Drilling & Processing
The topsides facilities on the Hibernia platform accommodate drilling, producing and utility equipment, as well as provide living quarters for platform workers. The topsides consist of five supermodules and seven smaller topsides mounted structures.
In order to reach the rich oil reserves deep beneath the ocean floor, wells have been drilled from the platform.
Long before the first well was ever drilled, geologists and geophysicists first had to determine the layout of the Hibernia field. Using extensive seismic data collected from the offshore location, geologists were able to identify which areas of the reservoirs would provide the most productive return. This data was used to develop a reservoir management strategy detailing the exact location and depth for each well.
The platform is designed to drill two wells at a time, using two drilling derricks. Drilling operations occur within the Wellhead Module, and the two drilling modules which are located on tracks above the Wellhead Module.
- During drilling operations, a drill bit is used to drill the wells into the ocean floor. Attached to the drill bit are long pieces of hollow pipe, called drill pipe or drill strings. The drill bit is spun around in the ground to enable it to shear or crush the rock on the bottom of the hole, while additional lengths of drill pipe are added at surface to drill deeper.
- The crushed rock and stone produced by the drill bit are called drill cuttings. These cuttings are removed from the well by drilling mud, a compound of water, clay and other chemical additives that are mixed together inside the Mud Module. Drilling muds are continuously pumped down the drill pipe and through holes in the drill bit to cool the bit, prevent the hole from collapsing and carry the drilled cuttings from the bottom of the hole to the surface. The drilling mud is constantly circulated from surface down the drill pipe, up the hole and back to the surface again, where the cuttings are separated from the mud to allow it to be circulated again.
- Drill cuttings are disposed of by either discharging them into the ocean, in compliance with regulatory guidelines or by injecting them back into the ground. Samples are preserved and stored onshore as per regulatory requirements set down by the Canada-Newfoundland and Labrador Offshore Petroleum Board.
- After the well has reached the desired location in the reservoir, steel tubes called "casings" are run into the well and cemented. This ensures that production from the reservoir is controlled safely. To allow oil to enter the well, the well must first be perforated. Tiny explosive charges are placed in assemblies and lowered into the bottom of the well where they are detonated before recovering the assemblies back to surface. The charges create small holes in the casing through which oil can flow.
- The pressure of the reservoir forces the oil into the well and pushes it upwards to the platform, where processing operations occur. Once a well becomes active, drilling operations cease, and processing commences.
Now that the oil has a path to follow from the reservoir to the platform, it can be converted into marketable crude. This is called processing, and it occurs inside the Process Module. Oil is collected from all active wells inside a gathering pipe called a manifold. It then flows from the manifold to the Process Separators. In the early stages of production, the fluid coming up from the reservoirs contains mostly crude oil, with some natural gas. As production continues and the reservoirs become depleted, more gas and eventually water are recovered with the oil. To improve the quality of the crude, the natural gas and water need to be separated from the oil.The processing occurs in three stages, where the fluids are passed through separators to remove gas and water from the oil. The oil first goes through a high pressure separator, then a medium pressure separator, and finally a low pressure separator. With each additional stage, more and more gas and water are extracted until the final product is a crude oil that is ready for the refinery. After final separation, the oil is then sent to the Gravity Base Structure for storage. The GBS contains storage space for approximately 1.3 million barrels of oil. The water, which is produced during processing, is treated and then released into the sea.
Gas and Water Injection
Both water and produced gas are injected into the Hibernia Reservoir, each for different reasons. Water is injected into the reservoir to maintain pressure levels which would otherwise be depleted by oil production. The water also pushes oil toward the producing wells, effectively 'sweeping' the fault block of its oil.Hibernia's Operational Plan states that, during steady state operations, all produced gas will be injected into the reservoir, except for that which is used as fuel for the platform. Flaring will only occur for safety reasons. The gas is injected for three reasons:
- it minimizes flaring;
- it conserves the gas for potential extraction at a later date;
- it provides pressure support to increase recoverable reserves in certain areas of the field.