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Journal ArticleDOI

Impact of dynamic slippage on productivity of shale reservoirs

12 Nov 2015-World Journal of Engineering (Emerald Group Publishing Limited)-Vol. 12, Iss: 5, pp 443-451
Abstract: Ultra low permeability rocks such as shales exhibit complex fracture networks which must be discretely characterized in our reservoir models to evaluate stimulation designs and completion strategies properly. The pressure (Darcy’s law) and composition driven (Fick’s law) flow mechanisms when combined result in composition, pressure and saturationdependent slippage factor. The approach used in this study is to utilize pressure-dependent transmissibility multipliers to incorporate apparent gas-permeability changes resulting from multi-mechanism flows in commercial simulators. This work further expounds on the effectiveness of the theory by presenting a descriptive analysis between two commercially utilized numerical simulators. The applicability of dynamic slippage as an effective flow mechanism governing gas flow mechanisms within the computational environment of two different simulators is attempted in this analysis. Results indicate that slippage-governed flow in modelling shale reservoirs should not be ignored.
Topics: Slippage (52%)
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Journal ArticleDOI
Abstract: Although previous research has provided useful insights into unconventional shale gas resources in recent years, the geochemical and geological characteristics of marine–continental transitional shale have not been studied systematically. During the Late Permian, Longtan Formation shales were widely deposited in the Yangtze area of South China. These shales clearly indicate the need to deepen our understanding of marine–continental transitional shales. This study describes the various characteristics of black shales from the Longtan Formation in this area on the basis of a field investigation and relevant laboratory analyses. Longtan shale reservoirs, with a thickness and burial depth range of 20–650 and 800–2400 m, respectively, are usually interbedded with coal and compact sandstone reservoirs due to their special sedimentary environment. Geochemical analysis of the samples of Longtan shales from seven wells in the Yangtze area indicates the presence of high organic matters (OMs), with a total organic carbon content in the range of 0.85%–35.7% (average of 7.33%) but low hydrocarbon genetic potential (S2) with a value below 3 mg HC/g rock. The analysis of carbon isotopes and organic macerals demonstrates that the investigated samples mainly contain type III kerogen. Data from gas chromatography and gas chromatography-mass spectrometry analyses illustrate a weakly oxidizing to a weakly reducing environment, with most organic materials originating from algal-bacterial organisms and terrestrial plants. The terrestrial plants contribute significantly to the OM. The Longtan shales are thermally over-matured, and they have entered the dry-gas generation window according to Ro, production index data, and biomarker maturity ratios. X-ray diffraction analyses show that the content of brittle minerals of the Longtan shales is generally lower than that of marine shales in North America. The Longtan shales show a high clay content averaging 60.32 wt% and low calcite mineral content averaging 3.73 wt%. Field emission scanning electron microscopy shows that various types of nanometer-to micrometer-scale pores, including interparticle and intraparticle pores, OM pores, and microfractures, are well developed in the shales. Generally, high OM abundance, thermal evolution degree, clay mineral content, and pore space (porosity of 0.56%–10.6%) positively influence shale gas content (1.0%–3.8%). However, high clay content and variable reservoir thickness hinder the successful production of shale gas.

17 citations

Journal ArticleDOI
Abstract: Shale pore structures and irregularities are significant for gas adsorption and interstifial flow. High complexity and nonuniformity, wide pore scales, and multiple morphology hinder the thorough characterization of multi-scale pore structure and heterogeneity in shales. In this work, the geochemistry, pore structure and fractal characteristics of the Upper Cretaceous Nenjiang shale in the Songliao Basin of NE China were investigated, combining geochemistry experiments, physical property analysis, FE-SEM and nano-CT image observation, CO2/N2 gas adsorption, mercury intrusion porosimetry, and methane methane sorption analysis. The results show that the Nenjiang shales are low-mature (Ro of 0.55%–0.93%) and rich in organic matters (OMs) and clays. The size diameters of shale pores are generally distributed in sizes of 0.3–0.8, 1.4–4.5, 80–600 nm and 10–80 μm. Shale pores have strong heterogeneity and complexity, good connectivity and openness, mainly with inkbottle- and slit-shapes. Total pore volume (PV) is positive correlate with specific surface area (SSA), porosity and permeability, but negative correlate with the average pore size. The development of micro-, meso-, and macro-pores were dominated by the contents of OM, clays, and quartz, respectively. Positive correlations were found among fractal dimension, contents of OMs and clays, total PV, SSA, and methane adsorption capacity, which would provides better understanding on reservoir assessment and shale gas storage capacity.

