medium, as a result of a more uniform distribution of the water isolating composition in the porous medium.