Low Permeability Gas Reservoirs: Problems, Opportunities and Solutions for Drilling, Completion, Stimulation and Production

This P8f»f -~ for p_tamn by Bn SPE Program Commfttae foIowi1g r.n.. d Wormadon ~ n Bn abIIract IUbmItad by 1h8 author!s). CooIIWWs d .,. peper, . ~, have ~ ~ r8IrieW8d by the Society of Petrolalm Engin... and ate slblec-.d to con8Cticw1 by the aulhor(s). The maI8ria~ as ,.~t8d. does n~ ~arily r8ft8d any ~ of 818 Society d ~ Engw-., is ~ or ~rs. PapeIW rx-II8d at SPE meetings are su~ to PIdC8tioo ,.new by EdtoriaJ Convnitlof the Sodety of P~um EngtI88rs. P~lslion to oopy Is ~8d to Bn absb8d d not more "300 words. IlusIratIons may n~ 'CXIPi8d. The absb8d Shoukl oontan ~ admowtedgemanl ofwi\-. and by wtIom tha peper p-'8d. Wrltellll8rl8n, SPE, P.O. Box 833838, RktIaIdson, TX 75083-3836, U.SA, Fax 01-214-952-9435. Introduction Vast reserves of valuable natural gas and associated liquids exist trapped in low penneability intercrystalline and microfractured carbonate and sandstone fonnations throughout the world. Due to the low inherent viscosity of gas, conditions can be such that these reserves can be recovered from these low permeability strata in situations where the economic recovery of conventional liquid hydrocarbons would be impossible. This paper describes various mechanisms which can influence the effective recovery of gas from low permeability formations and presents a variety of drilling, completion, production and remediation techniques that have proven useful recently in optimizing the recovery of gas from fonnations of this type. The definition of a "low" penneability reservoir is somewhat arbitrary, but for the purposes of this paper would be considered to be formations which have a surface routine average air absolute penneability of less than 20 mD. In-situ reservoir condition permeabilities in these types of reservoirs are generally less than 1 mD and can range down into the microDarcy range (10-6 D) in many situations. Although the emphasis in this paper is specifically on low permeability gas reservoirs, much of the infonnation presented is also applicable to higher permeability gas bearing fonnations.