Hydraulic fracturing has been widely used for enhancing gas and oil recovery. Often the desire is for the hydraulic fractures to be confined in the reservoir layer, while in other cases the desire is to grow through barriers in order to connect production across multiple strata. In either case, accurate prediction of height growth is important for successful design. This research is oriented to study the hydraulic fracture propagation in the layered reservoirs using: 1) fully coupled, lattice type Distinct Element (DEM) simulator, and 2) laboratory experiments carried out using an analogue three-layered medium constructed from transparent polyurethane.
The work is presented in three parts. Firstly, I present experimental validation of several theoretically-predicted asymptotic behaviors, namely for hydraulic fracture growth under conditions of negligible fracture toughness, with growth progressing from early-time radial geometry to large-time blade-like (PKN) geometry. Secondly, I present laboratory experiments comprising a parametric study in hydraulic fracture containment/height growth. There are four observed geometries generated by these experiments: containment, height growth, T-shape growth and the combination of height growth and T-shape. The results indicate that these cases fall within distinct regions when plotted in a parametric space defined by horizontal confining stress contrast between the reservoir and barrier layers as well as the vertical confining stress, both normalized by the fluid pressure. Finally, a numerical study of hydraulic fracture containment in layered reservoirs is carried out. Again, four distinct geometries are observed, depending on the input parameters. These numerical results match well to relevant experimental benchmarks, and they extend the dimensionless parameters beyond what can be considered in the laboratory configuration.
The results presented in this paper show the vital role of weak interfaces for determining hydraulic fracture height growth. This research shows that neglecting the role of weak interfaces on hydraulic fracture height growth must be done with the utmost of caution and only if the combination of stress conditions, rock strength, and horizontal interface strength can indeed show to correspond to a range where the interface is expected to play a negligible role in limiting the fracture height growth.
|School:||University of Pittsburgh|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Subjects:||Civil engineering, Petroleum engineering|
|Keywords:||Height growth, Hydraulic fracture simulation, Lattice media, Layered reservoirs, Weak interfaces|
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