Fluid Flow and Heat Transport Computation for Power-Law Scaling Poroperm Media

Abstract

In applying Darcy's law to fluid flow in geologic formations, it is generally assumed that flow variations average to an effectively constant formation flow property. This assumption is, however, fundamentally inaccurate for the ambient crust. Well-log, wellcore, and well-flow empirics show that crustal flow spatial variations are systematically correlated from mm to km. Translating crustal flow spatial correlation empirics into numerical form for fluid flow/transport simulation requires computations to be performed on a single global mesh that supports long-range spatial correlation flow structures. Global meshes populated by spatially correlated stochastic poroperm distributions can be processed by 3D finite-element solvers. We model wellbore-logged Dm-scale temperature data due to heat advective flow into a well transecting small faults in a Hm-scale sandstone volume. Wellbore-centric thermal transport is described by Peclet number ≡ 0 V 0 / ( 0 = wellbore radius, V 0 = fluid velocity at 0 , = mean crustal porosity, and = rock-water thermal diffusivity). The modelling schema is (i) 3D global mesh for spatially correlated stochastic poropermeability; (ii) ambient percolation flow calibrated by well-core porosity-controlled permeability; (iii) advection via faultlike structures calibrated by well-log neutron porosity; (iv) flow ∼ 0.5 in ambient crust and ∼ 5 for fault-borne advection.

Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data

“…Wellbore temperature events can be due to heat advective fluid flow into a newly-drilled wellbore via isolated fracture-connectivity networks in otherwise impermeable rock [5,6]. Isolated electrical conductivity deviations in the same wellbore at the temperature events may be due to chemical ion transport in the same or similar fracture-connectivity networks.…”

“…Rather, as in [5,6], we broaden the class of crustal flow structures to include the spatially-correlated percolation pathways. The existence of such fluid flow structures is attested by three empirical features of crustal rock observed worldwide:…”

Injection-Triggered Occlusion of Flow Pathways in Geothermal Operations

“…Spectral scaling systematics in crustal well logs extends the observed range of scaling relations of porosity for five orders of magnitude. Spatial correlation extending to the grain scale means that few large-scale high permeable pathways control the fluid flow in the general crust (e.g., [1]). We discuss how applying the spatial correlation phenomenology to the connection of injection borehole to the formation results in exponentially declining injectivity curves ( Figure 6).…”

“…Fluid flow in geological media occurs at the grain scale in spatially correlated poroperm structures where a few high permeable flow paths control the main flow volume [1]. These highly permeable flow paths can be clogged by small particles due to physical, chemical, and biological processes.…”

“…In this study, we subdivided clogging processes as follows: (1) Physical processes refer to the structure and hydraulic properties of the aquifer. (2) Chemical processes represent mainly the composition of fluids and solids as well as chemical reactions between them, for example, dissolution and precipitation.…”