Drillstem Testing at 436°F Using a Retrievable Packer and Multicycle Circulating/Tester Valve: Case Study

Abstract

A leading exploration and production company in India drilled a high-pressure/high-temperature (HP/HT) well in eastern offshore India and required drillstem testing (DST) to be conducted using the service company's multiple-set HP/HT retrievable packer, multicycle circulating valve, and multicycle tester valve. The bottomhole temperature at reservoir depth was approximately 460°F. This case study discusses the recently conducted DST of the HP/HT well by one of the largest global oilfield service providers in collaboration with the operator. The HP/HT environment presented many challenges. The operator initially decided to deploy a permanent packer; however, after comprehensive preoperation planning with the service provider, the decision was made to run a retrievable packer to save time and costs associated with setting and milling/retrieving a permanent packer. The hook-wall concentric bypass, 7-in. retrievable packer was designed and tested for HP/HT environments. It was decided to deploy a full-suite multicycle DST tool string rated to 450°F. To help ensure a higher success rate for the long duration of the test, a clear fluid system of lower weight (14.6 lbm/gal) was used for reliable functioning of the annulus pressure-operated DST tools after a hermetical test and heavy kill mud (15.7 lbm/gal) was used for the well kill operation. Deploying a full suite of annulus pressure-operated, multicycle DST string rated for HP/HT conditions permitted the testing of the well to be performed safely and efficiently without any breach to safety and service quality. The initial cleanup, three-bean study, and downhole buildup were successfully completed. Temperature recorded in this well at the 7-in. retrievable packer depth was 436°F, and the reservoir temperature was extrapolated to approximately 460°F. The reservoir was successfully tested with an annulus pressure-operated multicycle DST string designed to withstand the challenging HP/HT environment. The operation set a new global record, which is the highest recorded bottomhole temperature during DST using the service company's retrievable packer and multicycle DST tools.