In the last years, the growing needs to optimize the costs and to fulfil the environmental constraints paved the way for the Interval Pressure Transient Test, a.k.a. miniDST, as alternative to the conventional DST. The recently developed Deep Transient Testing tool improves the performance of the former miniDST technology: longer testing durations and higher amounts of formation fluid can be produced without any flaring and under operational safe conditions. That leads to collect almost no contaminated downhole samples and to characterize the formation within relevant radius of investigation. A proper up-scaling of DTT can also provide a sound estimate the well deliverability and, in some geographical areas, can fulfil regulators' requirements for discovery declaration as "DST replacement". The aim of this paper is to present some relevant Eni applications.
As the current oil industry trend is moving toward more and more challenging reservoirs and in high-cost and high-risk environments, an efficient formation testing and fluid sampling method is crucial to assess the discovered object and for a proper decision making.
During the exploration phase, the main goal is to prove the hydrocarbon finding; at the same time, guaranteeing high quality sampling volumes and understanding the reservoir production potential are the key to assess the future project development strategy.
For years, the conventional way to characterise a new reservoir has been to run a DST: it is still often used to collect representative formation fluid samples and to provide crucial information, such as average reservoir pressure and temperature, flow capacity (kh), formation damage, well productivity, completion efficiency, reservoir heterogeneities, distance to boundaries and hydraulic connectivity and could help to reduce uncertainties in reserves estimations.
However, the execution of a DST can imply several preliminary operations, such as the casing of the well, perforations and the clean-up; this, together with the large duration of the whole testing operation (order of magnitude of days), in deep and ultra-deep water exploration this can lead to relevant cost.