16 citations

Journal ArticleDOI
Abstract: Purpose Because of the increasing global oil demand, efforts have been made to further extract oil using chemical enhanced oil recovery (CEOR) methods. However, unlike water flooding, understanding the physicochemical properties of crude oil and its sandstone reservoir makeup is the first step before embarking to CEOR projects. These properties play major roles in the area of EOR technologies and are important for the development of reliable chemical flooding agents; also, they are key parameters used to evaluate the economic and technical feasibilities of production and refining processes in the oil industries. Consequently, this paper aims to investigate various important physicochemical properties of crude oil (specific gravity; American Petroleum Institute [API]; viscosity; pour point; basic sediment and water; wax; and saturate, aromatic, resins and asphaltenes components) and sandstone reservoir makeup (porosity, permeability, bulk volume and density, grain volume and density, morphology and mineral composition and distributions) obtained from Malaysian oil field (MOF) for oil recovery prediction and design of promising chemical flooding agents. Design/methodology/approach Three reservoir sandstones from different depths (CORE 1; 5601, CORE 2; 6173 and CORE 3; 6182 ft) as well as its crude oil were obtained from the MOF, and various characterization instruments, such as high temperature gas chromatography and column chromatography for crude’s fractions identification; GC-simulated distillation for boiling point distribution; POROPERM for porosity and permeability; CT-Scan and scanning electron microscopy-energy dispersive X-ray for morphology and mineral distribution; wax instrument (wax content); pour point analyser (pour point); and visco-rheometre (viscosity), were used for the characterizations. Findings Experimental data gathered from this study show that the field contains low viscous (0.0018-0.014 Pa.s) sweet and light-typed crude because of low sulfur content (0.03 per cent), API gravity (43.1o), high proportion of volatile components (51.78 per cent) and insignificant traces of heavy components (0.02 per cent). Similarly, the rock permeability trend with depth was found in the order of CORE 1 < CORE 2 < CORE 3, and other parameters such as pore volume (Vp), bulk volume (Vb) and grain volume (Vg) also decrease in general. For grain density, the variation is small and insignificant, but for bulk density, CORE 2 records lower than CORE 3 by more than 1 per cent. In the mineral composition analysis, the CORE 2 contains the highest identified mineral content, with the exception of quarts where it was higher in the CORE 3. Thus, a good flow crude characteristic, permeability trend and the net mineral concentrations identified in this reservoir would not affect the economic viability of the CEOR method and predicts the validation of the MOF as a potential field that could respond to CEOR method successfully. Originality/value This paper is the first of its kind to combine the two important oil field properties to scientifically predict the evaluation of an oil field (MOF) as a step forward toward development of novel chemical flooding agents for application in EOR. Hence, information obtained from this paper would help in the development of reliable chemical flooding agents and designing of EOR methods.

4 citations

Journal ArticleDOI
10 Jun 2020-
Abstract: This manuscript primarily focuses on the constraints associated with the extended version of Darcy’s law that is used to describe the multiphase flow through a porous media; and in particular, a petroleum reservoir. This manuscript clearly brings out the basics associated with the usage of Darcy’s law, and reasons out the inapplicability of the Navier-Stokes Equation in order to describe the momentum conservation in a typical petroleum reservoir. Further, this work highlights the essence of continuum-based Darcy’s macroscopic-scale equation with that of Navier-Stokes’s microscopic-scale equation. Further, the absence of capillary forces in original Darcy’s equation and extending the same by considering the concept of ‘capillary pressure’ in order to accommodate the multi-phase flow has several critical constraints associated with it. In this manuscript, all these constraints or limitations have been posed in the form of a list of basic queries that need to be addressed or at least to be understood with clarity, when applying the multi-phase fluid flow equations associated with a petroleum reservoir. This study is limited to an oil-water two-phase system.

