Using CHARM Modelling to Decide the use and Discharge of Surfactant at an Offshore EOR Project

Abstract

The application chemicals such as surfactants for Enhanced Oil Recovery (EOR) has caught the attention of various stakeholders especially regulators and operators - raising concerns of the impact of these chemicals to the ocean when they are back-produced. The current approach in mitigating the toxicity at production is the dilution of produced fluids to a lower concentration before disposal to sea. However, how confident are we that EOR chemicals do not cause environmental impact to marine life? Due diligence conducted showed that there are no environmental regulations or guidelines in Malaysia for the application of EOR chemicals at an offshore platform. For this reason, our team refers to the strictest of regulation for chemicals' use and discharge for an offshore environment used at the North/Norwegian Sea, adopting all qualification criteria from Harmonized Ocean Chemical Notification Format (HOCNF), of the OSPAR Harmonised Mandatory Control System (HMCS), developed through the OSPAR Decision 2000/2. HOCNF ranks chemical products according to Hazard Quotient (HQ), calculated using the Chemical Hazard and Risk Management (CHARM) model. CHARM is a set of rules to determine the risk and extent of surfactant formulation's movement in the ocean - a vital decision making tool to determine if EOR chemicals are safe for use and overboard discharge. This paper describes the ‘environmental-friendliness’ of a newly developed surfactant formulation which will be applied in a Water-Alternating-Gas (WAG) operation at an offshore field in Malaysia using CHARM. First, a comprehensive review of the components of the formulation was conducted, leading to sound selection and/or synthesis of chemistries that confers good environmental properties i.e. non- or low toxicity, persistency, bioaccumulation, with high biodegradability. Next was to determine the degree of toxicity of the formulation at three trophic levels. Using the lowest acute toxicity value, we apply this value to the CHARM model to calculate the dilution of the formulation 500 m radius from the point of discharge - given the expected adsorption, application concentration, and the volume ratio between squeeze vs. produced water. Whether CHARM is exhaustive to decide if the surfactant formulation can be discharged overboard is still being debated. Many argued that it is the responsibility of the chemical manufacturer or product inventor to select or synthesize chemistries with good ecotoxicity properties in the first place. Product innovation has to be aware on new regulation(s) e.g. the banning on the use of a chemical currently used in manufacturing so that the company develops an alternative ahead of its competitors. In the operator's viewpoint, even if the model indicates that the chemical pose a low hazard, physicochemical parameters of the produced fluids has to be monitored beyond the pilot implementation period.