Crude Oil/Brine/Rock Interactions during Simulated Petroleum Migration

Barry Bennett¹, Bernard F.J. Bowler², Arnaud Lager², James O. Buckman³, Randy Winans⁴, and Steve R. Larter^5
1 University of Calgary, Calgary, AB
² Newcastle University, Newcastle upon Tyne, United Kingdom
³ Heriot-Watt University, Edinburgh, United Kingdom
⁴ Argonne National Laboratory, Argonne, IL
⁵ University of Calgary, Calgary

Reservoir wettability is controlled by crude oil / brine / rock interactions that are not well understood. It is commonly accepted that the interfacially active component of crude oil is prevalent in the highest molecular weight, most polar fraction, namely the resins and asphaltenes.

We describe the results from a core-flood experiment which suggests there is a role for low molecular weight multifunctional compounds towards enabling surface property alteration. During the core-flood experiment, oil was flowed through a water saturated 1m length siltstone core (porosity, 12%; permeability, 0.01mD) under subsurface conditions (70°C and 7,000psi). Approximately one pore volume of oil was flowed through the core and the experiment was terminated. The siltstone was cut into sections and the core extract petroleum was extracted using organic solvents. The core extract petroleum displayed changes in colour intensity, increasing towards the inlet end of the core. High resolution mass spectrometry indicated the samples from the inlet end of the core were enriched in low molecular weight (100-200 Daltons) pigmented compounds containing one or more; nitrogen, oxygen or sulphur atoms.

Environmental Scanning Electron Microscopy was used to observe water spreading phenomena on freshly exposed core surfaces. The changes in water spreading behaviour as described by ESEM along the core indicates that changes in surface wetting tendencies changed gradually from oil-wet at the inlet to water wet at the outlet. We propose that the removal of key surfactant during petroleum migration may impact the nature of crude oil / brine / rock interactions in petroleum accumulations.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005