Demulsification of heavy oil without the use of solvents

Abstract

Heavy oil viscosity is one of the few reservoir characteristics that can determine the exploitation strategy for a hydrocarbon pool. It can help predict whether cold production of the reservoir will reach economic rates, or whether thermal techniques need to be employed. In order to determine the viscosity of an oil sample taken from the field, it is necessary to remove all the water and sediment that is typically co-produced along with the oil. With the case of heavy oil, the water and oil tend to bind together in tight emulsions that make separation difficult. Current techniques for water and oil separation make use of demulsifiers, which are typically solvents and chemicals that break the emulsion and allow the two phases to separate. Unfortunately, removing these additives from the oil after separation has proven to be difficult and has significant effects on the measured oil viscosity. An experimental study was carried out to investigate if water and sediment could be removed from heavy oil without altering the physical characteristics of the oil and to obtain repeatable oil viscosity measurements. Field samples were heated to a temperature of 160°C and a pressure of 1931 kPa (280 psig) and forced through a series of filters. The different hydrocarbon fractions were collected and recombined to form a sample with the same physical properties as the original oil. Results showed that the oil samples processed in this manner were devoid of water and had viscosities similar to that of the original oil.