A novel method to determine total petroleum hydrocarbon (TPH) and water contents in reservoir drill cuttings

Abstract

It is very well known that crude oil is extracted from the earth crust by drilling process and when the drill bit reaches the oil reservoir, the drill cuttings are being mixed with oil. The reservoir drill cuttings with oil are hazardous to the environment and cannot be disposed as such and an appropriate method is needed for disposal. To perform an appropriate disposal, it is necessary to determine the toxicity of reservoir drill cuttings by the polycyclic aromatic hydrocarbons or total petroleum hydrocarbon contents. A standard for evaluation of heavy and light petroleum content in a sample is not available, and some alternative techniques require specialized operators and facilities suitable for the equipment; therefore, they have a high cost. For this reason, an innovative technique based on Soxhlet extraction and retort method is named as hybrid method, which was developed to determine the petroleum levels in reservoir drill cuttings to have better control of disposal. The optimal extraction and drying time for different solvents, the influence of the oil content and gravity were evaluated to validate the method. The results showed that the hybrid method could accurately determine the petroleum and water content of the reservoir drill cuttings with error less than 1%, for an extraction with hexane or dichloromethane/acetone solution for 24 h, with solvent renewal in a half of total time and 3 h of oven drying. The method can be employed as an alternative technique to determine petroleum content when it is below 15%, which is cheaper and more practical than current methods. Thus the disposal control of drill cuttings containing oil can be improved and besides making the petroleum content analysis technique more accessible and useful.