Innovative Solution for Selective Testing of Horizontal Well Saves Seven Days Rig Time

Abstract

The Ufuq field, operated by Petroleum Development Oman (PDO), is located in Oman in close proximity to the Lekhwair field, the discovery well being drilled in early 2006. An appraisal well was subsequently drilled with the objective of further evaluating the discovery and delineating its' extent so that early commercial development decisions could be made. This second well was drilled with an extended horizontal section which identified a second zone of reservoir quality rock above the main zone of interest. As a consequence a second horizontal section was drilled to optimize the intersection of the two reservoir units and plans were made for evaluation testing. The first part of the test was planned to evaluate commingled flow while the second was to plug off the additional zone and flow test the main zone. To achieve these objectives, a unique combination of a 92º well inclination and an open hole scab liner were used with the scab liner providing a seat for an inflatable bridge plug to be set to isolate the upper zone once commingled testing was complete. Following testing of the main or lower zone the plug was retrieved thru-tubing and the well returned to commingled flow. In this paper the authors will review in detail the planning and execution of this procedure which avoided a workover, thereby saving 7 days of rig time, and was a "first" for both Operator and supplier. Introduction The Ufuq field is located close to the existing Lekhwair field and (See Fig. 1). Following the drilling of the discovery well in early 2006 a second well was drilled commencing in June 2006. The primary objective of the Ufuq-2 appraisal well was to provide the data needed to enable early decisions to be made as to the commercial viability of the discovery. Two vertical pilot holes were drilled which confirmed the presence of hydrocarbon bearing reservoir quality rock and established the presence of an Oil/Water contact (OWC).