Poroelastic model for induced stresses and deformations in hydrocarbon and geothermal reservoirs

• Published in: Journal of petroleum science & engineering Vol. 80; no. 1; pp. 41 - 52
• Main Author: Chen, Z.R.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.12.2011; Elsevier
• Subjects: Applied sciences; Crude oil, natural gas and petroleum products; Crude oil, natural gas, oil shales producing equipements and methods; Energy; Enhanced oil recovery methods; Exact sciences and technology; Fuels; hydraulic fracturing; induced deformation; monitoring; poroelasticity; Prospecting and production of crude oil, natural gas, oil shales and tar sands; reservoir; thermoelasticity; hydraulic fracturing; poroelasticity; induced deformation; reservoir; monitoring; thermoelasticity; Deformation; Hydrocarbon; Hydraulics; Poroelasticity; Pore pressure; Mechanical properties; Tilt; Hydraulic fracturing
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2011.10.004

Fluid migration and heat transport result in changes in pore pressure and temperature within a reservoir, which can induce stresses and deformations in the reservoir and the bounding rock system through poroelastic and thermoelastic couplings. Analytical and semi-analytical solutions for investigating the induced stresses and deformations are therefore extremely useful when applied to both predicting and monitoring the reservoir volume changes and associated subsurface and surface deformation. The poroelastic and thermoelastic eigenstrains are used here to characterize the pore pressure change and temperature variation, respectively, in the reservoir. The induced stresses and deformations are then obtained by using the single- and double-inclusion models, and are expressed in terms of the Galerkin vector stress function, which is related to the corresponding eigenstrains in a straightforward way. The difference in mechanical properties between the reservoir and the bounding rocks is accounted for using the theory of inhomogeneous inclusions. The effect of the reservoir shape, elastic properties, and the distribution of pore pressure change within the reservoir on the surface deformation has been investigated. The magnitude and pattern of the induced surface tilt have been compared with those produced by a hydraulic fracture. The analytical expressions obtained here for the displacement and tilt fields can serve as a useful forward model for monitoring and mapping hydraulic fractures, subsurface fluid migration and heat transport associated with injection or production of fluid into or from a reservoir by surface deformation-based monitoring techniques, such as tiltmeter monitoring. ► Induced stresses and deformations associated with reservoir production or injection (for the case of half space). ► Effect of the reservoir shape on the status of the induced strain. ► Effect of elastic properties of the reservoir, and the distribution of pore pressure change on the surface deformation. ► Relationship between the total work (or the total fluid mass change) and the Galerkin vector function. ► An efficient forward model for the inverse analysis in reservoir monitoring.