Coal Particles Cleanout Technology in Coal Bed Methane Wells


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Coal particles cleanout which is regarded as the key technology in the operation of coal bed methane (CBM) wells, play an important part in making steady production. In oil wells, Sand cleanout is operated by circulating a liquid or a multiphase fluid into the wellbore to bring sand particles to the surface. Although the sand cleanout operations have been applied successfully in most wells with high efficiency and negligible leakage, it would leak working fluid into coal bed formation, destroy the structure of coal bed and jam the formed channel of gas production. In this paper, a new continuous vacuum cleanout technology has been developed to effectively remove coal particles in CBM wells by employing a jet pump. The Concentric Tubing String (CTS) which is assembled by 3.5 inch tubing and 1.5 inch tubing is also introduced in, because there is no CCT technology in China at the moment. Detailed structure and principle of the coal particles cleanout technology system are described, while a theoretical model is formulated to optimally design the system based on the coal particles settling experimental data and jet pumping theory. It has been shown from field applications that the coal particles cleanout technology makes significant improvements in achieving high efficiency and preventing leakage in CBM wells. Moreover, the new technology reduces the skin damage and increase the production compared to non-vacuum CBM wells.



Edited by:

Mohamed Othman




B. Liu et al., "Coal Particles Cleanout Technology in Coal Bed Methane Wells", Applied Mechanics and Materials, Vols. 229-231, pp. 2470-2473, 2012

Online since:

November 2012




[1] Liu Xinfu, Qi Yaoguang and Liu Chunhua, Prediction of flowing bottomhole pressures for two-phase coalbed methane wells; ACTA PETROLEI SINICA, Vol. 31, No. 6, pp.998-1003, October (2010).


[2] XIAO, Z., SHAHIN, M., HOSEIN, P., et al, laboratory Investigation and Field Use of a Novel Sand Cleanout Fluid System for High Temperature Applications; paper SPE 84887 presented at the SPE International Improved Oil Recovery Conference in Asia Pacific, Kuala Lumpur, Malaysia, 20-21 October (2003).


[3] TOMREN, P.H., IYOHO, A.W. and AZAR, J.J., Experimental Study of Cuttings Transport in Directional Wells; SPE Drilling Engineering, Vol. 1, No. 1, pp.43-56, February (1986).


[4] OKRAJNI, S. and AZAR, J.J., The Effects of Mud Rheology on Annular Hole Cleaning in Directional Wells; SPE Drilling Engineering, Vol. 1, No. 4, pp.297-308, August (1986).


[5] SIFFERMAN, T.R. and BECKER, T.E., Hole Cleaning in Full-Scale Inclined Wellbores; SPE Drilling Engineering, Vol. 7, No. 2, pp.115-120, June (1992).


[6] NGUYEN, D. and RAHMAN, S.S., A Three-layer Hydraulic Program for Effective Cuttings Transport and Hole Cleaning in Highly Deviated and Horizontal Wells; SPE Drilling & Completion, Vol. 13, No. 3, pp.182-189. September (1998).


[7] LI, M., WANG, W., HE, Y. and YUAN, M., Experimental Study on the Performance of Sand Moving in vertical Wellbore; Journal of the China University of Petroleum (Natural Science Edition), Vol. 24, No. 2, pp.33-35, April (2000).

[8] LI, A., WANG, S. and WANG, W., Study on Settling Rule of Formation Sand in the liquid; Petroleum Geology and Recovery Efficiency, Vol. 8, No. 1, pp.70-73, February (2001).

[9] WAlTON, I.C., Computer Simulator of Coiled Tubing Wellbore Cleanouts in Deviated Wells Recommends Optimum Pump Rate and Fluid viscosity; paper SPE 29491 presented at the SPE Production Operations Symposium, Oklahoma, OK, 2-4 April (1995).


[10] BLOT, M.A. and MEDLIN, W.L., Theory of Sand Transport in Thin Fluids; paper SPE 14468 presented at the SPE Annual Technical Conference and Exhibition, Las Vegas, NV, 22-26 September (1985).


[11] KHAN, A.R. and RICHARDSON, J.F., The Resistance to Motion of a Solid Sphere in a Fluid; Chemical Engineering Communications, Vol. 62, Nos. 1-6, pp.135-150, (1987).

[12] LI, M., WANG, W. and ZHAO, G., The Flowing Rules of Sand Carrying Well Fluid in vertical Wellbores and Its Application in Oil Production; Journal of Experimental Mechanics, Vol. 17, No. 3, pp.385-391, September (2002).

[13] Hawksley P G. The Effect of Concentration on the Settling of Suspensions and Flow Through Porous Media: In Some Aspects of Fluid Flow. Edward Arnold Co., London, 1951, (4): 114~135.

[14] LI, S., Engineering Fluid Mechanics; China Machine Press, Beijing, China, (1980).