FAQ
Q: What is the maximum pressure the SPIDR can record?
A: The SPIDR is calibrated to a full scale pressure of 15,000 PSIA.
Q: How accurate is the SPIDR?
A: The SPIDR's internal quartz transducer has a resolution of 0.01 PSI and an accuracy of < 0.01% of full scale.
Q: How much data can the SPIDR store?
A: The exact number of samples that can be stored depend on the programming configuration and whether any external transducers are being used.
Q: How long will the batteries last?
A: The SPIDR is powered by three "D" cells that can power the SPIDR for 1,500,000 samples or 2 years.
Q: When the batteries run out will I lose all the stored data?
A: No. Every time the SPIDR takes a measurement it checks the battery voltage. If the voltage drops to an unacceptable level, the system will shut down and use the remaining battery voltage to preserve stored data.
Q: Will the SPIDR lose its memory when I change the batteries?
A:
No. There are safeguards in place within the SPIDR that will preserve the memory contents for several years.
Q: How can I check the battery voltage?
A: The battery voltage can be monitored using our free software without interrupting sampling.
Q: When I download the SPIDR will it affect any measurements?
A: No, you can communicate with the SPIDR and download the memory contents without any interruption to your test.
Q: What exactly does the SPIDR store?
A: Each sample the SPIDR makes includes: date, time, sample number, pressure from the internal transducer, and readings from the external transducers (if present).
Q: Can the sample rate be varied?
A: Yes, the sample rate is programmable and the interval can be varied from a tenth of a second to hours or days! The sample rate can not be changed after the SPIDR has been programmed.
Q: How big is the SPIDR and how much does it weigh?
A: The SPIDR is extremely compact and measures just 5 3/4in. x 5 3/4 in. x 9 in. and weighs just 8lbs.
Q: Is the SPIDR safe?
A:
The SPIDR has been certified by ATEX and is CSA certified Intrinsically Safe.? The SPIDR is also suitable for sour gas service.
Q: How is the measured pressure converted to bottom hole pressure?
A: After downloading the SPIDR the data is imported into our proprietary report generating software CSPRG. Using a modified Cullender-Smith routine the data is converted to bottom hole pressure. This optimized routine has been proven in thousands of tests. It accounts for the quantity and properties of produced fluids, divides the tubing into discrete elements with a unique 'Z' factor for each and computes a theoretical temperature profile based on well depth and well head and bottom hole temperatures. The software also uses different friction loss models for increasing flow rates and incorporates a thermal decay option to compensate for cooling of the gas column when flowing well head temperatures exceed 120 F.
Q: Can you get valid results?
A: Yes, you can, if:
1. you are testing a gas well with liquid production under 150 bbl/mmcf, no significant retrograde condensate, no slug flow at the wellhead, and no liquid column in the well bore (
Click here to calculate minimum flow rate required to prevent liquid slugging). And
2. you acquire and process the wellhead pressure data using a SPIDR
pressure-transient test kit and associated report generating software from Data Retrieval Corporation.
The SPIDR (Self-Powered Intelligent Data Retriever) automatically measures wellhead pressure, adjusting its data storage rate to the rate of pressure change. The 9-lb unit will operate up to 2 years unattended, storing up to 130,000 date/time-coded readings. It can also monitor a second and third variable, such as flow, pressure, or temperature.
Cullender-Smith, optimized
The key to the accuracy of test data provided by the SPIDR system is a proprietary modification of the Cullender-Smith routine for converting wellhead pressures to bottom-hole pressures. To optimize the Cullender-Smith routine so that it accurately models a broader range of gas wells, Data Retrieval Corporation has made several important modifications:
- The quantity and properties of produced fluids are accounted for.
- The tubing is divided into discrete elements, with a unique "Z" factor for each.
- A theoretical temperature profile is computed for the well bore, based on well depth and wellhead and bottom-hole temperatures.
- Different friction loss models are used for increasing flow rates.
- A thermal-decay option compensates for cooling of the gas column on wells with flowing wellhead temperatures above 120? F.
Using the optimized routine, Data Retrieval's report generating software converts wellhead pressures to bottom-hole pressures with exceptional accuracy, as long as the well meets the criteria given at the beginning of this ad. If there might be a liquid column in the bore, but the other criteria are met, you can still test the well by running a two-rate test instead of a build-up test (call for details). Built-in subroutines calculate all the information you need for plotting and analysis. You get plots, print-outs, and an ASCII file of bottom-hole pressures, pseudo pressures, delta time and pressure, cumulative production, elapsed time, Horner time, rates, and more -- everything you need for comprehensive reservoir analysis.
Proven accurate on thousands of wells around the world
The SPIDR system has been used in major gas fields throughout the world, and it has always delivered well analysis data equal to or superior to that provided by conventional downhole testing. This has been confirmed by using the SPIDR system in parallel with downhole gauges on hundreds of wells.
Want more proof? Try it for yourself.
The SPIDR pressure-transient test kit is available for rental or purchase. Call today to arrange a test or for additional technical information, case histories, and descriptions of other applications.