1 citations

Cites background from "Impact of dynamic slippage on produ..."

  • ...…2017; Berlin et al., 2018a, 2018b; Omkar et al., 2019a, 2019b; Berlin and Kumar, 2019; Mohanasundaram et al., 2019, 2020; Patwardhan et al., 2014; Patwardhan et al., 2015; Patwardhan et al., 2016; Patwardhan et al., 2017a, 2017b; Kidambi et al., 2017; Vasudevan et al., 2014a, 2014b; Vasudevan et…...


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Journal ArticleDOI
Abstract: Gas-producing mudrock systems are playing an important role in the volatile energy industry in North America and will soon play an equally important role in Europe. Mudrocks are composed of very fine grained particles, and their pores are very small, at the scale of nanometers. Gas production from these strata is much greater than what is anticipated given their very low Darcy permeability. In this paper, images of nanopores obtained by Atomic Force Microscopy (AFM) are presented for the first time. Gas flow in nanopores cannot be described simply by the Darcy equation. Processes such as Knudsen diffusion and slip flow at the solid matrix separate gas flow behaviour from Darcy-type flow. We present a formulation for gas flow in the nanopores of mudrocks based on Knudsen diffusion and slip flow. By comparing this new gas flow formulation and Darcy flow for compressible gas, we introduce an apparent permeability term that includes the complexity of flow in nanopores, and it takes the form of the Darcy equation so that it can easily be implemented in reservoir simulators. Results show that the ratio of apparent permeability to Darcy permeability increases sharply as pore sizes reduce to smaller than 100 nm. Also, Knudsen diffusion's contributions to flow increase as pores become smaller. Unlike Darcy permeability, which is a characteristic of the rock only, permeation of gas in nanopores of mudrocks depends on rock, gas type and operating conditions.

1,068 citations

Proceedings ArticleDOI
01 Jan 2009-

468 citations

Journal ArticleDOI
Abstract: A mathematical formulation, applicable to both numerical simulation and transient well analysis that describes the flow of gas in very tight porous media and includes a dual-mechanism transport of gas is developed. Gas is assumed to be traveling under the influence of a concentration field and a pressure field. Transport through the concentration field is a Knudsen flow process and is modeled with Fick's law of diffusion. Transport through the pressure field is a laminar process and is modeled with Darcy's law (inertial/turbulent effects are ignored). The combination of these two flow mechanisms rigorously yields a composition-, pressure-, and saturation-dependent slippage factor. The pressure dependence arises from treating the gas as a real gas. The derived dynamic slippage is most applicable in reservoirs with permeabilities less than or equal to0.01 md. The results indicate that in reservoirs of this type, differences between recoveries after 10 years of production with the dynamic-slip and constant-slip approaches were as great as 10%, depending on the initial gas saturation. If an economic production rate is considered, differences as great as 30% can be expected.

257 citations

"Impact of dynamic slippage on produ..." refers background or methods in this paper

  • ...Gas slippage factor and permeability-multiplier calculation using dynamic (Ertekin et al., 1986) and static (Jones-Owens) slippage1. Samarth D. Patwardhan et al./World Journal of Engineering 12(5) (2015) 443-451 445...


  • ...Gas slippage factor and permeability-multiplier calculation using dynamic (Ertekin et al., 1986) and static (Jones-Owens) slippage1....


  • ...Gas flow through the shale matrix is anticipated at several scales and by several mechanisms including advective, slip flow and diffusion (Javadpour, 2009); Ertekin et al., (1986) also demonstrated the pressure-temperature-gas composition-pore size dependence on apparent permeability (ka)....


Proceedings ArticleDOI
01 Jan 2007-
Abstract: This work addresses the problem of estimating Klinkenbergcorrected permeability from single-point, steady-state measurements on samples from low permeability sands. The "original" problem of predicting the corrected or "liquid equivalent" permeability (i.e., referred to as the Klinkenbergcorrected permeability) has been under investigation since the early 1940s — in particular, using the application of "gas

233 citations

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