An algorithm to calculate permeability and original gas in place for a bounded gas reservoir from daily gas rate and wellhead pressure was published (Kanji Kato, 1987). This method is slightly modified in order to apply for gas production data to handle shale gas production data from horizontal well and the developed program is named Shale Gas Property Estimator (SGPE). It can calculate apparent permeability (Permeability
K). of shale after hydraulic fracturing, Original Gas In-Place (GIP
K) and drainage distance from a horizontal well (Spacing
K).
In this paper, the original algorithm is proved to be valid first and modification to SGPE is explained. However, obtaining these values by SGPE are not straight forward because the properties of shale after hydraulic fracture is complex and also assumption employed in the original algorithm is pseudo radial flow in bounded gas reservoir. The purpose of this paper is to demonstrate implication of these values by using simulation model.
In our study, gas production performances was assumed and a set of Flowing Bottom Hole Pressure (FBHP) data was calculated by simulation model. A set of gas rate and FBHP are then entered into SGPE in order to calculate values mentioned above as an output of SGPE. Since all unknown values in real field needs to be assumed in simulation model, then it is possible to compare results of SGPE and input data in simulation model and to examine what SGPE is calculating.
· After close examination and discussion, following conclusion was obtained;
· Permeability
K represents average permeability of hydraulically fractured shale including matrix permeability, average permeability of fractures, fracture density distribution and fracture penetration
· Spacing
K is representing Effective Drainage Area (EDA) for any type of shale, tight or permeable and is representing fracture penetration depth
· GIP
K could be an excellent indicator for recoverable gas
· Analysis by SGPE brings much more information than daily monitoring and decline curve analysis.
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