Abstract

An operator in the Taranaki Basin, offshore New Zealand, employed resin sealant technology in a recent shelf development to isolate the vertical pilot hole from the production formations. This paper details the success of the operation in which the resin sealant was placed in the pilot hole through the drilling bottomhole assembly (BHA) by using a pump and pull technique without needing to trip out to change the BHA, resulting in time and cost savings.

The operator drilled a pilot hole to gather petrophysical data to assess the geological model and formation pressures of the field. Afterward, the pilot hole was to be permanently abandoned, blocking any flow between the pilot hole and the horizontal production wellbore. Conventional practice would be to pull the drilling BHA to surface and then trip in with a dedicated cementing work string to abandon the pilot hole with a series of cement plugs. In this case, abandonment was executed by placing resin sealant in the pilot hole through the drilling BHA without tripping out and changing the BHA.

The dynamic tools on the BHA were unaffected by the resin and drilling continued without incident. When the BHA was pulled out and examined, there was no evidence of the resin within the drilling/placement BHA string. The operator commenced drilling in the main wellbore, and set a 9 5/8-in casing at 3055 m measured depth (MD). The well has since been completed, and the lack of any observed pressure in the production string annulus indicates that full isolation was achieved in both the pilot and main production wellbores. This approach has since been adopted by the operator as the standard procedure for the remainder of the wells in the program.

Using resin technology to abandon a pilot hole through the drilling BHA allowed the operator to avoid tripping in with a dedicated cementing work string, resulting in reduction of both time and overall cost.

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