Quad-porosity shale systems – a review

2016 ◽  
Vol 13 (6) ◽  
pp. 529-539 ◽  
Author(s):  
Samarth D. Patwardhan ◽  
Fatemeh Famoori ◽  
Suresh Kumar Govindarajan
Keyword(s):  
Shale Gas ◽  
Experimental Studies ◽  
Gas Diffusion ◽  
Gas Production ◽  
Total Production ◽  
Actual Process ◽  
Coupled Flow ◽  
Production Forecast ◽  
Content Type ◽  
Flow Mechanisms

Purpose This paper aims to review the quad-porosity shale system from a production standpoint. Understanding the complex but coupled flow mechanisms in such reservoirs is essential to design appropriate completions and further, optimally produce them. Dual-porosity and dual permeability models are most commonly used to describe a typical shale gas reservoir. Design/methodology/approach Characterization of such reservoirs with extremely low permeability does not aptly capture the physics and complexities of gas storage and flow through their existing nanopores. This paper reviews the methods and experimental studies used to describe the flow mechanisms of gas through such systems, and critically recommends the direction in which this work could be extended. A quad-porosity shale system is defined not just as porosity in the matrix and fracture, but as a combination of multiple porosity values. Findings It has been observed from studies conducted that shale gas production modeled with conventional simulator/model is seen to be much lower than actually observed in field data. This paper reviews the various flow mechanisms in shale nanopores by capturing the physics behind the actual process. The contribution of Knudson diffusion and gas slippage, gas desorption and gas diffusion from Kerogen to total production is studied in detail. Originality/value The results observed from experimental studies and simulation runs indicate that the above effects should be considered while modeling and making production forecast for such reservoirs.

scholarly journals Numerical Simulation Study on Seepage Theory of a Multi-Section Fractured Horizontal Well in Shale Gas Reservoirs Based on Multi-Scale Flow Mechanisms

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2329 ◽  
Author(s):  
Chao Tang ◽  
Xiaofan Chen ◽  
Zhimin Du ◽  
Ping Yue ◽  
Jiabao Wei
Keyword(s):  
Shale Gas ◽  
Large Scale ◽  
Gas Diffusion ◽  
Gas Production ◽  
Hydraulic Fractures ◽  
Klinkenberg Effect ◽  
Stimulated Reservoir Volume ◽  
Multi Scale ◽  
Reservoir Volume ◽  
Flow Mechanisms

Aimed at the multi-scale fractures for stimulated reservoir volume (SRV)-fractured horizontal wells in shale gas reservoirs, a mathematical model of unsteady seepage is established, which considers the characteristics of a dual media of matrix and natural fractures as well as flow in the large-scale hydraulic fractures, based on a discrete-fracture model. Multi-scale flow mechanisms, such as gas desorption, the Klinkenberg effect, and gas diffusion are taken into consideration. A three-dimensional numerical model based on the finite volume method is established, which includes the construction of spatial discretization, calculation of average pressure gradient, and variable at interface, etc. Some related processing techniques, such as boundedness processing upstream and downstream of grid flow, was used to limit non-physical oscillation at large-scale hydraulic fracture interfaces. The sequential solution is performed to solve the pressure equations of matrix, natural, and large-scale hydraulic fractures. The production dynamics and pressure distribution of a multi-section fractured horizontal well in a shale gas reservoir are calculated. Results indicate that, with the increase of the Langmuir volume, the average formation pressure decreases at a slow rate. Simultaneously, the initial gas production and the contribution ratio of the desorbed gas increase. With the decrease of the pore size of the matrix, gas diffusion and the Klinkenberg effect have a greater impact on shale gas production. By changing the fracture half-length and the number of fractured sections, we observe that the production process can not only pursue the long fractures or increase the number of fractured sections, but also should optimize the parameters such as the perforation position, cluster spacing, and fracturing sequence. The stimulated reservoir volume can effectively control the shale reservoir.

