Schlumberger

Case Study: FAZEBREAK System Removes Solids Without Losses in Openhole Completion Offshore West Africa

Challenge: Avoid premature filtercake breakthrough and unplanned losses in horizontal well program offshore Angola, West Africa.

Solution: Apply FAZEBREAK water-base chelant technology filtercake breaker system to reverse filtercake to a water-wet state, ensure uniform cleanup, and optimize a gravel-pack completion.

Result: Destroyed filtercake, avoided losses, and enhanced completions, resulting in higherthan- expected well performance throughout the horizontal well program.

Premature degradation of residual filtercake hinders openhole completion

An operator offshore Angola, West Africa, sought improved results in its horizontal drilling program after an initial well completed with a stand-alone screen resulted in low production. The initial well had been drilled with a conventional oil-base mud (OBM) with acetic acid used to remove filtercake, but inefficient cleanup contributed to subpar production that resulted in the well being shut in.

For the second well, the operator selected an openhole gravel-pack (OHGP) completion drilled with a reversible invert-emulsion reservoir drill-in fluid system. However, using the same acid that was deployed in the first well to reverse the filtercake to a water-wet state required an unplanned round trip. Premature degradation of the residual filtercake in the heel also prevented uniform cleanup. Specifically, the acid treatment had been performed with a short stinger after gravel packing and resulted in immediate breakthrough, allowing the acid to bypass most of the filtercake.

Uniform dispersal of filtercake

To avoid postcleanup trips and the risk of wormholing, the operator requested an alternative filtercake breaker that, unlike the acid, would provide a delayed and uniform breakthrough, thereby ensuring full coverage of the filtercake. M-I SWACO recommended the FAZEBREAK system for dispersion of residual FAZEPRO system filtercakes.

In addition to thorough destruction of the filtercake, the operator needed a delayed reaction from the breaker to permit the completion of full mechanical isolation. The FAZEBREAK system would be pumped during the gravel-pack operation just prior to extracting the washpipe to enable uniform placement across the entire horizontal interval and to meet the requirements of the well.

Improved results for the horizontal well program

The slow reaction rate of the FAZEBREAK system provided optimal control and resulted in no unplanned losses, even during the gravel-pack operation. As a result of this success, the strategy has been deployed on six OHGP completions for the operator with similar results. In each well, the FAZEBREAK system diffused through the gravel and destroyed the filtercake over several days. The wells have since produced above expectations and without requiring any postcompletion intervention.


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