Consulting: Petroleum

Flow in Fractured Reservoirs

Fluid flow in naturally fractured reservoirs is essentially a dual porosity flow that takes place predominantly along existing joints. Using an equivalent continuum model to represent these flows is often inaccurate, especially during early production where time and length scales are small. Furthermore, the permeability of naturally fractured reservoirs changes in response to fluid injection and extraction, causing sudden pressure drops near the borehole and possibly leading to a dramatic reduction in near-well permeability.

Two-dimensional analysis of fracture patterns

Itasca Consulting Group offers software and engineering expertise in the simulation of coupled hydro-mechanical problems that occur during hydrocarbon extraction from naturally fractured reservoirs. Itasca’s programs UDEC (2D) and 3DEC (3D) simulate fluid two-phase flow through complex networks of fractures in a fully coupled fashion, i.e. fluid pressure causes the deformation and displacement of solid blocks, which, in turn, affect the hydraulic aperture and permeability of the joints. Significant mud infiltration can cause the loss of near-well permeability and a dramatic reduction in wellbore stability. UDEC results above show the evolution of the invading mud front for different fracture patterns and mud weights, thereby enabling optimization for stability and producibility which are key for horizontal drilling in fractured reservoirs and drilling in coal bed methane reservoirs.

Three-dimensional fractured networks

Fluid flow in a complex fracture network around wells at the Soultz-sous-Foręts geothermal facility in France was simulated with 3DEC in order to understand the hydraulic mechanisms governing the extraction of heat from deep fractured granite by the forced circulation of fluid between wells. 3DEC results illustrate the importance of the orientation of the fractures with respect to orientation of the stress field. Shear displacements, which may lead to fracture dilation, may help explain the observed irreversible increase in permeability.

References

Tan, C.P., C. Detournay and X. Chen (2005) "Factors governing mud filtration and impact on wellbore stability in fractured rock mass," ARMA/USRMS 05-834.

S. Gentier, X. Rachez, C. Dezayes, A. Blaisonneau, A. Genter (2005) "How to Understand the Effect of the Hydraulic Stimulation in Terms of Hydro-Mechanical Behavior at Soultz-sous-Foręts (France)," GRC Transactions, Vol. 29, 2005.