One of the problems that occurs during offshore well testing has been the discharge of unburned hydrocarbon emissions into the air and sea that leave deposits of oily slicks or "sheen" on the water surface. This residue results from inefficient flaring operations and can have adverse effects on marine environment.
This paper will discuss a new burner that has been developed to address the environmentally unfriendly fallout conditions that have occurred from crude oil disposal during traditional well testing operations. To support a broad range of applications, the design criteria for this burner included not only the capability to perform fallout free in the wide range of conditions expected during well testing but also to be simple to operate, have a compact lightweight design with a stable pilot and igniter system, provide clean startup, and require low oil pressure.
Burner performance is significantly affected by fuel oil properties and its atomization characteristics. The paper will include an overview of these topics and their relationship to the combustion process, how these topics were addressed in the development of the design, and the testing that was performed by an independent Norwegian environmental testing company to verify the burner's efficiency.
The burner designed to these specifications includes an array of atomizers, uniquely placed to improve flame turbulence and air ingestion important to efficient combustion. Engineering tests performed with 18 degree API crude oil were fallout free and smokeless, and tests performed by the independent environmental testing company verified that the new burner design performed with 99.9 percent efficiency as a burning disposal system.
Well testing during exploration and appraisal includes the production of hydrocarbons with a temporary production facility to obtain fluid samples, flow rate and pressure information for interpretation to help characterize the reservoir. Important decisions such as production methods, facilities and well productivity improvement are made from this information.
Disposal of produced hydrocarbon liquids during well testing is typical when facilities are not available for storage as in the case of mobile offshore drilling rigs and remote locations onshore. Although it is understood that there would be benefit, both economically and environmentally, from collecting the produced hydrocarbons, disposal via burning is generally the accepted method for a short-duration test since it offers the most cost efficient solution.
Alternatives to disposal for offshore testing include well test vessels or producing to tankers or barges while onshore alternatives require a transportation infrastructure, all of which incur additional expense. These alternatives are most likely to be cost effective for long duration or high rate tests or where environmental regulatory restrictions dictate that they be used.
The oil industry has been committed to environmentally friendly exploration and appraisal, and with this improved burner technology, the fallout of unburned hydrocarbons and dense smoke clouds can be significantly reduced or eliminated during well testing operations. Thus, disposal by flaring during testing operations can now be an environmentally acceptable solution. Fig 1 shows the burner in operation during prototype testing, flowing at approximately 6300 BOPD.
Burners, which may be referred to as "Well Test" or "Crude Oil" burners, have been used for over 25 years (Fig 2). Prior to their development, only gas wells were tested offshore as gas flaring was generally considered to be an acceptable and efficient practice. After the development of the burners, oil well testing could be accomplished, which provided the opportunity to acquire and use important reservoir information.
Liquid hydrocarbon flaring during well testing operations presents a problem when incomplete combustion results, and there is fallout of unburned hydrocarbons and objectionable gaseous emissions.