This paper describes the applications of annular chemical packer (ACP) with highly tailored thixotropic characteristics in horizontal wells completed with slotted liners. The purpose of the applications was to provide a cost effective annular isolation method for water control in horizontal sections.

The rheological properties of ACP, the placement techniques of ACP, the subsequent treatment procedures, and the uncertainties involved were provided.

The oil rate of the candidate onshore horizontal well M28-P7 was only 0.5m3/d, with 99% water cut. Production logging identified that about 86% of liquid rate was produced from the toe section. The ACP was placed across the shale between the two different liquid-producing zones, and a mechanical plug was dropped at middle of the ACP site. Then effective acidizing was performed for the heel section in order to gain higher permeability. After the treatments, the water cut decreased to 83% while the corresponding oil gain reached up to 5.3m3/d, 20 times that of the pre-treatment scenario.

The other similar treatment was performed in offshore horizontal well A2h after production logging. Two ACP plugs were designed and an optimized recompletion string was put into the well. The water control operation went smoothly, which significantly decreased the water cut to 3% from 74% and the oil rate was increased to 187m3/d, with the net oil increased by about 100m3/d over the pre-treatment scenario. This is the first ever successful water control operation with water diagnosis in an offshore well with a tough completion in the South China Sea.

Case histories indicate that using ACPs was the right choice for blocking water in the sand screen liner completion with high level technical success and economic feasibility. Also a comprehensive and detailed water control design based on production logging results, completion, and reservoir permeability distribution is the key for successful water shutoff.

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