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Weversbaan 1-3
2352 BZ Leiderdorp
The Netherlands
P +31 71 581 3505
F +31 71 301 0802
info@panterra.nl

Foam Core Stabilisation

Unconsolidated sediments might be recovered during coring, usually caused by a shallow burial depth and/or by the absence of sufficient cementing materials, which may result in (very) fragile core material easily being disintegrated during core movement. It is therefore important to protect these sediments from internal displacement, by means of a core stabilization technique, prior to transporting the core barrels to the laboratory. PanTerra’s foam stabilization technique is performed at the wellsite by injecting foam into the full length (9m) and/or short length (1m) core barrels. The core stabilizing system is applied to fragile and/or unconsolidated sediments in order to reduce the risk of core damage during transportation. The two-component foam is characterized by low injecting pressures and a fast reaction rate, securing and encapsulating the inner tube, even in case of a mud-saturated core, thereby preserving the total integrity of the core without disturbing and altering the rock properties.

PanTerra, as a provider of geological and petrophysical data, fully appreciates why proper well-site handling, system core stabilization and transportation is mandatory for core study.

Procedures and Techniques

Full length foam core-injection is usually advised for extremely fragile sediments prior to cutting into smaller, meter-sized core barrels. Injection holes are pre-drilled prior to injecting a two-component foam into the barrel. The pre-drilled holes serve both as foam-injection points (ensuring full-core encapsulation) as well as outlets for expulsing the mud out of the barrel during injection.

The number and position of the foam-inlet points depend on the characteristics of the material itself, which is determined by our engineer. During injection, the core remains horizontal and it can then be subsequently cut into smaller sections for further processing.

Injection of 1m (or 3 ft.) core sections is the standard method of stabilizing medium cemented to consolidated core material. Similar to injecting foam in a full length core, the tube is laid out in a horizontal position and injected at multiple, pre-drilled inlet points carefully selected by our engineer.The multi-point injection technique secures the core by encapsulating the inner tube with stabilizing foam which will fill the annulus as well as any fractures present without invading into the sediment itself.

The stabilizing foam will be injected with low pressure, minimalizing the risk of core damage. Once injected, the expanding foam will drain out the drilling mud by means of the injection-points. The end-caps remain in place in order to prevent core displacement which may result from mud-drainage. A securing cushion will be created on the ends of the core barrels preventing axial movement during core movement and transport.

Vertical injection may be applied whenever the sediment consists of very loose sand or rubble, lacking any cohesiveness. This technique is generally being preferred to avoid the possibility of gravity sliding of loose sediment when moving the core from its original (i.e. vertical) orientation. Once injected, the core can be re-positioned horizontally and can be safely re-located and transported. A special technique can then be applied at the drill-floor when the core might be cut into smaller sections of 1 meter (using a pipe cutter).  The result is a fully stabilized core suitable for shipment.

Foam quality characteristics and core processing
The foam consists of a 2-component fluid and is able to react and solidify in the presence of fluids (i.e. drilling mud). The foam will expand and harden out quickly and will be ready immediately afterwards for further core processing/transport.  PanTerra’s core stabilizing foam system prevents the fragile core from being internally displaced and without altering the lithological characteristics and rock properties. After shipment, the foam can be mechanically and safely removed and analyses to the undisturbed core can be conducted. The materials contain liquids which are within acceptable limits concerning health and safety and with respect to the environment.
Evaluation at Laboratory
Once the core barrels arrive in our core analysis laboratory, we have the ability to evaluate the core using x-ray tomography, or by slabbing the cores. When onsite core stabilisation is performed at the wellsite, PanTerra provides a full report to the client, describing the process, noting observations, photographs, documenting the onsite activities that could have an impact on the core integrity.

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