This research utilizes the imbibition experiments and X-ray tomography results for modeling fluid flow in naturally fractured reservoirs. Conventional dual porosity simulation requires large number of runs to quantify transfer function parameters for history matching purposes. In this study empirical transfer functions (ETF) are derived from imbibition experiments and this allows reduction in the uncertainness in modeling of transfer of fluids from the matrix to the fracture. The application of the ETF approach is applied in two phases. In the first phase, imbibition experiments are numerically solved using the diffusivity equation with different boundary conditions. Usually only the oil recovery in imbibition experiments is matched. But with the advent of X-ray CT, the spatial variation of the saturation can also be computed. The matching of this variation can lead to accurate reservoir characterization. In the second phase, the imbibition derived empirical transfer functions are used in developing a dual porosity reservoir simulator. The results from this study are compared with published results. The study reveals the impact of uncertainty in the transfer function parameters on the flow performance and reduces the computations to obtain transfer function required for dual porosity simulation.

More than 60% of the original oil in place (OOIP) is left in the ground after the primary and secondary recovery processes. With the introduction of enhanced oil recovery (EOR), that number goes down to about 40% of the OOIP. Carbon dioxide (CO2) injection is one of the most effective EOR methods in naturally fractured reservoirs. The fracture network provides a faster means for fluid flow due to its high conductivity but it is also the cause of premature breakthrough of the injected fluids. However, if employed efficiently, fractures can help push the injected CO2 to the reservoir boundaries so that a large portion of the reservoir fluid interacts with the injected CO2. Zones swept by miscible CO2 reported the lowest residual oil saturation.Continuous CO2 injection is becoming more and more preferred to the popular cyclic pressure pulsing. Continuous CO2 injection has no down time and could potentially provide better CO2 interaction with the reservoir fluid which provides a higher recovery. In this research, artificial neural networks (ANNs) are used to construct robust proxy models with highly predictive capabilities for naturally fractured reservoirs undergoing continuous CO2 injection. The main purpose of this research is to shed more light and understanding on continuous CO2 injection in naturally fractured reservoirs and provide a tool that empowers engineers to make decisions on the fly while evaluating uncertainty and mitigating risk rather than wait months or years to do so. In light of the above, various ANN designs and configurations undergo development and evolution to ultimately be able to provide valuable insights regarding reservoir performance, history matching, and injection design for naturally fractured reservoirs undergoing CO2 injection. Initial ANN designs targeted specific reservoirs using specific fluid compositions from the literature. The designed ANNs were able to provide predictions with a low degree of error. ANN designs went over many complex adjustments, variations, and enhancements until final configurations were reached. The final ANN designs developed in this research surpass previously developed ANNs in similar projects with its capability to handle a huge range of reservoir properties, relative permeability, capillary pressure, and fluid compositions under uncertainty.The reservoir simulation model used in this research is a two-well, two-layer, miscible compositional simulation model working in a dual-porosity system. Critical parameters affected the accuracy and predictability of the ANN designs and they were an essential part of the final ANN configurations. The parameters that a major effect on continuous CO2 injection are reservoir fluid composition, fracture permeability, well spacing, bottomhole flowing pressure (BHFP), thickness, and CO2 injection amount under miscible conditions had the highest impact on recovered oil.The final ANN designs were encompassed inside a graphical user interface that equipped the ANN with uncertainty evaluation capabilities. The ease to use nature of the GUI allows anyone to use the developed ANNs in this research, as well as provide a simple intuitive interface to manipulate input data, run simultaneous sensitivity and uncertainty analysis. The developed ANNs in this research bring us a step closer to achieving real-time simulation for naturally fractured reservoirs undergoing CO2 injection. The correlations embedded in the ANNs were able to overcome reservoir fluid, relative permeability, and capillary pressure limitations that existed in the previous ANN studies.

