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Advancing Technology in Formation Evaluation

Formation Evaluation Products

Our Flagship product is the Formation Evaluation Tool (FET).

The FET’s foremost feature is its ability to pump from the formation until a representative sample is present. That is until the characteristics of oil, gas or water are exhibited in the resistivity, conductivity and density sensors of the FET. Once a representative sample is flowing through the tool the FET has the ability to capture a predefined volume of this sample. This predefined volume is based on the multisampler configuration which is set prior to down-hole operation.

In addition the FET contains two Quartz Pressure Gauges which posses an accuracy of 0.01psi. This in conjunction with the tools pumping ability allows for accurate shut-in pressures (SIPs) to be obtained with controlled draw downs. The FET pump can be manually controlled enabling any user defined draw down volume to be acquired, lowest being 1cc. In addition the FET has the ability to reverse pump. That is pump fluids from the borehole into the formation.

The proven benefit of reverse pumping is the tool’s ability to “pump off” the formation, beneficial for situations where the tool has been set for long periods of time. It is this feature which has ensured that the FET has never been stuck down-hole. The FET has been designed such that if there is a loss of tool power for whatever reason the tool will automatically retract (unset itself from the formation) enabling it to be retrieved via the wireline cable.

During the operation of the tool, Crocker Research is able to give the following information to the client upon request:

For Pretests;
  • Draw Down Pressure (DDP) in PSIA,
  • Draw Down Volume in cc,
  • Shut In Pressure (SIP) in PSIA,
  • Fluid temperature in °C,
For Constant Flow Tests (for every litre pumped);
  • Resistivity in Wm, Conductivity in mho/m,
  • Density in g/cc,
  • Temperature in °C,
  • Reservoir pressure in PSIA,
  • Flow rate in L/min,
  • and Permeability in mDarcy.
For Each Sample taken;
  • Resistivity in Wm,
  • Conductivity in mho/m,
  • Density in g/cc,
  • Temperature in °C,
  • Reservoir pressure in PSIA,
  • Flow rate in L/min,
  • Permeability in mDarcy,
  • Pressure at surface in PSIA,
  • and Volume captured at surface in cc.

The Constant Flow Test

The primary purpose of a constant flow test is to ensure that an uncontaminated sample of the Reservoir fluid or gas is flowing through the tool. During a constant flow test, for every litre pumped the resistivity, conductivity and density of the hydrocarbon or water is monitored in search for a “breakthrough”. Meaning, when all the mud filtrate has been pumped from the reservoir and the actual uncontaminated hydrocarbon or water is present. When this occurs there is a noticeable difference in the FET’s sensor readings which corresponds to the properties of the hydrocarbon or water expected. It is at this stage that a sample is taken upon the client’s request. Therefore, a constant flow test must be performed before a sample is taken to ensure a representative (uncontaminated) sample is taken.

Secondarily, a constant flow test may be performed to gather the properties of the hydrocarbon or water present after breakthrough in terms of resistivity, conductivity and density. This may be used to confirm the depth pressure gradients as well as reservoir contact depths.

In addition to this a constant flow test also results in the flow rate and permeability of the fluid to be determined.

Hydrocarbon Samples

Reservoir samples are captured within the multisampler component of the FET (see schematic). The configuration of the multisampler depicts the quantity and volume of samples captured.

In addition to this the FET has the capability of attaching a PVT sampling assembly to the bottom of the tool to capture 2 x 524.4cc formation fluid samples per run.

Gamma Ray Plot

Before any pretests are performed the tool packer must be set at the correct depth. This is achieved via a gamma ray plot. A gamma ray plot is printed and correlated with an existing gamma ray plot and the packer depth adjusted accordingly. The requirement for the gamma ray correlation is that the FET Software must be connected to the logging unit’s depth system. The FET Software can connect to the logging unit’s depth system via an RS-232 serial port. Both Schlumberger and Kerr depth system protocols are supported, and others can be configured as required.


Once the down-hole job is completed, the end result in the FET Software is a graphical log illustrating all sensor measurements over time for pretests, constant flow tests, and samples captured. The client receives a hardcopy and softcopy of this data in the following file formats:

Hardcopy format

  • ASCII format (CSV)
  • LAS format
  • PDF format
  • XPS format