CASE HISTORY - HDC XREAM Mark II

Water Injector West of Shetlands

This well was drilled using synthetic oil based mud in the North Sea off Shetland. The concept of the field trial was to attempt to inject through the oil based mud cake without the normal procedures of producing the well conventionally to remove the filter cake by placement of the HDC XREAM Mark II chemical in the screens.

The procedure was deemed particularly challenging because it had never been done successfully before and the BHT of the well at 148 ° F was considered very low for an unconventional or conventional dissolver of any sort.

The well was completed and the HDC placed across the screens using coiled tubing. The CTU was pulled and the chemical allowed to soak for 24 hours before injection was attempted.

When the well was put on injection, it was established at a high back pressure ( ± 2000 psi) with a constant rate. The pressure was higher than expected although this part of the field and this formation had not been injected before and the productivity of the operation was still largely in doubt.

In order to determine if the filtercake had indeed been removed, the well was cleaned up conventionally using CTU/EDTA/Acid and produced – with poor results. Injectivity went to zero indicating the acid treatment had in all probability compromised the formation.

The decision was made to perforate through the screens to establish exactly what the injectivity of the formation was. Consequently it was found the injection rate perforated, was identical to the rates and pressures established with the original clean up of the HDC Mark II product – indicating it had in fact, yielded total cake dissolution and maximum injectivity at the outset.

Although the well was not in an ideal location for an injector, the establishment of the HDC Mark II as a filtercake dissolver, which could eliminate the need for CTU use and conventional flow back and clean out using OBM, has been established – even at low bottom hole temperatures.