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System upgrade

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Hydrocarbon Engineering,

GE Oil and Gas, USA, explain the benefits of investing in an effective downhole system in order to reduce non-productive time and maximise profits.

In today’s challenging energy economics, it is imperative to safely reduce the cost of well construction, while maximising reservoir exposure and minimising formation damage. When a downhole tool ceases to operate, bringing it to surface to conduct repairs incurs a multitude of costs in terms of downtime. Daily rig rates can run into millions of dollars, including labour costs associated with keeping drilling contractors, geologists and other specialised workers on the job. To achieve this reliability goal, drilling technologies focus on improving rate of penetration (ROP) and reducing non-productive time. Reliable, precise, and efficient downhole measurement while drilling (MWD) systems are key prerequisites for accurate well placement with an optimal ROP. Downhole directional sensor related failures are the second largest source of failure, and constitute approximately one-fifth of all the MWD failures that require operators to pull out of hole (POOH) to change out equipment. Today’s drillers need downhole tools they can trust to reduce drilling costs, and minimise total cost of ownership.

Upgrading to improve performance

High drilling rig rates and compressed drilling schedules make downhole tool reliability critical to success in terms of time, money and future opportunities. Upgrades and improvements to MWD and LWD tools must be continually implemented with the aim of improving drilling performance and reducing NPT to help bring wells in on time and on budget. This article explains the relevance of those improvements in relation to the development of the Tensor line of MWD/LWD tools.

Tensor–compatible MWD system

The GE Oil & Gas range of MWD equipment aims to provide simple, dependable functionality for all types of directional surveying and steering operations. The probe-based Tensor-compatible MWD platform is designed to be retrievable and re-seatable to reduce lost-in-hole risk. Tensor modular architecture enables the driller to drill the top hole, sidetrack and drill lateral sections with the same set of tools. The system is scalable to add LWD services such as natural gamma ray and multiple propagation resistivity in a seamless manner. The ruggedised Tensor MWD platform is suitable for operating in HPHT environments (up to 175°C and 20 000 psi).

Critical directional measurements of tool face, hole inclination and azimuth in order to drill directional or horizontal wells is offered in the DirectiveTM system. These measurements can be thought of as a ‘downhole GPS’. The accuracy and reliability of these directional measurements over an extended period of time under harsh drilling conditions is an absolute prerequisite, since survey errors can be very costly. Tensor is the cornerstone of GE’s downhole technology drilling measurements portfolio, and therefore demands continual attention in order to maintain its technological edge in today’s competitive oil and gas market. The OM instrument provides accurate and stable measurements of the earth’s gravitational and magnetic fields using measurements from accelerometer and magnetometer packages. This data is processed and converted to digital output using a total of 6 PCBAs (X, Y, Z, TROD and two DAQ boards). The data is used to calculate critical Directional Drilling measurements such as wellbore inclination, azimuth and toolface.

Figure 1. The Directive™ MWD Directional System is re-engineered to enable users to detect well vibrations in real time and to take corrective measures quickly.

Supporting functionality

The Directive microprocessor unit (MPU) is part of the Tensor-compatible DM and is the unit responsible for all functionality of the MWD and LWD systems. As part of this MWD system, it is designed to work with the Safe Area Interface and qMWD software package to provide reliable downhole information, allowing the operator to act swiftly and appropriately at all times. The MPU’s efficiency has been increased by a factor of four and its reliability has been rigorously verified by more than 10 000 hours of bench testing at temperatures up to and beyond 175°C, more than 1000 hours of drilling and more than 50 000 ft drilled in various formations in North America and mud pulse telemetry. The memory functionality can be customised using Memory I/O.


A choice between retrievable and non-retrievable configurations allows the user to select the most appropriate for drilling conditions. A choice of solenoid positive pulser or motor driven pulser allows the customer to select the most appropriate for their application. Additional modules for gamma and Centerfire resistivity are available to enable expansion of services into the LWD operations.

Providing power downhole

The Triple Power Supply (TPS) is a modular switching power supply assembly designed for use in downhole drilling applications. The TPS converts the battery voltage to the DM into +5 and ±13 V supplies. Both durable and reliable, the tool provides an efficient instrument for downhole power needs, ensuring that instances of downtime are kept to an absolute minimum.

The quest to reduce NPT

Nowadays, crucial customer needs include providing real-time shock and vibration measurement and improved diagnostics capabilities in order to reduce NPT. Directive is GE’s upgraded Tensor MWD that improves performance and reliability and seeks to address these needs.

The Tensor MWD system is suitable for all types of drilling muds, while the highly stable sensor is compatible for use in EM for drilling with both air and mud. The new TPS offers increased reliability and efficiency, and the new MPU firmware version (v3.02) enables clients to do more with current MPU hardware. With the new firmware, MEMS accelerometers incorporated into the new MPU design have been activated to perform real time shock and vibration measurements. Additionally, it provides enhanced diagnostics by storing the details of shock levels coupled with temperature for the life of the tool. Thus, the new firmware enables not only improvement in real-time measurements of drilling dynamics, but also helps with monitoring the health of the tool with an objective of preventive maintenance.

Figure 2. The microprocessor unit (MPU) is designed to work with the Safe Area Interface and qMWD software package to provide reliable downhole information, allowing the operator to act swiftly and appropriately at all times.

Key system modifications

All Directive components have been redesigned to improve downhole reliability and durability. The complete system is contained on just two printed circuit boards, cutting the number of potential failure points in half. Sensor packs and the processor unit provide real time shock and vibration measurement to help maximise drilling performance. System memory has been expanded to 32 MB, to accommodate extended drilling durations.

Figure 3. The Directive MWD system is both retrievable and reseatable, minimising rig downtime and the lost-in-hole financial risk.


Improved systems, such as Directive, extend product life, improving reliability and cost-effectiveness of complex directional or multilateral drilling operations. The system ensures tighter industry standard compliance, provides higher mean time between failure and allows for preventive maintenance. Overall, systems such as Directive will serve to address significant oil and gas industry requirements in the area of high temperature, high shock and vibration drilling measurement; minimising downtime incidents and reducing the total cost of ownership.

Adapted by David Bizley

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