Diffusion-Dominated Proxy Model for Solvent Injection in Ultratight Oil Reservoirs

SPE Journal ◽  
2018 ◽  
Vol 24 (02) ◽  
pp. 660-680 ◽  
Author(s):  
Michael Cronin ◽  
Hamid Emami-Meybodi ◽  
Russell T. Johns
Keyword(s):  
Diffusion Process ◽  
Primary Production ◽  
Oil Recovery ◽  
Contact Area ◽  
Darcy’S Law ◽  
Convective Transport ◽  
Darcy's Law ◽  
Oil Reservoirs ◽  
Solvent Injection ◽  
Proxy Model

Summary Enhanced oil recovery (EOR) by solvent injection offers significant potential to increase recovery from shale oil reservoirs, which is typically between 3 and 7% original oil in place (OOIP). The rather sparse literature on this topic typically models these tight reservoirs on the basis of conventional-reservoir processes and mechanisms, such as by convective transport using Darcy's law, even though there is little physical justification for this treatment. The literature also downplays the importance of the soaking period in huff ’n’ puff. In this paper, we propose, for the first time, a more physically realistic recovery mechanism based on solely diffusion-dominated transport. We develop a diffusion-dominated proxy model assuming first-contact miscibility (FCM) to provide rapid estimates of oil recovery for both primary production and the solvent huff ’n’ soak ’n’ puff (HSP) process in ultratight oil reservoirs. Simplified proxy models are developed to represent the major features of the fracture network. The key results show that diffusion-transport considered solely can reproduce the primary-production period within the Eagle Ford Shale and can model the HSP process well, without the need to use Darcy's law. The minimum miscibility pressure (MMP) concept is not important for ultratight shales where diffusion dominates because MMP is based on advection-dominated conditions. The mechanism for recovery is based solely on density and concentration gradients. Primary production is modeled as a self-diffusion process, whereas the HSP process is modeled as a counter-diffusion process. Incremental recoveries by HSP are several times greater than primary-production recoveries, showing significant promise in increasing oil recoveries. We calculate ultimate recoveries for both primary production and for the HSP process, and show that methane injection is preferred over carbon dioxide injection. We also show that the proxy model, to be accurate, must match the total matrix-contact area and the ratio of effective area to total contact area with time. These two parameters should be maximized for best recovery.

scholarly journals Flat-radial stationary motion of incompressible oil in a uniform horizontal circular formation according to diffrent filtration laws

2021 ◽  
Vol 1 ◽  
pp. 43-52
Author(s):  
Maral G. Alieva ◽  
◽  
Niiaz G. Valiev ◽  
Vagif M. Kerimov ◽  
◽  
...  
Keyword(s):  
Oil Recovery ◽  
Darcy’S Law ◽  
Practical Importance ◽  
Darcy's Law ◽  
Oil Field ◽  
Scientific Article ◽  
Filtration Flow ◽  
Plane Parallel ◽  
Reservoir Development ◽  
Oil Flow

Relevance. The article considers the issues of flat-radial motion of incompressible oil in a uniform horizontal circular formation. Taking into account that filtration obeys different laws, the research was carried out according to the linear Darcy's law, the generalized Darcy's law and the modified Kesson model. Methodology. Each of the tasks was solved using mathematical methods. The corresponding algorithms were obtained, taking into account the forms of oil movement in a porous medium. Plane-parallel simple filtration flow of oil moves from a strip-like reservoir to a straight gallery. This fluid flow occurs when the oil field under development has several parallel, straight rows of production producing wells. In oil-bearing areas between parallel adjacent rows, oil filtration is also plane-parallel, which implies the practical importance of solving the problem of plane-parallel oil flow in this scientific article. For each filtration law, calculated hydrodynamic formulas for well operation parameters and oil reservoir development indicators are derived. Results. The obtained models of oil flow rate, filtration rate, distribution law of current pressure, current pressure gradient, duration of oil advance in the drainage zone is expedient to use both in drawing up an optimal reservoir development project and for regulating and adjusting the oil recovery process of operating fields. Three stationary-hydrostatic problems are solved, in which the filtration processes obey only a general nonlinear law. All the basic calculation formulas that characterize the filtration processes are derived. By analyzing these formulas, it is possible to identify the nature of the influence of each well parameter and each reservoir development indicator. It is also possible to apply the obtained results to solve vatious theoretical problems of oil field development and when planning new fields development.

scholarly journals Proper Use of Capillary Number in Chemical Flooding

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Hu Guo ◽  
Ma Dou ◽  
Wang Hanqing ◽  
Fuyong Wang ◽  
Gu Yuanyuan ◽  
...  
Keyword(s):  
Number Theory ◽  
Oil Recovery ◽  
Capillary Number ◽  
Darcy’S Law ◽  
Capillary Tube ◽  
Darcy's Law ◽  
Mobility Control ◽  
Chemical Flooding ◽  
Displacement Efficiency ◽  
End Effects

