| ||Dr. Jean-Claude Roegiers|
Borehole Stability: The stability of a circular hole, even in an isotropic medium, cannot be predicted by the classical strength theories. Although fracture initiation seems to occur at stress values which are close to the linear elasticity prediction, the subsequent stress redistribution has the following consequences; (i) stronger hole; and (ii) broken zone of lesser extent. Phase I of this research project will be the acquisition of a broad data base via servo-controlled laboratory experiments. Existing theories and numerical techniques will be applied in an attempt to determine the pertinent parameters. Phase II will call upon the newly-developed bifurcation theory which, after being adapted to this particular geometry, will be used as a predictive failure criterion.
Pore Collapse Mechanism: Upon producing poorly-consolidated and unconsolidated formations, the resulting effective stress can easily reach values in excess of the rock strength. The consequence is a sudden collapse of the rock matrix, accompanied by a drastic reduction in permeability; hence, a rapid production decline once a critical pore pressure value has been reached. This research project will first evaluate the importance of this mechanism and investigate if the "cap model" is applicable.
Fracture Toughness of Rocks: This is essentially an experimental project consisting of developing a technique to measure the fracture toughness under simulated downhole pressure and temperature conditions. The geometry is based on the Modified Ring Test which needs to be extended from its original laboratory conditions. Potential methods to determine the in-situ fracture toughness need to be evaluated.
Poroelastic Effects: Due to mathematical complexity and computational intensity, the full coupling fluid pressure/matrix deformation prevailing in porous rock formations is usually relaxed. Recent developments and breakthroughs in solving fundamental problems have, however, made such non-linear considerations more tractable. The coupling is affecting the required fracturing energies as well as introducing new potential failure mechanisms. More general and complex geometries need to be investigated in order to assess the importance of ignoring poroelastic effects. Concurrently, laboratory techniques will be developed to measure all pertinent poroelastic constants. Ultimately, the fully coupled poroelastic solution should replace the classical concept of leak off coefficients.
Micro-Hydraulic Fracturing Stress Determinations: This technique, developed mainly for elastic, impervious rocks, and in the case of boreholes drilled parallel to one of the principle stress components, is presently extended and applied to situations which do not conform to the fundamental assumptions. The recorded pressure data becomes difficult to interpret, leading sometimes to illogical results. This project will attempt to develop a rationale based on vigorous theoretical considerations, validated with controlled laboratory experiments.
Large-Scale Validation of Numerical Hydraulic Fracturing Simulators: Sophisticated three-dimensional models are being developed by the oil and gas industry to simulate hydraulic fracture simulation treatments. In order to make the problem tractable, various assumptions have been introduced by the researchers, leading to different design criteria. It is proposed to develop and build large-scale physical models to validate numerical algorithms for fracture propagations, fracturing fluid rheology and proppant transport. Dimensional analysis requirements will have to be satisfied.
Fracturing Fluid Characterization Facility: A large man-made deformable fracture will be built above ground on campus to characterize the rheological characteristics of fracturing fluids. This physical model will simulate downhole conditions of pressure and temperature and will include leak-off capabilities. In order to reproduce the in-situ shear history, field pumping/blending equipment will be used and a deep well will be drilled near the simulator.
Expert Systems Applied to Completion & Stimulation: Recent developments in artificial intelligence have resulted in the availability of robust expert system architectures. It is proposed to develop a user friendly computer program that will lead the engineer through design and recommendations regarding the completion and the stimulation needs of a particular well.