Multiple episodes of sand injection leading to accumulation and leakage of hydrocarbons along the San Andreas/San Gregorio fault system, California

Giuseppe Palladino, Roberto Emanuele Rizzo, Gustavo Zvirtes, Antonio Grippa, Ruy Paulo Philipp, David Healy, G. Ian Alsop

Research output: Contribution to journalArticle

Abstract

The presence of sand injections has been shown to enhance the likelihood of hydrocarbon traps within siliciclastic successions. Through the development of large interconnected networks of sills and dykes, sand injection complexes provide a volume of porous and permeable rocks within the low permeability host units. Overall, the formation of sand injection complexes requires extensive fracturing and hydrofracturing, which can be particularly pronounced when sand injections are coupled with brittle tectonic deformation. In some circumstances, this process may threaten the integrity of the reservoir top seal thereby preventing further hydrocarbon accumulation. Studying exceptional exposures along the coastal area of Santa Cruz in California, we report evidence for top seal failure associated with injection episodes. Two distinct sand injection episodes are proposed. The first event, datable to the Late Miocene, resulted in large volumes of sand being emplaced within the top-seal units, and was followed by accumulation of hydrocarbons within the newly injected sandstones. Later, a series of brittle tectonic events, associated with the San Andreas/San Gregorio Fault System, caused remobilization and accumulation of sand along newly formed fault planes. Our case study documents this combination of pervasive brittle deformation and sandstone injection along fault structures, which can ultimately disrupt the integrity of a host unit leading top seal failure and leakage of hydrocarbons.

Original languageEnglish
Article number104431
Number of pages16
JournalMarine and Petroleum Geology
Volume118
Early online date30 Apr 2020
DOIs
Publication statusPublished - Aug 2020

Keywords

  • California
  • Hydrocarbon leakage
  • San andreas/San Gregorio fault system
  • Sandstone intrusions
  • Sandstone-filled faults
  • Santa cruz injection complex
  • Santa cruz petroleum system

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