An Integrated Study with an Effective Strategy Leads to a Great Discovery in a Challenging Fractured Jurassic Reservoir in West Kuwait

Abstract

Abstract To overcome the challenges in drilling, completion and testing for one of the highly fractured reservoir in West Kuwait oil field by intercepting the natural fractures and eliminating the causes of formation damage. An integrated multi-disciplinary study was carried out, to understand the underlying drivers of success and causes of failure in Najmah/Sargelu (NJ/SG) reservoirs in west Kuwait area and propose solutions to improve the chance of success. High reservoir pressure, high API oil and the limited success in some areas suggest that this reservoir has significant potential, despite the poor matrix permeability. The key to well success is to intercept the natural fractures and connect them to the production system without damaging them. Various potential damage mechanisms have been encountered, including mud invasion, cement plugging, formation solids plugging and formation collapse. The previous wells were drilled vertically with heavy oil based mud (OBM) and completed with cemented liner against the zone of interest. The study has identified robust well types that are designed to intercept the maximum number of natural fractures with high angle and open hole section with un-cemented 5" slotted liner. In addition, the plan was to drill the wells with high angle (80°) in the Lower Najmah Limestone and Upper Sargelu Limestone Formations but due to some drilling difficulties the plan was changed to 50° only. Therefore, number of wells in west Kuwait were planned to be drilled and completed as per the above strategy. The first well drilled and completed as per the new strategy did not reach the expectations after inconclusive test, and it needs to be revisited for better evaluation. The second well was drilled in a very challenging environment with high angle trajectory to encounter the natural fractures in the targeted zone. The un-cemented perforated liner was run and installed as planned, which eliminated the usual damage by cementation. During the well activation using Coiled Tubing and without any stimulation treatment, the targeted reservoir became active and the well showed commercial production of oil and gas with high well head pressure, which was announced as a great discovery in west Kuwait. This discovery is considered as a significant mark in Kuwait and opens a new window for exploring and developing of NJ/SG reservoir in other areas. New drilling, completion and testing strategy was applied in the challenging Jurassic reservoir, which lead to a great discovery in the state of Kuwait. Detailed drilling, completion, testing strategy and production performance with the lessons learned will be discussed in this paper.