Diffusion and Flow Mechanisms of Shale Gas through Matrix Pores and Gas Production Forecasting

2013 ◽  
Author(s):  
Juntai Shi ◽  
Lei Zhang ◽  
Yuansheng Li ◽  
Wei Yu ◽  
Xiangnan He ◽  
...  
Keyword(s):  
Shale Gas ◽  
Gas Production ◽  
Production Forecasting ◽  
Flow Mechanisms

Algeria will struggle to halt gas production slide

2018 ◽  
Keyword(s):  
Natural Gas ◽  
Shale Gas ◽  
Oil Production ◽  
Poor Performance ◽  
Gas Production ◽  
Content Type ◽  
The Poor ◽  
Local Opposition ◽  
Limited Scope ◽  
Petrochemical Industries

Significance This drag on the economy stems mainly from the poor performance of the natural gas sector, as investment in new projects has been inadequate to compensate for the decline in output from mature fields. Impacts Natural gas might be a driver of growth, despite limited scope to increase oil production due to depleted reserves. Development of Algeria’s abundant reserves of shale gas may face strong local opposition. Increased gas production could facilitate progress on long-stalled plans to expand fertiliser and petrochemical industries.

Fracking may be key to meeting Colombia's gas demand

2016 ◽  
Keyword(s):  
Natural Gas ◽  
Shale Gas ◽  
Gas Production ◽  
Annual Rate ◽  
Natural Gas Production ◽  
Content Type ◽  
The Past ◽  
Political Uncertainties

Subject Potential for the development of shale gas in Colombia. Significance Colombia's gas demand has risen steadily over the past decade, but its natural gas production appears to have peaked, falling from 12.6 billion cubic metres (bcm) in 2013 to 11.8 bcm in 2014. The trend has continued this year. Gas production was down 7.3% year-on-year in March to 29.9 million cubic metres (mcm) per day, equivalent to an annual rate of less than 10 bcm. Impacts Given the economic and political uncertainties in Venezuela, Colombia cannot rely on Venezuelan gas imports. Electricity shortages will increase pressure on President Juan Manuel Santos and may lead to protests. Colombia could come to rely more on LNG imports as a stopgap measure while shale gas is developed.

scholarly journals A Two-Phase Flowback Model for Multiscale Diffusion and Flow in Fractured Shale Gas Reservoirs

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Huimin Wang ◽  
J. G. Wang ◽  
Feng Gao ◽  
Xiaolin Wang
Keyword(s):  
Shale Gas ◽  
Fracture Network ◽  
Gas Diffusion ◽  
Gas Production ◽  
Gas Reservoir ◽  
Two Phase ◽  
Fractured Zone ◽  
Shale Gas Reservoir ◽  
Diffusion Mechanisms

A shale gas reservoir is usually hydraulically fractured to enhance its gas production. When the injection of water-based fracturing fluid is stopped, a two-phase flowback is observed at the wellbore of the shale gas reservoir. So far, how this water production affects the long-term gas recovery of this fractured shale gas reservoir has not been clear. In this paper, a two-phase flowback model is developed with multiscale diffusion mechanisms. First, a fractured gas reservoir is divided into three zones: naturally fractured zone or matrix (zone 1), stimulated reservoir volume (SRV) or fractured zone (zone 2), and hydraulic fractures (zone 3). Second, a dual-porosity model is applied to zones 1 and 2, and the macroscale two-phase flow flowback is formulated in the fracture network in zones 2 and 3. Third, the gas exchange between fractures (fracture network) and matrix in zones 1 and 2 is described by a diffusion process. The interactions between microscale gas diffusion in matrix and macroscale flow in fracture network are incorporated in zones 1 and 2. This model is validated by two sets of field data. Finally, parametric study is conducted to explore key parameters which affect the short-term and long-term gas productions. It is found that the two-phase flowback and the flow consistency between matrix and fracture network have significant influences on cumulative gas production. The multiscale diffusion mechanisms in different zones should be carefully considered in the flowback model.

