Effect of Flow Rate on Stability of Unconsolidated Producing Sands

Abstract

This paper was prepared for the 48th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Las Vegas, Nev., Sept. 30-Oct. 3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgement of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Stabilization of unconsolidated sand during production by sand arching was confirmed with a sand-pack model of a well completion. Fluid was flowed radially through a sand pack which was loaded vertically to simulate over burden pressure. Flow rates were gradually increased to the point at which sand flowed and the arch then examined. Larger arches resulted from higher flow rates. Critical rate for the sand production depended on rate history as well as rate magnitude and arch size. Introduction In December, 1970, the offshore oil industry in the United States' Gulf Coast region entered a new phase of unprorated production. Operational management emphasis shifted from its past concern with reservoir control to concern past concern with reservoir control to concern with well conditions which permitted the highest possible rates of production. With maximum rates possible rates of production. With maximum rates of production determined by physical restrictions rather than by legal limits, engineering attention was directed to well designs which would allow wells to be produced at the highest possible rate. Physical limitation of production in many fields in the Gulf Coast region was in the form of sand production; i.e., a high sand content in produced fluid when wells were flowed above a certain critical rate, and, in many cases, when wells were flowed at all. Most fields in the Gulf Coast region are in young (Pliocene and Miocene) reservoirs in which the reservoir rock is an unconsolidated (namely, uncemented) fine- to very fine-grained sand. From widespread experience in the area, it was known that some wells produced sand and others did not. Also many wells produced sand and others did not. Also many wells which produced clean oil with no sand started to produce large quantities of sand when water production produce large quantities of sand when water production began. Sand content in a flow stream causes definite limitations on production rate in two ways. First, a well in which large amounts of sand are washed into the bore by the produced fluids will in many cases be shut in by sand bridges blocking production in the well bore, plugging down-hole equipment, or plugging surface equipment. Such plugging must be removed at considerable expense and nuisance; production is lost during the plugged period. Second, if the sand content is insufficient to block the production stream, it is carried by the flow stream through the equipment. In the same manner as a sand-blast machine, the fluid-sand mixture rapidly erodes surface and down-hole equipment, possibly causing loss of well control, blowouts, fires, production shut-in, repairs, and possible loss of other wells. Such results to life and possible loss of other wells. Such results to life and equipment can be catastrophic; sand production is noted with considerable alarm.