In order to evaluate the long-term behavior of crude and distillate fuel oil stored in salt caverns, investigations were carried out on three caverns in West Germany, which have contained either crude or distillate fuel oil for several years.


In the United States, the Energy Policy and Conservation Act of 1975 established the requirement for a Strategic Petroleum Reserve (SPR) of up to one billion (109) barrels of oil. The Federal Energy Administration, now a part of the Department of Energy (DOE) was given the task of implementing the SPR. Because there was very little information available on the effects of long-term storage on the physical, chemical, refining and/or marketing characteristics of crude oil and fuel oil, DOE contracted KBB to perform pertinent studies. This paper presents a comprehensive evaluation of the effects of long-term storage in salt-solution caverns on the properties of certain crude and distillate fuel oils. In order to obtain conclusive results, investigations were carried out between August 1978 and July 1979 on three caverns in West Germany, two of them containing crude oil and one containing distillate fuel oil. In the northern part of West Germany 33 caverns, each of them designed for an initial capacity of 500 000 m3, are leached in the Etzel salt dome. One of the two crude oil caverns investigations were made on is one of these 33, which were leached in the Etzel salt dome near Wilhelmshaven to hold the emergency crude oil reserves of the Federal Republic of Germany. This Etzel cavern contains a variety of light and heavy crude oils, thus it is especially suitable for studies of stratification and mixing. In addition to the fuel oil which was used as a blanket medium in the initial phase of solution mining, the following types of crude oil are stored:

  1. Arabian Light

  2. Arabian Heavy

  3. Iranian Light

  4. Iranian Heavy

  5. Basrah

  6. Nigerian Light

  7. Khafji

The other two caverns samples were taken from belong to Mobil Oil AG, Germany. One of these caverns situated at Lesum, near Bremen, contains only one generic type of crude oil, e.g. Arabian Light. The other cavern is filled with distillate fuel oil. The storage time of these investigated caverns varies between four and seven years.


Since a lot of requirements were set the development of the sampling device took more than half a year. Some of these requirements are:

  1. In order to obtain a sufficient volume for the planned chemical analyses, a sampler capacity of 6 1 was required.

  2. The probe has to be equipped with a swing-out cantilever for taking samples at a distance of about 4.5 m from the perpendicular.

  3. For Etzel cavern between 20 and 30 samples, for the Lesum caverns between 10 and 15 samples had to be collected.

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