Effect of hysteresis on petrophysical properties of limestone hydrocarbon reservoir rock

Yaser Salimidelshad, Ali Moradzadeh, Ezatallah Kazemzadeh, Peyman Pourafshary, Abbas Majdi

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The petrophysical properties of carbonate reservoirs may change when they are subjected to mechanical loadings due to the softness of the formation. As the reservoir fluid pressure declines due to production, the net load on the rock increases, which leads to compaction of the rock and decrease in its pore volume, causing blocking of pore throats and the permeability reduction. In this study, we experimentally investigated the hysteresis effect of petrophysical properties of two carbonate core samples during the loading using CMS-300 apparatus. The structure of samples was processed by CT scan images and analysis of the pore size distribution was also conducted using mercury injection testing followed by scanning electron microcopy (SEM). Our results indicate that isotropic long-term and short-term loading considerably change the grain structure, while the petrophysical properties do not have a clear effect. The porosity induced by the cyclic loading was affected by intergranular micro-extension fractures. The results also indicate that the greatest reduction of porosity in fractured limestone occurred at the first loading step; however, further reduction was strongly due to the consolidation and adherence of the grain matrix. This fluctuating trend was also observed for the permeability, with a severe reduction in the permeability when crushed grains were placed in the connected pore path. The measured porosity and permeability of carbonated rocks, as stress-sensitive parameters, along analysis of the micro-fracture effects during loading and unloading, can be considered in production and injection management of reservoirs. They are also useful for predicting of any possible risks during different periods of reservoir life and determining the optimum production pressure of the reservoir.

Original languageEnglish
Pages (from-to)745-755
Number of pages11
JournalJournal of Petroleum Science and Engineering
Volume177
DOIs
Publication statusPublished - Jun 1 2019

Keywords

  • CT scan
  • Hysteresis
  • Petrophysical properties
  • Pore size distribution
  • SEM

ASJC Scopus subject areas

  • Fuel Technology
  • Geotechnical Engineering and Engineering Geology

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