Abstract

Deepwater is an extremely cost-intensive exploration frontier representing a high-risk/high-reward scenario. After the world’s largest deepwater gas discovery in on the east coast of India, the area has attracted several operators and activity has picked up considerably in recent years. Currently, five deepwater rigs and drillships are operating in water depths ranging from 1500 m to 3000 m. This cost-intensive scenario dictates the use of techniques which maximize quality information while minimizing rig time. Interval pressure transient testing (IPTT) on wireline and conventional testing acquire essentially the same data and use the same analytical tools. Conventional well testing methods obtain the average properties of multiple layer systems but turn out to be time-consuming and hence expensive, especially if the fluid is only water. However, wireline acquisition is much more appropriate for accessing multiple layers and is far less time consuming; additionally, it can be carried out in open holes as well. The radius of investigation identified by the progressive pressure transient is sufficiently large to determine essential reservoir properties. With IPTT, the evaluation can be made layer-wise, and these evaluations are very critical for both the exploration and appraisal stages of the field development.

IPTT has been performed in deepwater wells in India using the dual-packer configuration of wireline formation testers. IPTT is used to evaluate reservoir parameters, capture representative fluid samples, and assess commercial viability and flow potential for multiple reservoir intervals. This potentially eliminates the need for conventional well testing on expensive deepwater rigs, thus significantly reducing operating cost by use of state-of-the-art technology. This paper showcases the workflow and process involved in the impact area of formation evaluation from a reservoir dynamics perspective and use of a calibrated, continuous permeability curve in calculations of full well deliverability in case of gas discovery.

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