Capillary number theory is very important for chemical flooding enhanced oil recovery. The difference between microscopic capillary number and the microscopic one is easy to confuse. After decades of development, great progress has been made in capillary number theory and it has important but sometimes incorrect application in EOR. The capillary number theory was based on capillary tube bundles and Darcy’s law hypothesis, and this should always be kept in mind when used in chemical flooding EOR. The flow in low permeability porous media often shows obvious non-Darcy effects, which is beyond Darcy’s law. Experiments data from ASP flooding and SP flooding showed that remaining oil saturation was not always decreasing as capillary number kept on increasing. Relative permeability was proved function of capillary number; its rate dependence was affected by capillary end effects. The mobility control should be given priority rather than lowering IFT. The displacement efficiency was not increased as displacement velocity increased as expected in heavy oil chemical flooding. Largest capillary number does not always make highest recovery in chemical flooding in heterogeneous reservoir. Misuse of CDC in EOR included the ignorance of mobility ratio, Darcy linear flow hypothesis, difference between microscopic capillary number and the microscopic one, and heterogeneity caused flow regime alteration. Displacement of continuous oil or remobilization of discontinuous oil was quite different.

scholarly journals Experimental Study of Heavy Oil Recovery Mechanisms during Cyclic Solvent Injection Processes

SPE Journal ◽  
2020 ◽  
pp. 1-16
Author(s):  
Maria Plata ◽  
Jonathan Bryan ◽  
Apostolos Kantzas
Keyword(s):  
Experimental Study ◽  
Primary Production ◽  
Oil Recovery ◽  
Heavy Oil ◽  
Process Conditions ◽  
Heavy Oil Recovery ◽  
Oil Saturation ◽  
Solvent Injection ◽  
Pressure Depletion ◽  
Multiple Cycles

Summary The cyclic solvent injection (CSI) process has recently shown to be a promising method for enhanced heavy oil recovery in Canada. Laboratory testing is often run before development of field pilots to assess the effect of parameters, such as solvent choice and process conditions, on the CSI response. However, differences between laboratory results vs. field applications have been observed. CSI laboratory studies work for only two to three cycles due to low incremental oil in subsequent cycles, whereas field pilots continue for years over multiple cycles. This experimental study is intended to capture the production mechanisms responsible for heavy oil production in CSI. Primary production and CSI tests were conducted using sandpack models saturated with live heavy oil of 9530 mPa·s viscosity. The experiments were conducted in horizontal and vertical mode injection at high- and low-pressure depletion rates using two solvent mixtures of CH4 and C3H8. The sandpacks were scanned after every cycle to analyze the evolution of gas and oil saturations using computed tomography (CT). Three cores were used to study the effect of several parameters: gravity forces, pressure depletion rate, solvent composition, and initial oil saturation on the performance of CSI processes. CSI cycles run after primary production in horizontal systems produced negligible incremental oil for both slow and fast drawdown rates due to the large void space and high free gas saturation inhibiting the pressure buildup to push the solvent-diluted oil. These CSI experiments were only initially successful in dead oil systems, in which the initial oil saturation was higher and appropriate pressure gradient was generated through fast depletion rates. During the vertical alignment, CSI cycles exhibited higher incremental oil recovery per cycle. Slow depletion cycles were more efficient in terms of pressure and incremental recovery per cycle; however, faster depletion cycles performed better as a function of time. These results are more in line with the repeated recoveries measured over multiple cycles in field CSI pilot studies. More volume of diluted oil was drained out of the core when the solvent mixture with higher propane (C3H8) content was injected. These results demonstrate the importance of gravity drainage in the CSI process and its significance on successful oil recovery rates. This study illustrates the limitations of previous horizontal laboratory tests and shows an improved test configuration for modeling and prediction of the improved response observed in CSI pilots.

Diffusion Equations for Fluid Flow in Porous Rocks

2017 ◽  
Vol 9 (01) ◽  
pp. 05-13
Author(s):  
Pramod Kumar Pant
Keyword(s):  
Fluid Flow ◽  
Diffusion Equation ◽  
Flow Rate ◽  
Oil Recovery ◽  
Darcy’S Law ◽  
Volume Flow Rate ◽  
Petroleum Industry ◽  
Darcy's Law ◽  
Flow In Porous Media ◽  
Porous Rocks

The multiphase flow in porous media is a subject of great complexities with a long rich history in the field of fluid mechanics. This is a subject with important technical applications, most notably in oil recovery from petroleum reservoirs and so on. The single-phase fluid flow through a porous medium is well characterized by Darcy’s law. In the petroleum industry and in other technical applications, transport is modeled by postulating a multiphase generalization of the Darcy’s law. In this connection, distinct pressures are defined for each constituent phase with the difference known as capillary pressure, determined by the interfacial tension, micro pore geometry and surface chemistry of the solid medium. For flow rates, relative permeability is defined that relates the volume flow rate of each fluid to its pressure gradient. In the present paper, there is a derivation and analysis about the diffusion equation for the fluid flow in porous rocks and some important results have been founded. The permeability is a function of rock type that varies with stress, temperature etc., and does not depend on the fluid. The effect of the fluid on the flow rate is accounted for by the term of viscosity. The numerical value of permeability for a given rock depends on the size of the pores in the rock as well as on the degree of interconnectivity of the void space. The pressure pulses obey the diffusion equation not the wave equation. Then they travel at a speed which continually decreases with time rather than travelling at a constant speed. The results shown in this paper are much useful in earth sciences and petroleum industry.

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