عنوان مقاله [English]
The mudlogging data during excavation provide valuable information to assess the quality of reservoir rocks, fluid contact, and reservoir permeability based on the formation gases. In this research, the gases along with drilling mud, released from the E1P5-ST2 well drilled in the Mishrif reservoir located in the Esfand oil field, the upper part of Sarvak at the age of late Albian - Cenomanian - early Turonian, were recorded at the depth of 3802-4270 m using advanced gas chromatography. Moreover, continuous measurement of the concentration of the formation gases, from very light components like methane to the heavy ones like hydrocarbon species C7, C6, and C8, including n-hexane, n-heptane, n-octane, benzene, and toluene, was conducted. In this regard, after elimination of the background gas and ignoring the trip gas, a combination chart of drilling properties, gas data, and strength log were plotted. The type of reservoir fluid was also recognized and proved by strength logs. Accordingly, 11 zones were detected in the E1P5-ST2 well in Esfand oil field. Zone 1 was nonproductive, and zones 4, 6, 8, and 10 had a high average effective porosity, low water saturation, and good reservoir quality. The other zones, although had high effective porosity, due to the water saturation, they produced an amount of water along with their average produced oil and were weak in terms of the reservoir. Furthermore, the trend of porosity changes in the reservoir zones was determined according to the ROP changes against the gas data, especially C1.