Extending The Stress-Testing Deployment Envelope to Highly Deviated Wells
Authors: Rylance M. , Naidu R. , Hoq A. , Mossop K. , Smithells S. , Ronald A. , Masson L. 
Published: October 2017

Open-hole in-situ stress measurements have gained increasing significance in recent years, from front end loading of major hydraulic fracturing campaigns, as well as cap-rock integrity assurance and management of Out Of Zone Injection (OOZI) for pressure maintenance or secondary recovery purposes. The latter has become particularly important in recent years, with an increasing scrutiny of injection operations and their containment assurance. In response to this requirement, wireline deployed dual-packer micro-fracturing has been the most commonplace approach taken to obtain such data. However, such Wire-line Formation Tester (WFT) measurements have their own technical limitations, particularly with respect to the wellbore deviation, hole-size and pressure differential limits that can be applied.

Just such a scenario was faced where a number of planned development wells were being drilled and were radiating from a suite of fixed drill centres, resulting in extensive and large sail angle sections in the zones within and across the cap-rock of interest. The use of conventional WFT micro-fracturing operations was considered to be too challenging under this scenario; due to the wellbore inclinations, the pressure limits, the probability of failure, the timings, the costs and the operational complexity in such a difficult environment. The proposed solution was to resurrect a technique that had been used on just very few occasions some 30 years ago, prior to the availability of the WFT approach, which was the use of drill-string deployed dual-packer tools for stress measurements.

Due to the lack of recent industry experience with this type of application, the tool and equipment selection, the Bottom Hole Assembly (BHA) design and operational considerations were of paramount importance and required considerable planning. This paper describes the technology selection, planning, contingency options, risk mitigation, operational aspects and the outcome of the first operation from the initial concept to its final execution. It includes how the tools were successfully selected, tested and deployed, the packers inflated and set, and injection tests made within the target formation; with a number of lessons learned on the tool behaviour, the injection and the test approaches taken. The downhole data was efficiently retrieved and a suite of recommendations have resulted from the operations in general.

Accurate in-situ stress measurements have been successfully made in a cap-rock formation from an open-hole section of a well at high-angle, using a pipe-deployed dual-packer approach. While the often used WFT micro-fracturing technique can address the majority of scenarios, situations can arise where a pipe-deployed approach offers the only effective and economic means of obtaining such data. The data that can be obtained is helpful for designing wells and defining the operational envelope for increasing the reliability and efficiency of injector wells to achieve field development objectives.