Summary
Well KAL-5, completed in the Moslavacka Gora formation of the Pannonian basin in Yugoslavia, was tested at a flow rate of 75 Mscf/D [2124 std m3/d] of gas and 2.8 B/D [0.45 m3/d] of condensate and at a last bottomhole pressure (BHP) of 1,083 psi [7.5 MPa]. Pretreatment evaluation determined a reservoir permeability in the 0.003- to 0.004-md range. The high formation temperature (354°F [179°C]) poses problems for most fracturing fluids.
This paper presents a pretreatment analysis of the well, its geologic setting, and thermal and lithological characteristics as they relate to the choice of the fracturing-fluid system. An outline of the stimulation design and execution is included.
After a modest hydraulic fracture treatment, the well flowed for 21 days at a last flow rate of 1,925 Mscf/D [55×103 std m3/d] of gas and 117 B/D [18.7 m3/d] of condensate at a flowing BHP of 912 psi [6.3 MPa]. This substantial increase was apparently caused by the successful hydraulic fracture; geometric features of the fracture were estimated from interpretation of a posttreatment well test. Posttreatment evaluation assesses the effectiveness of the job, calculates the geometric dimensions and the conductivity of the fracture, and presents forecasts of future performance. Finally, the effects of the evolved gas condensate on the reduction of the apparent reservoir permeability are investigated and evaluated. A correlation between pressure, in-situ condensate saturation, and permeability is offered.