Formation Evaluation

Gamma Ray Annulus Pressure Total Vibration

Gamma Ray

This service measures the naturally occurring Gamma radiation in the formation, indicating the composition or type of rock. The log is used to locate sands, which generally are areas of production, or reservoirs. Wellserv currently provides two types of tools for Gamma measurement.

Sensors are often used in borehole applications to provide measurements from the surrounding formation. Often these sensors respond equally to the characteristics of all the formation which surround the borehole A combination of a focused sensor, rotary drilling and accurate rotational positioning can be a powerful means of determining important characteristics of the formation.

In a Focused Gamma tool the sensor is designed to be radially focused and measure only the characteristics of the formation in a relatively narrow slice or radial section of the borehole margin. In such applications, the orientation of the sensor(s) may be an important part of the data set.

Focussed Gamma

The Dynamic Rotation Gamma (DRG) tool provides the ability to collect an accurate measurement of natural radioactivity emitted from either the high side or the low side of the borehole while drilling. DRG technology allows the driller to make rapid determination of an approaching geological boundary and to adjust his drilling operation to stay within the desired zone. This improved method of geo-steering uses our ability to record oriented Gamma measurements while the drill string is rotating or stationary.

DRG provides rotational positioning information in open hole applications. It is compatible with rotary drilling methods, thus allowing the rotational positioning of measurements using focused sensors. A Wellserv sensor combines a precision flux-gate magnetometer with specially designed high-speed measurement and processing electronics to determine rotational positions using the Earth’s magnetic field. The DRG has a wide dynamic range capability, allowing its use in applications where the well path is very nearly that of the magnetic dip angle.

The position of the sensor relative to the well’s high side, or any synchronizing reference, will be transferred to the DRG Sensor as an angle, Φ, in degrees. Once loaded, the microprocessor in the DRG sensor will calculate the offset values to correct the reading to high side or the synchronizing reference.



Annulus pressure

Downhole Pressure Sensors are drilling performance tools that provide continuous and direct downhole measurement of internal and annular pressure. These pressure measurements provide information on downhole hydraulics and fluid performance that help the driller avoid problems and to optimise the drilling process.

Absolute downhole pressure is measured using pressure transducers and is best utilized in real-time. An annular pressure sensor is used to provide an accurate downhole pressure reading, used to calculate equivalent circulating density. (ECD)

Applications Pressure Response
Formation Integrity Test Lack of pressure bleed-off after shutting in the well indicates the formation will withstand the tested pressure.
Leak Off Test The pressure at which there is a break in the slope of the LOT pressure curve indicates the fracture pressure of the formation
Measuring Pumps-Off Swab and Surge Pressures and Gel Strength of the mud The pumps-off maximum pressure captures the largest surge or gel pressure experienced during the pumps-off cycle
Detecting Packoff The appearance of a series of positive spikes in the EMW indicates packoff

Total Vibration

Shock in a drilling environment is the sudden input of energy, when the BHA, bit or drillstring impacts with the borehole. Vibrations are the response of the bit/BHA/drillstring to the shock. Vibration sensors utilize three mutually orthogonal, DC-coupled accelerometers to measure three axes of acceleration

Importance of monitoring Vibrations

If not monitored, understood and mitigated, excessive shock and vibrations may cause:

Mitigating shock and vibrations and monitoring drilling mechanics allows us to improve drilling efficiency, thereby reducing total time and cost to drill the well. Shock and vibrations and poor drilling mechanics take energy away from the drilling process, which can effect the overall average ROP and drilling efficiency.

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