scholarly journals A review of pressure transient analysis in reservoirs with natural fractures, vugs and/or caves

2020 ◽  
Author(s):  
Isah Mohammed ◽  
Teslim O. Olayiwola ◽  
Murtadha Alkathim ◽  
Abeeb A. Awotunde ◽  
Saad F. Alafnan
Keyword(s):  
Transient Analysis ◽  
Dynamic Pressure ◽  
Flow Dynamics ◽  
Reservoir Pressure ◽  
Natural Fractures ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Analysis Techniques ◽  
Basic Model ◽  
Insight Into

Abstract A review of the pressure transient analysis of flow in reservoirs having natural fractures, vugs and/or caves is presented to provide an insight into how much knowledge has been acquired about this phenomenon and to highlight the gaps still open for further research. A comparison-based approach is adopted which involved the review of works by several authors and identifying the limiting assumptions, model restrictions and applicability. Pressure transient analysis provides information to aid the identification of important features of reservoirs. It also provides an explanation to complex reservoir pressure-dependent variations which have led to improved understanding and optimization of the reservoir dynamics. Pressure transient analysis techniques, however, have limitations as not all its models find application in naturally fractured and vuggy reservoirs as the flow dynamics differ considerably. Pollard’s model presented in 1953 provided the foundation for existing pressure transient analysis in these types of reservoirs, and since then, several authors have modified this basic model and come up with more accurate models to characterize the dynamic pressure behavior in reservoirs with natural fractures, vugs and/or caves, with most having inherent limitations. This paper summarizes what has been done, what knowledge is considered established and the gaps left to be researched on.

A Semianalytical Model for Pressure-Transient Analysis of Fractured Wells in Unconventional Plays With Arbitrarily Distributed Discrete Fractures

SPE Journal ◽  
2018 ◽  
Vol 23 (06) ◽  
pp. 2041-2059 ◽  
Author(s):  
Zhiming Chen ◽  
Xinwei Liao ◽  
Kamy Sepehrnoori ◽  
Wei Yu
Keyword(s):  
Fluid Flow ◽  
Hydraulic Fracture ◽  
Transient Analysis ◽  
Fractured Reservoirs ◽  
Naturally Fractured Reservoirs ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Fracture Networks ◽  
Pressure Transient Analysis ◽  
Pressure Transient

Summary In this paper, we present an efficient semianalytical model for pressure-transient analysis in fractured wells by considering arbitrarily distributed fracture networks. The semianalytical model included three domains: matrix, hydraulic-fracture networks, and discrete natural fractures. Using the line-source function, we developed the diffusivity equation for fluid flow in matrix. By applying the vertex-analysis technique, we eliminated the flow interplay at fracture intersections and established the diffusivity equations for fluid flow in hydraulic-fracture networks and isolated natural fractures. The pressure-transient solution of these diffusivity equations was obtained using Laplace transforms and the Stehfest numerical inversion. Results showed that with the discrete natural fractures, a “V-shaped” pressure derivative (the classical dual-porosity feature of naturally fractured reservoirs) emerged. With the hydraulic-fracture networks, the reservoir system would exhibit pressure behaviors such as “pseudoboundary-dominated flow,” “fracture-interference flow,” and “fluid-feed flow.” All these pressure characteristics were dependent on the properties and geometries of natural/hydraulic fractures. In addition, through synthetic field application, we found that different (natural/hydraulic) fracture distributions and geometries had distinct behaviors of pressure derivatives, which may provide an effective tool to identify the properties of randomly distributed natural fractures as well as complex hydraulic fractures in unconventional plays.

Investigation of permeability change in the Bandanna Coal Formation of the Fairview Field using time-lapse pressure transient analysis

2019 ◽  
Vol 59 (1) ◽  
pp. 289 ◽  
Author(s):  
A. Salmachi ◽  
J. Barkla
Keyword(s):  
High Resolution ◽  
Transient Analysis ◽  
Time Lapse ◽  
Production Performance ◽  
Reservoir Pressure ◽  
Permeability Change ◽  
Pressure Transient Analysis ◽  
Pressure Transient ◽  
Coal Permeability ◽  
Rate Transient Analysis

Permeability of coal seam gas (CSG) reservoirs is stress/desorption dependent and may change during the life of the reservoir. This study investigates permeability change with depletion in several CSG wells in the Fairview Field: a prolific reservoir in the Bowen Basin, Australia. High-resolution pressure gauges at surface provide an opportunity to conduct time-lapse pressure transient analysis (PTA) on the wells that have multiple shut-ins. Pressure build-up tests can be replicated by calculating bottom-hole pressure when surface pressure (tubing and/or annulus) is recorded at high-resolution during any shut-in event. This eliminates the need to perform multiple well tests, which are time consuming and costly to run. The production history of 100 CSG wells was examined to find suitable candidates to perform time-lapse PTA. This was used to investigate how Bandanna Coal permeability changes with depletion. Three wells with high-quality shut-ins were identified and analysed to calculate effective permeability to gas and average reservoir pressure. The results indicate that coal permeability can enhance up to one order of magnitude during the life of a CSG well in the Fairview Field, and this can significantly improve production performance. These wells, located in a depleted area of the field, show rapid increase in permeability with decline in average reservoir pressure. The integration of rate transient analysis with the results of time-lapse PTA for one of the study wells reveals that the functional form of permeability increase is exponential in the study area, and a permeability modulus of –0.00678 psia–1 was obtained.

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