Successful Discovery of Light Oil From an Unsuccessful Well Through Re-Entry

Abstract

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 147247, ’Successful Discovery of Light Oil From an Unsuccessful Paleozoic Well Through Re-Entry - A Case Study of an HP/HT Well,’ by Haifa Al-Bader, SPE, Yousef Zaid Al-Salali, SPE, Vidya Sagar Duggirala, SPE, A. Manimaran, and S. Packirisamy, SPE, KOC, prepared for the SPE Annual Technical Conference and Exhibition, Denver, 30 October-2 November 2011. The paper has not been peer reviewed. An exploratory well, the second deepest in Kuwait, had been drilled in the Mutriba field to 22,094 ft. Two formations, Kra-Almaru and Khuff, were perforated and tested. The tests revealed the presence of sparse gas, and it was decided to test and complete this well in the Jurassic formation through re-entry. The re-entry in this ultradeep well was full of challenges; however, by overcoming all the challenges, this well was successfully perforated, stimulated, and tested, which led to the first commercial discovery of oil and gas within the Jurassic reservoir in the Mutriba field. Introduction Two zones in Paleozoic and Triassic sections were perforated and tested separately to evaluate the presence of hydrocarbon between 18,500 and 21,500 ft. The well was completed in 2004. After undesirable results were obtained from the Triassic and Paleozoic formations, exploration teams studied the feasibility of testing Jurassic formations in this well through re-entry. Testing Jurassic formations in the Mutriba field from an existing well will be more economical than drilling a new well. A snubbing unit was deployed in 2008. In 2009, a suitable workover rig was deployed to test Jurassic formations in this previously drilled well. The location of the Mutriba field is shown in Fig. 1. A snubbing unit had been used to isolate the open perforations of the Triassic zone with cement. Subsequently, a workover rig was deployed to test the prospect of a Jurassic reservoir. Testing the Jurassic reservoir behind two heavy-walled casings (7 in. 46.4 lbm/ft and 8⅝ in. 40 lbm/ft) combined with extreme sour and high-pressure/high-temperature (HP/HT) conditions warranted high health, safety, environment, and technical precautions. Challenges for re-entry to this well included HP/HT conditions, a high surface pressure, and well-killing issues. Testing of the formation fluid revealed the presence of an unexpectedly high concentration of H2S (20%) and CO2 (2%), which presented challenges for coiled-tubing (CT) operations, stimulation, flowing the well, and fluid disposal.