Thermally enhanced oil recovery (EOR) operations in the southern San Joaquin Valley (SJV) of California increase oil recovery, but also cause excessive sand production. Sand and heavy hydrocarbon materials removed from tanks and other production facilities are typically non-hazardous by California waste characterization criteria. The tank bottom hydrocarbons exhibit cohesive properties that support the beneficial reuse of these materials as binders in road paving materials. Tank bottoms mixed with local aggregate yields a product that has minimal environmental impact.
Road mix variability can be high due to the nature of the materials used, but does not severely impact the overall quality of the final product. Process and issues that directly or indirectly impact road mix variability include: free liquid removal, aggregate mining, produced sand characteristics, oil/binder viscosity and mixing operations. Despite the variability of road mix materials and processes, test results show that heavy oil road mix products meet most of the minimum standards for commercial cold mix paving products.
Potential environmental concerns with oilfield road mix are offset when net air and waste management benefits of this process are considered. Air emissions are a potential concern and are related to the level of volatile organic constituents (VOC) in the oil. Offsetting this concern are:
Low VOC content in most SJV heavy crude.
Particulate reduction from paving onsite roads.
In addition, offsite disposal of tank bottoms yields higher emissions from transport and disposal and fills up valuable landfill space with non-hazardous materials.