Reservoir compaction and land subsidence

Abstract

Subsurface hydrocarbon removal induces a reservoir compaction that migrates to the ground surface and causes the land to subside. While compaction depends primarily on the fluid pore pressure drawdown, the thickness and the mechanical compressibility of the depleted formation, the amount of compaction reaching the surface depends on the depth and size of the producing field and the stiffness of the overburden. This paper presents a list of the most famed sites worldwide that have experienced anthropogenic land subsidence because of underground fluid withdrawal and reviews the basic mechanisms controlling the reservoir compaction and the related ground settlement. Finally, some mathematical models, that can be effectively used to simulate and predict the occurrence, and the most recent techniques for accurately and timely measuring and monitoring the deep compaction and the land surface displacements are described.RÉSUMÉ. L'exploitation d'hydrocarbures provoque une compaction souterraine qui se propage à la surface et cause des affaissements. Tandis que cette compaction dépend essentiellement de la diminution de pression intersticielle et de la compressibilité mécanique de l'encaissant, la magnitude de la subsidence résultante en surface dépend de la profondeur, des dimensions du réservoir, et de la rigidité des couches de sol sus-jacentes. Ce papier présente une liste de sites mondialement connus qui ont subi des subsidences anthropogéniques, à cause de la baisse de la nappe d'eau, et passe en revue les mécanismes essentiels qui contrôlent la compaction mentionnée et la subsidence superficielle relative. Finalement, quelques modèles mathématiques qui peuvent être effectivement utilisés pour simuler et prévoir le phénomène, aussi bien que les techniques les plus récentes pour mesurer précisément la compaction en profondeur et les déplacements de surface sont décrits.

Mechanical Compaction of Crustal Analogs Made of Sintered Glass Beads: The Influence of Porosity and Grain Size

“…Viscous sintering is driven by interfacial tension between the glass beads and the interstitial gas between the beads (Kuczynski, 1949). During viscous sintering, an initial system of viscous droplets evolves with time through two main stages: (1) the growth of necks between droplet-droplet pairs that share a contact (Frenkel, 1945), and (2) the shrinkage and closure of the pores between the droplets (Mackenzie & Shuttleworth, 1949). The initial system of viscous spherical droplets and interstitial pores evolves into a system of isolated pores within a viscous liquid continuum.…”

“…When heated above the glass transition temperature interval, glass beads become viscous droplets. If these glass beads are packed together when heated then, as they transition from glass beads to viscous droplets, they can interact and coalesce in a process referred to as viscous sintering (Frenkel, 1945;Mackenzie & Shuttleworth, 1949;Wadsworth et al, 2016). The dominant consequence of viscous sintering is that the porosity is reduced with time.…”

“…Therefore, implications, and applications, of our results for natural systems are broad. For example, in the context of hydrocarbon and/or geothermal reservoirs, depletion‐induced reservoir compaction is an ubiquitous phenomenon that eventually leads to surface subsidence (Gambolati et al., 2006; Nagel, 2001). On assessing which sedimentary layer compacts first and/or to the highest extent, unconsolidated upper formations and clay‐rich formations are usually considered as the best candidates.…”