HYDROCARBON FLUID IDENTIFICATION BASED OF GAS CHROMATOGRAPHY ANALYSIS, IN THE UPPER GABUS RESERVOIR, GRIGIO FIELD, WEST NATUNA BASIN

• Main Author: Herki Priambodo, Yosef
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/73125
• Institution: Institut Teknologi Bandung

Gas measurement which was recorded by the mudlogging company is a standard measurement in oil and gas drilling activity, both in the exploratory or development wells. Continuously data monitoring was performed during drilling, and integration with cuttings analysis allows us to identify the presence of hydrocarbon in the formation. The use of gas chromatographic data in drilling activity is still minim and the application of gas chromatography data for identification hydrocarbon fluids which are integrated with geological data has not been accomplished in the Grigio field. Gas ratio analysis correlated with the analysis of Petrophysics, reservoir pressure data and supporting data, including PVT data and regional geological data to identify patterns of gas that can be used for identify fluid types and their contacts. The ratio of gas chromatography; characters, wetness and balance; introduced by Haworth is used as a means of identification of hydrocarbons by looking at the differences in patterns or log shapes of gas ratio. Low ratios in characters indicated the existence of hydrocarbon and log shape of the wetness and balance are far apart indicate of gas zone while log shape of balance and wetness are not separated far is an indication the oil zone. In addition to oil and gas, a quick way to look at water zone is by looking at the total gas value, if there is no total gas, most likely in the hydrocarbon reservoir is missing, and supported by the pattern of characters that indicates the ratio of relatively higher value. In addition Haworth methods, Kandel method was used to notice change fluids. Making cross plot between C1 and C2 and C1 and C3 showed the changes in the patterns that show tendencies of straight line due to reaction of the gas chromatography in two different fluids. The ratio of other gases that can demonstrate a change in fluid is C1/C2 vs. C2/C3, gas data collection indicate two different fluids. To simplify the analysis, the ratio of C1/C2 and C1/C3 cross plot will be put into the log, a higher value or deflection curve to the right shows the gas while a low value or deflection to the left shows the oil. Based on gas chromatography ratios, the fluid contact on the western part of Grigio structure, the GOC is at 3765 feet TVDSS and OWC at 4080 ft TVDSS, while in the eastern Grigio structure, the GOC is at 3805 ft TVDSS feet and OWC at 4035 feet TVDSS. The differences in these contacts are caused by the existence of fault structure which makes sealing off between these two structures. This evidence is supported by the difference of reservoir pressure in the same interval and no juxtaposition from Allan diagram in hydrocarbon zone. Fluid contacts from the gas chromatographic analysis possess the same depth of petrophysical analysis and only differ five feet from the formation pressure analysis. The results of gas chromatographic analysis could be used to identify the fluid and its contacts if the data logs or formation pressure data not available.