DtSTI_BUTION OF THIS DOOUMENT IS UNLIMITED DISCI,AIMER This document was prepared as an account of work sponsored by the United States Government. Neither the United States Government nor any agency thereof, nor The Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any lesal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents

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... its use would not infrinse privately owned rishts. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or The Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any asency thereof or The Regents of the University of California and shall not be used for advertising or product endorsement purposes. This n_ort has been n_produced dinu:tly from the best available copy. Available to DOB and DOE Coatmmom from the Offiee of Seimefic sad Teelmieal Infolmation P.O. Box 62, O_ P.idSe, TN _831 Pziem avsilable X_em(615) $?64401 Available to the public from the N_ T_ l_mnstiea ,f,_viee U.S. _ d Ccmmeme 52g5 Port l_oy_dtoad, Spmff_e._d, VA 22161 Lawrence Berkeley Laboratory is an equal opportunity employer. Abstract Pressure and flow rate data from a water sampling test, which also produced gas, at the Wellenberg site are analyzed using inverse modeling techniques. Two conceptual models are . developed and used for parameter estimation. The ftrst model assumes that the gas observed at the surface is dissolved in the pore water under natural pressure and temperature conditions and comes out of solution due to the pressure reduction during pumping. The second model considers a mobile gas phase originally present in the formation. While both models are able to explain the observed pressure response as well as the gas seen at the surface, large uncertainties in the data and in the model assumptions inhibit the determination of two-phase flow parameters. The analysis indicates, however, that the formation has a very low permeability and that formation head is far below hydrostatic.