Successful DST Operation in Deep, HPHT, Wildcat Exploration Well Deploying the Newest Technology in Wireless Telemetry SRO and Upgraded Bottomhole Sampling System
Authors: Paluruan Firman , Rama Abilana Dwi , Sitompul Lennon Panuturi , Jatikusuma Rahmad , Tokoh Kristoforus Widyas 
Published: October 2022

An Operator wanted to perform a Drill Stem Test (DST) using wireless Surface Read Out (SRO) and downhole sampling of a deep wildcat exploration well (∼4200 mMD) with limited reference from adjacent wells. This first high-pressure, high-temperature (HPHT) exploration well to be attempted in the area was particularly challenging, because it lay in a swamp and had to be drilled with a swamp rig. Immediate, fast decisions would be needed during the DST operation.

To ensure accurate DST results in this deep, HPHT well with challenging swampy conditions and lack of adjacent well data, Company deployed its newest wireless acoustic telemetry SRO system, in conjunction with the latest generation tubing-conveyed bottomhole sampling system. A globally proven DST tool string was configured with a retrievable cased hole packer, tubing string testing valve, downhole tester valve, multi-cycle circulating valve, and single-shot rupture disk circulating valve. This innovative solution was engineered to meet the Operator's requirement for reliable, real-time downhole data and representative bottomhole samples of the well.

The DST system delivered results was met the Operator's expectation, with successful execution and acquisition of all requested downhole data despite interference from well intervention activity, and collection of all bottomhole samples although killing pressure exceeded the original plan. The wireless SRO system, rated up to 20K psi and 350° F (177°C), allowed the Operator to monitor and analyze real-time bottomhole pressure (BHP) and bottomhole temperature (BHT) for quick decision-making while receiving continuous assurance of downhole tool status.

The modular concept supports efficient preparation and testing of tools offline, so risk can be reduced compared to other systems available that can only be tested online (on the rig floor before running in hole). The tubing-conveyed bottomhole sampling system captures more bottomhole samples (9x 400c) than traditional, slickline-conveyed sampling (2-3x 600cc in one run). It also minimizes risk as no well intervention is required and does not add additional time to DST operations.

The annulus-pressure-activated bottomhole sampling system incorporated enhancements to upgrade internal sampler tubing pressure from 12k to 15k psi. These enhancements enabled higher well kill pressure for more flexibility, without risk to captured samples.

This combined solution provided ongoing reservoir insights that enhanced decision-making, avoided wasted rig time (saving 36 hours), and led to significant cost savings. The wireless SRO system increased confidence in well kill operations, due to observation of actual BHP at surface in real time. The tubing-conveyed bottomhole sampling process worked successfully, without losing the contents of any samplers, even with higher than planned well kill pressure. Overall performance improved compared to slickline-conveyed bottomhole sampling runs.