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Gulf Keystone Petroleum Ltd. (GKPI) was managing the risk of drilling their first wild cat well in the Iraqi Kurdistan region. They were drilling in an unproven region with limited well data and required early indications of formation potential to support future planning. Initial plans called for a deep well in the Triassic and the Permian formations, however, during drilling there became evidence of other secondary targets. GKPI needed a flexible test package to properly evaluate each reservoirs potential and possible relation to each other.


Zones of interest in multiple hole sizes and behind multiple casing sizes necessitated a variety of drill stem test (DST) solutions on GKPI’s SH-1 well. Northstar was able to offer a variety of different testing operations at the well site.

Northstar conducted early open hole DSTs in both 12-1/4” and 8-1/2” hole sizes, testing the Jurassic (Shargelu, Mus & Buthmah) and Upper Triassic formations. Northtars was able to attain a benchmark flow rate and formation pressure in order to prove each formation’s potential in isolation before drilling fluid invasion influenced results. Stable carbonate formations and a salt-water mud system allowed open hole tests to be prolonged up to 54 hours (total flow and shut in time). Post DST gauge data confirmed interval isolation in the highly fractured carbonates was achieved on all open hole tests. In addition to extended open hole test times, Northstar was able to support an open hole acid stimulation job that cleaned up damage from drilling operations which significantly increased production flow rates. Northstar then used cased hole DST equipment combined with Tubing Conveyed Perforating (TCP) to perforate and test the Kurre Chine, Butmah and Mus targets behind both 7” and 9 5/8” casing. Further evaluation of the Mus zone was done using Northtar’s cased hole DST string in conjunction with artificial lift from an electrical submersible pump (ESP).

Northstar maintained a 100 per cent success rate, recovering valuable data from all nine DSTs using three different DST technologies with no misruns.


Northstar DST - Downhole Testing Specialists Shaikan
Case Studies