Schlumberger Rotary steerable Technology

Rotary steerable summarize

It is well known that the highest stage of drilling technology development is automated drilling.

The so-called automatic drilling is:

the whole process of drilling depends on sensors to measure various parameters, and the use of computer acquisition, comprehensive interpretation and processing, and then issued instructions, and finally by the relevant equipment automatic execution.

so that the whole drilling process into a unmanned automatic control process. In the process of automatic drilling control, downhole measurement while drilling (MWD) and automatic downhole control are the key links and also the key technologies. The combination of the two is actually the automatic control technology of borehole trajectory — guiding drilling technology.

Guided drilling technique

Guided drilling technology is a new and high technology in the field of drilling engineering and represents the most advanced development direction of drilling in the world. At present, the complex Wells with high difficulty, such as horizontal Wells, extended reach Wells and lateral Wells, are booming in the world and have been appling on a large scale. The traditional drilling technology cannot meet the operation needs of these difficult Wells, and advanced guiding technology must be reling on to ensure the accuracy of the well trajectory.

Drilling steering mode

Rotary steerable there are two main guiding methods:

• 1) Geometric orientation:

The geometric parameters are measurin by the MWD/LWD tool, and the values of inclination, orientation and toolface are transmitting to the control system, which corrects and controls the wellbore trajectory in a timely manner.

• 2) Geological orientation:

Geosteering combines geometric steering with the ability to control the wellbore trajectory in real time based on geologic parameters (formation lithology, formation level, reservoir characteristics, etc.) derived from logging while drilling (LWD), enabling the bit to drill optimally along the formation. This enables optimal control without prior knowledge of formation characteristics.

Geosteering uses geological and stratigraphic parameters collected in real time near the bit to predict and identify hydrocarbon zones in advance, adjust the wellbore trajectory as needed, and guide the bit to accurately drill into hydrocarbon enrichment areas. The key technology of geosteering is the real-time measurement of formation parameters, borehole trajectory parameters and bit operating parameters near the bit.

Steering tool

Guided drilling is mainly achieved by steering tools, which are divided into two categories:

• 1) Sliding guide tool

The characteristics of the sliding guide tool are that the drill string does not rotate during the steering operation.

and the drill string moves forward with the bit and slides along the wall.

Sliding guide has many disadvantages: high torque and drag of drill string; Incomplete borehole cleaning; It’s slow and so on, but it’s still dominant.

Most directional drilling tools use downhole power drilling tools. The main sliding steering tools include curved casing motors, adjustable bend joints, variable diameter stabilizer, etc. Sliding guide tool combination: drill string +MWD/LWD+ power drill + bit

• 2) Rotary Guide System (RSS)

The rotary guide tool guides the bit directly along the desired trajectory, preventing the drill string from lying on the wall, allowing the hole to be well cleaning, and allowing the right bit to be selecting accorded to the formation. This can significantly reduce or eliminate the shortcomings of sliding guide tools.

At present, rotary steering tools mainly include VDS automatic vertical well drilling system, SDD automatic vertical well drilling system, ADD automatic directional drilling system, RSD rotary steering drilling system, RCLS rotary closed-loop drilling system, etc.

Rotary steerable drilling features

• 1) In the case of drill string rotation, with steering ability;
• 2) Can be using with downhole motors;
• 3) Equipped with a full range of standard formation parameters and drilling parameters testing instruments;
• 4) Equipped with the surface and downhole two-way communication system.
• according to the downhole data, can be sent from the surface to change the well trajectory without drilling;
• 5) Modular and integrated tool design and manufacturing;
• 6) can be using in high temperature Wells above 150℃;
• 7) No special drilling parameters are requiring to ensure an optimal drilling process;
• 8) Automatic steering control to ensure accurate and smooth wellbore trajectory.

Rotary steerable measurement parameters

• 1) Measured well depth: refers to the actual length of the hole between the wellhead and the measuring point.
• 2) Vertical depth: the distance from the wellhead through the horizontal plane of a point on the wellbore trajectory.
• 3) Inclination point: the starting point of inclination from the vertical section.
• 4) Well inclination Angle: the Angle between the borehole direction line at the measuring point and the gravity line.
• 5) Azimuth Angle:
• take the north direction line as the beginning edge, rotate clockwise to the Angle turned by the azimuth line.
• the direction line refers to the horizontal plane, the azimuth Angle can be changing between 0-360°.
• 6) Well deviation rate: Well deviation rate refers to the variation of well deviation Angle within a unit length. In degrees / 100 meters can also be using in degrees / 30 meters, etc.).
• 7) Rate of azimuth change:
• rate of azimuth change refers to the change of azimuth Angle in unit length, expressed in degrees / 100 meters (can also be using in degrees / 30 meters, etc.).
• 8) Dogleg severity:
• Dogleg severity is a parameter,used to measure the curvature of the well or the sped of change (expressed in degrees / 30 meters).
• Dogleg severity includes both the change of well inclination Angle,and the change of azimuth Angle,.
• which is the data that needs to be paid attention to during drilling.