Understanding Shale Gas Flow Behavior Using Numerical Simulation

SPE Journal ◽  
2015 ◽  
Vol 20 (01) ◽  
pp. 142-154 ◽  
Author(s):  
Hao Sun ◽  
Adwait Chawathé ◽  
Hussein Hoteit ◽  
Xundan Shi ◽  
Lin Li
Keyword(s):  
Mass Transfer ◽  
Organic Matter ◽  
Shale Gas ◽  
Inorganic Material ◽  
Gas Transport ◽  
Knudsen Diffusion ◽  
Gas Production ◽  
Gas Reservoir ◽  
Shale Gas Reservoir ◽  
Flow Mechanisms

Summary Shale gas has changed the energy equation around the world, and its impact has been especially profound in the United States. It is now generally agreed that the fabric of shale systems comprises primarily organic matter, inorganic material, and natural fractures. However, the underlying flow mechanisms through these multiporosity and multipermeability systems are poorly understood. For instance, debate still exists about the predominant transport mechanism (diffusion, convection, and desorption), as well as the flow interactions between organic matter, inorganic matter, and fractures. Furthermore, balancing the computational burden of precisely modeling the gas transport through the pores vs. running full reservoir scale simulation is also contested. To that end, commercial reservoir simulators are developing new shale gas options, but some, for expediency, rely on simplification of existing data structures and/or flow mechanisms. We present here the development of a comprehensive multimechanistic (desorption, diffusion, and convection), multiporosity (organic materials, inorganic materials, and fractures), and multipermeability model that uses experimentally determined shale organic and inorganic material properties to predict shale gas reservoir performance. Our multimechanistic model takes into account gas transport caused by both pressure driven convection and concentration driven diffusion. The model accounts for all the important processes occurring in shale systems, including desorption of multicomponent gas from the organics' surface, multimechanistic organic/inorganic material mass transfer, multimechanistic inorganic material/fracture network mass transfer, and production from a hydraulically fractured wellbore. Our results show that a dual porosity, dual permeability (DPDP) model with Knudsen diffusion is generally adequate to model shale gas reservoir production. Adsorption can make significant contributions to original gas in place, but is not important to gas production because of adsorption equilibrium. By comparing triple porosity, dual permeability; DPDP; and single porosity, single permeability formulations under similar conditions, we show that Knudsen diffusion is a key mechanism and should not be ignored under low matrix pressure (Pematrix) cases, whereas molecular diffusion is negligible in shale dry gas production. We also guide the design of fractures by analyzing flow rate limiting steps. This work provides a basis for long term shale gas production analysis and also helps define value adding laboratory measurements.

scholarly journals Gas Flow Tightly Coupled to Elastoplastic Geomechanics for Tight- and Shale-Gas Reservoirs: Material Failure and Enhanced Permeability

SPE Journal ◽  
2014 ◽  
Vol 19 (06) ◽  
pp. 1110-1125 ◽  
Author(s):  
Jihoon Kim ◽  
George J. Moridis
Keyword(s):  
Shale Gas ◽  
Shear Failure ◽  
Double Porosity ◽  
Gas Production ◽  
Coupled Flow ◽  
Gas Reservoirs ◽  
Shale Gas Reservoirs ◽  
Tightly Coupled ◽  
Secondary Fractures ◽  
Porosity Model

Summary We investigate coupled flow and geomechanics in gas production from extremely low-permeability reservoirs such as tight- and shale-gas reservoirs, using dynamic porosity and permeability during numerical simulation. In particular, we take the intrinsic permeability as a step function of the status of material failure, and the permeability is updated every timestep. We consider gas reservoirs with the vertical and horizontal primary fractures, using the single- and dynamic double-porosity (dual-continuum) models. We modify the multiple-porosity constitutive relations for modeling the double porous continua for flow and geomechanics. The numerical results indicate that the production of gas causes redistribution of the effective-stress fields, increasing the effective shear stress and resulting in plasticity. Shear failure occurs not only near the fracture tips but also away from the primary fractures, which indicates the generation of secondary fractures. These secondary fractures increase the permeability significantly, and change the flow pattern, which, in turn, causes a change in the distribution of geomechanical variables. From various numerical tests, we find that shear failure is enhanced by a large pressure drop at the production well, a high Biot's coefficient, and low frictional and dilation angles. Smaller spacing between the horizontal wells also contributes to faster secondary fracturing. When the dynamic double-porosity model is used, we observe a faster evolution of the enhanced-permeability areas than that obtained from the single-porosity model, mainly because of a higher permeability of the fractures in the double-porosity model. These complicated physics for stress-sensitive reservoirs cannot properly be captured by the uncoupled or flow-only simulation, and, thus, tightly coupled flow and geomechanical models are highly recommended to describe accurately the reservoir behavior during gas production in tight- and shale-gas reservoirs and to design production scenarios smartly.

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