Diagnosing Fracture Network Pattern and Flow Regime Aids Production Performance Analysis in Unconventional Oil Reservoirs

In this paper, the mathematical model of production performance analysis for horizontal wells in composite coal bed methane reservoir is introduced. In this model, two regions with different formation parameters are distinguished, and multiple mechanisms are considered including desorption, diffusion, and viscous flow. Then the solution of horizontal well performance analysis model is obtained by using point source function method, Laplace transform, and Stehfest algorithm comprehensively. The solution of the proposed model is verified with previous work thoroughly. The pressure transient analysis for horizontal well when producing at a constant rate is obtained and discussed. At last, different flow regimes are divided based on pressure transient analysis curves. They are early wellbore storage period, skin factor period, first radial flow regime, transition regime, second radial flow regime, transfer regime, and late pseudo-radial flow regime. The effects of related parameters such as storativity ratio, transfer coefficient, adsorption coefficient, ratio of vertical permeability to horizontal permeability, skin factor, horizontal well position in vertical direction, and inner region radius are analyzed as well according to pressure transient analysis and rate transient analysis curves. The presented work in this paper can give a better understanding of coal bed methane production performance in composite reservoir.

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Performance Analysis and Flow Regime Identification of Fractured Horizontal Wells in Tight Oil Reservoirs

10.2118/188071-ms ◽

2017 ◽

Author(s):

Peng Hui ◽

Ran Qiquan ◽

Li Yong ◽

Tong Min

Keyword(s):

Performance Analysis ◽

Flow Regime ◽

Horizontal Wells ◽

Oil Reservoirs ◽

Tight Oil ◽

Flow Regime Identification ◽

Tight Oil Reservoirs ◽

Fractured Horizontal Wells

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Effect of Fracture Characteristics on Behavior of Fractured Shale-Oil Reservoirs by Cyclic Gas Injection

SPE Reservoir Evaluation & Engineering ◽

10.2118/168880-pa ◽

2016 ◽

Vol 19 (02) ◽

pp. 350-355 ◽

Cited By ~ 15

Author(s):

T.. Wan ◽

J. J. Sheng ◽

M. Y. Soliman ◽

Y.. Zhang

Keyword(s):

Oil Recovery ◽

Gas Injection ◽

Fracture Network ◽

Production Performance ◽

Oil Reservoirs ◽

Shale Oil ◽

Well Production ◽

The Matrix ◽

Stress Dependent ◽

Shale Oil Reservoirs

Summary The current technique to produce shale oil is to use horizontal wells with multistage stimulation. However, the primary oil-recovery factor is only a few percent. The low oil recovery and abundance of shale reservoirs provide a huge potential for enhanced oil-recovery (EOR) process. Well productivity in shale oil-and-gas reservoirs primarily depends on the size of fracture network and the stimulated reservoir volume (SRV) that provides highly conductive conduits to communicate the matrix with the wellbore. The fracture complexity is critical to the well-production performance, and it also provides an avenue for injected fluids to displace the trapped oil. However, the disadvantage of gasflooding in fractured reservoirs is that injected fluids may break through to production wells by means of the fracture network. Therefore, a preferred method is to use cyclic gas injection to overcome this problem. In this paper, we use a numerical-simulation approach to evaluate the EOR potential in fractured shale-oil reservoirs by cyclic gas injection. Simulation results indicate that the stimulated fracture network contributes significantly to the well productivity by means of its large contact area with the matrix, which prominently enhances the macroscopic sweep efficiency in secondary cyclic gas injection. In our previous simulation work, the EOR potential was evaluated in hydraulic planar-traverse fractures without considering the propagation of a natural-fracture network. In this paper, we examine the effect of fracture networks on shale oilwell secondary-production performance. The impact of fracture spacing and stress-dependent fracture conductivity on the ultimate oil recovery is investigated. The results presented in this paper demonstrate that cyclic gas injection has EOR potential in shale-oil reservoirs. This paper focuses on evaluating the effect of fracture spacing, the size of the fracture network, fracture connectivity (uniform and nonuniform), and stress-dependent fracture-network conductivity on well-production performance of shale-oil reservoirs by secondary cyclic gas injection.

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Numerical Investigation of Fracture Compressibility and Uncertainty on Water-Loss and Production Performance in Tight Oil Reservoirs

Energies ◽

10.3390/en12071189 ◽

2019 ◽

Vol 12 (7) ◽

pp. 1189 ◽

Cited By ~ 4

Author(s):

Kai Liao ◽

Shicheng Zhang ◽

Xinfang Ma ◽

Yushi Zou

Keyword(s):

Water Loss ◽

Fracture Network ◽

Production Performance ◽

Oil Reservoirs ◽

Natural Fracture ◽

Tight Oil ◽

Fracture Density ◽

Breakthrough Time ◽

Complex Fracture ◽

Fracture Closure

Multi-stage hydraulic fracturing along with horizontal wells are widely used to create complex fracture networks in tight oil reservoirs. Analysis of field flowback data shows that most of the fracturing fluids are contained in a complex fracture network, and fracture-closure is the main driving mechanism during early clean up. At present, the related fracture parameters cannot be accurately obtained, so it is necessary to study the impacts of fracture compressibility and uncertainty on water-loss and the subsequent production performance. A series of mechanistic models are established by considering stress-dependent porosity and permeability. The impacts of fracture uncertainties, such as natural fracture density, proppant distribution, and natural fracture heterogeneity on flowback and productivity are quantitatively assessed. Results indicate that considering fracture closure during flowback can promote water imbibition into the matrix and delay the oil breakthrough time compared with ignoring fracture closure. With the increase of natural fracture density, oil breakthrough time is advanced, and more water is retained underground. When natural fractures connected with hydraulic fractures are propped, well productivity will be enhanced, but proppant embedment can cause a loss of oil production. Additionally, the fracture network with more heterogeneity will lead to the lower flowback rate, which presents an insight in the role of fractures in water-loss.

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