Growing global energy demand has prompted the exploitation of non-conventional resources such as Coal Bed Methane (CBM) and conventional resources such as gas-condensate reservoirs. Exploitation of these resources primarily depends on stimulation by hydraulic fracturing. Traditional hydraulic fracturing practices, however, are in many ways inadequate in addressing difficulties associated with these non-conventional and conventional resources. For example, complex in-situ stress distribution, large material property contrasts and unique production mechanism complicate the implementation of hydraulic fracture treatments in CBM and gas-condensate reservoirs respectively. An integrated approach to optimise hydraulic fracture treatments in reservoirs under complex conditions is developed in this thesis. The optimisation methodology integrates a fracture geometry model which predicts fracture geometry for a given set of treatment parameters, a production model which estimates reservoir productivity after stimulation and an economic model which calculates net present value. A stochastic optimisation algorithm combining features of evolutionary computations is used to search for the optimum design. Numerical techniques such as finite element analysis, iterative semi-analytical methods and evolutionary computation are also used. The following are the major contributions of this thesis: 1. A three-dimensional hydraulic fracture geometry model which accounts for poroelastic effects, in-situ stress and rock material properties, has been developed to provide a more realistic description of the hydraulic fracture geometry. This served as a tool to visualise hydraulic fracture propagation for a given in-situ stress distribution, rock material properties and treatment parameters. Furthermore, by accounting for poroelastic effects, it is possible to identify the causes of exceptionally high treatment pressures. 2. An innovative production model was formulated in this thesis to quantify the well deliverability due to hydraulic fracturing. The production model has been used for a range of production scenarios for CBM and gas-condensate reservoirs such as: multiple wells at arbitrary locations and various well types (stimulated and unstimulated wells). 3. The optimisation methodology presented in this work provides a platform for operators to assess risks and gains associated with different field development scenarios. The added feature of sub-optimal NPV contouring provided flexibility to calibrate the treatment design in real-time. The strength of the optimisation methodology lies in the flexibility to: (1) impose design constraints, (2) optimise multiple variables and (3) simulate multiple objectives.
| Identifer | oai:union.ndltd.org:ADTP/225549 |
| Date | January 2005 |
| Creators | Valencia, Karen Joy, Petroleum Engineering, Faculty of Engineering, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Petroleum Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Karen Joy Valencia, http://unsworks.unsw.edu.au/copyright |
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