Petrophysical Analysis Of Lower Goru Sandstone,A Case Study From Kadanwari Gas Field Lower Indus Basin,Pakistan

Formation evaluation is the detailed analysis and interpretation of geophysical data so that information about productive zones in geological formations can be extracted.It is the key to determine whether a well can have some hydrocarbon output or it is just a dry hole.Depends on the data available,formation evaluation for a zone can be carried from the analysis of well logs,coring technique and initial production data.During the study of petroleum reservoir characterization,it is important to understand mineralogy of hydrocarbon-bearing rocks such as shale,sandstones,or fractured limestone in most cases.Accurate evaluation of porosity and permeability from the grain size of a rock is very significant in a petrophysical study.This is the case in Lower Indus Basin,Pakistan where petrophysics is extensively used to predict physical properties of Kadanwari gas reservoir.Kadanwari gas field exhibits Cretaceous lower Goru Formation which is one of the most important hydrocarbon bearing reservoir in Pakistan.The aim of this study is to carry out formation evaluation in order to determine porosity,permeability,water saturation and lithology prediction based on these factors using petrophysical parameters from wireline logs.All the petrophysical properties were computed with Techlog by generating summaries module for each of the petrophysical property determined.The summaries module for each well is a representation of the computed average for all the reservoir properties including the volume of shale,effective porosity,permeability and computed water saturation so that pay zones in the reservoir can be determined.ELAN module was used at the end to calculate for multi-minerals of reservoir which shows shale and sandstone dominant lithology as well.The prediction of gas recovery from the reservoir was based on effective porosity,water saturation,permeability and net productive thickness average for all the wells.Effective porosity and all the other pertophysical properties calculation is highly dependent on the accuracy with which the proper lithology is identified.Determining lithology with neutrondensity cross-plot is a well established technique and hence applied here as well.Picket plots for all wells were drawn to confirm for hydrocarbon bearing zones in the reservoir which indicated water,gas-water and gas zones that are well in agreement with ELAN module results as well.The reservoir has good porosity values between 0 to 20 percent but there is high water saturation up to 50% in reservoir production zones.The presence of shale in the entire reservoir interval has negative influence on the permeability value but the petrophysical properties of Kadanwari gas reservoir are good enough to permit hydrocarbon production.