The gamma module is a high-efficiency natural-radiation detector that transmits an inverted pulse train with a repetition rate proportional to the amount of detected naturally occurring gamma radiation. With this data, geologists can readily identify “markers” or boundaries to help establish targets and recommend course corrections. DDC operates a fully equipped MWD/Gamma repair facility where all service work and testing is done by qualified service technicians. Gamma can be added to the MWD system as a component making the overall length of the MWD/Gamma assembly 34 feet with the second battery pack.
A flexible dynamic sleeve surrounds and protects the modules scintillation and overall assemblies, absorbing external shock and vibration while maintaining concentric position within the pressure housing. This ensures accuracy and stability, contributing to reliable on-the-job performance.
The photomultiplier tube (PMT) suspension system uses radial springs to support and stabilize the PMT. Minimizing the transfer of vibration to the PMT ensures downhole reliability.
Exclusive packaging technology enables use of a larger crystal within the same geometric envelop, improving sensitivity to naturally occurring gamma radiation, by 20 percent. Sapphire windows are used to improve tool robustness and transmission properties, improving tool reliability and gamma count accuracy.
The high-strength titanium housing permits tool wall thickness to be reduced promoting lower gamma attenuation while providing a robust housing for optimum tool performance and reliability.
Specially designed amplifiers, discriminators and high voltage power supplies can be packaged with the detector to provide optimal electrical performance while consuming minimal space. Such components ensure optimum transmission performance and run longevity.
Positive mud pulse telemetry data transfer is the most widely used and reliable transmission system in the industry and provides DDC with the level of performance reliability demanded by today's customers. Positive pulse systems have fewer moving parts reducing the risk of tool failure and simplifying system repair and maintenance.
The entire system is designed around a platform for reduced energy consumption. High performance lithium batteries provide over 200 hours of downhole service in temperatures up to 150°C (302°F). At temperatures up to 175°C (347°F) battery life will be reduced slightly to 175 hours. Battery life can be doubled by adding a second battery pack. Energy efficient hardware such as low power components, on demand sensors, down linking capability and operational setup options integrated into the MWD system minimize power consumption and maximize battery life. An electronic flow switch powers down the system when circulation stops and powers up when flow commences, extending battery life.
The rig floor display is designed to be intrinsically safe. The color graphics LCD screen is easy to read in normal rig operating conditions providing the directional driller and company man ready access to information needed to make timely decisions. A depth tracking option is available in addition to several screens for numeric and graphical analysis. Communication between the rig mounted transducers, safe area laptop and rig floor display is distributed through a safe area interface. This interface contains the necessary barriers and protection circuitry to ensure intrinsically safe operation of the system.
|Inclination||+/- 5.0° to 150°C (302°F)|
|Azimuth||+/- 10.0° to 175°C (347°F)|
|Input voltage||22 - 30Vde|
|Input power||250mW typical|
|Pulse output line||0 - 5Vdc pulses|
|Pulse duration||2 microseconds nominal|
|Gross Counting Discriminator set at 15KeV|
|Operational Time: (pulse duration and gamma sensor use dependent)|
|Single battery pack||200 hours at 150°C (302°F)
175 hours at 175°C (347°F)
|Dual battery pack||400 hours at 150°C (302°F)
350 hours at 175°C (347°F)
|Shock||1000g, 0.5msec. ½ sine all axis|
|Vibration||5 - 20Hz, 1 inch double amplitude
20 - 200 Hz, 30rms, all axis
|Operating temp||-20°C (-4°F) to 175°C (347°F)|