Is Water Washing An Important Petroleum System Process?

Abstract

Water washing is one of the in-situ natural alteration processes affecting geochemical composition and bulk physical properties of petroleum accumulations but it remains only qualitatively described and the extent and true importance of the process remains unknown. It causes removal of the more water soluble light alkanes, aromatic hydrocarbons and other non-hydrocarbons from petroleum through contact with moving formation waters in reservoirs, during migration, reservoir storage and potentially during production. Therefore, quantitative determination of organic compound partitioning, between oils and water phases in the subsurface, which occur during water washing, is necessary to better understand the distribution of these compounds and hence develop reliable parameters that can be used to assess the real impact of water washing on crude oil composition with realistic subsurface water flow rates. However, most of the geochemical literature is qualitative in nature and no data has been reported on the quantitative aspects of the oil-water partition process at subsurface conditions for aromatic species, especially heteroaromatic compounds such as alkylated benzothiophenes and derivatives, which have commonly reported in “water washing” studies. In this study we quantitatively assess the effect of water washing on petroleum by conducting water washing experiments in the laboratory to determine partition coefficients of aromatic species in dead crude oil/brine systems under nominal deep reservoir temperature and salinity conditions (90°C; 35,000 mg/L Sodium chloride; 1 bar). Also, we describe the distribution properties of water-soluble acids, bases, and neutral NSO compounds of the washed oils using high-resolution FTMS in ESI and APPI ionisation modes. We assess the viability of water washing as a geochemically important process.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016