Evaluation of abnormality in pore-pressure prediction in Sarvak formation in an offshore field in Persian Gulf

Knowledge of pore pressure is essential for cost-effective, safe well planning and efficient reservoir modeling. Pore pressure prediction has an important application in the proper selection of the casing points design and reliable mud weight too. In addition, using cost-effective methods of pore pressure prediction which give an extensive and continuous range of data is much more affordable than direct measuring of pore pressure.Pore-pressure prediction of Sarvak formation south of Kharg Island in the offshore Persian Gulf was done and some anomaly in pore-pressure founded. Details of this anomaly, the procedure of pore-pressure prediction, and the geological and reservoir descriptions are explained in this study. Based on petrophysical data, the Sarvak formation is a poor reservoir with low porosity and hydrocarbon saturation, where this trend can be seen in other wells.Sarvak formation is vertically confined by two layers, Ilam and Kazhdomi from top and bottom respectively. Both of them have enough shale content and are low porous layers with sufficient thickness to behave as impermeable layers. This sequence was checked in other wells for validation and confirmed the conclusions.The Sarvak formation looks to be a low porosity limestone with high water saturation and depleted rapidly during drilling. Since the log data was acquired just after drilling, and because of poor reservoir property and the short time, it did not reach its original pressure. It should be noted that here the depletion term is used in the vicinity of the wellbore which could be detected by logging tools.

کلیدواژه ها:

Pore pressure ، Eaton’s method ، porosity ، saturation ، permeability