HIBERNIA- a Petrophysical And Geological Review

Abstract

Abstract Since the discovery well, Chevron et al. Hibernia P-15, was drilled in late 1979, five step-outs have subsequently been drilled on the Hibernia structure. This paper focuses on a detailed petrophysical and geological evaluation of the three main reservoirs in the Hibernia field. These zones include: the Avalon zone, the "B" Seismic Marker zone and the Hibernia zone. Detailed petrophysical analyses were conducted on these zones generating: effective porosity corrected for shaliness, hydrocarbon effect and compaction; litho logy calculated using matrix solution, shale volume and water saturation. Cross plots of porosity, permeability and individual log responses were used to calibrate the log data and select evaluation parameters. The results of the petrophysical analyses were summarized on depth plots and used to prepare stratigraphic and structural cross sections in order to illustrate the complex lateral and vertical relationships of the reservoirs. Cutoffs were applied to the calculated profiles over the reservoir intervals in order to provide data on reservoir distribution and quality. These results were used to prepare a suite of geological maps for each reservoir. The resource potential of each of the three main reservoirs was determined by a Monte Carlo simulation technique. This analysis indicates that the Hibernia is truly a "Giant Oil Field". The study was conducted by the Newfoundland and Labrador Petroleum Directorate and Intercomp Resource Development and Engineering Ltd. Introduction Surficial Geology The Hibernia Field is located on the Grand Bank of Newfoundland approximately 315 kilometres (170 nautical miles) southeast of St. John's, in water depths ranging from 76 to 86 metres (249 to 282 feet) (Fig. 1). Extending more than 400 kilometres eastward into the Atlantic Ocean, the Grand Bank lies exposed to Greenland icebergs drifting southward in the cold Labrador current. On the average, 400 bergs each year drift into the Grand Banks area. Most bergs are swept with the main branch of the current around the eastern flank of the Grand Bank; others are carried by the western branch down the Avalon Channel close to the island of Newfoundland. Many bergs, however, deviate from these paths onto the bank itself. The Hibernia discovery area is clearly vulnerable both to the iceberg scouring threat and to disturbance by currents and waves from ocean and storm-generated water movement(5). Welisite surveys of the Hibernia area indicate the seabed to be a very gently dipping surface toward the east. One to five metres of surficial sediment overlying semi-consolidated Tertiary bedrock are largely composed of coarse-grained material. Zones of well-rounded lag gravel with shell debris are aligned north-south alternatively with zones of well-sorted sand possibly over gravel (Fig. 2). Ripple marks within the well-sorted sand indicate at least sporadically active transport by current and wave action within the area. The bedrock geology of the Hibernia area and areas westward is shown on Figure 3. In the Hibernia area, the bedrock- (Figure in full paper) consists of Cretaceous and Tertiary rocks.