In a mature Texas field, a new repeat formation tester performed 53 pressure tests in less than 8.5 hours with no sticking problems.

Logging service provider Reeves Oilfield Services recorded 53 pressure tests using the new compact repeat formation pressure tester tool in difficult well conditions in Bethany field.

TotalFinaElf operates Bethany field, located in Panola County, Texas. The field produces gas from the lower cretaceous Travis Peak sandstone and Pettit limestone formations. The Roquemore Gas Unit D-22 well was drilled to 9,398 ft (2,866 m) to gather data as part of a depletion study across the field.
TotalFinaElf wanted to identify any Travis Peak sands with pressures sufficient to warrant re-completion.
Formation pressure testers measure the pressure of in-situ formation fluids by packing off part of the borehole wall with a small rubber seal before allowing fluid to flow into the tool. During a test, the tool is stationary in the well, and a pressure differential can develop across the tool, causing it to become stuck. That risk increases in partially or fully depleted reservoirs.

Hole conditions in Bethany field are typically poor, and it is not uncommon for formation testers to become stuck in this way. There is a substantial history of expensive fishing operations. To avoid such problems, TotalFinaElf selected the compact repeat formation pressure tester (MFT). This 2¾-in. diameter tool provides multiple formation pressures in a wide range of well types, including high-angle and horizontal wells, re-entries and sidetracks, and slimhole wells.

The tool has two unique characteristics that make it much less likely to get stuck. The diameter is 2.75 in. - about half that of conventional testers - which means it exposes less surface area to the borehole wall, reducing the total differential sticking force. It also has a self-centering mechanism that forces the main body of the tool into the middle of the hole (away from the borehole wall) as the packer is set. This dramatically reduces the differential sticking risk and allows the tool to operate in a wide range of hole sizes (37/8 in. to 11 in.) Supercharging the flow line before the arms are retracted generates an overpressure at the face of the packer, further reducing the sticking risk.

The MFT has a programmable testing sequence as well as variable sidewall force that can reach up to 3,300 lb. It also has a highly accurate quartz gauge plus strain gauge transducers. The MFT operates from a Compact surface unit, or with a PC and third- party wireline, including monocore wireline. It is combinable with other Compact tools, including Triple and Quad Combo strings. Its small diameter and short length provide unrivaled well access, and its low weight makes it easier and safer to operate.
In an operation that lasted 8 hours and 22 minutes, crews performed 53 pressure tests (including one casing check) with only three "no-seals." The bit size was 77/8 in. There were no tight pulls during the operation, showing that differential sticking had been avoided. "Bethany field has been producing oil and gas since the 1930s," said TotalFinaElf geologist Jayne Rava. "It is imperative that we gather pressure information in order to target zones for drilling and re-completion activities. This is especially vital through the 2,500-ft (763-m) thick Travis Peak Section, where the majority of the 50+ MFT tests were taken. Considering our usual hole problems, the lack of any problems in gathering this many tests is remarkable."

With conventional formation testers it is common to see 2,000 lb of overpull. However, since the MFT was introduced into the United States in January 2002, not a single test required more than 400 lb of overpull to free the tool after taking samples. For more information, visit www.reeves-wireline.com.

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