Offshore oil and gas extraction carried out on large drilling platforms around the world faces many technical challenges and risks. Offshore drilling requires specially formulated drilling fluid, also known as mud. The mud is used to lubricate drilling equipment and to prevent potentially catastrophic blowouts.
A blowout is the uncontrolled release of hydrocarbons under extremly high pressure that can erupt from the subsea well hole. Very specific measures are deployed to prevent blowouts, and, should they occur, to contain them.
For sea-based drilling, the drilling fluid is weighted with the mineral barite, which is both very heavy and non- magnetic. The weight allows the fluid to create a heavier-than-water blanket on top of pressurized pockets during drilling. The non-magnetic properties of barite also ensure there is no interference with sensitive drilling instrumention. The deeper the hole, the more barite is needed as a percentage of total fluid mix. The fluid makeup may be further tweaked to adjust for different geological conditions, as drilling permeates various layers.
Offshore drilling requires large, bulk quantities of blended mud. Turnkey bulk systems are used to transport, mix and dispense drilling mud. In addition to barite, bentonite clay is used to maintain fluid viscosity. Additional chemicals in the fluid can include sodium bicarbonate, soda ash, oils and other specialty products.
Barite has to be ground to a small, uniform size before use in mud. The required properties are specified by the American Petroleum Institute or other agency. Precise mixing of the mud is carried out by drilling fluid companies, which have their own engineers on site, mixing and controlling the fluid before pumping it down the hole. Fluid is further analyzed when it comes up again in laboratories on the rig.
Drilling packages are delivered from suppliers in Scandanavia to platform construction facilities, mainly located in Singapore, Malaysia, Korea, Brazil or China. The packages include one or more bulk solid holding tanks containing drilling cement used for stabilizing the drillhole with casings.
The number of bulk system units on a drilling platform or ship depends on the size of the rig. Normally, it is 4, but can range from 2 to 12. As soon as the rig platform or ship has arrived at its drilling location, it needs to fill bulk solids tanks with barite, bentonite and drilling cement. Supply vessels carry these materials from a base situated onshore near the rig, and the dry powders are blown from the supply vessel into the bulk tanks on the platform. During this process, samples of the solids need to be obtained. This process may happen once a week or every two weeks, depending on the activity on the rig and the need for material.
Properties that need to be sampled in the dry powders are specific weight, size fraction and humidity. Rigid quality control and documention are needed due to the extreme costs involved if a catastrophic event (like a blowout) should occur. Additionally, these rigs need to have appropriate sampling equipment to have a drilling license.
Working together with the drilling rig manufacturers in Scandanavia, our partner Aker Byggsystem of Norway devised a reliable bulk solids sampling solution for the offshore industry. Because of its ability to handle nearly any bulk solids and powder sampling application, customers chose the Sentry® PR automatic point sampler.
This sampling package for the bulk systems on offshore platforms or ships has become the gold standard due to the continual superb, trouble-free operation of the samplers in harsh conditions.
Our company and Aker have worked closely with drilling package suppliers to provide variants, depending upon exact operational requirements. Product configurations can vary by size, flow, materials required, accessories and more.
As a critical yet relatively inexpensive part of each complete bulk system and drilling platform, the Sentry PR samplers operate well for many years and are considered well worth the price. The world’s leading producers of offshore drilling packages rely on the Sentry PR sampler to provide a safe, efficient operating environment in some of the harshest conditions on earth.
Application information courtesy of Hans-Petter Frisholm, Aker Byggsystem, Oslo.