This paper was selected for presentaticm by an SPE Program Commntee fdbwing revbw 01 Information contained in an abstmct aubmNted by the author(s). Contents 01 the paper, as P-ntd, have not bean reviewed by the Society of Petrobm Engimaem and are eubject to cem'ectbn by tlw autl'mr(s). Tha mabfbl, as preeented, does not necesewliy reflect my p@ktn of the Society of Petroleum Engineers, its offb.sm, or membws, Papem presented at SPE meatings em WQW to publicatkm review by Editorial (%nmltha of the Socbty 0! Petweum Engirwers, PwmiiiOn to qis reetrkbd to a"~of Nt mom than 300 **, lllumt-a~~M h~. w~shW@~n~" of where and by whmn the paper is presented. Write Librarian, SPE, P.O. Sox SSSSSS,Richerdeon, TX cmepkwua =~ment ZWS&SBW, U.S.A., Telex, 1SS245 SPEUT. AEsmAm-