electronics for high-temperature drilling environments

7/30/2019 Electronics for High-Temperature Drilling Environments

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24 JPT JANUARY 2011

Globally, increasing amounts of hydro-carbon resources are being found infields that have very high thermal gra-dients. (It gets hot very quickly as youmove downward.)

On the drilling side, challenging,high-pressure/high-temperature (HP/

HT) wells customarily have beendrilled with the simplest of tools, suchas turbines and mud motors, whichhave minimal electronics and make nomeasurements. Logging-while-drillingtools, which do contain electronics andrequire electrical power to operate, havenot been used thus far in these wells.

Most formation-evaluation toolshave lots of electronic components, andso initially couldnt be used in HP/HTwells. However, these wells are oftenlocated offshore, where high rig ratesforce operators to look for all possiblemeans to increase drilling efficiencyand optimize wellbore placement formaximum production.

Meeting HT ChallengesThe main challenges in these environ-ments are preventing the electronicsfrom becoming damaged, maintainingmeasurement accuracy and precision,and generating or supplying the regu-lated power to the electronics reliablyover the duration of the drilling effort.

Several parallel technologies have

been developed over the past 5 to 6years that can be used on their own or incombination to address these issues. Thetechnology developments have concen-trated on three main themes: HT elec-tronics and the operating environment,new sensor technologies and measure-ment methodologies to improve accu-racy and precision, and active cooling.

In this connection, a 2-year projectto develop measurement-while-drillingtools that can record and transmit dataat temperatures of 230Crunning for

14 days continuouslyhas been initi-ated by Halliburton. The purpose ofthis project was to finalize some of theongoing developments in high-temper-ature electronics and sensor technolo-gies and package them into a tool capa-ble of performing in this environment.

In considering the operating life ofelectronics, one of the main issues inHT environments is the increased rate ofchemical reactions that cause the elec-tronics to fail. In 1889, Svante Arrheniusdocumented the fact that chemical reac-tions require activation energy to pro-ceed. The Arrhenius equation providesthe quantitative relationship betweentemperature and the rate at which achemical reaction occurs. This rela-tionship is important for our industrybecause it governs many of the failuremechanisms for downhole electronics.

The rate of chemical reactions isdefined by the equation

K=AeEa/RT,

which documents the exponential rela-tionship between rate (K) and tem-perature (T). Ea is the activation energyfor a particular process, and this valuecan be changed (by adding catalyst orinhibitor). Ae (pre-exponential factor)and R (gas constant) are empiricallyderived constants. Many reactions dou-ble their rate every 10C.

Chemicals Removed,Electronics HardenedRemoval of the chemicals causing thesereactions and hardening the electron-ics, i.e. increasing the activation energyrequired to start chemical reactions,have been the main factors in success-fully developing HT electronics.

In a cooperative effort between theE&P industry and several leadingelectronic-component manufacturers,technology has been developed to get

most out of the electronics required formeasurement-/logging-while-drilling(M/LWD) tools to operate for extendedperiods at, or even above, 230C.

The main developments were inhardening the circuitry, repackaging theelectronics and removal of chemicals

in the electronics and their immediateenvironment that otherwise would havereduced the effective life of the electron-ics, as a result of accelerating chemicalreactions at higher temperatures.

New Sensors,Measurement MethodologiesNew sensors and new measurementmethodologies have been developedfor the measurement of the earths mag-netic and gravity fieldsessential indetermining the wellbore trajectory inthe hydrocarbon-bearing reservoirs.

The existing sensors that measure boththe earths magnetic field and the gravityfield have stability issues throughoutall of the temperature-operating ranges,which unless addressed effectively causetheir calibration to drift and thus resultin inaccurate measurements.

Both sensor packages needed to beredesigned for the HT operating envi-ronment for higher reliability and lowercalibration drift. The electronics thatsupply the power to these instrumentsand collect the measurement values

also have been redesigned to reducethe amount of drift with temperature.The methodology used to make themeasurement has been upgraded toaccount for calibration drift, ensuringstable, calibrated measurements overthe life of the instruments. When theseinstruments are used, the measure-ments are as accurate and precise asthose taken with current low-tempera-ture instruments used by the industry.

Existing, proven technologies formeasuring natural gamma rays, vibra-

Upgrading Formation-Evaluation Electronics

for High-Temperature Drilling EnvironmentsRon Dirksen, SPE, Halliburton

TECHNOLOGY UPDATE

JPT JANUARY 2011


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tion, and pressure have been hardenedand made suitable for HT operationover a prolonged period.

