Dick Ghiselin
Contributing Editor
The annualOffshore magazine MWD/LWD services directory is packed with details about the downhole technology that is currently available in the market. To clarify the terminology, MWD refers to all measurements having to do with drilling efficiency and well geometry; LWD refers to all petrophysical measurements used in formation evaluation. A third category that applies to both MWD and LWD is telemetry, typically mud pulse telemetry, but the category can also include electromagnetic (EM) telemetry or wired drillpipe.
Offshore asked MWD/LWD providers to highlight their latest advances and the responses demonstrate the growth of applications for real-time information. Responses appear below in the order they were received.
Formation evaluation service
Schlumberger has introduced its NeoScope sourceless logging-while-drilling service. The service is based on pulsed-neutron generator technology that totally eliminates chemical radioactive sources. It delivers a full suite of formation evaluation services including compensated neutron porosity, neutron-gamma density, spectroscopy, and sigma measurements. In addition, it offers natural gamma ray images and array resistivity measurements for well placement, along with a set of electronic calipers and a full drilling mechanics package.
Because there is no chemical radioactive source, the tool can be transported to any location worldwide without restriction or special permits. When turned off, the tool is completely benign and requires no special handling or packaging.
Nuclear magnetic resonance
The popular lithology-independent NMR porosity and continuous permeability service previously available only with wireline-conveyed equipment has been introduced to the LWD market as the ProVISION service for real-time assessment of reservoir producibility. Capable of hydrocarbon identification, the new service can locate reservoir "sweet spots" while drilling using its deep-reading measurements. Equally at home in clastic reservoirs or carbonates, the new service can enhance production rate estimates in sandstones. In complex heterogeneous carbonates, the tool effectively describes pore-size distribution along with porosity and permeability. It is fully combinable with Scope-series tool systems.
Fast-data telemetry tool
The newest member of the Schlumberger Scope-series systems is the DigiScope slim-hole MWD service. Transmitting real-time well data at 36 bps, the new service supports a variety of compatible LWD systems six times faster than conventional mud pulse telemetry devices. Using the Orion II data compression platform, the new telemetry tool provides high-quality real-time data from the deepest wells and longest extended-reach wells for advanced formation evaluation and drilling optimization. Combinable with all 4.75-in. diameter LWD systems, the new service includes direction and inclination measurements, four-mode vibration, shock and rpm, directional gamma ray, and internal/external pressure measurement. A mud turbine provides electrical power for the tool and combined LWD tools, but the tool is also capable of making and storing pumps-off measurements for evaluation of wellbore stability and geomechanics.
Drilling optimization
The SureShot MWD system from APS Technology is a versatile system designed to provide drilling optimization measurements. Powered by batteries, a turbine generator, or both, the basic system provides direction, inclination, and gamma ray. The rugged pulser is capable of shredding lost circulation material to operate continuously in spite of drilling difficulties. The SureShot PWD (pressure-while-drilling) sensor measures annular and in-pipe pressures, transmits the data in real-time, or stores it in non-volatile memory.
The system also includes the SureShot VMM (vibration memory module) software and VMS (vibration memory sub). These can measure, analyze, store and report axial, lateral and torsional vibration and shock. A unique Active Vibration Damper Sub (AVD) is a stand-alone tool that autonomously adjusts damping in real-time to minimize axial and torsional drillstring vibration. Based on the magnetorheological (MR) adaptive variable suspension system found in Ferraris, Acuras and HumVees, the system combines Belleville springs with an oil-filled MR damper which varies the oil viscosity as required to dampen vibrations. According to the company, as much as 50% improvement in penetration rates have been observed when the AVD is deployed, as well as improved bit life. The DDM (Drilling Dynamics Monitor) measures and records weight-on-bit, torque-on-bit, bending force on bit, temperature, and internal/external mud pressure, all transmitted to surface by the SureShot telemetry.
LWD resistivity logs
APS' Wave Propagation Resistivity Sub (WPR) is a spatially compensated 400 kHz/2MHz tool that delivers wireline equivalent LWD resistivity logs in all mud types. The tool is available in all standard collar diameters, including a slim-hole 3.5-in. version. A subwall-integrated PWD sensor is optional.
The company's SureDrill surface system combines pre-job finite element analysis-based static and dynamic BHA modeling with real-time shock and vibration data from downhole and surface sensors to derive drilling optimization data to maximize ROP and to extend bit life. Interpreted results are output to a multi-gauge dashboard display that shows drillers the combinations of drilling inputs that will produce the best results. The system also recognizes drilling dysfunctions and alerts the driller in time for remedial action to correct the problem.
Real-time orientation
Intelligent Well Controls (IWC) has successfully demonstrated the wall-mounted telemetry pulser that allows transmission of downhole data via fluid pulse telemetry while allowing cementing or fracing operations that require thru-bore access to deploy wiper plugs or actuating balls. The system uses two-way communication via surface pump sequences to issue commands to downhole tools, and receives confirmation that those commands have been executed.
The unique sacrificial casing orientation tool has been developed to orient pre-milled windows. The retrievable work string orientation tool, with identical technology, has been developed to provide orientation data for any downhole equipment. The company says additional features are under development, including the ability to correlate using formation markers, gamma pips, or magnetic profiles such as casing collars. Also, the real-time ability to measure and transmit accurate weight-on-tool data to surface will facilitate the setting of packers or liner hangers that require precise applications of weight, torque, and pipe pressure.
Real-time sampling
According to Baker Hughes, its FASTrak LWD service has mitigated sampling and testing risks in a highly deviated unstable formation in the Netherlands. The operator needed high-quality fluid analysis to resolve oil/water and gas/oil contacts in a formation where wireline testing was deemed too risky due to unstable geomechanics. Using the FASTrak LWD testing system in combination with the OnTrak LWD service, all of the formation and fluid analysis measurements were acquired while drilling. With the drillstring in the hole, the risk from the unstable formation was minimized. The testing tool was able to acquire representative formation fluid tests, analyze them in real-time and select those it wished to sample. A total of 12 samples were sequestered - six oil, three water, and three gas - with 100% sealing efficiency. The samples were accompanied by precise formation pressure measurements which, when plotted, clearly defined the fluid contacts. Based upon analysis of the pressure data, four zones of interest were targeted for sampling.
Steering to target
In the North Sea's Statfjord field, the Baker Hughes SureTrak steerable drilling liner service used near-bit gamma ray imaging to drill in a 7-in. 837-ft (255-m) liner in a single run while simultaneously logging and steering the well trajectory. Previous success in the well's 8 ½-in. section encouraged the operator to continue drilling the 7-in. section which was deviated between 40° and 43° from vertical. An average penetration rate of 40 ft/hr (12 m/hr) was achieved. Upon reaching total depth, the liner was successfully cemented in place and the production packer was set in one run.
Expanded service offerings
Ryan Directional Services acquired the assets of Navigate Energy Services in January 2013. Navigate was a provider of unmanned MWD services to the market place and has proprietary MWD and LWD technology specifically for drilling unconventional wells. Recently commercialized technologies include the AccuPulse positive pulse MWD and AccuWave EM MWD system. Both of these systems are capable of operating in 175°C (347°F) and include an option for continuous inclination while rotating or sliding. This enables rig time savings and improves wellbore placement. Additional measurements designed specifically for drilling unconventional wells, including LWD sensors for geosteering, are being tested.
