Successful DST Methodology Adopted in Highly deviated, Deep, Sour & HPHT Exploratory well: A Case Studie

Abstract

Abstract Exploration in the state of Kuwait focuses on finding light oil and gas from deeper, HPHT and naturally fractured tight gas and condensate Jurassic Reservoirs. These reservoirs are drilled with high Oil Base Mud (OBM) densities(16-20.8ppg). The existing surface and subsurface constraints resulted in changing the proposed well location, which resulted in changing the well profile from vertical to highly deviated well. Having a deep HPHT well in highly deviated manner causes more complexity while drilling and testing the Jurassic formations. 78.2-degree angle deviated well with several side tracks and two doglegs was drilled to a depth of around 20,000-ft.(MD) to delineate the potential of the deep reservoirs. Well intervention operations were considered potentially risky due to the presence of hazardous well conditions such as HPHT and high H2S concentration. Keeping in view of well profile and hostile environments, it was very challenging task to conduct a short term well testing (STT) in these deep reservoirs. Tractor was used in the highly deviated sections with more than 50-degree angle to record the cement quality logs with Wireline. The target formations were perforated using high temperature and high shot density TCP guns in overbalance condition using drill-pipe. Two separate Drill Stem Tests (DST) consist of tester valve, multi-cycle circulating valve, two rupture disc valves, Down-hole sampler and Down-Hole memory gauges were used to test two different deep high pressure and sour reservoirs. Using of 15K Coiled Tubing with total length of 20,000ft for well activation and stimulation assisted the well intervention during the STT. Careful planning, proper selection of equipment & materials, detailed well test program and procedures resulted in a safe and successful testing operations in such extreme well conditions such as unconventional well profile, HPHT, and presence of H2S. For the first time in Kuwait, a highly deviated exploratory well with complete set of DST tools was successfully tested and proved significant amount of light oil and gas from a hostile reservoir. This paper describes and discusses the challenges encountered while drilling and testing an exploratory well and the achievement of overcoming these challenges which leads to successful well testing.