Some Considerations in the Selection and Installation of Gravel Pack for Oil Wells

Abstract

Sand produced with the oil in many fields is one of the major causes of wearand down time on pumps, tubing, gas anchors and other equipment. Arresting thisproduction of sand at its source would materially increase the life of suchequipment and reduce production costs. It is possible to materially reduce or eliminate sand trouble in some fieldsby the judicious selection of the openings in perforated liners. However, inother fields this is impossible because of fineness of the sand, poorcompaction of the formation, low bottom-hole pressures, or other conditions. Insuch cases, gravel packing seems to offer a practical and relatively simplesolution of the problem. Gravel packing of wells, especially water wells, is not new. However, theselection and placing of the gravel have heretofore not been given sufficientstudy, and for that reason the results often have been unsatisfactory. Ananalysis of the problem is presented herein, with the hope of showing thatgravel packing can be put on a rational basis and made a practical method ofcorrecting a condition that has been a constant source of trouble to the oilindustry. Three problems are considered:selection of the proper mesh"gravel" to hold the formation in question,proper placing of thegravel,selection of a properly perforated liner to hold the gravel. Selection of Liner The third problem named is the most readily solved. It would seem that aperforated liner that will hold back all of the gravel should be selected. Inthis way the pack will remain permanently intact. This will require a slothaving a width equal to or less than the diameter of the smallest grains in thegravel pack. While a slot with a width twice the grain size at the tenpercentile of the gravel pack would hold the gravel in the accepted sense, thesmall quantity produced during the period the slot bridge is being built upmight be enough to cause the pack to settle, allowing the production ofsufficient formation sand to brand the installation a failure. T.P. 960