Abstract

Kra Al-Maru 3 (KM-3) is a deep vertical exploration well originally drilled to investigate the hydrocarbon potential of the Jurassic formations. Investigation of the open hole logs/cores indicated that there was limited porosity development in the Marrat zones of interest. Therefore an operational opportunity became available to deepen the well to explore the deeper Triassic horizons which had gas bearing potential.

The main challenges of this well were to design an extended casing program within the constraints of the present wellbore to allow for drilling/testing of the well with a wellhead rating of 20,000 psi whilst assuring the collection of maximum amount of useable data (cores, logs, rates, pressures and samples).

In order to meet these challenges a special casing design was employed, based on the experiences of other deep wells. Special HPHT cement additives were specified for the cementing of the deep liner strings. Application of turbine and slim hole motor technology was tried and a HPHT well test operation was planned including the use of a state of the art 20,000 psi surface test package.

During the well re-entry major complications were encountered due to high pressure profile, high mud weights, severe losses and well control situations. During the initial short term test the well produced gas, condensate/light oil along with highly saline water which caused salt plugging of tubing and surface lines. Plans are in hand to re-enter the well for long term test after solving the problem of salt plugging.

This paper will present a case history of the well including the planning, design process, implementation and lessons learned from the drilling and testing operations. These conclusions will then provide the basis for future optimization in the design of these types of wells.

Introduction

The search for commercial quantities of non associated gas from the Lower Mesozoic and Paleozoic horizons has been an important part of the exploration strategy of Kuwait Oil Company (KOC) over a number of years. Four deep wells were drilled down to the Pre-Khuff formation in the existing oilfield areas of Burgan, Umm Gudair and Sabriyah, before gas shows were recorded from the Sudair formation in the fifth well, KM-1, in the Kra Al-Maru area (Figure 1).

Following this result, further evidence of gas shows were recorded from the Unayzah formation in North West Raudhatain-1 and strong indications of a free gas potential were seen during the drilling phase on Mutriba 10, where high pressure influxes were encountered while drilling the Sudair formation. This potential was borne out in the subsequent Mutriba well, MU-12, which tested the first measurable quantities of non-associated gas in Kuwait from the Sudair in 2004.

Following the success in MU-12, and the indications of gas in KM-1, it was decided to return to the Kra Al-Maru area for the re-entry and deepening of KM-3.

The well KM-3 was located near the crest of the Kra Al-Maru structure some 450 meters away from KM-1. Although the original drilling and evaluation of KM-3 had indicated some hydrocarbon potential in the Najmah / Sargelu, logs and cores suggested that there was only limited porosity development in the primary targeted Marrat zones. The well was therefore suspended without running the liner across the open hole with a future possible decision to deepen the well depending on engineering feasibility as well as the test results from MU-12, which had not been completed at the time of KM-3 suspension.

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