This paper presents an innovative workflow for characterization and reservoir simulation of the tight gas Nikanassin Group in the Western Canada Sedimentary Basin. Petrographic studies of the Nikanassin Group show the presence of (1) intergranular, (2) microfracture + slot, and (3) isolated (non effective) porosities. These porosities are handled with a mathematical triple porosity model for improved petrophysical analysis of the Nikanassin Group. Determination of pore throat apertures (r p35 ) facilitates facies mapping for reservoir simulation purposes. Numerical well testing of hydraulically fractured wells provides a way of tuning the static model with dynamic well testing information. In the case of open uncemented fractures and slots, numerical well testing indicates that the reduction of in-situ permeability can be more than two orders of magnitude. On the other hand in the case of partially cemented fractures and slots the reduction in permeability might be negligible. The approach permits an efficient representation of hydraulic fractures using transmissibility multipliers for the full field simulation of commingled tight reservoirs with multi-wells and multi-stage fractures.The result is a sound full field simulation model that permits a reasonable match of production and pressure histories, and forecasting of gas recovery under different well-spacing and depletion scenarios. As most Nikanassin tight gas wells are completed commingled, this research develops a procedure for production allocation of individual contributing formations.The study shows that there is a very large gas potential in the Nikanassin Group, particularly in the Lower Monteith Formation that can be exploited by reducing significantly the well spacing. The finding is significant as the tight gas Nikanassin Group extends for more than 15,000 km2 within Alberta and British Columbia, which suggests the potential for drilling thousands of wells in the region.

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Industry is currently using mini-frac analysis for the determination of fracture closure stress and after-closure reservoir properties. The foundation of all mini-frac analysis is the one dimensional Carter leak-off model, which leads directly to the concept of G Time. For 30+ years, G Time (or the G function) has played the dominant role for the determination of closure stress. The current norm uses combination G function and combination square root Δt plots for closure pressure determination. Each combination plot has three plotting functions associated with it. These combination plots also allow the identification of non-ideal behavior. Additionally, various log-log derivative techniques based on pressure transient analysis concepts have been developed to act as a guide for determining flow regimes and closure pressure. These PTA based techniques also allow the determination of after-closure flow regimes and properties. Concurrently, various specialized afterclosure plotting techniques have been developed for fracture/reservoir property determination. Despite all these techniques, there remains ambiguity in performing mini-frac analysis. Part of the problem is that the recommended plots do not rigorously identify the various flow regimes that occur during a mini-frac fall-off. Mini-frac analysis requires a general theory that accounts for all of the actual observed flow regimes. A systematic approach based on pressure transient analysis (PTA) concepts has been developed to identify the various flow regimes (Carter leak-off being only one of them). The starting point is the Bourdet log-log derivative plot, accompanied by the primary pressure derivative (PPD) function. It will be shown that the PPD on its own has independent flow regime identification capabilities. Once specific flow regimes have been identified, specialized log-log plots can be constructed for further flow regime verification. New combination plots are then developed for each flow regime to further assist in closure pressure determination. The theory will first be developed and illustrated with various example problems.

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The History of Simulation The use of computer simulation in petroleum engineering started in the area of reservoir fluid flow where it was called reservoir simulation. Although today, simulation is finding acceptance in other related areas, reservoir simulation is still the dominant area of application, and therefore will be the focus of this review. In order to appreciate the advances made in reservoir simulation, and to see the current trend in its development, one needs to look back at its history. Although the first attempts at simulation date back to the 1950s, the first useful numerical models for solving reservoir flow problems were developed in the 1960s. Athat time, the mainframe computers barely reached the power of today's PCs and the first commercial simulators were able to solve only relatively simple problems of two-dimensional flow, first single-phase and then multi-phase, using what is now called the IMPES method. The lecture of Donald Peaceman, one of the pioneers of simulation is an illuminating reminiscence of these early days(1) The 1970s saw tremendous activity both in the development of numerical techniques and in the applications of simulation models. By the end of the decade, the major techniques which are still used today were firmly established, and the acceptance of-simulation by practising engineers was growing. At the same time several books on simulation appeared(2–5). However, the application of simulation models to real problems was still a rather specialized activity, requiring experience in their use and in the interpretation of the results, because the models were not too reliable. With the 1980s came the explosion in computer hardware as well as in software and computer literacy. The vectorrocessing machines provided computing power for solving larger and/or more complex problems. Compositional, steam flooding, in situ combustion, and micellar-polymer flooding simulators were developed, and simulation studies with many thousands of computational cells became possible. Also, simulation ceased to be the domain of major oil companies or specialized consulting firms and became accessible to smaller companies or even individuals. Today's phase of this process is marked by the migration ofoftware to PCs and its extensive packaging with emphasis an graphical user interfaces. This development is recorded in the growing volume of literature(6–11). Current State of Simulation Tools Reservoir simulation has now matured to the point that most models are regarded as tools which can be used by a wide range of users, and very cost-effectively. Some of the current developments which have contributed to this transition are described below. Model Formulations From the multiplicity of different formulations of both the physics and numerics, emerged the generalized black oil/miscible/compositional model as the most practical and widely-used. The black oil model with a miscible option (sometimes called a four-component model) is now the "workhorse" of reservoir simulation. Fully compositional models can now be used as a rule in black-oil mode, facilitating studies of tertiary processes after primary or waterflood. Efficient methods have been developed for characterizing the compositional PVT and their implementation in simulators.