Reservoir Fluids

Is Your Reservoir Brine "Worth its Salt"?
How confident are you of the composition of formation water in your reservoir? Almost every time we manage a SCAL, formation damage or EOR project there are question marks about the formation water composition. This can range from no water sample at all, to widely ranging compositions from the same reservoir to samples contaminated with drilling fluid filtrate. Many times only basic checks are performed (ion balance for example) before using the water in the lab.

Does it matter?
Any brine that is not representative of the reservoir formation water will not be in ionic equilibrium with the rock and may be too saline or fresh. This can result in a number of problems arising including:

• Clay swelling and fines mobilisation – induced damage
• Incorrect salinity – resistivity / conductivity for petrophysical SCAL
• Incorrect viscosity – mobility ratio for reservoir engineering SCAL
• Formation of mineral scale
• EOR with polymer and surfactants need to be accurately matched to a correct formation water salinity
• EOR by low salinity water flooding – de-risking the formation water composition is of profound importance

Verdict: In most situations getting the brine composition correct matters.

Core Specialist Services have partnered with Ross McCartney of Oilfield Water Services (OWS) to provide the option of de-risking your formation water composition before embarking on a laboratory test program.

We were impressed by Ross’s ability to back out the contaminating ions from a water sample for a recent study we managed. The client used the service on the next well and was delighted with the results. We offered the service as an option to another client on the next new study – again approved to proceed.

We now plan to offer the "brine de-risking" as an option accompanying all studies we manage. Typically this type of basic de-risking may require a day of consultancy time. In our view this is a small and very worthwhile investment to constrain a common uncertainty.

You can find out more about Ross and OWSC by visiting: www.oilfieldwaterservices.co.uk