Fills Cleanout With Coiled Tubing in the Reverse Circulation Mode

Abstract

fax 01-972-952-9435. AbstractRemoving sand fills from wellbores is one of the major applications for coiled tubing (CT). For the fills cleanout process, the fluid could be circulated in two different modes: forward circulation and reverse circulation. In the forward circulation mode, the carrying fluids are pumped through the CT down to bottom and flowed back to surface in the CT/casing annulus. For reverse circulation, fluids are pumped down the CT/casing annulus and back up the coil. In many cases with large completions and low reservoir pressures, the forward circulation mode cannot effectively clean the fills out of the annulus with only a limited available flow rate or without circulating expensive gel fluids, especially for the heavier particulates in deep and/or highly deviated wells. Due to the smaller flow areas and therefore higher velocities, fills may be more readily transported inside the CT flow channel. Therefore, reverse circulation may be an option to overcome the above constraints associated with forward circulation.Several major risks for reverse circulation with CT include coil collapse, loss of well control and sand bridging in the coil. Controlling the rate of penetration (ROP) of the CT into the fill is very critical for the reverse circulation sand cleanout process. There is a lack of knowledge on the effect of as well as optimum ROP during reverse circulation. In this paper, the maximum ROP for different sand types at different deviated angles and water flowrates for reverse circulation cleanouts are investigated with a full scale flow loop test facility. Based on these test results, empirical correlations have been developed and incorporated into an existing proprietary solids transport computer algorithm, which can now be used to optimize the hole cleaning process for both the forward and reverse circulation modes of solids transport.

Sand Cleanouts With Coiled Tubing: Choice of Process, Tools and Fluids

“…Several cleanout techniques have been developed over the years, these include stationary circulation, wiper tripping (1,2,(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) , reverse circulation (19)(20)(21)(22) , sand vacuuming technology (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)36,37) , and venturi sand/junk bailers (4,22,(38)(39)(40) .…”

“…Reverse Circulation Cleaning (5,(19)(20)(21)(22) In some cases the forward circulation mode cannot effectively clean the fill out of the wellbore because the size of CT limits the achievable circulation rate required for circulation/wiper trip methods. Because of the smaller internal flow area of CT, it is often possible to achieve higher circulation velocities inside the CT and, where appropriate, fill can be effectively transported by reverse circulating up the CT.…”

Effect of Different Qualities of Foam on Fill Particle Transport in Horizontal Well Cleanup Operation Using Coiled Tubing

“…On the other hand, reverse circulation mode involves the pumping of fluid down through casing and the suspension fines are routed back to the main reservoir via the tubing string. Reverse circulation cleanup mode is used for large particles cleanout [2].…”

Factors affecting fill removal from horizontal well during colied tubing cleanout operation

“…Present study is focused on the forward circulation flow of the cleaning fluid. Solid particles transport is problematic in horizontal wellbore [2]. In this situation, fill particles drop down the lower side of annulus and form a solid bed.…”