Technology Focus: Well Testing (February 2020)
Authors: Mimoun Jordan 
Published: February 2020

Technology Focus
In my inaugural column as editor of the Well Testing Technology Focus feature, I want to shine a light on the notable trend among operators of seizing on the tremendous untapped potential that exploration and appraisal wells represent for far-field reservoir characterization and connectivity.
The concept is straightforward. Upon reaching total depth and running a suite of logs and tools (which may or may not include a well test), gauges are installed as part of the plug-and-abandonment phase, thus turning an otherwise throw-away reservoir penetration into a long-term observation well. Brilliant! The gauges communicate wirelessly by electromagnetic telemetry, cleverly capitalizing on the well’s casing. Well tests conducted elsewhere in the field then can be monitored from these gauges, thereby providing valuable insight into reservoir connectivity, interwell average properties to further calibrate geologic/reservoir models, and in-place resources (or at least a minimum connected volume).
This is not new; however, the technology has become more powerful and reliable, now lasting longer and withstanding more-challenging environments. Fast forward to 2020. These systems are remarkably seamless add-ons to an exploration well design. The advances epitomize the virtuous circle of service company research and development tailored to meet the needs of operators, who, in turn, test these systems and help build a track record. Issues and failures are part of the game of innovative technologies, improving robustness and adding features, job after job.
The value proposition is undoubtedly appealing. The marketing around it is compelling but rarely dwells on the implications of installing such systems. What will it take to yield a conclusive test? Two common pitfalls are the false negative and false positive. The former misleadingly suggests no connectivity when the signal is merely not strong enough or is not given enough time. With the latter, an unrelated response is misconstrued for evidence of connectivity. Successfully designing and interpreting an interference test amid subsurface unknowns, tidal effects, and gauge drift, to name but a few, remains an engineering feat.
While compartmentalization is often flagged as an uncertainty in field-depletion plans (and as a fatal flaw in some instances), only after start-up is its severity revealed—for example, production falling off plateau early or producer/ injector pair not in communication. Early dynamic data collection from well tests paired with such long-term systems may help minimize or circumvent this altogether. This enabling technology truly gives a whole new meaning to “data wells.”
This month’s feature illustrates the vitality of our discipline. Deconvolution is being extended to multiwell applications, opening the door to its use in production. Temperature is measured continuously from top to bottom of a test interval to determine zonal contribution over time, sans production logging intervention. Interval pressure transient tests are used for the consistent characterization of fractured carbonates. The diversity of original concepts and technologies is a reminder that well testing is far more than just pressure transient analysis.
Check out as well the additional-reading suggestions. Take a look back with a service company’s review of 40 years of operational best practices. Peruse an operator’s case study taking a formation tester to new limits. Look ahead to the elusive permeability log from an audacious joint industry project.
Recommended additional reading at OnePetro: www.onepetro.org.
IPTC 19369 Innovative Mini-DST and Production-Evaluation Approach at Challenging HP/HT Conditions for the KeShen Tight Gas Reservoir: A Case Study at Tarim Basin by Shichen Shuai, PetroChina, et al.
SPE 193195 Successful Well-Test Operations in Complex Reservoir Fluids: Lessons Learned and Best Practices Over 40 Years of Worldwide Operations by Yakov Shumakov, Schlumberger, et al.
SPE 196116 Permeability Logging Through Constant Pressure Injection Test: In-Situ Methodology and Laboratory Tests by Sivaprasath Manivannan, Ecole Polytechnique, et al.