For the gamma-ray measurement,Geiger-Mueller (GM) tubes are beingused. GM-tube technology has beenavailable for a long time in the indus-

try and has proved very reliable andcapable of operating over a large rangeof temperatures and pressures. Smallimprovements have been made in thematerial used to make the tubes, aswell as in the welding, braising, sol-dering technology, and sensor mate-rials to ensure reliable operation athigh temperature.

Vibration- and pressure-measurementsensors that operate at temperaturesabove 230C are commercially availableand being used in the new tools.

Cooling TechnologiesVarious technologies, such as cold plates,flasking, and refrigeration, have beendeveloped to keep the electronics cool.

Cold-plate technology consists ofmetallic plates in which temperatures canbe lowered by passing an electric current

through them in proximity to the sensorsand electronics. The plates can quicklycarry heat away from the electronic sen-sors components. A similar technologyis used in personal computers.

Flasking is a measure in which theelectronics are placed inside a specialchamber, which can be filled with alow-density gas or converted to a vac-uum. This reduces heat transfer fromthe environment to the electronics. Themethod itself is not new, having beenused in the wireline industry for years

to run relatively low-temperature-ratedelectrical components in HT wells.

Refrigeration also is being used. A unitnow being built will use phase-changetechnology (similar to a domestic refrig-erator) to cool the area surroundingthe sensors, creating a more benignenvironment in which instruments can

operate even when temperatures inthe wider operating sphere are muchhigher. A special liquid that evaporatesand becomes colder as it is allowed toexpand is pumped to the area aroundthe sensors and electronics to keep themcool, extending their effective lives andincreasing overall system reliability.

Other developments have been inthe area of the seals, which keep drill-ing and formation fluids from enteringthe tool. A combination of HT elas-tomeric and metal-to-metal seals has

been implemented for these new tools.

Ultrahigh-Temperature ToolsTo date, a couple of ultrahigh-tempera-ture tools, which can measure direction-al data, vibration, natural gamma rays,and pressure, have been built and tested.The data will be communicated to thesurface in real time, using pressure-pulsetechnology. A new mud-pulse pack-age for this tool was developed in theprocess. The power supply to the mudpulser, as well as the electronics and sen-sor packages, comes from a new power-supply generator and power-regulationsystem that was built using many newmaterials and methods not previouslyused in the oil-and-gas industry.

These developments will deliver tech-nology that enables the exploitation ofhydrocarbon resources in HT reservoirs.However, they will also improve theoverall performance and reliability ofM/LWD systems deployed in normaltemperature settings. (Figs. 1a and bshow the dividing lines between the dif-ferent operating environments defined

by ascending pressures and tempera-tures, in graph form, and the currentpressure and temperature capabilities ofselected downhole tools.)

Looking AheadThe progress made so far paves the wayfor the future development of other HTM/LWD technologies that are current-ly only available in environments withoperating temperatures not exceeding175C, such as resistivity, density, neutronporosity, and sonic measurements.

TECHNOLOGY UPDATE

26 JPT JANUARY 2011

JPT

Fig. 1a) Ascending pressure and temperature operating environmentsdisplayed in graph; b) current pressure and temperature capabilities ofselected downhole tools.

Temperature and Pressure CapabilityDecember 2010

ToolMaximum Operation Pressure (psi) and Temperature (C)

9 in. 8 in. 6 in. 4 in.

Rotary Steerable 30,000 175 30,000 175 30,000 175 30,000 175

Directional 30,000 175 30,000 175 30,000 175 30,000 175*

Pressure While30,000 175 30,000 175 30,000 175 25,000 175*

Gamma 30,000 175 30,000 175 30,000 175 30,000 175*

Resistivity 25,000 175 30,000 175 30,000 175 30,000 175

571000,03571000,03571000,03ytisneD

Neutron 30 000 175 30 000 175 30 000 17530,000 175 30,000 175 30,000 175

Sonic 25,000 175 30,000 175 30,000 175 25,000 175

Formation Tester 25,000 150 30,000 175 30,000 175 25,000 150

*200C tools now commercially available, and 230C tools will be field tested in Q1 2011.

Drilling

Extreme HP/HT

HP/HT

Ultra HP/HT

Standard

Temperature

Pressure

>300F

>150C

>20K psi

138 MPa

>15K psi

103 MPa

>10K psi

69 MPa

>350F

>175C

>400F

>200C

(a)

(b)


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electronics for high-temperature drilling environments

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