Two stimulation operations have been conducted to date in the paludal zone of the Mesaverde formation in one well, MWX-1, at the DOE's Multiwell Experiment test site in the Piceance Basin near Rifle, Colorado. Problems were encountered in the second stimulation: MWX-1 would not sustain production for several months and post-frac production was less than pre-frac rates. The laboratory program was expanded to examine these problems and these laboratory studies were integrated with well testing and other data to help explain MWX-1 production behavior. A unique explanation cannot be found for the failure of MWX-1 to produce; a combination of factors was responsible. Water probably inhibited matrix rock production. A system of naturally occurring microfractures is important in production from the paludal zone and it probably sustained damage by water and fracture fluids. The basic gel degraded slowly because only a small amount of breaker was used. The fracture closure (viscosity break) observed from the Nolte analysis of the stimulation was not the same as the breakdown of the basic gel. The remedial treatment conducted after the second stimulation was probably too reactive. A list of items has been developed from experience gained both inside and outside the laboratory that shows what work and which procedures should be emphasized or avoided in tight sand stimulations.

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