Application of a New Temperature Array System During Exploratory DST-TCP Operations for Greater Reservoir Understanding in a Cost-Effective and Environmentally friendly Manner

Abstract

A new technology consisting of a distributed temperature array system has been deployed for the first-time during exploration drillstem testing (DST). It was successfully used to evaluate fluid movements across and into the tested formation throughout operations and helped characterize vertical heterogeneities in a complex carbonate reservoir without in-well intervention. The distributed temperature array system was deployed to acquire temperature profile data during the entire sequence of drill-stem testing operations, from run in hole through perforation, stimulation, flow, and fluids re-injection operations. The data was acquired across and beyond the entire perforated interval. High-resolution temperature sensors were installed on the tubing conveyed perforating guns to provide an accurate temperature profile across the perforations. The sensors are resistant to high perforation shock and acidizing. The typical sequences of acid injection, subsequent fall-off, production and build-up during well testing create information-rich temperature transient responses in the wellbore that are used to evaluate the flow profile, leading to improved understanding of formation structure and properties. The distributed temperature array system was successfully deployed in an exploration well in UAE to minimize rig time and costs, while providing new type of measurement for interpretation. The lack of well logs because of the drilling and completions approach made the need for additional information critical. Conventional operations would require three separate runs to perforate the reservoir, run the DST string and perform production logging operations. The distributed temperature array system allowed to deploy the DST/TCP string in a single run without having to resort to a dedicated wireline run for PLT, which saved 3 days of rig time as well as an additional flow sequence for PLT data acquisition, thus significantly reducing flared volumes. The temperature profiles acquired during the test showed several interesting characteristics not available before and provided unique insight. It demonstrated perforation success, provided a detailed timeline of acid stimulation operations, and highlighted the presence of a thief zone preventing acid from reaching deeper zones. The existence of that interval was further confirmed by the warmback sequence, showing a slower temperature recovery. The subsequent flowing periods confirmed this interpretation by showing clear temperature inflection points across zones having demonstrated acid intake and complemented the pressure transient analysis highlighting a typical fracture-dominated system response as well as other heterogeneities consistent with the temperature-based observations. The combination of pressure transient data with temperature profile provided insights that would not be obtainable through available data.