Safety during drilling operations

Using leading-edge technologies, our aim is to prevent hydrocarbons from reaching the surface in an uncontrolled manner during drilling operations. We use a series of effective methods for preventing potential incidents or controlling and mitigating their impact. The safety technologies deployed during drilling operations encompass three key components:

• drilling mud
• the blow-out preventer
• cementing

Drilling mud

The first line of defence against the uncontrolled exit of oil or gas from a well is drilling mud, which is injected into the well in a closed circuit. The specific gravity of the drilling mud is adjusted based on detailed calculations that take into account the pore pressures that may be encountered in the rock formations to be drilled. The hydrostatic pressure produced in this way controls the formation pressures and prevents hydrocarbon leakage.

Blow-out preventer

Aside from the properly adjusted specific weight of the drilling mud, the so-called blow-out preventer is the most vital safety device. It is located directly at the wellhead and consists of several independently operating shutoff valves, each of a different design.

The well is shut off by means of a jaw-shaped slide valve and a ring-shaped cuff. Together they ensure that the drilling string in the well is enclosed in such a way that the well is completely sealed off in the event of an emergency. Should a complete shut-off become necessary, the shear jaws can be used to cut off the drilling string and shut off the well. High-pressure conduits mounted on the blow-out preventer allow fluids to be circulated in and out of the well even once it is shut off. The shut-off valves are connected to a hydraulic system through which each valve can be controlled individually.

The blow-out preventer can be operated manually or automatically. If it is located on the seafloor, it can also be operated by means of a Remote Operated Vessel (ROV) or by remote control using sound waves. The blow-out preventer is firmly connected to the well casing and is subjected to regular inspections and a range of function and pressure tests.

Cementing

A qualified cementing of the casing string also contributes to the safety of the borehole. Cement is used to stabilise and seal the individual casing sections. The cementing ensures a tear-proof connection to the surrounding loose rock that is impermeable to gas and fluids. This prevents the uncontrolled rise of hydrocarbons outside the casings as well as damage or corrosion. For this reason, cementing is always planned and executed in such a way that a permanent seal suitable for the prevailing reservoir conditions is created. The proper functioning of the seal is established using various measurement and monitoring methods.

source : http://www.rwe.com