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Optimizing Development Strategies to Increase Reserves in Unconventional Gas ReservoirsTurkarslan, Gulcan 2010 August 1900 (has links)
The ever increasing energy demand brings about widespread interest to rapidly,
profitably and efficiently develop unconventional resources, among which tight gas
sands hold a significant portion. However, optimization of development strategies in
tight gas fields is challenging, not only because of the wide range of depositional
environments and large variability in reservoir properties, but also because the
evaluation often has to deal with a multitude of wells, limited reservoir information, and
time and budget constraints. Unfortunately, classical full-scale reservoir evaluation
cannot be routinely employed by small- to medium-sized operators, given its timeconsuming
and expensive nature. In addition, the full-scale evaluation is generally built
on deterministic principles and produces a single realization of the reservoir, despite the
significant uncertainty faced by operators.
This work addresses the need for rapid and cost-efficient technologies to help
operators determine optimal well spacing in highly uncertain and risky unconventional
gas reservoirs. To achieve the research objectives, an integrated reservoir and decision
modeling tool that fully incorporates uncertainty was developed. Monte Carlo simulation
was used with a fast, approximate reservoir simulation model to match and predict
production performance in unconventional gas reservoirs. Simulation results were then
fit with decline curves to enable direct integration of the reservoir model into a Bayesian
decision model. These integrated tools were applied to the tight gas assets of
Unconventional Gas Resources Inc. in the Berland River area, Alberta, Canada.
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AN ADVISORY SYSTEM FOR THE DEVELOPMENT OF UNCONVENTIONAL GAS RESERVOIRSWei, Yunan 16 January 2010 (has links)
With the rapidly increasing demand for energy and the increasing prices for oil
and gas, the role of unconventional gas reservoirs (UGRs) as energy sources is becoming
more important throughout the world. Because of high risks and uncertainties associated
with UGRs, their profitable development requires experts to be involved in the most
critical development stages, such as drilling, completion, stimulation, and production.
However, many companies operating UGRs lack this expertise. The advisory system we
developed will help them make efficient decisions by providing insight from analogous
basins that can be applied to the wells drilled in target basins.
In North America, UGRs have been in development for more than 50 years. The
petroleum literature has thousands of papers describing best practices in management of
these resources. If we can define the characteristics of the target basin anywhere in the
world and find an analogous basin in North America, we should be able to study the best
practices in the analogous basin or formation and provide the best practices to the
operators.
In this research, we have built an advisory system that we call the
Unconventional Gas Reservoir (UGR) Advisor. UGR Advisor incorporates three major
modules: BASIN, PRISE and Drilling & Completion (D&C) Advisor. BASIN is used to identify the reference basin and formations in North America that are the best analogs to
the target basin or formation. With these data, PRISE is used to estimate the technically
recoverable gas volume in the target basin. Finally, by analogy with data from the
reference formation, we use D&C Advisor to find the best practice for drilling and
producing the target reservoir.
To create this module, we reviewed the literature and interviewed experts to
gather the information required to determine best completion and stimulation practices
as a function of reservoir properties. We used these best practices to build decision trees
that allow the user to take an elementary data set and end up with a decision that honors
the best practices. From the decision trees, we developed simple computer algorithms
that streamline the process.
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Numerical Modeling of Fractured Shale-Gas and Tight-Gas Reservoirs Using Unstructured GridsOlorode, Olufemi Morounfopefoluwa 2011 December 1900 (has links)
Various models featuring horizontal wells with multiple induced fractures have been proposed to characterize flow behavior over time in tight gas and shale gas systems. Currently, there is little consensus regarding the effects of non-ideal fracture geometries and coupled primary-secondary fracture interactions on reservoir performance in these unconventional gas reservoirs.
This thesis provides a grid construction tool to generate high-resolution unstructured meshes using Voronoi grids, which provides the flexibility required to accurately represent complex geologic domains and fractures in three dimensions. Using these Voronoi grids, the interaction between propped hydraulic fractures and secondary "stress-release" fractures were evaluated. Additionally, various primary fracture configurations were examined, where the fractures may be non-planar or non-orthogonal.
For this study, a numerical model was developed to assess the potential performance of tight gas and shale gas reservoirs. These simulations utilized up to a half-million grid-blocks and consider a period of up to 3,000 years in some cases. The aim is to provide very high-definition reference numerical solutions that will exhibit virtually all flow regimes we can expect in these unconventional gas reservoirs. The simulation results are analyzed to identify production signatures and flow regimes using diagnostic plots, and these interpretations are confirmed using pressure maps where useful.
The coupled primary-secondary fracture systems with the largest fracture surface areas are shown to give the highest production in the traditional "linear flow" regime (which occurs for very high conductivity vertical fracture cases). The non-ideal hydraulic fracture geometries are shown to yield progressively lower production as the angularity of these fractures increases. Hence, to design optimum fracture completions, we should endeavor to keep the fractures as orthogonal to the horizontal well as possible.
This work expands the current understanding of flow behavior in fractured tight-gas and shale-gas systems and may be used to optimize fracture and completion design, to validate analytical models and to facilitate more accurate reserves estimation.
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