1. Field of the Invention
The present invention relates to an environmentally-friendly base fluid and methods for producing alkyl esters useful as the base fluid in oil-based mud compositions and related compositions.
2. Description of the Related Art
Mineral oil-based base fluids are widely used in oil-based mud (OBM) formulations worldwide. These base fluids have lower fire and flash points compared to vegetable and waste vegetable oils, are poorly biodegradable and could contaminate soil and waterways if serious spills occur with drastic reduction in soil fertility and the water quality. Vegetable oils and their derivatives are highly biodegradable, have superior environmental characteristics and virtually non-toxic and thus expected to cause relatively no environmental impact. Besides use in oil-based mud formulations, other types of industries using mineral oil-based fluids to fulfill certain functional tasks also need an alternative to mineral oil-based fluids.
Vegetable oils and their derivatives could be a suitable replacement for mineral-oils in such applications. Other than highly favorable environmental and biodegradation characteristics, vegetable oils and their suitable derivatives have high fire and flash points. The high flash and fire points characteristics of vegetable and waste vegetable oils compared to mineral oils ensure better drilling safety in operation, handling, storage and transportation of vegetable and waste vegetable oil-based base fluids. The excellent fire safety characteristics of vegetable oil-based dielectric fluid will make them better candidates for high temperature, high pressure (HTHP) drilling operations.
Mineral oil-based drilling mud spills or discharges, whether accidental or intentional, can cause serious socio-economic and environmental problems as these muds typically have much higher toxicity and significantly lower biodegradation characteristics compared to vegetable and waste vegetable oils and their derivatives. It is well known that the detrimental effect of mineral oil-based base fluids can cause a drastic change in the health, mobility, mortality rate and life style of the population and the habitats of the affected areas, which can lead to a drastic increase in the total operating cost. For these reasons, a need exists for replacements for the non-environmentally friendly mineral oil-based muds.
Due to the increasing concerns of global and environmental protection agencies, government and environmental regulatory agents are enacting stringent environmental laws and regulations to minimize problems associated with mineral oil-based OBM systems and are imposing stiff penalties for spills, cuttings disposal, OBM mud discharges whether accidental or not. Government agencies in almost every area of the world are now aware of the potential damage caused by conventional oil-based muds and contaminated cuttings. There are now strict rules and legislations limiting the use of conventional oil-based drilling muds in the USA, the North Sea, the Adriatic and the CIS. The economic cost of remediation and reclamation of mineral oil-based mud contaminated lands, cuttings, disposal site is very high. The total loss in revenues associated with cuttings and mud transportation and also clean up can exceed thousands of dollars per well with a drastic increase in total operating costs. Any unwanted or accidental spills or discharges of mineral oil-based muds can increase the operating cost further due to penalties and fees to national oil spill recovery and reclamation schemes. The increase in operating cost for losses due to non-productive drilling time and also cost associated with site restoration can exceed millions of dollars per annum. The recent realization of the high economic impact of mineral oil-based drilling muds due to their short and long term consequences on the environment, ecosystem, and human health have made operators look for suitable alternatives for oil and gas industry applications. Due to excellent environmental and biodegradation properties of vegetable, waste vegetable oils and their derivatives, these oils are potential candidates for the development of a new generation of OBM systems.
Others have attempted to make products, such as lubricants or biofuels, from vegetable oils. These prior attempts generally did not use recycled waste vegetable oil. Furthermore, the processes used to produce such products were complicated and required cleaning reagents or absorbing materials, such as silicates and clays.
A need exists for a new type of OBM system that is environmentally friendly, as well as performs well. Vegetable oils are natural products and have renewable sources with plenty of supply as per consumer demand and thus the most suitable candidates for substituting petroleum-based fluids. The advantage of vegetable/plant oils is that they have renewable sources compared to the limited sources of mineral oils and need simple and low energy processing and simple equipment for the extraction of the oils. The disadvantage of vegetable oils is that they have lower oxidative stability, a higher pour point, and significantly higher viscosity compared to mineral oils. Their high viscosity and susceptibility to oxidation have been the primary obstacles to use them as a base liquid for oil-based mud formulation. The most attractive features of vegetable oil-based fluids are their high biodegradability, very low toxicity, and high fire and flash points to improve operational and transportation safety. Vegetable and waste vegetable oils are usually 95-100% biodegradable, virtually non-toxic and have no or negligible impact to the surrounding environment. OBM mud systems formulated using these vegetable oils or their derivatives pose little to no danger to aquatic or terrestrial, offshore or onshore, deep water or shallow water environments.