Since their introduction in 1943, emulsion muds have developed into an important class of drilling fluids, which now has its own place in modern drilling operations.
The report reviews the history of their development, their preparation, principal properties and present application and gives some suggestions for further research.
Depuis 1943, année OU elles furent lancées, les boues d'émulsion ont pris leur essor jusqu'à former une importante catégorie de fluides de forage, qui prend actuellement sa place dans les opérations de forage moderne.
La communication passe en revue l'historique de leur élaboration, de leur fabrication, de 'leurs principales propriétés et de leurs applications actuelles et donne quelques suggestions touchant la continuation des recherches en cette matière.
Development In so far as can be ascertained, the first application of an artificially prepared emulsion of crude oil in clay mud in normal drilling operations, took place in June 1943 at Shell Caribbean Petroleum Conipany's well hIG-470 in the Mene Grande field of Western Venezuela. This well was drilled on a southern extension of the field, where, due to peculiar formation characteristics, considerable drilling dif ficulties were being experienced. The producing formation consisted of a hard, well-cemented. sandstone occurring between 6,000 and 8,500', underlying a body of black, hard but brittle, caving shale which contained beds of concretions of clay ironstone.
Prior to the introduction of drilling emulsion, three had been completed with clay mud and two *' Shell Caribbean Petr. Co, Maracaibo, Venezuela. with oil base inud, all after considerable dif ficulties due to caving and stuck pipe had been experienced.
One hole had bccn abandoned after 3 attempts to reach the objective with clay mud had failed. The major cause of trouble appeared to be the presence of the concretions, which when dislodged from the shale formation, dropped on to the bit and becaine wedged between the bit and streaks of hard formation, causing stuck drill pipe. Free circulation was generally maintained.
Operations with oil base mud showed the great value of good lubricating properties, since, although caving was still experienced, it was now possible to pull out of the hole without having to back-off or cut the drill pipe. It should be mentioned, however, that probably due to the low viscosity of the oil base mud at bottom hole temperatures, fill-ups of 100-150' after round-trips were regularly experienced. As a result, one hole drilled with oil base mud was suspended when it proved to be impossible to recover a fish in the 55/8" hale.
In view of the improvements obtained with oil base mud, a study was begun of the possibility of irnparting the obviously very desirable lubricating properties to clay muds without introducing any of the undesirable properties of oil base ï-nuds, such as high cos
