Abstract

Traditional aromatic and chlorinated solvents typically utilized in oilfield applications are facing stricter governmental and environmental restrictions for their use and disposal. Concerns about flammability, acute toxicity, and environmental contamination have made their use less attractive. Furthermore, many countries in Central and South America have begun to closely monitor and regulate the manufacture, importation, and storage of typically utilized oilfield solvents such xylene and toluene due to their utilization in the manufacture of illicit drugs.

In an effort to be environmentally and socially responsible, greener alternative solvents from renewable resources are continually being investigated as possible cleaning and solvent solution substitutes. This paper discusses the properties and evaluation of a 100% biodegradable non-toxic solvent blend that is derived from two renewable resources produced both in the U.S. and world. In the past, due to its price and limited availability, the solvent's use has been limited to specialized cleaning applications in the electronics industry. However, due to improved manufacturing processes, the product is more available and affordable for wider applications. The totally biodegradable solvent blend is currently being utilized heavily in paint and coatings removal, ink and graffiti removal, and electronics component cleaning. It has a Kauri Butanol (KB) solvency value of approximately 500 and is a EPA approved SNAP solvent.

This paper discusses the evaluation of the biodegradable solvent blend to replace traditional solvents in stimulation packages for wellbore and formation cleaning applications. Laboratory studies were conducted to evaluate the solvent's efficiency to dissolve and remove pipe dope materials and OB/SOB mud residues and films at room temperature and 150°F. The solvent was also evaluated to determine its efficiency to dissolve and disperse paraffin and asphaltene solids, and to reduce the viscosity and enhance the flow characteristics of heavy crude oils.

Introduction

Crude oil present in a reservoir prior to production exist in equilibrium. As the oil is produced, changes in pH, temperature, pressure, and gas/fluid ratio can result in equilibrium upset. A by-product of this pressure and temperature drop is the precipitation of paraffin and asphaltene in the formation, flowlines, storage tanks, and surface flowlines. These deposits, as well as others such OB/SOB drilling muds and their sludges, excess residual pipe dope coatings, and thick oil sludges and deposits have a high potential to be formed both inside the wellbore and in the near well-bore formation during the life cycle of the well. Conventional acid treatments are ineffective in removing or cleaning these organic deposits, and their presence on the formation face or in the pore throats of the formation may actually prevent the acid from reaching the desired inorganic material or formation zone for the acid stimulation treatment.

These organic deposits are typically dissolved and removed by organic solvents in either circulating tubular cleanouts or matrix injections. Typically these solvent treatments are conducted as solvent pre-flushes or as solvent emulsified in acid to create an acid-in-solvent dispersion to dissolve the organic deposits before an acid stimulation treatment. The external solvent phase of the dispersion disseminates or dissolves the paraffin/asphaltene, pipe dope, hydrocarbon sludge, or OB/SOB drilling mud allowing the acid internal phase to react with the inorganic component.

Environmental Concerns

Traditionally, most operators consider xylene and toluene to be the most effective solvents for organic deposit dispersion and removal. However, governmental regulations regarding their use, storage, transportation and volatile emission limits are increasing in the world's oil-producing areas. Concerns about flammability, toxicity, and biodegradibility have made their use less advantageous. Furthermore, their usage in the manufacture of illicit drugs has further restricted the importation, production, transportation, and storage of these materials in some Central and South American countries. As a result, regulations of these materials has greatly restricted the use of these solvents in oilfield applications.

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