Wednesday, April 29, 2009

PUMP-OFF Control, an Inclinometer Application for Oil Field Industry

PUMP-OFF CONTROL AS A MATURE TECHNOLOGY, By: Alfred Majek

The level of technology offered by Pump-Off Controllers has reached a point of maturity that justifies application in most areas implementing artificial lift with beam pumps. The Cost savings offered by POCs is thoroughly proven, and economic analysis usually indicates system pay out within one to two years. In addition, equipment has been operating in a number of environments worldwide for over a decade.

Pump-off Controllers are micro-processor-based devices capable of autonomous operation, and are primarily applied in conjunction with sucker rod pumps. Controllers monitor for pump down conditions, defined as the state when fluid in a reservoir is insufficient to warrant continued pumping. When fluid falls below a certain level, pumps are shut down until those levels are restored. Allowing pumps to run only when sufficient fluid is available for lift provides clear advantages, including efficient use of Energy, minimal maintenance costs and optimum production.

The methods used by pump-off controller to attain those advantages vary, and most units use one or a combination of a number of system variables. Units can be configured to monitor:

  • Production flow;
  • Motor amperage draw;
  • Well load only, which is detected by using strain gauges; and
  • Load versus position, which combines strain gauge sensors with beam position monitoring devices to allow traditional dynagraph card creation.

Figure A illustrates typical techniques used to monitor these variables. Advanced POCs support provisions for telemetry to a master computer station, enabling all well parameters and control functions to be handled remotely. Furthermore, a single controller can be employed to control one or a number of wells at any one time.

One major oil company has been involved with computerized pump off control work since the late 1970's. Employing a variety of methods in the Permian Basin in West Texas through the years, fields have realized noticeable success utilizing a system based solely on load and position. Both single and multiple-well devices using a combination of radio and hard-wired cable communications have been installed. Figure B depicts a composite field application.

Load Monitoring

Load can be derived by two types of strain gauge transducers (or Load Cells) mounted either on beams or polish rods. Load Cells mounted on walking beam indirectly determine load through beam stress, while polish rod version measure the weight of the rod strings and fluid columns. Beam-mounted cells suffer minimum damage from well workover crews, since cable can be routed out of the way and cells do not have to be removed.

The constant movement of the beam has little or no effect. On the downside, temperature effects on the walking beam can be very pronounced, placing the burden of adjustment on the electronic package. Also, because the fundamental technique is indirect, it is inherently less accurate than a direct approach.

Polish Rod-mounted cells, on one hand, have to be removed during workover, require running cables somewhat obtrusively from the frame, and are under the constant grinding, sometimes pounding, action of the girdle. On the other hand, superior accuracy permits eventual processing by sophisticated computer analysis programs. Either type of cell functions suitably for simple pump-off control activity.

The position of the beam can be derived by using a proximity switch to monitor counterweights, a resistive pot mounted underneath the I beam, or an inclinometer mounted directly to the walking beam. Proximity switches are sufficient for low cost controllers, although POC systems based on proximity switches tend to assume that upstrokes and downstrokes are of equal duration. Of course, that is rarely the case.

Resistive pots have limited lifetimes, frequently rated at 1,000,000 rotations. For a rod pump running at six strokes a minute, resistive pot failure can occur in as little as four months. Inclinometers, while costing slightly more, have a virtually unlimited lifetime, which generally justifies the added expense.

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Friday, April 17, 2009

Tilt Indicators Beyond the Great Wall of China!

Rieker Incorporated, Aston, PA, USA: As part of our continued world wide growth strategy, we have recently provided representation directly in China and the Far East.

The Rieker Far East Office will now be able to facilitate direct contract negotiations and handling all dealings involving China's rapidly growing industrial market places. "These markets," said Skip Gosnell, Rieker's Marketing Director, "include but limited to those that utilize rugged accurate inclinometers - electronic and mechanical for construction and lift equipment, OEMs and end users, Government agencies and contractors."

Rieker Inc is a leading manufacturer and distributor of rugged accurate inclinometers - electronic and mechanical - world wide. Established in 1917, Rieker continues to introduce tilt indicating instruments that are considered "standards" in the industry.

For additional information please contact the marketing department at info@riekerinc.com or call 610-500-2000.

Thursday, April 09, 2009

New Dual Axis MEMs Based Inclinometer

Rieker Incorporated Introduces the New Dual Axis MEMs based inclinometer to the H4 Series

The H4PD sensor provides dual axis inclination sensing in a rugged environmentally protected housing. This unit incorporates a MEMS (Micro-Electro-Mechanical Systems) sensing element referenced to gravity with integrated temperature compensation over the industrial operating range of –40º to +85ºC. The PWM (Pulse Width Modulated) output is linear with respect to the input angle directly.

Small dimensions and common footprint make it easy for field replacement.

The housing footprint is designed for retrofitting in the field without re-drilling mounting holes (common placement of center and slider flanges).

Features:

  • Dual Axis Angle Measurement
  • Digital Pulse Width Modulated Output

  • Range: ±22º
  • Temperature Compensated Output
  • Operating Temperature -40/+85ºC (-40/+185ºF)
  • Vibration and shock resistant
  • Environmentally sealed to IP66
  • Rugged die-cast zinc housing
  • EMC protected
  • Mechanical Zero adjustment

Applications:

  • Leveling and Tilt/Slope Monitoring
  • Platform Leveling

Equipment:

  • Material Handling/Process Control Equipment
  • Aerial Lifts
  • Scissor Lifts
  • Boom Lifts

  • Cranes and Derricks
  • Lift Equipment/Vehicles

OEM Ready

Tuesday, April 07, 2009

Determination of P-Y Curves Using Inclinometer Data

Abstract: Derivation of p-y curves from lateral load tests on deep foundations is a tedious and expensive task, requiring large numbers of strain gages along the length of the pile to develop bending moment versus depth relationships. A method is proposed which allows derivation of p-y curves from simple inclinometer data using a least-squares regression technique. Inclinometer measurements can and have been routinely made on lateral load tests of piles and drilled shafts. The method outlined in this paper provides a means of “calibrating” p-y curves using data from tests where only inclinometer data are available and promises to allow a substantial improvement in the database of load tests from which the empirical p-y curves used in design are based.

Keywords: piles, lateral loads, load tests, p-y curves, instrumentation

Determination of P-Y Curves Using Inclinometer Data
Brown, DA
Assistant professor, Auburn University, AL

Hidden, SA
Project engineer, Ground Engineering and Testing Service, Inc., AL

Zhang, S
Graduate student, Auburn University, AL

Paper ID: GTJ10087J
DOI: 10.1520/GTJ10087J
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