This book deals exclusively with naturally fractured reservoirs and includes many subjects usually treated in separate volumes. A highly practical edition, Naturally Fractured Reservoirs is written for students, reservoir geologists, log analysts and petroleum engineers.

The development of naturally fractured reservoirs, especially shale gas and tight oil reservoirs, exploded in recent years due to advanced drilling and fracturing techniques. However, complex fracture geometries such as irregular fracture networks and non-planar fractures are often generated, especially in the presence of natural fractures. Accurate modelling of production from reservoirs with such geometries is challenging. Therefore, Embedded Discrete Fracture Modeling and Application in Reservoir Simulation demonstrates how production from reservoirs with complex fracture geometries can be modelled efficiently and effectively. This volume presents a conventional numerical model to handle simple and complex fractures using local grid refinement (LGR) and unstructured gridding. Moreover, it introduces an Embedded Discrete Fracture Model (EDFM) to efficiently deal with complex fractures by dividing the fractures into segments using matrix cell boundaries and creating non-neighboring connections (NNCs). A basic EDFM approach using Cartesian grids and advanced EDFM approach using Corner point and unstructured grids will be covered. Embedded Discrete Fracture Modeling and Application in Reservoir Simulation is an essential reference for anyone interested in performing reservoir simulation of conventional and unconventional fractured reservoirs. Highlights the current state-of-the-art in reservoir simulation of unconventional reservoirs Offers understanding of the impacts of key reservoir properties and complex fractures on well performance Provides case studies to show how to use the EDFM method for different needs

Oil recovery by steam injection is a proven, successful technology for nonfractured reservoirs, but has received only limited study for fractured reservoirs. Preliminary studies suggest recovery efficiencies in fractured reservoirs may be increased by as much as 50% with the application of steam relative to that of low temperature processes. The key mechanisms enhancing oil production at high temperature are the differential thermal expansion between oil and the pore volume, and the generation of gases within matrix blocks. Other mechanisms may also contribute to increased production. These mechanisms are relatively independent of oil gravity, making steam injection into naturally fractured reservoirs equally attractive to light and heavy oil deposits. The objectives of this research program are to quantify the amount of oil expelled by these recovery mechanisms and to develop a numerical model for predicting oil recovery in naturally fractured reservoirs during steam injection. The experimental study consists of constructing and operating several apparatuses to isolate each of these mechanisms. The first measures thermal expansion and capillary imbibition rates at relatively low temperature, but for various lithologies and matrix block shapes. The second apparatus measures the same parameters, but at high temperatures and for only one shape. A third experimental apparatus measures the maximum gas saturations that could build up within a matrix block. A fourth apparatus measures thermal conductivity and diffusivity of porous media. The numerical study consists of developing transfer functions for oil expulsion from matrix blocks to fractures at high temperatures and incorporating them, along with the energy equation, into a dual porosity thermal reservoir simulator. This simulator can be utilized to make predictions for steam injection processes in naturally-fractured reservoirs. Analytical models for capillary imbibition have also been developed.

In the modem language of reservoir engineering by reservoir description is understood the totality of basic local information concerning the reservoir rock and fluids which by various procedures are extrapolated over the entire reservoir. Fracture detection, evaluation and processing is another essential step in the process of fractured reservoir description. In chapter 2, all parameters related to fracture density and fracture intensity, together with various procedures of data processing are discussed in detail. After a number of field examples, developed in Chap. 3, the main objective remains the quantitative evaluation of physical properties. This is done in Chap. 4, where the evaluation of fractures porosity and permeability, their correlation and the equivalent ideal geometrical models versus those parameters are discussed in great detail. Special rock properties such as capillary pressure and relative permeability are reexamined in the light of a double-porosity reservoir rock. In order to complete the results obtained by direct measurements on rock samples, Chap. 5 examines fracturing through indirect measurements from various logging results. The entire material contained in these five chapters defines the basic physical parameters and indicates procedures for their evaluation which may be used further in the description of fractured reservoirs.