Schlumberger

MicroPilot Single-Well In Situ EOR Evaluation

Save time and costs with rapid screening of chemical mixtures and lithologies

In the process of screening for enhanced oil recovery (EOR), MicroPilot EOR evaluation fulfills an industry demand for a quick and inexpensive intermediate step between initial fluid core displacement in the laboratory and a single or multiple pattern field pilot —a single-well test to confirm laboratory results in situ before committing to drilling a multiwell pattern. The service uses only a small volume of premixed injectant, requiring no surface facilities for mixing or processing, and delivering results in just a few days. Although small, the MicroPilot flood volume is much larger than that of a typical coreflood in a laboratory, allowing for testing of some formation heterogeneity.

Assess chemical EOR effectiveness in a matter of days

MicroPilot evaluation comprises a log-drill and inject-log sequence of operations to assess the improvement in oil recovery resulting from the addition of chemicals, such as an alkali-surfactant-polymer (ASP), to injected water. 23 L of fluid is transported downhole in a sample chamber and injected into the formation, in a reversal of the conventional reservoir fluid sampling operation.

The sample chamber, pump, and drilling assembly used to inject the chemical are modules of the field-proven MDT modular formation dynamics tester. A 6-in-deep, pencil-sized hole is drilled from the center of the sealing pad with the OHDT openhole driller tool, to provide hydraulic access to the reservoir. The hole is drilled underbalanced to keep it free of mud.

Determine EOR flood geometry and change in Sor

Log measurements before and after the injection record the resulting changes in saturation proximal to the wellbore.

  • The high-resolution CMR-Plus combinable magnetic resonance tool enhances the precision of nuclear magnetic resonance (NMR) logging. Its high vertical resolution is an essential feature for accurately evaluating the distribution of the fluids in the flood volumes typical of MicroPilot tests. Direct hydrocarbon characterization is provided through magnetic resonance fluid characterization stations recorded at various positions within the flooded zone.
  • Dielectric Scanner service accurately quantifies residual hydrocarbon volume with a direct measurement of water volume, also constructing an accurate radial profile of the close-borehole region.
  • FMI fullbore formation microimager reveals the dimensions of the swept zone and surrounding oil bank.

Within just a few days, MicroPilot evaluation thus confirms the development of an oil bank and provides an in situ measurement of EOR flood geometry and the change in residual oil saturation Sor resulting from the action of the surfactant. The service can rapidly screen various chemical mixtures and specific lithologies for applicability before committing to single well tracer tests or pilot injection projects, which are both time-consuming and expensive.

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MicroPilot Procedure

The region of interest is logged.The toolstring is positioned at a selected depth. The interval is logged again to determine the EOR flood geometry and the saturation change in the formation.
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