Constant GOR as an infinite acting effect in reservoirs producing below (dew/bubble) saturation pressure

Miao Zhang, Luis F. Ayala

Research output: Chapter in Book/Report/Conference proceedingConference contribution

13 Scopus citations


In recent years, constant producing gas-oil-ratio (GOR) trends have been repeatedly observed in many unconventional oil and gas reservoirs. This effect can last many years, even after the depleting system is believed to have crossed its saturation pressure. In this study, we corroborate that constant GOR could indeed be expected in depleting reservoir systems exhibiting early-transient infinite-acting flow under constant bottomhole pressure (BHP) production constraint for both linear and radial flow geometries. This effect had been shown to be present in infinite-acting linear systems by previous authors; but this study shows how this GOR trend and value can be fully predicted prior to availability of production data. Focusing on liquid-rich gas systems, we start with the applicable multiphase governing flow equations and provide semi analytical and rigorous solutions. Similarity theory is applied to transform the resulting system of equations and achieve the multiphase solution. The results show that a constant GOR effect could be maintained as long as the flow regime remains infinite-acting, which is a typical condition to be found in unconventional systems. Also, it is found that, in both linear and radial multiphase systems, this constant or stabilized GOR is shown to be present regardless of condensate phase mobility at sandface conditions.

Original languageEnglish (US)
Title of host publicationSociety of Petroleum Engineers - SPE Annual Technical Conference and Exhibition, ATCE 2015
PublisherSociety of Petroleum Engineers (SPE)
Number of pages26
ISBN (Electronic)9781510813229
StatePublished - 2015
EventSPE Annual Technical Conference and Exhibition, ATCE 2015 - Houston, United States
Duration: Sep 28 2015Sep 30 2015

Publication series

NameProceedings - SPE Annual Technical Conference and Exhibition
ISSN (Electronic)2638-6712


OtherSPE Annual Technical Conference and Exhibition, ATCE 2015
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Fuel Technology
  • Energy Engineering and Power Technology


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