New Gravel Pack Tool for Improving Pack Placement

A new type of gravel packing tool may eliminate the need for the pressure washing and repacking that are frequently required. This tool performs equally well in vertical wells and in highly deviated wells; it improves gravel placement in vertical wells, and in a single pass can pack wells inclined as much as 110 deg. from vertical. Introduction Gravel packing highly deviated wells has long been a source of completion problems. The gravel packing operation consumes much time, and its results are often of doubtful effectiveness because of improper gravel placement. Our assumption was that in highly deviated wells, gravel does not fill the hole uniformly when packed by conventional methods. A history of numerous premature sand-outs supported this belief. Settling of packs has been monitored with radioactive pellets, and survey results show excessive movement over short periods of time if wells are not fully packed.Our objectives were to decrease the amount of time required for packing and to increase the effectiveness of the gravel pack. We hoped to achieve a full pack in one pass and to eliminate the need for pack "compacting" procedures such as pressure washing.We approached the problem by observing laboratory-scale models and full-scale models of gravel packing. We devised and tested a tool for improving packing. We devised and tested a tool for improving the packing operation in the models. By using transparent laboratory models we could repeat the tests under controlled conditions and could easily watch the packing process. Later we built several full-size tools based on the model studies and tested them in actual gravel packing jobs in oil wells. Gravel packing processes are most effectively depicted in motion processes are most effectively depicted in motion pictures and they were studied by that means. The pictures and they were studied by that means. The following is a discussion of the dynamic processes observed. This paper describes the basis for efficiently gravel packing high-angle holes in thick intervals without the need to wash down the pack in several stages. Construction of One-Tenth-Scale Laboratory Model We developed a 1/10-scale laboratory model to permit controlled testing of gravel packing in vertical permit controlled testing of gravel packing in vertical and deviated holes. Fig. 1 shows details of the first smooth-walled model. It was constructed of a transparent 1 1/4-in.-ID Lucite outer tube to simulate the inner wall of a section to be gravel packed. A transparent 5/8-in.-OD Lucite slotted liner was centered in the outer tube. A 1/4-in.-OD stainless steel tube was placed inside the liner to simulate the tailpipe (or placed inside the liner to simulate the tailpipe (or stinger) on the bottom of conventional gravel packing tools.Gravel-water slurry entered the model through the inlet port at the top, pointing radially inward (180 deg. opposite the field crossover tool). Then the fluid descended to the bottom of the model, and ascended inside the stinger just as in a field well.The entire model was mounted on a rotatable frame allowing us to run model tests at all angles of hole deviation. Tests were run at angles from the vertical to 110 deg. from vertical. This model gave a good representation of a conventional gravel packing job in a smooth wellbore. JPT P. 19